CA1039180A - Downhole recovery system - Google Patents

Abstract

Abstract of the Disclosure:
The specification discloses a recovery process and system wherein hydrogen and oxygen are introduced into a vented pressure vessel, known as a gas generator, located at the bottom of a borehole, and ignited and burned to produce steam. The hydrogen and oxygen may be introduced either as a stoichio-metric mixture or the combustible mixture may be hydrogen-rich.
The gas generator comprises a cooling annulus surrounding a combustion and mixing zone for cooling the gas generator and the combustion products. Hydrogen or water may be supplied to the cooling annulus for cooling purposes. Remotely controlled valves are located downhole near the gas generator for positive control to the gas generator of the hydrogen and oxygen and of the water, if it is employed for cooling purposes. The well casing is sealed just above the gas generator by an inflatable packer. Provision is made for maintaining the desired hydrogen-oxygen ratio either by a hydrogen flow control slaved to a downhole thermocouple or by a special hydrogen-oxygen flow control employed in the event that ignition is carried out by a DC power supply located downhole. Although the preferred embodiment employs a fuel-oxidizer cooling fluid combination of hydrogen and oxygen or hydrogen, oxygen, and water, provision is made for employing other fuel-oxidizer-cooling fluid combinations.

Description

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Background of the Invention:
This invention relates to a system and process for recovery wherein steam and other hot gases are produced downhole in a gas generator located at the bottom of a borehole.
For the recovery of highly viscous oil from oil reservoirs, it has been found that hot water and steam piped downhole have been effective in reducing the viscosity of the oil so that it will flow and can be pumped to the surface. One of the problems encountered in piping steam downhole has been associated with heating and expansion of the well bore casing often results in severe damage to the casing. Another problem arises from loss of heat exchange through the casing from steam enroute to the bottom of the well.
Moreover, the known systems cannot pump steam downhole or generate steam downhole at a depth below about 3,500 feet.
It is an object of the present invention to provide a system and process for generating steam and hot gases downhole, for recovery purposes, at a depth down to and below 3,500 feet.
Thus, the invention provides a system for use for recovering hydro-carbons or other materials from underground formation by a borehole comprising a gas generator located in the borehole at or near the level of said formations, said gas generator comprising a housing forming a chamber defining a combustion zone and having an upper inlet end for receiving fuel and an oxidizing fluid for forming a combustible mixture of gases in said combustion zone for ignition, and a restricted lower outlet for the passage of heated gases, means, including conduit means extending from the surface, for supplying fuel from the surface to said inlet end of said gas generator located in said borehole, means, including conduit means extending from the surface, for supplying an oxidizing fluid to sa.id inlet end of said gas generator located in said bore-hole, and valve means located in said borehole near said gas generator for controlling the flow of fuel and oxidizing fluid to said gas generator. An 3~ igniter may be provided for igniting combustible gases in the combustion zone.
Also therè may be provided a cooling fluid annulus surrounding the chamber and having passages leading to the chamber.

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1~3~180 The invention also provides a recovery process for recovering hydro-carbons or other materials from underground formations penetrated by a borehole, comprising the steps of locating a gas generator in the borehole at or near the level of said formations, said gas generator comprising a housing forming a chamber defining a combustion zone and having an upper inlet end for receiving fuel and an oxidizing fluid for forming a combustible mixture of gases in said combustion zone for ignition, and a restricted lower outlet for the passage of heated gases, flowing through said borehole from the surface to said gas gener-ator, by way of separate passages, a fuel and an oxidizing fluid to form a combustible mixture in said combustion zone, and burning the combustible mix-ture in said combustion zone. The invention may supply hydrogen and oxygen downhole to the gas generator for the formation of a combùstible mixture which is ignited and burned in the combustion zone. The combustible mixture may be a stoichiometric mixture of hydrogen and oxygen or it may be hydrogen-rich. The gas generator and the combustion products may be cooled by introducing hydrogen into the cooling annulus or water supplied downhole to the gas generator. The hydrogen exhausted into the reservoir either by the burning of a hydrogen-rich mixture or by the hydrogen supplied to the cooling annulus, contains heat which is transferred to the oil to reduce its viscosity. Because of low lecular weight and high diffusivity, the hydrogen has the added advantage of being able to re readily penetrate the bed containing the oil and can therefore heat a larger bed volume more rapidly than can other gases. In addition,wl~ certain - bed compositions which may act as catalysts, the hydrogen can enter into a pro-cess normally referred to as hydrogenation to form less viscous hydrocarbons, thus reducing oil viscosity, both by heating and by combining with the oil.
For positive control of the flow of hydrogen and oxygen and to prevent the gas generator from being prematurely flooded, in the event that water is applied to the cooling annulus, remotely controlled valves are provided down-hole near the gas generator. These valves are controlled from the surface for controlling the flow of hydrogen and oxygen to the gas generator and for con-trolling the flow of water to the cooling annulus, if water is employed for ooling purposes.

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In the embodiment where water is employed for cooling purposes, water is supplied downhole through the borehole casing and hydrogen and oxygen are supplied through separate conduits extending through the borehole. In the embodiment wherein hydrogen is supplied to the cooling annulus, hydrogen may be supplied downhole through the borehole casing and oxygen is supplied through a separate conduit extending through the borehole.
The well casing may be sealed just above the gas generator by an in-flatable packer surrounding housing structure above the gas generator. In the embodiment employing water for cooling purposes, the packer is inflated by the hydrogen, whereby sealing is effected initially from the hydrogen pressure and finally from the pressure exerted by the water column in the oasing. In the embodiment wherein hydrogen is supplied to the cooling annulus of the gas gen-erator, the packer may be inflated by the pressure of the oxygen, whereby seal-ing is effected initially by the oxygen pressure and then from the hydrogen pressure supplied through the well casing.
The remotely controlled valves, in one embodiment, are solenoid valves located downhole and controlled from the surface. In another embodiment, a single spool valve having separate valve passages in a valve spool is employed downhole and which is controlled remotely from the surface by a separate solen-oid or by the hydrogen pressure.
Hydrogen may be supplied from the surface by way of a hydrogen supply, a hydrogen metering valve, and a hydrogen flow meter, all of which are located at the surface. Ihe oxygen may be supplied from the surface by way of an oxy-gen supply, an oxygen metering valve, and an oxygen flow meter which also are located on the surface. In one embodiment, the desired hydrogen-oxygen ratio is maintained by the use of a hydrogen flow control located at the surface and which is slaved to a thermocouple supported by the gas generator. The hydrogen flow control outlet is coupled to the hydrogen metering valve for controlling the desired amount of hydrogen flow therethrough.
In order to reduce the number of conduits and electrical leads extend-ing from the surface through the borehole, to the gas generator, a DC power igniter control may be located downhole to control ignition of the combustible :~a39~lt30 mixture in the gas generator. The igniter control is actuated by a switch supported by the valve spool of the spool valve which is remotely controlled by the hydrogen pressure. In this embodiment, the desired hydrogen/oxygen ratio is maintained by a hydrogen-oxygen flow control coupled to the hydrogen metering valve and hydrogen flow meter and coupled to the oxygen metering valve and oxygen flow meter.
Although the preferred embodiment employs a fuel-oxidizer-cooling fluid combination of hydrogen and oxygen or hydrogen, oxygen, and water, pro-vision is made for employing other fuel-oxidizer-cooling fluid combinations.

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., ~ff--1~3~9~8() Bricf_Descript~on of_the Drawings:
Fig. 1 schematically illustr2tes one embodiment of the uphole and do~rnhole system of the presen~ invention;
Fig. 2A is an enlarged cross sectional view of the top portion of the do~lnhole housing structure for supporting the gas generator of Fig. 1 in a borehole;
Fig. 2B is an enlarged partial cross sectional Vie~J
of the lower portion Or the housing of Fig. 2A supporting the gas generator Or Fig. 1. The complete housing, with the gas generator, may be vie~ed by connecting the lower portion o~
Figs. 2A to the top portion of Figs. 2B;
~ig. 3 is a cross sectional view of Figs. 2B taken through the lines 3-3 thereof;
Fig. 4 is a cross sectional view of Fig. 2B taken through the lines 4-4 thereof;
Fig. 5 is a cross sectional view of Figs. 2A taken through the lines 5-5 thereof;
Fig. 6 is a cross sectional vie~l of Fig, 5 taken through the lines 6-6 thereof;
Fig. 7 is a cross sectional view of Fig~ 5 taken through the lines 7-7 thereof;
Fig. 8 is a cross sectional view of Fig. 2B taken through the lines 8-8 thereof;
Fig. 9 is a cross sectional view Or Figs. 2B taken through the lines 9-9 thereof;
Fig. 10 illustrates in block diagra~, one Or the downhole remotely controlled valves of Fig. l;
Fig. 11 is a curve useful in understanding the presen~
invention;

~ 03~3~8() Fig. 12 ls a modification of a portion of the assembly of Fig. 2B;
Fig. 13 illustrates a modified arrangement for inflating the packer of a modification Or the system of Figs. 1, 2A and 2B;
Fig. 14 is another embodiment of the present invention employing a modified downhole remotely controlled valve system;
Fig. 15 is an enlarged cross-sectional view of the re-motely controlled valve system of Fig. 14;
Fig. 16 is an enlarged view Or a portion of the valve of Fig. 15;
Fig. 17 is an enlarged cross-sectional view of a gas generator similar to that of Fig. 2B but wi~h certain modifications;
Fig. 18 is a schematic illustration of another embodiment of the present invention;
;~ 15 Fig. 19 is a block diagram of the hydrogen-oxygen flow ; control system of Fig. 18;
~' Fig. 20 schematically illustrates the gas generator ~` located in a borehole which penetrates a hydrocarbon bearing formation and a spaced production well for recovering hydrocarbons from the formations;
Fig. 21 schematically illustrates the uphole nnd down-hole system of another embodiment of the present invention;
Fig. 22A is an enlarged cross-sectional view of the ~; top portion of the downhole housing structure for supporting the gas generator of Fig. 21 in a borehole;
Fig. 22B is an enlarged partial cross-sectional view of the lower portion of the housing Or Fig. 22A supporting the ~- gas generator of Fig. 21; and Fig. 23 is an enlarged partial cross-sectional view of the gas generator of Fig. 22B.

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Detailed Description Or the Invention:
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Rererring now to Figs. 1-.9,.there ~`lill be described one embodiment of the recovery system Or the present invention which generates steam downhole in a borehole 31 to stimulate oil production from a subsurface reservoir 33 penetrated by the borehole (see Fig. 1). The steam generated drives the oil in the formation 33 to other spaced boreholes (not shown) which penetrate the formation 33 ~or recovery purposes in a manner well known to those skilled in the art.

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The system of the present invention comprises an uphole system 35 and a downhole systern 37 including a gas generator 39 to be located in the borehole at the level o~
or near the level of the oil bearing formation 33. In the embodiment of Fig. 1, oxygen and hydrogen are supplied ~rom the surface to the gas generator to form a combustible mixture which is ignited and burned in the generator to form steam.
The gas generator and steam generated are cooled by water also supplied from the surface.
Referring to Figs. 2A and 2B, the gas genera'cor 39 comprises an outer cylindrical shell 41 supported in a housin~
43 located in the borehole. T~e outer shell 41 has an upper end 45 through which supply conduits and other components extend and a lower end 47 through which a small diameter outle~
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nozzle 49 extends. Supported within the outer shell 41 is an inner shell 51 which forms a cooling annulus 53 between the inner shell and the outer shell. The inner shell has an upper wall 55 which is connected to a conduit 57 which in turn extends through upper wall 45 and is connected thereto. The s 20 conduit 57 forms one of the supply conduits, as will be described ~i~
subsequently and also supports the inner shell 51 within the outer shell, forming the annulus 53 and also formin~ an upper space 59 between the walls 45 and 55. The space 59 is in com-munication with the annulus 53, as illustrated in Fig. 9. The opposite end of the inner shell 51 is open at 61. Formed through the inner shell at the lower ~nd thereol ls a plurality of apertures 63 which provide passages from the annulus 53 to the interior of the inner shell for the flo; of cooling L luld 103~3~t~
Supported in the inner shell at its upper end is a hea~
resistant liner 65 which defines a primary combustion zone 67.
The liner is supported by a retention ring 53A and has an upper wall portion 65A through which supply conduits and o~ner components extend. The portion o~ the interior shell at the level of the apertures 63 is defined 2S a mixing zone 69.
Conduit 57 extends through walls 45 and 55 and through the upper liner wall 65A to the primary combustion zone 67.
Concentrically located within the conduit 57 and spaced inward there~rom is a conduit 71 which also extends to the combustion zone 67. Fuel is supplied through the annulus ~ormed between conduits 57 and 71 while an oxidizing fluid is supplied through conduit 71. Swirl vanes 73 and 74 are provided-in the annulus between conduit 57 and conduit 71, and in condui~ 71 to mix 1~ the oxidizer with the fuel to form a combustible mixture ~rhich is ignited in the combustion zone by an igniter 75 and burned.
As illustrated, the igniter 75 comprises a spar~ plug or electrode which extends through walls 45 and 55 and into an aperture 65B
formed througn the upper liner wall 65A whereby it is in ~luid communication with the gases in the combustion zone 67.
In the present embodiment, the oxidizing ~luid is oxygèn and the fuel is hydrogen whereby steam is ~ormed upon combustion of the hydrogen and oxygen mixture, Cooling fluid is supplied to annulus 53 by way of a condui~ 77 (see also Flg.
4) formed through the upper wall 45 of the outer shell 41. In the present embodiment, the cooling fluid is w2ter. ~rom the conduit 77, the water flows to the annulus 53 by ~ray of the space lC~3~

59 formed betweell the ~ralls 45 and 55. The ~rater cools the inne~ shell 51 and flows through apertures 63 to cool the combustion gases to the desired temperature. The stea~ derived from the combustion of the hydrogen and oxygen and fro.n the cooling water then flows through the outlet nozzle 49 into the formations. Since the exhaust nozzle 49 is small compared with the diameter of the combustion ~one, the pressure generated in the gas generator is not affected by the external pressure (pressure of the oil reservoir) until the external pressure approaches approximately 80,~t o~ the value o~ the internal pressure. Therefore, for a set gas genera~or pressure~
there is no need to vary the flow rate o~ the ingredients into the generator until the external pressure (oil reservoir pressure) approaches approximately 80% of the internal gas pressure.
Referring to Fig. 1, the hydrogen, oxygen, and water are supplied to the generator located downhole by way of a hydrogen supply 81, an oxygen supply 83, and a water supply 85. Hydrogen is supplied by way o~ a compressor 87 and then ; through a metering valve 89, a flow meter 91~ and throu~h conduit 93 which is inserted downhole by a tubing reel and app~ratus 95.
Oxygen is supplied downhole by way of a compressor 101, and then throùgh a metering valve 103, a flow meter 105, and through conduit 107 which is inserted downhole by way of a tubing reel and apparatus 109. From the ~rater reser~oir 85, ~he ~rater is supplied to a ~rater treatment system 111 and then pumped b~y pump 113 through conduit 115 into the borehole 31. In Fig. 1, ~rater in the borehole is identified a~ 117.

1~)3~.1t 8() The borehole 31 is cascd ~rith a steel casing 121 and has an upper wel:l head 123 through ~hich all of the conduits, leads, and cables extend. Located in the borehole above and near the gas generator is a packer 125 through which the conduiis, cables, and leads extend. The flo~ of hydrogen, oxygen, and water to the generator is controlled by solenoid actuated valves 127, 129, and 131 which are loca~ed downhole near the gas generator above the packer. Valves 127, 129, and 131 have leads 133~ 135, and 137-which extend to the surface to solenoid controls 141, 1ll3, and 145 for separately controlling the opening and closing of the downhole valves from the surface.
The controls 141~ 143, and 145 in effect, are switches which may be separately actuated to control the application of electrical energy to the downhole coils of the valves 127, 129, and 131. Valve 127 is coupled to hydrogen conduits 93 and 57 while valve 129 is coupled to oxygen conduits 107 and 71.
Valve 131 is coupled to water conduit 77 and has an inlet 147 for allowing the water in the casing to flow to the gas generator when the valve 131 is opened.
The igniter 75 is coupled to a downhole trans~ormer 149 by way of leads 151A and 151B. The transformer is coupled to an uphole ignition control 153 by way of leads 155A and 155B. The uphole ignition control 153 comprises a s~ritch for controlling the application of electrical energy to the downhole transformer 149 and hence to ~he igni~er 75.
A thermocouple 161 is suppor~ed by the gas generator and is electrically coupled to an uphole hydro~en flor, control 163 by ~Jay of leads illustrated at 165. The hydrogen flo~i control 103~

s~nses the temperature detected by the thermocouple and produces an output which is applied to the metering valve 89 for con-trolling the flow of hydrogen to obtain the desired hydrogen-oxygen ratio. The output from the flow con~rol 163 may be an electrical output or a pneumatic or hydraulic output and is applied to the val~e 89 by way of a lead or conduit illus~rated ` at 167.
Also supported by the gas generator is a pressure transducer 171 located in the space between the gas generator and packer for sensing the pressure in the generator. Leads ' illustrated at 173 extend from the transducer 171 to the surface where they are coupled to a meter 175~ for monitoring purposes. Also provided below and above the packer are pressure -~ transducers 177 and 179 which have leads 181 and 183 extending i~ 15 to the surface to meters 185 and 187 for monitoring the , pressure differential across the packer.
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,'; Referring again to Figs. 2A and 2B~ ~he gas generator 29 is secured to the housing 43 by way of an annular member 191. The housing in turn is supported in the borehole by a 20, cable 193. As illustrated, cable 193 has its lower end secured ; to a æinc lock 195 which is secured in the upper portion 43A
of the housing. As illustrated in Figs. ~, 5, and 8,'the upper portion of the housing has conduits 77, 57, 201-203, 71 ~d 204 extending therethrough for the water, hydrogen~ igni~er wires, thermocouple wires, pressure lines, oxygen, and a dump conduit, the latter of which will be described subsequently. The upper portion of the housing also has an annular slot 209 formed in ~ ` ' t 1~3~}6) its periphery in ~rhich is supported the packer 125. The paclcer is an elastic member that may be expanded by the injection of gas into an inner annulus 125~ formed between the inner and outer portions 125B and 125C of the packer.
(See also Fig. 6.) In the present embodiment, hydrogen fro~.
the hydrogen conduit is employed to inflate the packer ~o form a seal between the housing 43A and the casing 121 of the borehole. Hydrogen is preferred over oxygen since it is non-oxidizing and hence will not adversely affect the packer.
Hydrogen from the hydrogen conduit 57 is injected into ~he annulus 12~A by way of a conduit 211 which is coupled to the hydrogen conduit 93 above the downhole valve 127. See Figs.
1 and 6.
~lith the downhole system in place in the borehole, as illustrated in Fig. 1, and all downhole valves closed~ the start-up sequence is as follo~s. Hydrogen and oxygen are admitted to the downhole piping and brought up to pressure by opening metering valves 89 and 103. The hydrogen inflates the packer 125 and forms a seal between the hous~ng 43A and the borehole casing 121, upon being admitted to the downhole pipe 93. Water, then is admitted to the well casing and the casing filled or partially filled. This is accomplished by actuating pump 113. Water further pressurizes the downhole packer seal. The ignition control 153 and the oxygen, hydrogen and water s~lenoid valves 127, 129, and 131 are se~ to actu~te, in the proper sequence, as follows. The igni~er is started by actuating control 153; the oxygen valve 129 is opened by actuating control 143 to give a slight oxygen lead; the hyd~ogen ~ (~39~30 valve 127 is then opened, followed by the opening of the water valve 131. Valves 127 and 131 are opened by actuating controls 141 and 145 respectively. This sequence may be carried out by manually controlling controls 141, 143, 145 and 153 or by automatically controlling these controls by an automatic uphole control system. At this poin~, a characteristic signal from the downhole pressure transducer 171 will sho~r on meter 175 whether or not a normal star~ was obtained and the thermocouple will show by meter 164, connected to leads 165, whether or not the desired steam temperature is being main-tained. The hydrogen ~low controller 163 is slaved to thermo-couple 161 which automatically controls the hydrogen flow.
The hydrogen to oxygen ratio may be controlled by physically coupling the hydrogen and oxygen valves, electrically coupling :: .
~i 15 the valves with a self synchronizing motor or by feeding the ou~put from flo~r meters 105 and 91 into a comparator 9Q which will provide an electrical output for moving the oxygen metering valve in a direction that will keep the hydrogen-oxygen ratio constant. The comparator may be in the form of a computer which takes the digital count from each flow meter, computes the re-quired movement of oxygen metering valve and feeds ~he req~ired electrical, pneumatic, or hydraulic power to ~he valve controller to accomplish it. Such controls are available co.~mercially The lower the gas generator temperature, the grea~er the flow of hydrogen required. The flow rate through the metering valve 89 is controlled by electrical communicaiion ~hrough conduit 167 from the hydrogen ~101J controller 163 Communica~ion fro~ the ( ~3~ O
hydrogen flo~ controller 163 to metering valve 89 optionally may be by pneumatic or hydraulic means th~ough an appropriate conduit. ~t this point~ the flow quantities of hydrogen, oxy~en, and water are c~ecked to ascertain proper ratios of hydrogen and oxygen, as ~lell as flo~J quan~ities of hydrogen~
oxygen, and water. Monitoring of the flow o~ hydrogen and oxygen is carried out by observing flow meters 91 and 105~
The flow rate meters or sensors 91 and 105 in the hydrogen and oxygen supply lines at the surface also may be employed to detect pressure changes in the gas generator. For example, if the gas generator should flame out, t~e flo~;r rates of ~uel and oxidizer will increase~ giving an indication o~ malfunction~
If the reservoir pressure should equal ~he internal gas gene-rator pressure, the flow rates of the fuel and oxidizer ~lould drop, signaling a need for a pressure increase ~rom the supply.
Adjustment of the ~low quantities o~ hydrogen and oxygen can be made by adjusting the supply pressure. Both valves 8~ and 103 may be adjusted manually to the desired initial set value.
At this poin~ the gas generator is on s~ream~ As , the pressure below the packer builds up, there may be a tenden~y for the packer to be pushed upward and ho~ gases to leak upwzrd into the well casing both of which are undesirable and po~entially damaging. This is prevented, however, by the column o~ wate~
maintained in the casing and which is main~ained a~ a pressure that will equal or exceed the pressure of the reservoir below the packer. For shallow wells, it may be necess2ry ~o maintain pressure by pump 113 in addition to that exer~ed by ~he ~a~er column. For the deep ~Jells, it may be necessary to control the l~J3~;t8~ -height of the water column in the casing. This may be accomplished by inserting the water conduit 115 in the bore-hole to a-n intermediate depth with a float opera~ed shut off valve; by measuring the pressures above and below the packer;
by measuring the pressure differential across,the packer; or by measuring the change in tension on the cable that supports the packer and gas generator as water is added in the column.
Flow of water into the casing 121 will be shut off i~ the measurement obtained becomes too great. Water cut-off would ` 10 be automatic. In addition, a water actuated s~itch in the - well may be employed to terminate flow after the well is fiiled to a desired height. The pressure and pressure dif-ferential can be sensed by co~mercially available pressure transducers, such as strain gages, variable reluctance elements !~ 15 or piezoelectric elements, which generate an electrical signal with pressure change. Changes in the cable tension can be sensed by a load cell supporting the cable at the sur~ace. In the embodiment of Fig. 1, pressure above and below the packer is measured by pressure transducers 177 and 179~ their ou~puts of ~hich are monitored by meters 185 and 187 for con~rolling flow of water into the casing 121. On stream operation of the gas generator may extend over periods of several weeks.
In shut down operations, the following sequ,ence is followed. The downhole oxygen valve 129 is shu~ off first, follolJed by shut off of the hydrogen valve 127 and then the ~- water valve 131. The water valve should be allowed to remain open just long enoug'n to cool the generator and eliminate heat soak back after shut down. Shut off of the igni~er is accom-~C~39~
plished manually or by timer after start-up is achieved.
In one embodiment of the oil recovery system, steam is produced by the dol~nhole generator by employing hydrogen and oxygen in a stoichiometric ratio. The steam may be produced `~ 5 at an output of 20 x 106 BTU/hr. at 1,000 psi and 600F at a depth of 5,000 feet. The downhole generator may be employed in a borehole casing having an inside diameter of 6.625 inches.
Under these conditions, the total weight of hydrogen required for combustion can be found by calculation to equal 327.6 pounds Or hydrogen per hour. A total of eight pounds of oxygen is required for each pound of hydrogen or a total of 2620.8 pounds of oxygen per hour. The maximum temperature produced in burning hydrogen stoichiometrically with oxygen is 5,270F
at atmospheric pressure. As the pressure increases, the maximum temperature also increases as there is less dissociation of water. The amount of cooling water required to cool the hot gases can be shown to equal to 13,579 pounds per hour or `~ 3.77 pounds per second. Hydrogen and oxygen conduits 93 and ~ . .
107 may be 1.00 inch tubing to 1.25 inch schedule pipe. T~e well casing can be used for the supply of water. Where the water places excessive stress on the suspension system, the water depth in the casing must be controlled, as indicated~
above. The column pressure of water at 5,000 feet is 2,175 psi.
No pumping pressure is needed at this depth. Instead, a pressure regulator orifice will be employed at the well bottom to reduce the pressure at the gas generator. 11ater is fed directly from the supply in the well casing to the regulator orifice.

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It is necessary for start-up and operation of the gas generator to locat~ the valves do~;nhole just above the packer to assure an oxygen lead a~ start-up and positive response to control. Use of the do~rnhole remotely controlled valves 127, 129, and 131 has advantages in that they provide positive control at the gas generator for the flo~ of fluids to the generator. The downhole remotely controlled ~Jater valve 131 has advantages in that it prevents premature ~looding of the gas generator. The downhole valves 127, 129, and 131 may be cylinder actuated ball type valves which may be operated pneumatically or hydraulically (hydraulically in the embodiment of Fig. 1), using solenoid valves to admit pressure to the actuating cylinder. Where the well casing is used as one of the conduits for water or fuel (to be described sub-sequently), it will be necessary to exh~ust one port of the solenoid valves below the downhole packer. Further, for more positive actuation, it may be desirable ~o use unregulated water pressure as the actuating fluid, as it will provide the greatest pressure differential across the pacXer. A schema~ic - 20 diagram of the valve arrangement for each of the vaives 127, 129, and 131 is illustrated in Fig. 10. In this figure, the valve is identified as valve 127. The valves 129 and 131 ~ill be constructed in a similar manner. As illustrated, the valve shown in Fig. 10 comprises a ball valve 221 ~or controlling ~he flow of fluid through conduit 57. The opening and closing o the ball valve is controlled by a lever 223 ~Ihich in turn is controlled by a piston 225 and rod 226 of a valve actuating c~linder 227. T~o three-way solenoid valves 229 and 2~1 are ' ( ( ( ~39~
employed for actuating the cylinder 227 to open and close the ball valve 221. As illustra~ed, the three-way solenoid valve 229 has electrical leads 232 extending to the sur,ace and which form a part of leads 133. It has a water inlet conduit 233 with a filter and screen 235; an outlet conduit 237 coupled to one side Or the cylinder 227; and an exhaust port 239. Similarly, the valve 231 has electrical leads 241 extending to the surface and which also form a p2rt o~ leads 133. Valve 231 has a water inlet conduit 243 ~lith a fil~er and screen 245 coupled therein; an outlet conduit 247 coupled to the other side of the cylinder 227, and an exhaust port 249. Both of ports 239 and 249 are connected ~o the dump cavity 204 which extends through the upper housing portion 43A from a position above the packer to a position ~elow the packer. Hence, both ports 239 and 24~ are vented to the pressure below the packer 125. In operation, valve 229 is energized and valve 231 de-energized to open ball valve 221.
In order to close ball valve 221, valve 229 is de-energized and valve 231 energized. When solenoid valve 229 is energized and hence opened~ water pressure is applied to one side of the cylinder 227 by way of conduit 233, valve 229, and conduit 237 to move its piston 225 and hence lever 223 to a position ~o open the ball valve 221 to allow fluid flow through conduit 57.
When valve 231 is de-energized and hence closed, the opposite

2~ side of the cylinder 227 is vented to the pressure below the packer by way of conduit 247, valve 231 and condui~ 249. I~Jhen . valve 231 is opened, water pressure is applied to the other side of the cylinder by way of conduit 243, valve 231 and conduit 247 1~39~30 to move the actuating lever 223 in a direc-tion to close the valve 221. t~hen valve 231 is closed, the opposite side of the cylinder is vented to the pressure belo~r the packer by way of conduit 237, valve 229, and conduit 239.
Referring again to the packer 125, initlal sealing is effected by pneumatic pressure on the seal from the hydro-gen pressure and finally from pressure exer~ed by the water column. Thus~ the packer uses pneumatic pressure to insure an initial seal so tnat the water pressure will build up on the top side of the seal. Once the water column in the casing-reaches a height adequate to hold the seal out ag~inst ~he - casing, the pneumatic pressure is no longer needed and the hydraulic pressure holdinG the seal against the casing increases with the water column height. Hence, with water exertlng ! 15 pressure on the pneumatic seal in addition to the sealing pressure from the hydrogen, there will be li~tle or no leakage past the packer. More important, however~ is the fac~ that no -hot gases will be leaking upward across the packer since the down side is exposed to the lesser of two opposing pressures.
In addition to maintaining a positive pressure gradien~ across the packer, the ~ater also acts as a coolant for ~he packer seal and components above the packer. The seal may be made of viton rubber or neoprene. The cable suspension system ac~s to support the gas generator and packer from the water colu~n load. In one embodiment, the cable may be made of plo~ steel rope.
In one embodiment, the ou~er shell 41 (Fig. 2B) and the inner shell 51 of the gas generator may be formed of 30 ( 1()39~30 stainless steel. The wall o:~ the outer shell 41 ma~ be 3/8 o~ an inch thic~ while the wall o~ the inner shell 51 may ~e 1~8 of an inch thick. The liner 65 may be formed of graphite with a wall thickness of 5/16 of an inch. It extends along the upper 55~ of the inner shell. As the inner shell 51 is kep~
cool by the water, it will not expand greatly. The graphite also will be cooled on the outer surface and there~ore will not reach maximum temperature. The guide vanes 71~ in the oxygen tube 71 swirl the incoming oxygen in one direction and gu~de vanes 73 in the hydrogen annulus between tubes 71 and 57 swirl the hydrogen in a direction opposite that of the oxygen. The oxygen, being heavier than the hydrogen, is centrifuged ou~ward5 mixing with the hydrogen. A spark is provided for igniting the hydrogen by means of the electrode 75, as mentioned above. The thermocouple 161 is housed in a sheath of tubing 162 running ~- ~rom the top of the generator to a point near the exhaust nozzle 49 and senses the temperature at that point. This temperature measurement is used to control the fuel-oxidizer ~low to the gas generator to maintain an exhaust temperature of 600F. The leads of the thermocouple extend through conduit 202 or the housing (~ig. 8) and at 165 (~ig. 1) to the sur~ace. The pressure transducer 171 (Fig. 1) allows monitorin~ of the generator pressure. It-is located in the space between the generator and packer and is connected to the generator at 2Q3A ~Fig. 4). The transducer 171 has leads 173 extending througn conduit 203 Or the housing to the surface. The diameter of the oxygen inlet tube 71 is sized to produce a weight flow of 2,621 pounds o.
oxygen per hour at 1,000 psig and 34.6 feet per second The hydrogen inlet annulus between tubes 71 and 57 is sized to ~3'~80 provide 328 pounds Or hydrogen per hour at 1,000 psig and 3~.6 feet per second. As the two gases swirl into the combustion zone, their average designed precombus~ion velocity in the through ~low direction is 9.8 fee~ per second to allow for stable combustion. Upon completion OL combustion and cooling of the combustion gases to 600F, the velocity is 32 fee~ per second. As the steam derived from combus~ion o~ hydrogen and oxygen and from the cooling water moves into the ou~let nozzle~
it reaches a velocity of 1,630 ~eet per second for a total weight flow of 4.6 pounds per second. The area of ~he exhaus~
nozzle ~or a nozzle coefficient of lOO~ is .332 lnches square.
For a nozzle coefficient of .96, the area is 0.346 inches square for a diameter of .664 of an inch. The inside diameter of ~e outer shell 41 may be 4.3 inches, and the inside diameter o~ the inner shell 3.65--inches. ~or these dimensions, the nozzle ! 49 may have a minimum inside diameter of .664 of an inch. The flow quantity from the gas generator is not a~fec~ed by oil reservoir pressure until the reservoir reaches the cr~tical pressure o~ approximately 550 psi. It is not greatly affected un~il reservoir pressure reaches 800 psi, a~ter which flow rate drops off rapidly. With the high pressures tha~ are associated with a gas generator, a plug can be inser~ed in the nozzle 49 before the generator is lowered ~nto ~he borehole~
so that it can be blown out upon star~-up of the gas genera~o~.
The plug will be employed to prevent borehole liquid from entering the generator ~rhen it is lowered in place in the borehole. ~urther, because of the continued availability o~
high pressure and small area required, a check valve downs~ream ( ( ( ( ~ 3~
of the nozzle c~n be provided so that upon shut down of the gas generator, the check valve will close, keeping out any fluids which could otherwise flo~r back in~o the generator.
Although not sho~rn, it is to be understood tha~
suitable cable reeling and insertion appar2tus will be employed for lowering the gas generator into the borehole b~ ~i2y 0 cable 193. In addition, if the water conduit 115 is to be inserted into the borehole to significant depths, suitable water tubing reel and apparatus similar to that iden~ified at 95 and 109 will be employed for inserting the water tu~ing downhole.
The hydrogen and oxygen me~ering valves 89 and 103 wîll have controls for manually presetting the valve openings for a given hydrogen-oxygen ratio. Valve 103 is slaved to valve 89, as indicated above. The valve openings may be changed automatically ~or changing the flow rates therethrough by the use of hydraulic or pneumatic pressure or by the use o~ electrical energy. If the metering valves are of the type which are actuated by hydraulic or pneumatic pressure, ~hey may include a spring loaded piston con~rolled by the hydraulic or pneumatic pressure ~or moving a needle in or out of an ori~ice. If the metering valves are of the type which are actuated electrically, they may include an electric mo~or for controlling the opening therethrough. Suitable meterin~ valves 89 and 103 may be purchased commercially fro~ companies such as Allied Control Co., Inc. of New York, N. Y., Repub~ ic M~g. Co.
of Cleveland, Ohio, Slcinner Uniflow Valve Div. o~ Cranford, New Jersey, etc.

-2~l-1(3363~
In the embodiment of F'ig. 1, valve 89 is actuated automatically by thermocouple signal. The do~rnhole thermo-couple 161 produces an electrical signal representative of temperature and which is applied to the hydrogen flo~r control 163. If the metering valve 89 is electrically activated, ~he hydrogen flow control produces an appropria~e electrical output, in response to the thermocouple signal, and which is applied to the valve by way of leads 167 for reducing or in-creasing the flow rate therethrough. ~or example~ if the thermocouple senses a low temperature, the hydrogen flow control 163 will cause the metering valve 8~-and hence valve 103 to increase their openings to increase the flow rate therethrough to provide more heat downhole. I~ the valve 8 is hydraulically or pneumatically actuated, the hydrogen flow control 163 will convert the thermocouple signal to hydraulic or pneumatic pressure for application to the valve 89 for control purposes.
The flow meters 91 and 105 may be of ~he type having rotatable vanes driven by the flow of fluid therethrough.
The flow rate may be determined by measuring the speed o~ the ~anes by the use of a magnetic pickup which detects the vanes upon rotation past the pickup. The output coun~ of the magnetic pickup is applied to an electronic counter for producing an output representative of flow rate.
In the above embodiment, a stoichiometric mixiure of hydrogen and oxygen was disclosed as being introduced and burned in the gas generator to produce steam for reducing the viscosity of the oil by heat and by pressure for secondary ~3~8V
recovery purpos~s. In another embodiment~ an excess of hydrogen (hydroOen-rich) may be introduced into the combustion zone of the gas generator for reducing the temperature in the primary combustion zone of the gas generator; for be~ter pene-tration of the formation bed due to the lower molecular weiGht of hydrogen; and for hydrogenation of the oil to ~orl~ less viscous hydrocarbons. Reduction of the temperature in the primary combustion zone with a hydrogen-rich mixture has advantages in that it allows the gas generator to be fabricated out of more conventional materials. In this respect, a 107.'i melting point material such as aluminum oxide or silicon dioxide re~ractory material or even plain stainless steel may be employed as the liner instead of graphite, In order to reduce the temperature in the primary combustion zone to 2,600~F, a ~low o~ approximately 1,675 pounds of hydrogen per hou~ may be required. This is slightly more than ~ive times the hydrogen flow rate required for stoichiometric burning~ T~e ~low rates of hydrogen in pounds of hydrogen per hour required to produce 20 million BTU/hour at primary combustion zone ~emperatures ; 20 ~rom 2,000F to 3,200F are illustrated in ~lg. ll.for a constant oxygen flow rate of 2,616 pounds per hour. Because of the low molecular weight and high dif~usivity, ~he hydrocen has the added advantage of being able to more readily penetrate the bed containing the oil and can therefore heat a larger bed volume more rapidly than can other gases. Xn addition, ~rith cer-tain bed compositions which may act as catalysts, tne hydrogen can enter into a process normally referred to as hydrogena~on to form less viscous hydrocarbons, thus reducinG oil viscosity ` ;~ ' ( 1~ 0 both by heating and by cor,lbining with the oil. In the hydro-genation process, the hydrogen will dissociate the crude oil molecules and theIl combine t~rith the dissociated components to form lighter, less viscous hydrocarbons, In the absence of bed compositions which may act as catalysts, the time required to achieve a substantial amount of hydrogena~ion may be reduced by injecting a catalyst downhole. ~or example~ the ca~alyst molybdic acid in solution with ammonium hydroxide can be poured into the well sometime before the heating process is begun, thus allowing the solution to penetrate ~he bed and move ahead o~
the pressure ~ront created by the generator exhaust gases.
The system of Figs. 1-10 can be opera~ed hydrogen-rich by forming the annulus between conduits 71 and 57 to the desired size and by obtaîning the desired hydrogen/oxygen ratio by setting the metering valves 89 and 103 and the hydrogen flow control 163 to the proper se~tings and automatically correcting the hydrogen flow rate through the metering valve 89 by use o~
the thermocouple 1~1 and hydrogen flow control 163~ as described previously. In addition, correction may be done manually if desired, by monitoring the flow meters 91 and 105 and-the ther,mo-couple output meter 164.
In a ~urther embodiment, hydrogren may be used a~ the cool.ant of the.gas generator rather than wa~er. This has the added advantage in that the water treatment sys~em may be eliminated and only one string of pipe downhoIe is required~
In this embodiment, hydrogen will be in~roduced ~hroucrh the annulus formed between conduits 71 and 57 for combustion and through the annulus 53 surroundin~ ~he combus~ion zone for cooling ~ll73~

purposes. ~Iydrogen will be supplied through the annulus bet~seen conduits 71 and 57 in adequate excess to the primary cornbustion zone to keep the temperature below 2,000F. The resulting steam and hot gases ~rill pressurize, heat and reduce the viscosity of the oil, as described previously. The hydrogen flowing throuGh the annulus 53 around the primary combustion zone will further reduce the gas temperature to 600~. The hot hydrogen from annulus 53 that has been used as a coolan~ ~rill also penetrate and heat the bed and also enter into the hydrogenation process.
Any hydrogen that is pumped do~mhole and unburned can be re-covered at the surface.
The system of Figs. 1-10 can be modified to 2110w hydrogen to be used as a coolant by eliminating the water supply system, including the water reservoir 85, wa~er treatmen~
system 111, water pump 113, water conduit 115, and the downhole water valve 131. The well casing itself may be used as ~he hydrogen supply conduit. In this case, the hydrogen line 93 ; may extend into the well only a short distance and will not be-connected ko downhole valve 127. T~e valve 221 o* 127 will be provided an inlet to allow the hydrogen supplied into ~he borehole to flow through valve 221 of 127 to the conduit 57 when the valve is opened. Hydrogen may be supplied ~o the annulus 53 by connecting the upper portion of condui~ 77 to conduit 57 rather than to valve 131. This may be done by removinC the top portion of conduit 77 and connecting an L-shaped conduit 77' to conduit 77 and to conduit 57, as illustra~ed in Fig. 12 Thus~ conduit 77 has one end coupled to conduit 57 by ~iay of L-shaped conduit 77' and its other end in fluid communication ~rith -2~-' ( ( ( 1~3~ 30 the zone 59 and hence the annulus 53 of the gas generator.
In this embodiment, the valve 127 will be employed to control the flol~ of hydrogen both to the primary combustion zone and to the annulus 53 around the primary combusiion zone. Both of the valves 127 and 129 ~rill employ pneumatic pressure ~rom the hydrogen in the borehole for operating their ball valves.
In this respect, each o~ the Yalves 127 and 129 will allol, hydrogen to flow through their inlet and exhaust conduits 233, 2~l3, 239, and 249 for controlling its ~ctuating cylinder 227 ~see Fig. 10) for controlling its ball valve 221. As indicated previously, the exhaust ports 239 and 2~9 will be vented to the lesser pressure belol~ the packer. In operztion,-the hydrogen pressure in the borehole will be maintained higher than that in the oil reservoir below the packer. Thus, any leakage at the packer is of hydrogen into the oil reservoir~
' ReXerring to ~ig. 13, the packer 125 may be inflated with a silicone ~luid 251 located in a chamber 252 and ~rhich is in ~luid communication with the pac~er annulus 125A by way of conduit 211. The chamber 252 contains a bellows 253 which may be expanded by oxygen supplied through inlet 254~ which is coupled to the oxygen conduit 107~ to force ~he silicone fluid 251 into the packer annulus 125A when ~he oxygen is admitted into the conduit 107.
In the start-up sequence~ the igniter 75 wlll be energized and the ox.ygen va-ve 129 will be opened to allo-.r flos~J of oxygen into the combustion zone follo~,ea by the o~ening of the hyctrogen valve 127 to allo~. the flo.w ol hydrogen into the combustion zone and into the surrounding cooling annulus _~9_ ~ Q~
53. Upon ignition, the igniter 75 will be automatically shut off by a timer or by hand after ignition is.verified by pres-sure readings. In the shut down sequence, ~he oxygen valve 129 will.be shut off first, follo~red by the shutting down of thQ
hydrogen valve 127.
In the event that liquid is in the borehole, the hydrogen line 93 may be connected directly to the v~lve 221 o 127, as described previously, and hydrogen or oxygen pressure ~using the embodiment o~ Fig. 13) may be employed to inflate the packer. In this embodiment, the liquid in the borehole or hydrogen from line 93 may be employed by the valves 229, 231, and cylinder 225 to control the ball valve 221 of each of valves 127 and 129.
Referring now to Figs. 14-17~ there ~7ill be descrioed another embodiment o~ the do~nhole recovery system of the present invention which employs a downhole spool valve for controlling the flow of fuel, oxidizer, and cooling fluid to the gas generator. The spool valve is illustrated in Fig 15~ The uphole and downhole system is similar to that of ~he embodimQnts of Figs. 1 9, however, certain changes are incorporated therein.
In Figs. 14-17, like components have been identified by like re~erence numeral~, as those employed in the embodiment o~
Figs. 1-9. In Fig. 14, line 261 indicates ground level. The box identified by reference numeral 31 depicts the cased borehole while reference numeral 33 identifies the oil bearing formation 33. All of the components above line 261 are located at the surface while those below line 261 are located in the boreho'e.
Although not illustrated, the system o~ Fig. 1ll will also employ the igniter 75, a heat s~/itch 157, the transducer 171 and its uphole readout 175 and the transduccrs 177 and 179 and their -3o-1~3~SV
uphole readouts 185 and 187. All of these components are not shown in Fig. 14 for purposes of clarity. The spool valve of Fig. 15 is illustrated in Fig. 14 at 263 and is controlled by an uphole solenoid control 265 which is electrically coupled to a downhole solenoid valve 267 by way of electrical leads illustrated at 269. When valve 267 is opened by actuating solenoid control 265, pneumatic pressure (hydrogen) is admitted to the valve 263 by way of branch conduit 271, valve 267, and conduit 273 for controlling the spool valve 263, as will be described subsequently. The system of Figs. 14-17 employs hydrogen and oxygen which is burned in the combustion zone of the downhole gas generator to produce steam. The hydrogen-oxygen mixture may be a stoichiometric mixture or it may be hydrogen-rich, as described previously. The system also can employ hydrogen as the cooling fluid in the surrounding cooling annulus 53, or it may employ water as the cooling fluid. The system o~
; Figs. i4-17 first will be described as employing hydrogen as the cooling fluid in annulus 53. In this embodiment, the water supply comprising water reservoir 85, water treatment-111, pump 113, and water conduit 115 will not be employed.
Although the hydrogen conduit 93 is illustrated as coupled directly to the valve 263, in the first embodiment now to be described, there will be no direct coupling Or the conduit 93 to the valve 263. Rather, the conduit 93 will extend into the borehole and the borehole casing will be employed as the conduit for the hydrogen supply. Solenoid valve conduit 271 may be coupled to hydrogen conduit 93 or it may be opened to the borehole for receiving hydrogen ~or flow to conduit 273 for control purposes when valve 267 is opened. ~lthough not shown, in Fig. 17, the gas generator 39 will have an ` ( ( outer housing which will be supported by a cable in the same manner as described ~ith respect to Figs. 2h and 2B. Tne housing also will have an inflatable packer 125 which ~lill be inflated with the silicone fluid forced into the packer by the oxygen ~rom conduit 10~, as described with respect to Fig. 13. The spool valve of Fig. 15 will be supported by the cable above the packer.
The hydrogen supply system comprises supply 81, compressor 87, metering valve 89, and floT~ meter 91 operated in the same manner described previously. Similarly, the oxygen supply system comprises supply 83, compressor 101, metering valve 103~ and flow meter 105 operated in a manner similar to that described previously. This is true also with respect to the hydrogen flow control 163 and the ignition - 15 control 153.
The starting sequence for the downhole heating system is as follows. The metering valves 89 and 103, which also serve as shut of~ valves are opened, admitting hydrogen and oxygen to the system which are allowed to stabilize at operating pressure. The ignition control 153 is activated simultaneously with the solenoid valve 267. The solenoid ~alve 267 admits pressure to the valve 263 which in ~urn admits hydrogen and oxygen with a slight oxygen lead to the gas generator, The hydrogen and oxygen are ignited and as the tempera~ure rises, the thermocouple 161 senses and controls the temperature by r regulating the hydrogen ~low through the hydrogen flow control 163. Ignition is shut off manually or by a timer after s~ar~ up is achieved. In shut do~ln, the oxygen meter~ng valve 103 is o shut o~ irst. As the cornpressed ox~ygen in the sys~em becomes depleted, the flo~ of hydrogen can be programrned to automaticall~
drop until the valve 263 shuts o~f thereby shutting off the gas generator. The system can be operated manually or by autom.2tic controls.
Operation of the pneumatica-ly operated valve 263 now will be described with reference to Figs. 15 and 16. The valve comprises a housing 3~1 having a slidable spool 303 therein with two annular cavities 305 a~d 307~ Cavi~y 305 is adapted to provide cornrnunication between two ~orts 309 and 311 when the spool is moved downward to a given position.
Similarly, cavity 307 is adapted to provide communication between two ports 313 and 315 when the spool is moved downward to the given position. Qn inlet port 317 is in communication with port 309 by way of cavity 319 ~ while hydrogen conduit i 51 is in com~unication with port 311 by way of cavity 321.
In the present embodiment, inlet port 317 will be open to the hydrogen supply to the ~orehole. Oxygen conduit 107 is in communication with port 313 by way of cavity 323 and oxygen conduit 71 is in communication with por~ 315 ~y way of cavity 325. At the top of the valve, branch conduit 273 is threaded into conduit 327 formed in member 329. Operation begins by admitting pressurized fluid (hydrogen) into condui~ 273 by opening solenoid valve 267 to allow flow of hydrogen to conduit 273 by way of conduit 271, valve 267 and condui~ 273 Solenoid valve 267 is operated by actuating the solenoid control 265 which in effect is a switch which rnay be closed to supply electrical energy to the valve 267 by ~ay of leads 269. At ~.33~ 0 a pr~ssure predetermined by the se~ting Or spr:ing 331, poppet 333 moves away from its seat on member 329 and pressurized fluid is admitted to chamber 335. The settin~ o~ spring 331 is determined by the adjustment of scre~r fitiing 337. Pres-suri~ed fluid in chamber 335 is applied through conduits 339 to the top face of valve spool 303 forcing the spool do~mward inside housing 301. Cavity 305, which is in communication with pressurized hydlogen in cavity 319 by means of port 3bg, establishes communication with port 311 as the spool moves 10. downward thereby furnishi~g communication between cavities 319 and 321. Oxygen is supplied to the cav~ty 323 which establishes communication with cavi-ty 325 by means o~ port 313, cavity 307, and port 315. In order for cavity.305 to establish communic2tion with port 311, it must travel further than cavity 307 travels to-estab1ish communication with port 315. Therefore~ oxygen ! passes through the valve first and will be injecte~ into the ; generator first thereby providing a sligh~ oxygen lea~. As the valve spool 303 moves downward, seating on scre~ fitting 341, it compresses spring 343 so that when the hydrogen pressu~e 20. at,condui~ 327 is reduced to some value during shut down~
determined by the spring 343, the valve spool will move upward allowing'the valve to shut off the oxygen and hydrogen. ~en .
the poppet 333.reseats, any gas trapped in cavity .335 will be released into port 327 through port 345 (illustrated in more detail in ~ig. 16) as the residual pressure li~ts pintle 347 off of its seat against the spring pressure from spring 349.
Spring 34g is provided only to aSsllre seating of pintle 347 when pressure is applied against poppet 333 in the valve opening operation. At the lo~er end of the valve, a pressure contact _31~_ ` ( ' ( 1~3~V
s~r:itc}l :is provicled for automatLc downhole ba~tery ignition for a system which will be described subsequently. As the spool 303 moves do~mward, electrical conducting cap 351 provides electrical communication between conductive leads 353 and 355.
Plug 357 and rod 359 are made of dielectric materials, a nu~.. ber of which are available commercially. Spring means 361 assures continued contact between cap 351 and leads 353 and 355, as long as the valve is in the open position. The primary purpose oi the spring loaded poppet 333 feature is to assure achievement of hydrogen pressure downhole before the pneuma~ic valve opens and to assure rapid opening. The cavities 319, 321, 323, and 325 are arcua~e in form whereby multiple ports 309, 311, 313~
and 315 may be provided at each cavity 319, 321, 323, and 325 respectively.
Referring to Fig. 17, the gas generator 39 is similar to that shown in Fig. 2B. In this respect, it comprises an outer shell 41 having a lower wall 47 with a small outlet nozzle 49 formed therethrough. Located within ~he outer shell is an inner shell 51 forming a cooling annulus 53 between the inner shell and outer shell. ~ormed through the inner shell are a plurality o~ apertures 63 for the passage of cooling fluid from the annulus 53 to the interior of the chamber. The chamber comprises a primary combustion zone 67 and a mixing zone 69. Also provided is an ignition electrode 75, a heat switch 157 and a pressure transducer and a thermocouple (not shown).
The inner shell 51 is secured to a conduit 371 ~ihich extends into the top end of the inner shell and which in turn ~)3~0 is secured to an upper plat~ 373 connected be~reen the top outer wall L15 and the housing 41 of the gas generator. The oxygen conduit 71 extends through wall 45 and into conduit 371 formin~ a supply annulus 375 between condui~ 71 and 371.
Also extending through wall ~5 is an inlet 377 which is in fluid communication with chamber 379 formed bet~Teen ~rall 45 ' and plate 373. Extending through wall 45 and through plate ; ' 373 is another inlet 381 which,is in fluid co.~munication with the annulus 53 formed between the inner and outer cylinders `; 10 41 and 51. Also formed through plate 73 a~e a plurality of apertures 383. Although not shown, vanes 74 may be provided at the lower end of conduit 71 and vanes 73 provided in the annulus 375 at its lower end in a manner similar to that shown in Fig. 2B. Oxygen is supplied throligh conduit 71 while ~, 15 conduits 377 and 381 are connected to the hydrogen conduit 57 In the embodiment o~ Fig. 17, a refractory lining is not .
illustrated although such a liner could be located within the inner shell 51, if desired. Such a liner will have apertures corresponding in position with apertures 63. In operation, oxygen enters conduits 71, passes through,the orifice in orifice plate 71A and exits into the primary combus~ion zone 67. Hydrogen ~ enters inlet 377, passes through the orifice in orifice plate - 377A and into chamber 379. From chamber 379, part of ~he hydro~en passes through annulus 375 to the primary combustion zone 67 wher2 it is ignited by an electrically genera~ed spark from, ignition electrode 75 to conduits 71 and 371 which are grounded.
The remainder of the hydrogen that enters ch~rber 379 p2sses through the ports 383 into c'nam`oer or annulus 53. Still more 1~3~
hydrogen enters inlet 381, passes through the orifice in orifice plate 381A, and exits into chamber or annulus 63. This arrange-ment allows external adjustment of the hydrogen,flow entering annulus 375 to provide the most efficient mixture in the primary combustion zone 67. The hydrogen in annulus ~3 passes through the apertures 63 and enters the mixing zone 69 and the outer fringes of zone 67 to cool the gases produced in the primary combustion zone 67 before they pass out through the exhaust nozzle 49 into the oil reservoir. The thermally operated switch 157 turns the ignition system off when the outer shell reaches a temperature for which the switch is set.' In the embodiment of Figs. 14-17, if liquid is in the borehole, hydrogen line 93 may be connected directly to inlet line 271 of solenoid valve 267 and to inlet 317 of pneumatic valve 263. Hydrogen or oxygen pressure (using the embodiment . of Fig. 13) may be employed to inflate the packer.
~ The embodiment of Figs. 14-17 may be modified to :! ` .
, allow water to be used'as the coolant in cooling annulus 53.
~, In this embodiment, the water reservoir 85, water treatment system 111, pump 113 and water conduit 115 illustrated in Fig. 14 will be employed for supplying water to the borehole -' as described previously. ,In addition, the hydrogen conduit 93 will extend and be coupled to the inlet 317 of the spool valve 263 and to inlet 271 of solenoid valve 267. The spool ?5 valve of Fig. 15 will be modified to provide a third valve section similar to that of the two shown. In this respect, the housing 301 will have a third inlet/outlet arrangement and the spool 303 will be lengthened and will have a third cavity for allowing communication between the third inlet and outlet combination for .

1~,3~ 0 the passage of water from the borehole to the water conduit 77 previously described. The third inlet and outlet may be similar to ports 309 and 311 but formed in the housing above ports 309 and 311. The third inlet may have an inlet and cavity similar to 317 and 319 while the third outlet may have a cavity similar to 321 but coupled to inlet 381 of the generator of Fig. 17. The third cavity of the valve spool 303 will be located above cavity 305. The third cavity ~n spool 303 will be formed to allow water to flow through the valve after the flow of oxygén and hydrogen are allowed to flow therethrough. In this embodiment, plate 373 of the gas generator of Fig. 17 will not have the apertures 383 formed therethrough.
For deep wells, it may be desirable to eliminate th as many of the conduits and electrical leads extending from the surface to the downhole components, as possible. One arrange-ment for accomplishing this purpose is illustrated in Fig.
18 and which employs an uphole hydrogen-oxygen ratio control and a downhole battery for ignition purposes. High density batteries such as the silver-zinc are commercially available for this application. The system of Fig. 18 burns a hydrogen-oxygen mixture in the combustion chamber of the gas generator and also empioys hydrogen in the cooling annulus 53 ~or cooling purposes. The uphole hydrogen and oxygen supply system is similar to that described previously. The downhole generator employed may be that illustrated in Fig. 17 ~rhile the downhole control valve may be that illustrated in Fig. 15. In this embodiment, the oxygen conduit 107 is coupled to the oxygen lQ3~ V
cavity 323 while the hydrogen conduit 93 extends into the borehole for supplying hydrogen into the borehole and hence downhole by way of the borehole casin~. The hydrogen conduit 93 is not coupled to the hydrogen cavity 319 or to conduit 327 - 5 of the valve, however, the inlet 317 is open to the borehole for allowing hydrogen from the borehole to pass into the cavity 319 as described previously. Condui~ 327 is coupled to conduit 411 which may be open to the borehole. Inflation o~ the packer is carried out by the arrangement described with respect to Fig. 13. Also provided in the system of Fig. 1~ is a hydrogen oxygen flow control 401, the output of which is applied to the metering valve 89 by way of conduit or lead 403 for controlling the metering valve 89 in accordance with the hydrogen oxygen flow rate desired to maintain the desired downhole gas generator outlet gas temperature. The hydrogen flow meter 91 is in communication with the hydrogen-oxygen flow control 401 by way of conduit or leads ~05. The hydrogen oxygen ~lo~ control 401 also controls the oxygen metering valve 103 by way of conduit or electrical leads 407. In addition, the oxygen flow meter 105 is in communication with the hydrogen oxygen flow control 401 by way of conduit or elec~rical leads 409. In operation, the metering valves 89 and 103 are opened to allow flow of hydrogen through conduits 93 and 107. Downhole, hydrogen from the casing is applied to the conduit 327 of valve 263 by way of branch conduit 411 to move its valve spool downward to allow the flow of oxygen and hydrogen through the valve 263 with a slight oxygen lead, as described previously.
The valve 263 will open at a pressure prede~ermined by the setting of the spring 331, as described previously. A dos~!nhole

3~
battery powered igniter 413 comprises a battery 413A having one side, connected, by way of lead 415, to the lead 353 (see Fig.
15) of the valve 263. The other lead 355 of the valve 263 is electrically connected to the ground side of the electrode 75 5 by way of lead 417. The electrode 75 also is electrically connected to the heat switch 157 by way of lead 421 which in turn is connected to the other side of the battery by way of lead 423. When the spool of valve 263 is moved downward by the hydrogen applied to conduit 327 to connect contact 351 between leads 353 and 355, electrical energy is supplied to the electrode for igniting tne combustible mixture in the gas generator.
Start-up is accomplished as follows The oxygen metering valve 103 is opened to the predetermined run position and pressure allowed to stabilize. The hydrogen metering valve 89 then is opened to the predetermined run position. When the hydrogen reaches approximately 90-95% of run pressure, the downhole pneumatic valve 263 opens allowing hydrogen and oxygen to flow to the generator (with a slight oxygen lead) and at the same time turning on the battery powered igniter. When the gas generator shell approaches the stabilization tempera-ture, the thermoswitch 157 disconnects the battery powered igniter. To shut down the generator, the oxygen metering valve 103 is shut off and the system allowed to run down with a preprogrammed flow of hydrogen. The pneumatic valve shuts off as the hydrogen pressure is depleted. This system requires calibration with the downhole componen~s instrumented above ground. In the embodiment of Fig. 18, if liquid is in the _llo--1~3~0 borehole, hydrogen line 93 may be connected directly to inlet 317 of pneumatic valve 263 and to branch conduit 411. Hydrogen or oxygen pressure (using the embodiment of Fig. 13) may be employed to inflate the packer.
If the system of Fig. 18 is to be employed with water as a coolant for the annulus 53, then the water supply system previously discussed will also be employed for injecting water into the borehole casing. The hydrogen conduit 93 will be connected to the hydrogen inlet 317 of the valve 263 and to branch conduit 411. The valve 263 will be modified to provide a third cavity and a third inlet and outlet port for the passage of water to the annulus 53 by way of conduit 381, as described previously. In this embodiment, the packer 125 will be inflated by the hydrogen pressure, as described previously with respect ! 15 to the embodiment of Figs. 1-9. On start up, val~e 103 will beopened, followed by the opening of valve 8g an~ then the injection of water into the casing. On shut down, the valve 103 will be shut down and after the pneumatic valve automatically shuts off, the metering valve 89 will be shut down followed by shut down of the water pump system.
Referring now to Fig. 19, there will be described ~n more detail, the operation of the hydrogen-oxygen flow control 401. The signal from the flow meter 91 which varies with flo~J quantity, is fed through an output sensor 431 and then to a sensor amplifier 433. The signal from amplifier 433 is fed to a sensor comparator 435 which compares the signal with a preset signal. Any difference between the signal genera~ed by the flow meter 91 and the preset sign21 will be fed to the 1~3~
valve actuator pol~ler supply 437 for the metering valve 89 which in turn ~ill move the valve actuator 439 in such a direction as to result in a flow quantity that will cause the output of the flow meter 91 to equal the preset signal. The flow meter may be of the type which generates an electrical pulse for each revolution of a rotating flow element or vane. The count from the electrical pulses can be compared electronically to a set digital count in the comparator. The comparator will effect a varying of the flow rate until the count from the flow meter 91 equals the set digital count. The control by the hydrogen-oxygen flow controller may be by pneumatic or hydraulic means instead of electrical means. The oxygen control portion of the hydrogen-oxygen flow control 401 is the same as that for hydrogen except that instead of providing a preset signal to which the sensor signal is compared, the signal generated by the hydrogen flow meker 91 is fed to an oxygen flow meter sensor comparator 441 and is used as a set signal for the oxygen. The output of the oxygen flow meter 105 is applied to an oxygen flow meter output sensor 445 which may be the same as sensor 431 and whose output is applied to an oxygen flow meter sensor amplifier 447. The output of amplifier 447 is applied to the comparator 441 for comparison with the signal applied from the hydrogen flow meter. The gain of amplifier 447 will be appropriately set. Any difference between the signal outputs from amplifiers 435 and 447 will be fed to the valve actuator power supply 451 of the oxygen metering valve 103 which in turn will move the valve actuator 453 in such a direction as to result in a flow quantity which ~4Z-( (~ ( ( 1(~3~
will cause the output Or ampli~ier 447 to eaual the output Or amplifier 435. By this arrangement, the oxygen to hydroGen ratio can be maintained constant.
The advantages of the fuel-oxidizer combination of hydrogen and oxygen, whether as a stoichiome.ric mixture or hydrogen-rich and with ~rater or hydrogen as a coolant has been set forth above. In addition, the ability to produce hydrogen by electrolysis of water makes hydrogen attractive as a ~uel Obviously, oxygen is simultaneously produced in exactly the ratio that is required for stoichiometric burning downhole to produce steam. Further, the hydrogen and oxygen can be produced by electrolysis at the pressures required for use~ thus elimi-nating the requirement of compressors. If water is used for a coolant ~or hydrogen and oxygen burned stoicniometrically~ steam is the only end product. There are no contaminants. If excess hydrogen is used, the flame temperature resulting from the hydrogen-rich oxygen combustion can be tailored to the tempera-ture which conventional metal can withstand, as indicated above.
For example, if hydrogen and oxygen are combined in a ratio of 0.8 pounds of hydrogen to 1 pound of oxygen, the combustion temperature will be 2,000F, a temperature easily withstood by many of the stainless steel alloys. The resulting products can then be cooled to any desired temperature by additional hydrogen or water. ~ith the use of hydrogen only as a coo7ant, there is no need for water hardness treatment ~or downhole water, as there is no water used except ~;here hydrolysis is used for hydrogen-oxygen generation. The excass hydrogen, which is the same temperature as the steam that is produced, also serves --ll3-1(~3~

to heat the reservoir bed. Hydrogen, having an extremely lo~,r molecular weight and high diffusivity penetrates the bed more easily and rapidly than any other gas, vapor, or liquid. In the gaseous state, one pound of hydrogen can transfer to the bed, the same amount of heat as 13.5 pounds of steam, although, upon condensing, steam transfers significantly more heat to the bed in the smaller area that it has penetrated. ~urther, the hot hydrogen that has been used as a coolant, can dissociate the crude oil molecules and then combine with the dissociated components to form lighter weight, less viscous, hydrocarbons~
a process known as hydrogenation and which is greatly accelerated - by certain catalysts. Moreover, any hydrogen that is pumped downhole and unburned can be recovered at the surface.
Although the use of the fuel-oxidizer-coolant combinations of hydrogen and oxygen or hydrogen, oxygen~ and water mentioned above have advantages, it is to be understood that other fuel-oxidizer cooling medium combina~ions may be used in the present system. These combinations are set forth in Table I, along with the combination of hydrogen and oxygen and of hydrogen, oxygen, and water. Performance of the gas generator with hydrogen, ammonia, or methane as ~uel wi~h oxygen as an oxidizer and hydrogen, ammonia, water or methane as a cooling medium also is set forth in Table I. As an alternative, ammonium hydroxide may be used instead of ~Jater for the purpose set ~orth in Table I. Co,mpu~ations are based on 20,000,000 BTU per hour at 1,000 psi and 1,000F. The 20,000,000 BTU per hour computation is based on a high hea~
value of hydrogen at 61,045 BTU per pound, methane at 23,910 ~4L~_ ( ( ( ( 1(~3~
BTU per pound and c~mmonia at 6,870 BTU per pound. The fuel-oxidizer-cooling medium combinations listed in lines 3 and 5 in Table I will be employed in the same embodiments as the hydrogen-oxygen-water combination were described as employed and operation of these embodiments with the fluid combinations of lines 3 and 5 of Table I ~Jill be the same as described previously with respect to the hydrogen-oxygen-water combinations.
In the fluid combination of line 3 of Table I, ammonia may be used directly to inflate the packer while in the fluid combinat~on of line 5 of Table I, methane may be used directly to in~late the packer. The fuel-oxidizer-cooling medium combinations set forth in lines 4 and 6 of Table I, will be used in the same embodiments as the hydrogen-oxygen-hydrogen combination was described as employed, and operation of these embodiments -with the fluid combinations of lines 4 and 6 will be the same as described previously with respect to the hydrogen-oxygen-hydrogen combination. In both of the fluid combinations of lines 4 and 6 of Table I, oxygen may be applied to the device of Fi~. 13 for inflating the packer.
All products of combustion of ammonia wi~h oxygen .
are gaseous. Therefore~ there is no problem of clogging the bed. Nitrogen is produced, however, and may become a potential contaminant in the bed. Ammonia and ammonium hydroxide are excellent coolants and are very competitive with water. Both result in accumulation of ammonia do~Jnhole~ However~ ~he ammonia is recoverable at the surface. Both am~onia and ammonium hydroxide are liquid at relatively low pressures and can be stored or transported in tan~s in the liquid state (:

3~
at atmospheric temperatures. Thus~ handling, storage, and pumping of ammonia or ammonium hydroxide present no significant problems.
Although methane may be u~ed as a fuel, this gas is less contaminant f`ree than hydrogen, as it will break down into carbon and hydrogen at temperatures above 1200F. Upon combustion with oxygen, it produces C02 which is a contaminant gas in the reservoir bed. It may per~orm best~ when burned stoichiometrically, with oxygen and the resulting gases cooled with water. Excess methane can be used as a coolant~ but there is a risk of clogging the bed with carbon particles from dissociated methane.

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In addition to use of the steam as a steam drive and driving the oil to nearby wells, it is also an object of this invention to use the s~eam in a steam-soal- operation. In this method~ steam is usually injected for a fe~ days such ~s 5 to 5 15 and then the well is closed in for the soak period for about one ~leek, after which the well is put back on production. This technique is also called "huff and puff" by those skilled in the art and has been practiced on several thousand wells.
The gas generator may be applied to oil shales for insitu retorting. In this application~ a hole is drilled or mined into the shale. If the shale is naturally fractured sufficiently then the hot gases from the gas generator may be applied directly to the shale. At temperatures above abou~
900~F, the oil is released from the shale. The desired fluids may be driven to nearby wells or produced from the same well in either a continuous or cyclic fashion.
For hard~ impermeable shale, the shale may be fractured by the use of explosives. Such a fractured matrix will permi~
the hot vapors to come into contact with the shale in an easier manner.
It ls another object of this inven~ion to employ ~he gas generator to insitu gasification of coal. In this appl~cation~
a hole is drilled or mined into the coal bed and ~he hot gases from the gas generator are permitted to contzct the coal The high temperatures of the gases will result in a reaction ~Jith the coal resulting in the formation of carbon monoxide and hydrogen. This gas may be burned as a 10T,r grade fuel or it may be up-graded, if desired.

( (~ ( 11~3~

In some oil reservoirs, the oil recovery is increased by gas injection or pressure maintenance programs. In these operations, natural gas or ~lue gas may be used as the gas for injection purposes.
The subject gas generator may be used to supply the flue gases for gas injection purposes. ~or this operation, the apparatus is located in the well and operated for sus~ained periods. I~ air is used as the principal oxidizing media, then the flue gas will consist primarily of nitrogen and water vapor. If a hydrogen rich stream is used, then the excess hydrogen will be available for injection into the oil sand along with nitrogen or water vapor. The hot gases and volatile - hydrogen reduce the viscosity of the oil so that it flows ~ore rreely into the producing well.
In recovering oil by the insitu combustio~ recovery process, air or air diluted with flue gas or air and wa~er may be used. After combustion is caused to occur at an injection well then any o~ the above fluids may be used to sustain the combustion process and push the oil to a nearby oil proauc~ng well. -The subject gas generator may be operated in such a manner as to fulfil any of the above ~unctions. The gas generator may be operated with an excess o~ oxygen or air.
In which event the unused oxygen would be injected into the rock matrix and would serve to sustain the combustion zone in the usual manner.
The gas generator may be operated using water as a coolant and excess oxygen or air. In this case, the hot wa~er _119_ ( (~

lQ3~
or steam and excess oxygen would enter the oil sand. The steam or hot water serves to heat the oil sand and the excess oxygen sustains the combustion process within the pores of the rock.

3~
Referring now to Fig. 20, there will be described in more detail a process of hydrogenating hydrocarbons in the forma-tions employing the system of Figs. 1-10 and 12 with certain rnodifications. In ~ig. 20there is illustrated a cased injection borehole 31 which penetrates a subsurface oil bearing reservoir 33.
Spaced from the borehole 31 is a production borehole 501. Although not shown other spaced production boreholes may be employed. Lo-cated in the borehole 31 is the gas generator 39 which is supplied with hydrogen and oxygen from a hydrogen producer 81 and an oxygen supply 83 located at the surface. The borehole casing 121 is sealed above the generator by the packer 125. A cooling and sep-arating tower 503 is located at the surface and is coupled to the production well 501 by way of conduit illustrated at 505.
As indicated above, the gas generator 39 comprises a chamber having a combustion zone 67, a cooling annulus 53 and a restricted outlet 49. Hydrogen from producer 81 is delivered through modulating valve 89 and conduit 93 to the gas generator.
Similarly oxygen from supply 83 is delivered through modulating valve 103 and conduit 107 to-the gas generator. Hydrogen at the generator is admitted to the combustion zone 67 and cooling annulus 53 by means of solenoid valve 127 which is controlled at the surface by means of leads illustrated at 133. Oxygen is admitted to com-bustion zone 67 by means of solenoid valve 129 which is controlled at the surface by means of leads illustrated at 135. The amount of 25 hydrogen delivered is sufficient to form a hydrogen-rich mixture in the gas generator which lS ignited by applying electric current to leads 155A and 155B to energize glow plug or spark plug 75. Thermo-couple 161 senses the temperature near the gas generator exhaust port ( ( 1(~3~ V
and transmits temperat;ure data through leads illustrate~ at 165 to the surface. Similarly pressure transducer 171 transmits data through leads illustrated at 173.
In carryin~ out the recovery process, hydrogen and oxygen are fed to the gas generator 39 to for~. a hydroGen-rich combustible mixture ~hich is ignited and burned to generate ho~
gases which pass through the restricted outlet 49 and enter the well bore 31. From the well bore the gases pass into the bed 33 through perforations 507 formed through the well casing.
The hot gases which are composed primarily of steam and hydro-gen pass intG t~le reservoir 33.
By ~eans of modulating valves 89 and 103 the tem-perature of the exhaust gases from the gas generator is regu-lated to heat the oil in the forma~ions to a ~empera~ure su~-ficient to break the hydrocarbon chains into ligher segments and the segments react .- with hot hydrogen from the gas gen-erator~to form lighter and less viscous end producks. For ex-ample, the formations may be heated to temperatures of 750F
or greater at a pressure of approximately 2000 psi. The out-puts of thermocouple 161 and transducer 171 are monitored to aid in obtainin~ the desired temperatures and pressures, it being understood that the temperatures and pressures existing in the formation bed will be less than those measured in the borehole. For so called depleted reservoirs.which contain residual oil which occupy 20 to 24~ of the pore space in the bed formation, it is necessary to heat the bed above 750F and possibly as high as approxi~lately 1100~ to ade~uately craclc the oil. The 1100F upper limt t is des t rable to prevent de-~ompos:l.tion of methane into carbon and hydrogen and which occurs at about 1200~. The process is slightl~ different froi~ the normal hydrocrac~cing process ln that the ullderground bed may -52~

((~

not contain the proper catalytic agents and thermal cracking must occur before hydrogenation. Upon reaction Or the hydro-gen with the hydrocarbons segments, an amount of heat is re-leased which is equal 5 to 15~ of that required to raise the sand bed in the reservoir to 750F. The manner in ~rhich the insitu hydrogenation is pro~rammed is dependent upon the quan-tity of oil residing in the pore spaces ol the ~ormation. Nor-mally the pore space is 38 to 4~% of the reservoir volume. Sand~
llmestone, or shale formations occupy the remainder. If the 42%
pore space is fully occupied, the reservoir will contain ap-proximately 3100 barrels of oil per acre foot. Normally the space is not fully occupied. For reservoirs with high occupancy and using the present method, the tempera~ure is kept just high enough to thermally crack the oil for hydrogenation into liq-uids primarily. As the occupancy decreases towaPd 20g it isnecessary to increase the ~emperature to thermally crack and hydrogenatë the residual liquid converting it to gases which can escape the pores of the formation. The resulting hydro-genated products then contain a predominance o~ lighter ends such as methane, propane, and butane. The following table shows the quantity of heat required for el~vating the bed temperature to 750F ~or var~ous reservoirs depths.

, ! Rescr- Initial Btu In- % Oil Consumed in He~ting Bed /O Oil I voir ~ed put to . Consumed IDep~h Temper- Bed Per 22/, Pore 50% Pore lOOZ Pore in heatin ature Cubic Space Filled Space Filled Space Filled oil in Ft, of 680 bbls/ 1550 bbls/ 3100 bbls/ bed Ft F Sand ~cre Ft Acre Ft Acre Ft - ~, .

_ 70 11380 26,4 11.~ 5,8 2 6 10~00~ 270 8040 18.6 8.2 4,1 1.5 15,000 370 6370 14.7 6.5 3,2 ~,o 20,000 ~70 4680 10.9 4.8 _ 2 ~ _ 4 .

(( In the above table, the temperatures at various well depths were based on an increase in geothermal temper-ature of 2F per 100 foot of depth. The percent of the re-covered oil consumed in the process is based upon production of hydrogen from light ends by reforming with 2 50% efficiency.
Some of the heat from the recovered oil can be used in the re-forming process, but it was not considered in the calculation.
The heat generated in hydrogenation, taken as 30,000 BTUJBBL, was assigned to heating the oil and substracted from the oil heating requirements.
For some reservoirs, it may not be necessary to thermally crack the oil, but to apply hydrocracking because of the wide variety of trace elements present in some beds that may act as catalysts for the hydrocrackinc process. As is well known hydrocraclcing ls the combination of mil~ thermal cracking and hydrogenation which can be carried out at lower temperatures in the presence of a suitable catalyst. ~lith some catalysts, hydrocracking may proceed at tem~eratures as low as 500F and 500 psi. The temperatures, however, may be higher with an upper limit of about 8000F. For a detailed discussion of thermal cracking and hydrogenation and hydrocracking reference is made to the report "Impact of New Technology on the U. S. Pe~roleum Industry 1946-1965" by the National Petroleum Council, Library of Congress Catalog Card No. 67-31533.
For thin reservoirs, heat escape to the overburden and underburden mus~ be taken into acount in supplying heat.
This has not been done for the data presented in the ~able.
., If thermal cracking ~ithout catalysts follolred by hydrogenation is to be employed, initially the gases may be introduced at temperatures in the vicinity of 1300F to 1600F

(~

to compensate for rapld heat transfer in the bed. Subsequently the temperatures may be reduced to 900F to induc~ initial thermal cracking of the oil in the heated reservoir and as the reservoir reaches minimum thermal cracking temperature the gas generator exhaust may be reduced to 750F, with dependency upon heat of hydrogenation to raise the temperature in the front moving across the reservoir for cracking purposes.
If the composition of the bed is unknown, the gas generator may be initially operated to produce gases at a lower temperature ~o determine if lighter hydrocarbons can be recovered from well 501 by hydrocracking. If no recovery is had, the gas generator may be operated at the higher temperature to induce thermal cracking and then hydrogena~ion. The gas and liquids resulting from hydrogenation whether by thermal cracking without catalysts followed by hydrogenation or by hydrocracking move through perforations 509 formed through the borehole casing 511, and into the borehole 501 to the surface. At ~he surface the gases and liquids move through conduit 505 to the cooling and separating tower 503. The liquids and gases are separated in the tower and the liquids move through conduit 513 to a reservoir 515. The gases from the top o~ the tower 503 move through conduit 517 to a compressor 519 which recompresses the gases to 2500 psi plus whatever pressure drop may be encounter-ed in the system ahead of the well bore chamber 31. From co.m-pressor 519, the gases flow to hydrogen producer 81 by way o~
conduit 521. In some applications, for adequate control~ th~
pressure may have to be increased to 3800 psi so as to maintain sonic velocity across the generator nozzle or outlet 49. ~y-drogen production in hydrogen producer 81 may be by reform.ing with water or by partial oxidation If partial oxidation is used, a conduit, shown by broken line 523, is connected from the oxygen source 83 to the hydrogen producer 81. The oxygen source 83 May be a tan~ which is filled from a commercial sup-1~3~

ply or from an on site air to oxygen converter. The high pres-sure required may be from 25Q0 to 3800 psi and may be best achieve~ by vaporization of liquid oxygen in a closed container.
In the hydrogenation process of Fig. 20, hydrogen, rather 5 than water is supplied to the cooling annulus 53 Or the gas generator as indicated above. This may be accomplished by using the modifica-tion of Fig. 12. In the alternative apertures may be formed through conduit 57 of the gas generator at a level between walls 45 and 55 whereby hydrogen may flow from the annulus between conduits 57 and 71 through the apertures into the space 59 and then into annulus 53.
In this alternative the water control valve 131 will not be used nor will conduit 77 and its entrance to space 59 through wall 45 will be plugged. Downhole valve 127 will be employed to control the flow of hydrogen both to the primary combustion zone and to the annulus 15 53.
An excess of hydrogen is introduced into the combustion zone of the gas generator to form a hydrogen-rich mixture for re-ducing the temperature in the primary combustion zone of the gas generator and for providing an excess of hot hydrogen for insitu hydrogenation. Hydrogen also is supplied to annulus 53. The hydro-gen flowing through annulus 53 cools the inner shell 51 and flows through apertures 63 to cool the combustion gases to the desired temperature. As the hydrogen flowing through annulus 53 and into the mixing zone 69 performs its cooling function it is heated to pro-25 vide an additional supply of hot hydrogen for hydrogenation. Thesteam derived from the combustion of the hydrogen and oxygen and the excess hot hydrogen then flow through the outlet nozzle 49 into the formations. Water can be used in addition to hydrogen for cool-ing the generator, and it can be provlded from the uphole water 30 reservoir 85. From the water reservoir 85, the water is supplied to a water treatment system 111 and then pumped-by pump 113 through con-duit 115 into the borehole 31.

~3~
~ydrogen from the hydrogen condu;t is employed to inflate the packer to form a seal between the housing 43A and the casing 121 of the borehole. Hydrogen from the hydrogen conduit 57 is injected into the annulus 125A by way of a conduit 211 which is coupled to the hydrogen conduit 93 above the downhole valve 127. See Figs. 1 and 6.
With the downhole system in place in the borehole, as illustrated in Fig. 1, and all downhole valves closed, the start-up sequence is as follows. Hydrogen and oxygen are admitted to the downhole piping and brought up to pressure by opening metering valves 89 and 103. The hydrogen inflates the packer 125 and forms a seal between the housing 43A and the borehole casing 121, upon being ad-mitted to the downhole pipe 93. Water, may then be admitted to the well casing and the casing filled or partially filled. This is accomplished by actuating pump 113. Water further pressurizes the downhole packer seal. The ignition control 153 and the oxygen and hydrogen solenoid valves 127 and 129 are set to actuate, in the proper sequence, as follows. The igniter is started by actuating control 153; the oxygen valve 129 is opened by actuating control 143 to give a slight oxygen lead; the hydrogen valve 127 is then opened by act-uating control 141. This sequence may be carried out by manually controlling these controls 141, 143 and 153 or by automatically con-trolling these controls by an automatic uphole control system. At this point, a characteristic signal from the downhole pressure trans-ducer 171 Will show on meter 175 whether or not a normal start was obtained and the thermocouple will show by meter 164, connected to leads 165, whether or not the desired temperature is being maintained. The hydrogen flow controller 163 is slaved to thermo-couple 161 which automatically controls the hydrogen flow. The hydrogen to oxygen ratio may be controlled by physically coupling the hydrogen and oxygen valves, electrically coupling the valves o with a self synchronizing motor or by feeding the output from flow meters 105 and 91 into comparator 90 which will provide an electrical output for moving the oxygen metering valve in a direction that will keep the desired hydrogen-oxygen ratio.
In shut down operations, the following sequence is follow-ed. The downhole oxygen valve 129 is shut off first, followed by shut off of the hydrogen valve 127. Shut off of the igniter is ac-complished manually or by timer after start-up is achieved.
As indicated above, an excess of hydrogen (hydrogen-rich) is introduced into the combustion zone of the gas generator for re-ducing the temperature in the primary combustion zone of the gas generator and to provide an excess of hot hydrogen for hydrogenation of the oil to form less viscous hydrocarbons. The maximum temperature produced by burning hydrogen stoichiometrically with oxygen is about 5000F or slightly higher at atomospheric pressure. By employing a hydrogen-rich mixture the temperature in the primary combustion zone may be reduced to as low as 1800F without causing flame-out.
Reduction of the temperature in the primary combustion zone with a hydrogen-rich mixture has advantages in that it allows the gas gen-erator to be fabricated out of more conventional materials. In order to reduce the temperature in the primary combustion zone to the de-sired level the flow rate of hydrogen may be four to six times the hydrogen flow rate required for stoichiometric burning. Other flow rates may be employed dependent upon the amount of temperature re-duction desired.
As also indicated above, hydrogen is flowed through the annulus 53 for cooling the gas generator; for reducing the temperature of the exhaust gases further to the desired level below 1800F;
and for providing additional hot hydrogen for hydrogenation.

1~3~
In the hydrogenation process, in some instances it may be desirable to flow water through the annulus 53 for cooling purposes instead of hydrogen, although the amount of hydrogen otherwise pro-vided for hydrogenation will be reduced. Water may be flowed through the annulus 53 by employing the valve 131 and conduit 77 as described - previously.
Although the hydrogenation and recovery process was described as being directed to insitu hydrogenation of oil in subsurface forma-tions, it is to be understood that it may be employed for insitu hydrogenation of coal or oil shale employing the gas generator in a borehole traversing the coal or oil shale beds. When appliea to shale, the shale will be fractured before the process is carried out.
Although not shown, well known pumping equipment for the production well 501 may be used if necessary. In some cases it may be possible to use air instead of oxygen for the oxidizer.
Referring now to Figs. 21, 22A, 22B and 23, there will be described the system of the present invention for burning methane with oxygen with the resultant gases cooled with water for genera-ting hydrogen, steam, and carbon dioxide downhole in a borehole 31 to stimulate oil productlon from a subsurface reservoir 33 penetrated by the borehole. The steam and hot gases generated drive the oil in the formation 33 to other spaced boreholes (not shown) which penetrate the formation 33 for recovery purposes. The hydrogen also provides better penetration of the formation bed due to lower molecular weight f the hydrogen and acts to hydrogenate the oil to form less viscous hydrocarbons. The carbon dioxide also acts to expand the oil out of the said pores and to reduce its viscosity.
As illustrated in Fig. 21, the gas generator 39 is located in the borehole at the level of or near the level of the oil bearing formation 33. Oxygen and a hydrocarbon gas which preferably is methane, ~3~

are supplied from the surface to the gas generator to form a combus-tible mixture which :Ls ignited and burned in the generator. The flame temperature is maintained below the decomposition temperature of the methane to prevent carbon fall-out and to convert substantially the all of the methane to carbon monoxide and hydrogen gases which are burned with an additional supply of oxygen to produce carbon dioxide and hydrogen. The gas generator and carbon dioxide and hydro-gen gases generated are cooled with water which results in the prod-uction of steam whereby hydrogen, steam, and carbon dioxide are in-jected from the gas generator into the formations.
Referring to Figs. 22A, 22B and 23, the gas generator39 comprises an outer cylindrical shell 41 supported in a housing 43 located in the borehole. The outer shell 41 has an upper end 45 through which supply conduits and other components extend and a lower end 47 through which a small diameter outlet nozzle 49 extends.
Supported within the outer shell 41 is an inner shell 51 which forms a cooling annulus 53 between the inner shell and the outer shell.
The inner shell has an upper wall 55 which is connected to a conduit 57 which in turn extends through the upper wall 45 and is connected thereto. The conduit 57 forms one of the supply conduits, as will be described subsequently and also supports the inner shell 51 within the outer shell, forming the annulus 53 and also forming an upper space 59 between the walls 45 and 55. The space 59 is in com-munication with the annulus 53, as illustrated in Fig. 9. The opposite end of the inner shell 51 is open at 61. Formed through the inner shell at the lower end thereof are a plurality of aper-tures 63 which provide passages from the annulus 53 to the interior of the inner shell for the flow of cooling fluid. Supported in the inner shell at its upper end is a heat resistant liner 65 which de-fines a combustion zone 67 and a second zone 68 located downstreamof the combustion zone. The liner is supported by a retention ring ., }3~1~30 53A and has an upper wall portion 65A through which supply conduits and other components extend. The portion Or the interior shell at the level of the apertures 63 is defined as a gas and water mixing zone 69.

: ' ~ ~ .
`:

~` , ' .

1~3~ 0 Conduit 57 extends through walls 45 and 55 and through the upper liner wall 65A to the inside of the liner 65. Coaxially located within the conduit 57 and spaced in-ward therefrom are two coaxial conduits 71 nnd 72 which are spaced from each other and extend to the combustion zone 67.
Conduit 72 is held in place by spacers 72h connected betT:een conduits 57 and 72. A first annular passage 73 is formed be- -tween coaxial conduits 71 and 72 and a second annular passage 74 ls formed between coaxial conduits 72 and 57. Meth?ne is lntroduced into the combustion zones 67 of the gas gen-erator through the conduit 71 and oxygen is supplied through conduit 57A which is connected to conduit 57. The oxygen splits into two paths for flow through the two annular pas-sages 73 and 74. Oxygen flowing through the annular passage 73 flows into the combustion zone 67 where it combines with the methane to form a combustible mixtureof ~ases in the com-bustion zone. The combustible mixture of gases is ignited by an ignitor 75 and burned. Just enough oxygen is provided through annular passage 73 to keep the temperature of com-bustion below 1200 F. in the flame front whereby substantiallyall Or the carbon in the methane will react with the oxygen producing carbon monoxide and free hydrogen. Thus carbon fall-out is prevented or minimized which is desireable since the carbon may otherwise pack the combustion chamber and in do~mho1e operation clog the sand face.
The overall temperature in the combustion zone is about 2400 F. In order to obtain more BTU per pound Or each of methane and oxygen and hence to reduce the cost o~
methane and oxygen required, higher tempera~ures are de-~6)3~
s:ired. Increased temperatures are obtained by providing an additional supply of oxygen to burn the carbon monoxide and hydrogen. The additional supply of oxygen is added by way of the second annular passage 74. Oxygen thus flo~l-ing through annular passage 74 flows into the second zone 68 where the carbon monoxide and hydrogen from zone 67 are burned with the additional supply of oxygen which in-creases the temperature to about 3800 F to 4000 F and results in the production af carbon dioxide and hydrogen. The gases from zone 68 flow to zone 69 where they are cooled with water to approximatel~ 544 F before injection into the reservoir.
Enough water will be added to produce 80% quality steam at a chamber pressure of 1000 psia for injection along with the hydrogen and carbon dioxide. (Steam quality is percent of water in vapor form).Water is supplied to the annulus 53 by way of a conduit 77 (see also Fig. 4) extending through the upper wall 45 of the outer shell 41. From conduit 77, the water flows to the annulus 53 by way of a space 59 form-ed between the walls 45 and 55. The water cools the inner shell 51 and flows through apertures 63 to cool the com-bustion gases and form steam. The mixture of water vapor, water droplets, hydrogen and carbon dioxide passes through thè outlet nozzle 49 into the formation. Since the exhaust nozzle 49 is small compared with the diameter of the interior of the chamber, the pressure generatred in the generator is not significantly affected by the external pressure (pressure of the oil reservoir) until the external pressure approachesap-proximately 80% of the value of the internal pressure. Thus for, a set gas generator pressure, th~re is no need t~ vary the flow rate of the ingredients into the generator until the external ~Q3~

pressure (oil reservoir pressure) approaches approximately 80~ of the internal gas pressure.
The lowest ratio of oxygen to methane in the com-bustion zone that will convert all of the carbon to carbon monoxide is about 1.1 pound of oxygen to one pound of methane.
The amount of oxygen used in the second process in zone 68 will depend upon the amount required to convert all of the carbon monoxide to carbon d~oxide, the maximum specified temperature, and the amount of hydrogen that is desired to inject through the sand face into the oil reservoir. The divlsion of flow of oxygen to passages 73 and 74 is adjust-ed experimentally by means of an orifice plate 78 which can be sized to cover as much of the exit of the annular passage 74 as required. Although not shown, swirl vanes are pro-vided at the end of the passage 74 to swirl and centrifuge the oxygen flowing throu~h passage 74 outward past the zone 67 to the second zone 68. If desired swirl vanes may be provided at the end of conduit 71 and at the end of annular passage 73 to swirl the methane and oxygen in opposite directions to insure adequate mixing to form the desired combustible mixture in zone 67. Referring to Fig.2~ !, a cooling tubë
79 for the passage of water is provided for coollng the burner tip. The housing or jacket 43 enclosing the gas gen-erator forms an annulus 80 with the outer wall 41 of the gen-erator. Water is provided ln the annulus 80 and heat from the generator raises the water temperature in the annulus 80 which is then ~ixed by convection with the water in the chamber ~OA above the generator to heat the conduits 57A and 71. These conduits may be coiled if desired to prov:ide adequate sur-face area to preheat the methane and oxygen.

1~3~
Referring to Fig. 21, the methane, oxygen, and water are supplied to the generator located downhole by way of a methane supply 81, an oxygen supply 83, and a water supply 85. Methane is supplied by way of a compressor 87 and then through a metering valve 89, a flow meter 91, and through conduit 93 which is inserted down-hole by a tubing reel and apparatus 95. Oxygen is supplied downhole by way of a compressor 101, and then through a metering valve 103, a flow meter 105, and through conduit 107 which is inserted down-hole by way of a tubing reel and apparatus 109. From the water reservoir 85, the water is supplied to a water treatment system 111 and then pumped by pump 113 through conduit 115 into the borehole 31. In Fig. 21, water in the borehole is identified at 117.
The borehole 31 is cased with a steel casing 121 and has an upper well head 123 through which all Or the conduits, leads, and cables extend. Located in the borehole above and near the gas generator is a packer 125 through which the conduits, cables, and leads extend. The flow of methane, oxygen, and water to the genera-tor is controlled by solenoid actuated valves 127, 129, and 131 which are located downhole near the gas generator above the packer.
Valves 127, 129, and 131 have leads 133, 135, and 137 which extend to the surface to solenoid controls 141, 143, and 145 for separately controlling the opening and closing of the downhole valves from the surface. The controls 141, 143, and 145 in effect, are switches which may be separately actuated to control the application of electrical energy to the downhole coils of the valves 127, 129, and 131. Valve 127 is coupled to methane conduits 93 and 71 (Fig. 21) while valve 129 is coupled to oxygen conduits 107 and 57A (Fig. 21).
Valve 131 is coupled to water conduit 77 (Fig. 21) ,~

and has an inlet 147 f'or allo~intr the water in the casing to flow to the gas generator ~hen the ~alve 131 is opened.
The igniter 75 comprises a spark plug or electrode which extends through walls 45 and 55 and into an aperture 65R formed through the upper liner wall 65A ~Jhereby it is exposed to the gases in the combustion zone 67. The igni~er 75 is coupled to a downhole transformer 149 by way Or leads 151A and 151B. The transformer is coupled to an uphole ig-nition control 153 by way of leads 155A and 155B. The up-hole ignition control 153 comprises aswitch for controlling the application of electrical energy to the downhole trans-former 149 and hence to the igniter 75. A thermocouple 161 is supported by the gas generator in the combustion zone 67 and is electrically coupled to an uphole methane flow control 163 by way of leads illustrated at 165. The methane flow control senses the temperature detected by the thermocouple and produces an output which is applied to the metering ~alve 89 for controlling the flow of methane to obtain the desired methane-oxygen ratio. The output from the flow control 163 may be an electrical output or a pneumatic or hydraulic out-put and is applied to the valve 89 by way of a lead or con-duit illustrated at 167. A second thermocouple 156 is sup-ported by the gas generator near the restricted outlet 4~
to sense the temperature of ihe gases flowing out of the out-let 49. Its outlet is applied uphole by way of leads 157 to an electrical power supply and control sys~em 158?the out-p~t of which is coupled by way of leads 159 to an electrically controlled torque motor valve 160 coupled iIl the ~later inle~
147. This arrangement is provided to control the size of the opening of valve 160 to control the amount of ~ater flowing to the annulus 53 and hence through passagres 63 to control the tem-~3~
perature of the gases flowing from the generator outlet 49.
A meter 158A is also coupled to the leads uphole to allow the operator to obtain a visual reading of the gas temperature at the generator outlet 49 to allow manual control if desired through control system 158. In the alternative, valve 160 may be elimina-ted by controlling the water flow through conduit 115 at the sur-face so as to adjust the water column in the casing Or deep wells to a height which will induce the desired flow through the genera-tor. For shallow wells, control may be obtained by adjusting the pump output pressure. In the present embodiment, oxygen from the oxygen conduit is employed to pressurize a silicone fluid to in-flate the packer to form a seal between the housing 43A and the casing 121 of the borehole as described previously in connection with Fig. 13.
With the downhole system in place in the borehole, as illustrated in Fig. 21, and all downhole valves closed, the start-up sequence is as follows. Methane and oxygen are admitted to the downhole piping and brought up to pressure by opening metering valves 89 and 103. The oxygen pressurizes the silicone fluid in chamber 252 to inflate the packer 125 and form a seal between the housing 43A and the borehole casing 121, upon being admitted to the downhole piping 107. Water, then is admitted to the well casing and the casing filled or partially filled. This is ac-complished by actuating pump 113. Water further pressurizes the downhole packer seal. The ignition control 153 and the methane, oxygen, and water solenoid valves 127, 129 and 131 are set to actuate , in the proper sequence as follows. The igniter is started by actuating control 153; the oxygen valve 129 is opened by act-uating control 143 to give a slight oxygen lead; the methane valve 127 is then opened, followed by the opening of the water valve 131.

( Water valve 160 is always open but the size of its opening may be varied to control the amount of water flowing through annulus 53 as indicated above. Yalves 127 and 131 are opened by actuating controls 141 and 145 respectively. This sequence may be carried out by manually controlling controls 141, 143, 145 and 153 or by automatically controlling these controls by an automatic uphole control system. At this point, a characteristic signal from the downhole pressure transducer 171 will show on meter 175 whether or not a normal start was obtained and the thermocouples 156 and 161 will show by meters 158A and 164 whether or not the desired temperature are being maintained. The methane flow controller 163 is slaved to thermocouple 161 which automatically controls the methane flow. Similarly the control system 158 is slaved to thermo-couple 156 which automatically controls the water flow to annulus 53. The methane to oxygen ratio may be controlled by physically coupling the methane and oxygen valves, electrically coupling the valves with a self synchronizing motor or by feeding the output from flow meters 105 and 91 into a comparator 90 which will pro-vide an electrical output for moving the oxygen metering valve in a direction that will keep the methane-oxygen ratio constant. At this point, the flow quantities of methane, oxygen, and water are checked to ascertain proper ratios of methane and oxygen, as well as flow quantities of methane, oxygen and water. Monitoring of the flow of methane and oxygen is carried out by observing flow meters 91 and 105. The amount of oxygen flowing through annular passage 74 to zone 68 in the gas generator can be ascertained by obtaining the differential in oxygen flow reflected by the uphole meter 158A of the thermocouple 156 and the oxygen flow read from uphole meter 105.

U
In shut down operations, the f`ollowing sequence is followed. The downhole oxygen valve 129 is shut off first, followed by shut off of the methane valve 127 and then the water valve 131. The water valve should be allowed to remain open just long enough to cool the generator and eliminate heat soak back after shut down. Shut off of the igniter is accomplished manually or by timer after start-up is achieved.
If a stoichiometric mixture of methane and oxygen were burned to produce carbon dioxide and water, the final temperature of the exhaust gases will be greater than 5000F which is greater than desired for prolonged operation of the gas generator in down-hole operations. By partially oxidizing methane at a lower tempera-ture to form the stable gases carbon monoxide and hydrogen, and then by burning these gases with an additional supply of oxygen, it can be understood that the desired gases can be produced without carbon fall-out and at a temperature that is sufficient to obtain a high BTU per pound of each of methane and oxygen and that can be withstood by the gas generator.
In a further embodiment butane or propane may be used instead of methane in the gas generator to produce carbon monoxide and hydrogen by partial oxidation and which are converted to carbon dioxide and hydrogen by burning with an additional supply of oxygen. Preferably the supply pressures for butane and propane would be lower than that of methane.
In Fig. 22B the orifice plate 78 and cooling tube 79 are not shown for purposes of clarity. Water is supplied to the cooling tube 79 by way of conduits (not shown) coupled to the water in the borehole above the packer and extending through the housing within the packer to the tube 79. Similarly water is supplied to the annulus 80 by way of conduits (not shown) coupled to the water in the borehole above the packer and extending through the housing within the packer.

Claims (48)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A system for use for recovering hydrocarbons or other materials from underground formation penetrated by a borehole comprising a gas generator located in the borehole at or near the level of said formations, said gas generator comprising a housing forming a chamber defining a combustion zone and having an upper inlet end for receiving fuel and an oxidizing fluid for forming a combustible mixture of gases in said combustion zone for ignition, and a restricted lower outlet for the passage of heated gases, means, includ-ing conduit means extending from the surface, for supplying fuel from the surface to said inlet end of said gas generator located in said borehole, means, including conduit means extending from the surface, for supplying an oxidizing fluid to said inlet end of said gas generator located in said bore-hole, and valve means located in said borehole near said gas generator for controlling the flow of fuel and oxidizing fluid to said gas generator.

2. The system of claim 1 wherein said gas generator comprises a cool-ing annulus surrounding said chamber said annulus being in fluid communication with said chamber, said system comprising means coupled to said gas generator for diverting a portion of said fuel for flow into said annulus for allowing said fuel to be used as a cooling fluid.

3. The system of claim 1 wherein said gas generator comprises a cool-ing annulus surrounding said chamber, said annulus being in fluid communica-tion with said chamber, said system comprising means including conduit means for supplying a cooling fluid to said gas generator for flow into said cool-ing annulus, said valve means being adapted to control the flow of cooling fluid to said gas generator.

4. The system of claim 3 wherein said cooling fluid comprises water.

5. The system of claim 1 wherein said generator is supported by housing structure, cable means coupled to said housing structure and extending to the surface for supporting said housing structure and hence said gas generator in the borehole, said conduit extending from the surface for supplying fuel comprises a fuel conduit coupled to said gas generator, a flexible packer supported around said housing structure and adapted to be inflated outward against the walls of the borehole, and a passage leading from said fuel con-duit to the inside of said packer for allowing the fuel to inflate said packer.

6. The system of claim 5 wherein said gas generator comprises a cooling annulus surrounding said chamber, said annulus being in fluid communication with said chamber, said system comprising means, including conduit means for supplying water to said gas generator for flow to said cooling annulus, said valve means being adapted to control the flow of water to said gas generator.

7. The system of claim 2 wherein said conduit means extending from the surface for supplying fuel comprises the walls of said borehole, said conduit means extending from the surface for supplying said oxidizing fluid comprises a separate oxidizing fluid conduit extending from the surface through said borehole to said gas generator, said gas generator is supported by housing structure, cable means coupled to said housing structure and extending from the surface for supporting said housing structure and hence said gas generator in the borehole, a flexible packer supported around said housing structure and adapted to be inflated outward against the walls of the borehole, and a pass-age leading from said oxidizing fluid conduit and including means coupled to said packer for allowing the pressure of said oxidizing fluid to inflate said packer.

8. The system of claim 1 wherein said fuel is hydrogen and said oxidiz-ing fluid is oxygen.

9. The system of claim 2 wherein said oxidizing fluid is oxygen.

10. The system of claim 3 wherein said fuel is hydrogen and said oxidiz-ing fluid is oxygen.

11. The system of claim 4 wherein said fuel is hydrogen and said oxidiz-ing fluid is oxygen.

12. The system of claim 4 wherein said fuel is ammonia and said oxidizing fluid is oxygen.

13. The system of claim 2 wherein said fuel is ammonia and said oxidizing fluid is oxygen.

14. The system of claim 2 wherein said fuel is methane and said oxidizing fluid is oxygen.

15. The system of claim 1 comprising control means located at the surface for controlling said valve means.

16. The system of claim 3 comprising control means located at the surface for controlling said valve means.

17. The system of claim 1 wherein said valve means comprises first solenoid control valve means located in the borehole near said gas generator coupled to said conduit means for supplying fuel for controlling the flow of fuel to said gas generator, second solenoid control valve means located in the borehole near said gas generator coupled to said conduit means for supply-ing oxidizing fluid for controlling the flow of oxidizing fluid to said gas generator, and control means located at the surface for controlling said first and second solenoid controlled valve means.

18. The system of claim 3 wherein said valve means comprises first solenoid control valve means located in the borehole near said gas generator coupled to said conduit means for supplying fuel for controlling the flow of fuel to said gas generator, second solenoid control valve means located in the borehole near said gas generator coupled to said conduit means for supplying oxidizing fluid for controlling the flow of oxidizing fluid to said gas generator, third solenoid control valve means located in the borehole near said gas generator for controlling the flow of cooling fluid to said gas generator, and control means located at the surface for controlling said first, second, and third solenoid control valve means.

19. The system of claim 1 wherein said valve means comprises a valve housing having a first inlet and outlet pair and a second inlet and outlet pair, a movable valve member located in said valve housing having two passages for providing fluid communication between said first inlet and outlet pair and between said second inlet and outlet pair when said valve member is moved to a given position, said first inlet and outlet pair being adapted to supply fuel to said gas generator, said second inlet and outlet pair being coupled in said conduit means for supplying oxidizing fluid, and valve control means coupled between said conduit means for supplying fuel and said valve means for applying said fuel to said valve means for moving said movable valve means to said given position.

20. The system of claim 19 wherein said valve control means comprises a solenoid actuated valve for controlling the passage of fuel to said valve means, and control means located at the surface for controlling said solenoid actuated valve.

21. The system of claim 1 wherein said gas generator comprises a cooling annulus surrounding said chamber, said annulus being in fluid communication with said chamber, said valve means comprises a valve housing having a first inlet and outlet pair, a second inlet and outlet pair, and a third inlet and outlet pair, a movable valve member located in said valve housing having three passages for providing fluid communication between said first inlet and outlet pair, between said second inlet and outlet pair, and between said third inlet and outlet pair, when said valve member is moved to a given position, said first inlet and outlet pair being coupled in said conduit means for supplying fuel, said second inlet and outlet pair being coupled in said con-duit means for supplying oxidizing fluid, said third inlet and outlet pair being adapted to supply cooling fluid to said cooling annulus of said gas generator, and valve control means coupled between said conduit means for supplying fuel and said valve means for applying said fuel to said valve means for moving said movable valve means to said given position.

22. The system of claim 21 wherein said valve control means comprises a solenoid actuated valve for controlling the passage of fuel to said valve means, and control means located at the surface for controlling said solenoid actuated valve.

23. The system of claim 1 wherein said means, including said conduit means, extending from the surface for supplying fuel from the surface to said inlet end of said gas generator comprises a fuel supply and a fuel flow con-trol located at the surface, said means, including said conduit means, extend-ing from the surface for supplying oxidizing fluid from the surface to said inlet end of said gas generator comprises an oxidizing fluid supply and an oxidizing fluid flow control located at the surface, heat sensitive means supported by said gas generator for sensing the temperature thereof, and means located at the surface and coupled to said heat sensitive means and to said fuel flow control and responsive to the temperature sensed by said heat sensi-tive means for controlling the quantity of fuel flowing through said fuel flow control for maintaining a given fuel-oxidizing ratio.

24. The system of claim 23 wherein said gas generator comprises an igniter for igniting combustible gases in said combustion zone, said system comprising an ignition control located at the surface and coupled to said igniter of said gas generator for controlling the actuation of said igniter and hence the ignition of combustible gases in said combustion zone of said gas generator.

25. The system of claim 1 wherein said gas generator comprises an igniter for igniting combustible gases in said combustion zone, said system comprising a DC power supply located in said borehole near said gas generator, said valve means comprises a valve housing having a first inlet and outlet pair and a second inlet and outlet pair, a movable valve member located in said valve housing having two passages for providing fluid communication be-tween said first inlet and outlet pair and between said second inlet and out-let pair when said valve member is moved to a given position, said first inlet and outlet pair being adapted to supply fuel to said gas generator, said second inlet and outlet pair being connected in said conduit means for supply-ing oxidizing fluid, valve control means adapted to supply fuel to said valve means for moving said movable valve member to said given position, said movable valve member comprising switch means adapted to electrically connect said DC power supply to said igniter for actuating said igniter when said movable valve member is moved to said given position.

26. The system of claim 25 wherein said means, including said conduit means, extending from the surface for supplying fuel from the surface to said inlet end of said gas generator comprises a fuel supply, a fuel control, and a fuel flow meter located at the surface, said means, including said conduit means, extending from the surface for supplying oxidizing fluid from the surface to said inlet end of said gas generator comprises an oxidizing fluid supply, an oxidizing fluid flow control, and an oxidizing fluid flow meter located at the surface, and a fuel-oxidizing fluid control system coupled between said fuel flow control and said fuel flow meter and between said oxidizing fluid flow control and said oxidizing fluid flow meter for maintain-ing a given fuel-oxidizing fluid ratio.

27. A recovery process for recovering hydrocarbons or other materials from underground formations penetrated by a borehole, comprising the steps of locating a gas generator in the borehole at or near the level of said forma-tions, said gas generator comprising a housing forming a chamber defining a combustion zone and having an upper inlet end for receiving fuel and an oxid-izing fluid for forming a combustible mixture of gases in said combustion zone for ignition, and a restricted lower outlet for the passage of heated gases, flowing through said borehole from the surface to said gas generator, by way of separate passages, a fuel and an oxidizing fluid to form a combustible mixture in said combustion zone, and burning the combustible mixture in said combustion zone.

28. The process of claim 27 wherein said fuel is hydrogen and said oxidizing fluid is oxygen.

29. The process of claim 28 wherein said combustible mixture is hydrogen-rich.

30. The process of claim 27 wherein said fuel is methane and said oxidizing fluid is oxygen.

31. The process of claim 27 wherein said fuel is ammonia and said oxidizing fluid is oxygen.

32. A recovery process for recovering hydrocarbons or other fluids from underground formations penetrated by a borehole, comprising the steps of locating a gas generator in the borehole at or near the level of said bearing formations, said gas generator comprising a housing forming a chamber defining a combustion zone and having an upper inlet end for receiving fuel and an oxidizing fluid for forming a combustible mixture of gases in said combustion zone for ignition, and a restricted lower outlet for the passage of heated gases, flowing through the borehole, from the surface to said gas generator by way of separate passages, hydrogen and oxygen, to form a combustible mixture in said combustion zone, and burning the combustible mixture in said combustion zone.

33. The process of claim 32 comprising the step of flowing through said borehole from the surface to a cooling annulus of said gas generator, a cool-ing fluid comprising water.

34. The process of claim 32 wherein said combustible mixture formed is hydrogen-rich.

35. A recovery process for recovering hydrocarbons or other fluids from underground formations penetrated by a borehole, comprising the steps of locating a gas generator in the borehole at or near the level of said bearing formations, said gas generator comprising a housing forming a chamber defin-ing a combustion zone and having an upper inlet end for receiving fuel and an oxidizing fluid for forming a combustible mixture of gases in said combustion zone, and a restricted lower outlet for the passage of heated gases, flowing through said borehole from the surface to said gas generator, by way of separate passages, a fuel of ammonia and an oxidizer of oxygen, to form a com-bustible mixture in said combustion zone, and burning the combustible mixture in said combustion zone.

36. The process of claim 35, including the step of flowing through said borehole, from the surface to a cooling annulus of said gas generator, a liquid cooling fluid.

37. The process of claim 36 wherein said liquid cooling fluid is water.

38. The process of claim 36 wherein said liquid cooling fluid is ammonium hydroxide.

39. The system of claim 10 wherein said cooling fluid is ammonium hydroxide.

40. The system of claim 8 wherein said gas generator comprises a cooling annulus surrounding said chamber, said annulus being in fluid communication with said chamber, said system comprising means for flowing a portion of the hydrogen through said cooling annulus for cooling said gas generator and gases of combustion and for heating the hydrogen, and valve means located at the surface for controlling the flow of hydrogen and oxygen to said gas generator to maintain the temperature of the gases and fluids flowing through said out-let at a level sufficient to cause hydrogenation of the hydrocarbons in said formations.

41. The system of claim 40 comprising a spaced production borehole, means for recovering hydrocarbons from said spaced production borehole, a hydrogen producer located at the surface, and means for applying at least a portion of said hydrocarbons recovered, to said hydrogen producer for produc-ing hydrogen for supplying hydrogen to said gas generator.

42. The process of claim 28 comprising the steps of controlling the flow of hydrogen and oxygen to said gas generator to maintain the temperature of the gases and fluids flowing through said outlet at a level sufficient to cause hydrogenation of the hydrocarbons in said formations.

43. The process of claim 42 wherein the temperature of the gases flowing through said outlet is maintained at a temperature not higher than about 1100°F.

44. The process of claim 42 including the steps of recovering hydro-carbons from a spaced production borehole, and applying at least a portion of said hydrocarbons recovered, to a hydrogen producer located at the surface for producing hydrogen for supplying hydrogen to said gas generator.

45. The system of claim 3 wherein said gas generator comprises an igniter for igniting combustible gases in said combustion zone, said system comprising a second zone in said chamber located downstream of said combustion zone, a gas and water mixing zone in said chamber located between said second zone and said restricted outlet, said conduit means extending from the surface for supplying fuel comprises a fuel conduit means, a source of hydrocarbon gas coupled to said fuel conduit means for supplying a hydrocarbon gas to said inlet end of said gas generator, said conduit means extending from the surface for supplying an oxidizing fluid comprises an oxygen conduit means, a source of oxygen coupled to said oxygen conduit means for supplying oxygen to said inlet end of said gas generator, said chamber including means for flowing said hydrocarbon gas and oxygen, supplied to said inlet end of said gas generator, into said combustion zone for the formation of a combustible mixture of gases, said igniter being capable of igniting said combustible mixture of gases in said combustion zone for the production of carbon monoxide and hydrogen, means for injecting an additional supply of oxygen into said second zone of said chamber for burning the carbon monoxide and hydrogen from said combustion zone to increase the temperature and to form carbon dioxide and hydrogen for injection through said outlet, said conduit means for supply-ing a cooling fluid comprises a cooling fluid conduit means, a source of water coupled to said cooling fluid conduit means for supplying water to said annu-lus for injection into said gas and water mixing zone for the formation of steam whereby hydrogen, steam and carbon monoxide are injected from said re-stricted outlet.

46. The system of claim 45 wherein said means for flowing said hydro-carbon gas and said supply of oxygen in said combustion zone comprises first conduit means coupled to said one end of said chamber in fluid communication with said combustion zone in said chamber, second conduit means coaxial with and disposed about said first conduit means forming a first annular passage in fluid communication with said combustion zone in said chamber, said means for injecting said additional supply of oxygen in said chamber comprises third conduit means coaxial with and disposed about said second conduit means means forming a second annular passage in fluid communication with the interior of said chamber.

47. The system of claim 46 wherein said hydrocarbon gas is methane, means for supplying methane to said first conduit means, and means for supply-ing oxygen to said first and second annular passages.

48. The process of claim 27 wherein said chamber has a second zone located downstream of said combustion zone and a gas and water mixing zone located between said second zone and said restricted outlet, said fuel com-prising a hydrocarbon gas and said oxidizing fluid comprising oxygen, said process comprising the steps of maintaining the quantity of oxygen injected into said combustion zone at a level sufficient to maintain the flame tempera-ture below the decomposition temperature of the hydrocarbon gas into carbon while converting the hydrocarbon gas into carbon monoxide and hydrogen, inject-ing an additional supply of oxygen into said second zone to burn said carbon monoxide and hydrogen from said first zone to increase the temperature and to form carbon dioxide and hydrogen, and flowing water into a cooling annulus to cool said generator and for flow into said gas and water mixing zone for the formation of steam whereby hydrogen, steam, and carbon dioxide are injected from said restricted outlet for flow into said formation.