EP0119210A4

EP0119210A4 - Downhole well pump.

Info

Publication number: EP0119210A4
Application number: EP19830902739
Authority: EP
Inventors: John Dawson Watts
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-09-22
Filing date: 1983-08-11
Publication date: 1985-09-26
Also published as: EP0119210A1; CA1232194A; WO1984001191A1

Abstract

Methods and means wherein a downhole reciprocating oil well pump powered by a source of pressurized fluid via one tubing string (32) pumps liquid from the well through another tubing string (30). The downhole pump having internal means to vent gas and vapor from the pump chamber (52) and to cause a pump stroke only when the pump chamber becomes filled with liquid. The pump chamber is sensed to be filled with liquid by a flow sensitive flow restrictor (184) which monitors the venting of the gas and vapor and causes the vent to close when liquid flows past the restrictor thereby closing a power valve (150) to allow the flow of power fluid towards the pump plunger (74). The plunger has a dome shaped head (80) and the cylinder has ports (62) to expel sediment from the pump chamber. The pump stroke speed may be independently regulated by adjusting the output of source of pressurized fluid and the return stroke may be adjusted by proper sizing of ports for return flow.

Description

Downhole Well Pump

Technical Field

This invention relates generally to methods and means

05 for pumping oil and water from deep wells and more

* particularly to the use of reciprocating pumps powered by pressurized fluids such as gas, oil or water. Although fluid power has long been used to power such pumps, severe difficulties still exist in the pumps now available such

10 as sand cutting, sand fouling, vapor locking, excessive use of energy, excessive downtime, excessive replacement of downhole tubing and other equipment, pumping at too fast a rate, pumping at too slow a rate, damage to producing formations, to name a few.

15 Although the use of sucker rods to operate a downhole reciprocating pump is the oldest and most wide spread method, the well known high first cost and endless maintenance problems inherent in sucker rod systems have almost become accepted by many operators as inevitable

20 which unfortunately, drives up the cost of oil and gas and many "crooked holes" cannot be pumped at all with the use of ^"sucker rods. The practice of "gaslifting" liquids from wells by injecting pressurized gas into a column of liquid within a tubing is well known to be an inefficient system

25 when compressors are required to compress the gas before injection, and it cannot be used at all in most deep wells of toda .

Therefore, particularly with regard to such wells as offshore wells which are generally both deep and

30 directionally drilled, a more reliable and efficient method and means for pumping is needed by the industry to gain many millions of barrels of oil and billions of cubic feet of gas, as the present invention provides.

***⁵ Background Art

US Patents 2,362,777 and 3,123,007 disclose early systems for hydraulically driving a reciprocating well pump by hydrostatic and elevated pressures respectively "but neither have bearing on the present invention. Many similar patents exist, some having fluid motors for attachment to conventional pumps or to operate a string of sucker rods which in turn operate a conventional downhole pump.

Coberly patent 2,952,212 operates by co-mingling spent power fluid with produced liquid from the well which requires separation and purification of the power fluid before recirculation to the downhole pump. A later Coberly patent, 3,005,414 employs a power fluid string and a separate string to return spent power fluid and a production string to convey produced liquid to the surface so as to maintain the power fluid clean, in a closed circuit. The present invention may be operated by either method or by a reciprocation of power fluid within one string, the production tubing being used only for produced liquid and another conduit such as an annulus being used to convey gas to the wellhead, as disclosed by the first mentioned patent.

Roeder patent 4,268,227 provides a "free type" pump that may be removed from the well without removal of the tubing. Patent application SN 308,847 and recently filed CIP SN 401,644 by my partner Soderberg, bear the closest physical resemblence to the apparatus of my invention, however the present invention provides novel features specifically over and above Soderberg and in fact, we have pooled our efforts so as to make available to the industry, the most efficient and reliable downhole pump to date and one having selective features so as to meet a wide variety of well conditions.

Soderberg provides highly desirable features such as the venting of gas and vapor from the pump chamber before start of a pump stroke and filling of the pump chamber with liquid before start of the pump stroke but controlled from the well head. For some well conditions, it may cause

OMPI considerable difficulties to communicate between the pump •-and the power unit at the wellhead and therefore, the present invention comprises all intelligence in the downhole pump, to thereby eliminate the need for communication with the wellhead in order to function.

Whereas Soderberg requires a reciprocating column of fluid to power the downhole pump, the present invention may be operated by a reciprocating column or a non-reciprocating column of fluid. Soderberg provides a float valve to trigger a pump cycle whereas the present invention uses a flow restrictor sensitive to a difference in mass flow rate of a vapor as compared to a liquid. Also, the present invention may operate without a pressure buildup of power fluid above the normal operating pressure to cause a return stroke of the plunger, as does Soderberg, which therefore allows the use of lower pressure rated equipment and even further reduction of power usage.

All of the prior art known to the inventor, takes for granted: sand cutting of the pump and early replacement thereof; the pumping of all sediment that enters the pump chamber; no difference in speed between the pump and return strokes which often requires excessive energy usage because of a pump stroke faster than is required to pump at the rate that the well will produce. Said prior art has no provision within the downhole pump to sense when the pump chamber is full of liquid and to trigger a pump or return stroke but requires extensive communication equipment with the surface or worse still, it must often operate with an empty or partially empty pump chamber which wastes energy and causes premature pump failure because enough liquid is not present to carry heat of friction from the pump. Said prior art has no provision to make sliding seals resistant or immune to sand cutting and has no provision to prevent the pumping of sediment that enters the pump chamber which may cause excessive wear of standing valves or may fill the production tubing

I ^0M?I sufficiently to stop flow to the wellhead. Therefore, it is clear that the industry is in need of novel features afforded by the present invention. Disclosure of the Invention The present invention provides novel methods and means within a downhole well pump to accept a pressurized power fluid from an external source and to operate the downhole pump such that: no pump stroke occurs until gas is vented from the pump chamber and the pump chamber is filled with liquid to be pumped; the pump chamber is sensed to be filled with liquid by a flow sensitive flow restrictor which monitors the venting of gas and vapor from the pump chamber and causes the vent to close when liquid flows past the restrictor; a power valve may be caused to open when the vent is closed, so as to allow the flow of power fluid as required to cause a pump stroke; the inclusion of sand particles or the like in the liquid to be pumped do not adversely affect operation or life of the pump; the pump may operate freely without lockup of the plunger under rugged oilfield conditions; the pump stroke speed can be adjusted independently of the return stroke speed so as to allow for pumping at optimum flow rates and consume the least energy; the pump may operate automatically as desired when a proper supply of pressurized power fluid is furnished to the pump; power fluid furnished at a constant pressure may cause proper operation of the pump; a reciprocating column of power fluid may cause proper operation of the pump; sediment at the bottom of the pump chamber may be removed from the pump and not pumped to the wellhead; column members in the pump may be preloaded in tension so as to prevent buckling during operation of the pump; means to power return strokes of the pump are efficient, reliable and may be automatic. All necessary intelligence is within a downhole pump constructed and installed in accord with the present invention such that the pump may automatically in -sequence: receive liquid, gas and vapor into the pump chamber; vent gas and vapor from the pump chamber and up the well bore; sense when the pump chamber is filled with liquid; admit power fluid to the pump as required to cause a pump stroke at a predetermined speed best suited to the particular well conditions; stop the flow of power fluid to the pump near the end of the pump stroke; allow return of spent power fluid from the pump so as to allow a return stroke; use stored energy to cause a return stroke at an optimum predetermined speed; position all members of the pump as required to begin a subsequent pump cycle. The present invention may provide within the downhole pump: a lower wall of the pump chamber contoured so as to direct sediment out of the pump chamber prior to the pump chamber being pressured so as to begin a pump stroke; sliding sealing surfaces wetted by the produced liquid that are harder than sand particles entrained in the produced liquid; means to power a return stroke of the pump comprising a compressed gas-over-oil system with provision to bleed gas from the chambers requiring the presence of oil; quick acting valve means for controlling the flow of power fluid to and from the pump.

Other features and advantages of my invention will become obvious to those skilled in the art after review of these disclosures and review of the attached drawings. Brief Description of Drawings

Figure 1 depicts a downhole pump constructed in accord with the present invention, assembled and suspended in liquid to be pumped.

Figure 2 and 5 illustrate an arrangement for cooperation with a reciprocating column of power fluid and are vertical sections of Figure 1, taken 90 degrees apart. Figures 3 and 4, when placed below Figure 2, illustrate a vertical sectional view of Figure 1 in the same plane as Figure 2.

OMPI Figure 5 is a vertical sectional view taken along line '5-5 of Figure 2.

Figure 6 is a horizontal sectional view taken along line 6-6 of Figure 2. Figure 7 is a horizontal sectional view taken along line 7-7 of Figure 4.

Figure 8 illustrates an alternate arrangement to that shown in Figure 2, wherein fully automatic operations of the pump is effected without need to reciprocate the column of power fluid.

Figure 9 is a sectional view taken along line 9-9 of Figure 8.

Best Mode For Carrying Out the Invention The assembled pump depicted generally by 20 in Figure 1 is shown suspended in the liquid to be pumped, such that intake ports 22 are below the liquid surface 24 and such that the upper end 26 of vent pipe 28 is above surface 24. The pump 20 is shown suspended from tubing 30 which conveys produced liquid to the wellhead, and from tubing 32 which conveys power fluid from the wellhead to the pump. Surge chamber 34 may be attached at its lower end with tubing 30 for communications therewith, as at 36. At its upper end, head 38 is sealably attached with tubing 30, tubing 32 and vent pipe 28 for communication with each as is later described. Other major members attached in sequence below head 38 are tubular upper jacket 40, tubular middle jacket 42, connector 44, tubular lower jacket 46 and foot 48, all preferably having the same outside diameter as the head. Now referring to Figures 2 and 3, the upper end of centrally disposed tube 50 may be sealably connected with the lower end of head 38 so as to form annular pump chamber 52 between jacket 40 and tube 50, the lower end of head 38 defining the upper wall of chamber 52. The lower end of jacket 40 may be bored to receive seal rings 56 alternately with spacer rings 58 for purposes to be

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OMPI _ ^■described below. Lantern ring 60 may retain rings 56 and 58 against downward axial movement and may be aligned such that ports 62 formed through the wall of ring 60, allow communication through ports 22 and 62, between chamber 52 and the producing formation.

The periphery of rings 58 and 60 may be formed to receive seal rings as at 64 suitable to maintain a seal with the end bore of jacket 40. The end surfaces of rings 56 and 58 are formed flat and smooth such that an effective seal is maintained between said surfaces when held in contact by ring 60. Threaded tube 66 may cooperate with mating threads formed within jacket 40 to move rings 56, 58 and 60 into intimate sealing contact with one another, being retained against upward movement by shoulder 69 formed within jacket 40. Cooperating threads within the upper end of jacket 42 may be attached to threaded tube 66 so as to cause jacket 42 to abut jacket 40 and firmly secure the jackets together. The lower end of tube 50 may be sealably attached to fixed piston 68 having a maximum diameter greater than that of tube 50. Tube 70, having a maximum diameter less than -that of piston 68 may be attached to the lower end thereof and project downwardly through connector 44 as shown in Figures 3 and 4 so as to allow for nut 72 to be tightened on the lower threaded end of tube 70 against connector 44 through gland 140 and thereby preload tube 50, tube 70 and piston 68 in tension so as to preclude buckling of tubes 50 and 70. Annular plunger shown generally at 74, may be formed with bore 76 for slidable sealing cooperation with seals 78 positioned around fixed piston 68 to prevent flow around piston 68 within bore 76. Plunger 74 may be provided with end caps 80 which have end bores as at 82 so as to position seals 84 for slidable sealing cooperation against the periphery of tubes 50 and 70. Bore 86 of tube 50 may convey power fluid to ports 88 through the wall of

OMPI tube 50 just above piston 68 to act within chamber 89 'upwardly against the upper cap 80 and cause plunger 74 to move upwardly. Bore 90 of tube 70 may convey return oil to ports 92 and within chamber 93 to act downwardly against the lower cap and tend to cause plunger 74 to move ' downwardly.

The outer cylindrical surface 94 of plunger 74 may be of material harder than sand or foreign particles that may be entrained in the liquid to be pumped and the inner surface 96 of seal rings 56 may be sufficiently harder than surface 94 such that both sand cutting and gauling of the surfaces is precluded. For instance, surface 94 may be of chromium oxide and surface 96 may be of tungsten carbide which will provide such hardnesses and will also preclude corrosion of the seals.

The vertical motion of plunger 74 is limited when the lower cap abuts connector 44 and when the upper cap abuts head 38. Lateral movement of plunger 74 is limited by the sliding fit between surface 94 and surfaces 96 as well as by the contact of bores 82 with the outer surface of tubes 50 and 70. Surfaces 96 guide the portion of the plunger near piston 68 while tubes 50 and 70 guide the ends of plunger 74 near head 38 or connector 44, such that surface 94 is not allowed to contact the inner wall of jackets 40 or 42, even under normal flexing of the jackets during transport or operation of the pump.

The top of upper cap 80 is contoured so as to direct any sediment from chamber 52 outwardly through ports 22 when plunger 74 is near the lowermost position as shown in Figure 3.

Rings 98 may be provided within the ends of caps 80 so as to scrape tubes 50 and 70 and thereby preclude sand from entering bore 82 and cause excessive wear of seals 84. The outer surface of tubes 50 and 70 may be made similar to surface 94 and the inner surface of ring 98 may be made similar to surface 96 for reasons already 'described.

, • The lowermost ring 56 positioned immediately above member 66, prevents sediment from passing from chamber 52 into jacket 42 which if allowed to collect, could settle on the upper end of connector 44 and prevent movement of plunger 74 to its lowermost position. Ports 100 positioned within connector 44 to drain fluid from within jacket 42 may be provided with check valves so as to prevent inflow of fluid from the well bore upon upstroke of the plunger. Referring now to Figure 4, jacket 46, the lower end of connector 44 and the upper end of foot 48 define gas chamber 102 for containing pressurized gas such as nitrogen for use as a spring to store energy so as to power a return stroke of the plunger. Near the lower end of the gas chamber, oil surface 104 is maintained above the lower end of snorkle tube 106 so as to prevent entry of gas into tube 106. During a return stroke of the plunger, the compressed gas in chamber 102 acts on surface 104 and forces pressurized oil up tube 106, through ports 92 to act within the lower portion of plunger 74 against fixed piston 68 and against lower cap 80 to thereby force . plunger 74 downwardly. Surface 104 is lowered during a return stroke and is raised during a pump stroke as shown at 105, to again further compress the gas within chamber 102 which in turn stores energy for the next return stroke. Should gas enter tube 106 or plunger 74 through ports 92 sized for oil, the plunger action may become less controllable and therefore means to bleed gas is desirable. Tube 108 may be mounted within tube 106, tube 108 having an open upper end positioned near the upper end of tube 106 and having its lower end connected with conventional vent valve 110 such that when valve 110 is opened, gas acting on surface 104 forces oil up tube 106 which in turn forces gas trapped in the upper end of tube 106, into the top of tube 108 and out valve 110. To prevent gas from entering tube 106 during transport of the "pump, oil valve 112 may be provided to seal the lower end of tube 106. Rotation of valve 112 within foot 48 may advance valve 112 by means of cooperating screw threads as at 114 until seal 116 mounted around the upper circumference of valve 112 engages the inner diameter 118 of the lower end of tube 106 and effects a seal between them. With valve 112 closed, the pump may be laid horizontally without gas entering tube 106. To prevent leakage around valve 112 to atmosphere, annular seal 120 may be provided around the lower end of valve 120 for sealing cooperation with bore 122 of foot 48. Should it be desired to add or remove oil from chamber 102, conventional valve 124 may be provided within foot 48. Should it be desired to add or remove gas from chamber 102, conventional valve 126 may be provided within connector 44. Figure 7 illustrates a configuration for both valves 124 and 126 wherein plug 128 may be replaced with a pressure connection to a pump or to a bleed line, after which needle 130 is partially screwed out to allow fluid to pass seat 132 from or to chamber 102 while no flow is allowed to pass by seal 134 positioned around needle 130.

Packing 136 is retained in centrally disposed bore 138 within connector 44 by gland 140 so as to slidably seal between tube 70 and connector 44 such that nut 72 may be sufficiently tightened on tube 70 and against gland 140 so as to preload tubes 50 and 70 against buckling and reversal of stresses during operation of the pump. Now referring to Figure 2, tubing 30 is sealably connected with the upper end of head 38 and in communication with production flow path 142 from pump chamber 52. Located within path 142 are conventional standing valves 144 which allow upward flow from chamber 52 into tubing 30 but allow no return. Power fluid tubing 32 is sealably connected with the upper end of head 38 and

-§τj EΛ OMPI in communication with power fluid flow path.146 between _'tubing 32 and chamber 89, in which power valve 148 is positioned to control the flow. Differential piston 150 has: on its large end a first pressure area 152; on its small end, a second pressure area 154; on the annular surface between said first pressure area and said second pressure area, a third pressure area 156; around the cylindrical surface toward of the small end of piston 150, a fourth pressure area 158. Area 154 is exposed to the power fluid pressure within tubing 32; area 158 is exposed to the fluid pressure within path 146 which is always in communication with tube 50; area 156 is always in communication with open vent 158 shown in Figure 6; area 152 is in communication with flow path 160 which is opened and closed by valve 162 shown in Figure 5 and Figure 6.

Piston 150 is shown in its uppermost position for closure of flow path 146 but may be moved downwardly such that seal 164 around pressure area 154 disengages cooperating sealing surface on annular piston 166 to allow flow between areas 154 and 158. Annular piston 166 may be provided with a sliding seal 167 around its periphery for cooperating with bore 168 within which it is mounted such that a pressure below, will cause piston 166 to move upwardly, compressing spring 170 and allow flow between area 158 and area 154. When pressure above piston 166 is equal or greater than the pressure below it, piston 166 will remain in its lowermost position as shown, to allow for sealing contact with seal 164 when piston 150 is in an uppermost position and thereby stop flow between areas 154 and 158.

Differential piston 150 will remain in the closed upward position as shown as long as the force on area 152 exceeds the force on area 154 and conversely, it will move to the open lower position when the force on area 152 is less than the force on area 154.

OMPI A>> As best viewed in Figure 5, vent valve 162 may "comprise recess 174 formed around stem 176 slidably mounted within bore 178 formed axially within valve body 180. In the lowermost position shown, recess 174 provides for communication between flow path 172 which is in communication with power fluid tubing 32, and flow path 160 in communication with pressure are 152; vent 182 then being closed by the upper portion of stem 176 when in the position shown. In such position, it is clear that power fluid pressure from tubing 32 acts on both ends of piston 150 which causes piston 150 to close power valve 148 because area 152 is greater than area 154, resulting in a net upward force on piston 150. Flow restrictor 184 may comprise disc 186 mounted on the lower portion of stem 176, disc 186 being of such diameter and configuration as required to cause a suitable differential pressure across the disc when gas, vapor or liquid flows around the disc within vent path 188, formed axially within and through head 38. Compression coil spring 190 may be mounted around stem 176 below body 180 such that nut 186 may be adjusted along a threaded portion of stem 176 so as to create a desired compression load upon spring 190 and thereby prevent upward movement of stem 176 until a predetermined upward force on stem 176 is exceeded. The predetermined force must be greater than the differential force created across disc 184 by anticipated flowing gas through vent path 188 but less than the force caused by anticipated flowing liquid. Thus, as gas and vapor are vented from pump chamber 52 through path 188, stem 176 remains in the lower position but when chamber 52 becomes filled with liquid, liquid then flows upward through path 188 around disc 186 and creates an upward force on stem 176 sufficient to overcome the preload on spring 190 which in turn, causes stem 176 to move upwardly. As an alternate, selected weights may be used in place of spring 190 to provide the desired force. Plug 194 'may be mounted on the upper end of stem 176 for cooperation with vent valve seat 196 formed concentrically within body 180, such that the contact of plug 194 with seat 196 limits the upward movement of stem 176 and closes vent path 188. The spacing of flow paths 160, 172 and 182, together with the length of recess 174, are such that when stem 176 is in the lowermost position, paths 160 and 172 communicate and path 182 is closed and when stem 176 is in the uppermost position, paths 160 and 182 communicate and path 172 is closed. Cylindrical body 180 may have flats cut on opposite sides as shown in Figure 6 from the lowermost end of body 180 up to just below the level of seat 196 so as to allow the flow of gas and vapor to flow through seat 196 and out vent pipe 28 to the wellhead, when stem 176 is in the lower position. Body 180 has no flats above seat 196 so as to form a seal around body 180 against the bore of path 188.

It can now be understood that a downward acting preload suitable for a given well condition may be provided such that stem 176 remains in the lower position during venting of gas and vapor from chamber 52, maintaining vent path 188 open and maintaining pressure area 152 in communication with power fluid tubing 32 which in turn maintains power valve 148 closed as previously explained. It can also now be understood that when pump chamber 52 fills with liquid, liquid begins to flow around disc 186 to create the differential force required to overcome the downwardly acting preload and thereby move stem 176 to its uppermost position which in turn, closes vent path 188 and flow path 172 while allowing pressure area 152 to vent through paths 160 and 182 which in turn causes power valve 148 to move down to the open position. After assembly and installation of the invention as illustrated in Figure 1, operation may be described as follows. Beginning with the configuration as depicted in the drawings, power fluid is maintained under pressure -within tubing 32 by a suitable fluid power source near the wellhead (not shown) as is well known in the art. Because the downhole pump is suspended below the liquid level 24 in the well bore, the liquid together with entrained gas and vapor may flow into pump chamber 52 through intake ports 22, the liquid level rising in chamber 52 while gas and vapor escape through vent path 188, through open seat 196 and up vent pipe 28 toward the wellhead. Immediately after chamber 52 becomes filled with liquid, liquid flows around disc 186 which causes stem 176 to rise and move plug 194 against seat 196 to thereby close vent path 188 as before explained. The upward movement of stem 176 also vents pressure area 152, allowing power valve 148 to open and admit a flow of pressurized power fluid from tubing 32 through pressure area 158, flow path 146, tube 50, ports

88 and into chamber 89 to act against upper cap 80 in sufficient force to move plunger 74 upwardly against the force of liquid within chamber 52 and against the oil pressure within chamber 93 so as to cause liquid from chamber 52 to rise through path 142 past conventional standing valves 144 and upwardly to the wellhead through tubing 30. As upper cap 80 rises to contact the lower wall of head 38, the upward movement of plunger 74 is stopped which causes an increase of pressure within tubing 32 above the pressure necessary to raise the plunger. Upon a conventional pressure switch mounted with tubing 32 at the wellhead sensing such pressure increase, the pressure within tubing 32 may be automatically vented by a motor valve which serves to reduce the pressure within chamber

89 to hydrostatic pressure only. Gas within chamber 102 having been precharged to a pressure suitable for given well conditions, is further compressed as plunger 74 moves upwardly, forcing oil from chamber 93, through ports 92, tube 70 and into the bottom of chamber 102 to cause liquid surface 104 to rise. Now, after reduction of pressure within^' chamber 89 to -hydrostatic only, the oil pressure within chamber 93 driven by compressed gas within chamber 102 is sufficient to overcome hydrostatic pressure within chamber 89 and return plunger 74 to the lowermost position which in turn reverses the flow of the power fluid and returns gas pressure within chamber 102 to the precharge pressure.

Power fluid returning upwardly through power valve 148 will move annular piston 166 upwardly against spring 170 to allow free return of power fluid regardless of the position of piston 150, until pressures above and below piston 166 are substantially equal, at which time, spring 170 will force piston 166 to a lowermost position and thereby allow sealing contact with piston 150 to allow closure of valve 148.

As plunger 74 begins to descend from the uppermost position, a partial vacuum is created within chamber 52 which causes a downward differential pressure across plug 194 which acts together with said downwardly acting force to move stem 176 to its lowermost position and thereby reopen vent path 188, close vent 182 and admit power fluid from tubing 32 through paths 172 and 160 to act against pressure area 152 to move piston 150 upwardly to effect closure of valve 148 and thereby return the pump to the first configuration, ready to begin another pump cycle. A conventional flow sensor mounted with tubing 32 at the wellhead may be used to signal the motor valve to close and to cause repressurization of tubing 32, after return of the power fluid upon the return stroke of plunger 74. As the pump stroke begins, sealing surface 94 of plunger 74 is not in contact with any of the seal rings 56 that serve to seal chamber 52 from the well bore. Sediment that may settle from the liquid while chamber 52 is being filled will fall on the contoured upper surface of cap 80 to be directed towards ports 62. As plunger 74 begins to rise, a predetermined amount of liquid is forced out

^*^3 EΛ

OMPI v_W-_ ^lpo through ports 62 so as to return such sediment to the well -bore and down below the pump. Upon surface 94 rising high enough to contact the seal ring immediately above lantern ring 60, such flow through ports 60 ceases and liquid within chamber 52 becomes pressurized sufficiently to • force it toward the wellhead. Surface 96 of seal rings 56 may be of a slightly smaller diameter than surface 94 so as to maintain sealing contact, rings 56 being cut at one part of its periphery so as to allow minute expansion of the ring and intimate contact of sealing surfaces 94 and 96. Because both surfaces are harder than sand, no sand cutting will occur, causing a higher efficiency and longer operating life of the pump.

In some installations the pump may be operating with such a fast pump stroke that an excessive pressure buildup tends to occur within the pump chamber before flow to the surface within the production tubing begins, due to the inertia of liquid within the production tubing. To prevent such a pressure buildup and to maintain a more constant rate of flow within the production tubing, surge chamber 34 may be provided, being suitably precharged with gas above piston 35, to a pressure near the hydrostatic pressure within the production tubing. Then as a pump stroke starts and a pressure surge tends to build up before the column of liquid begins to rise, liquid flows into conduit 36 to act upwardly on piston 35 and further compress the gas above it. As the column of liquid begins to rise, the pressure surge reduces and the compressed gas forces piston 35 back down to help continue the flow, even after standing valves 144 have closed. Surge chamber 34 may be rotated inwardly from the position shown so as to pass within the same size pipe that the downhole pump will pass. Surge chamber 35 may be assembled from conventional oilwell tubing such that any required length may be readily assembled. For slow stroking pump installations, surge control -may be accomplished by controlling the pump stroke speed as described below, so as to start slow and increase the stroke speed as the column of liquid begins to rise. Wells bored into the earth have infinite combinations of conditions such as depth, pipe diameter, pressures, fluid characteristics, temperature, pressure ratings of tubing joints and other equipment. Therefore, it may be desirable under some well conditions to furnish fluid power to the downhole pump at a constant pressure and to return spent power fluid from the pump up the production string, tubing 30, or up a separate return string, tubing 200 as depicted in Figure 9, both methods of return well known in the art. To operate the present invention by such a method, alternate head 202 may be provided to replace head 38.

Referring to Figure 8, conventional standing valves 144 are positioned to recieve produced liquid from pump chamber 52, through flow path 122 and- to convey it to tubing 30 as described above for Figure 2. Tubing 32 is sealably attached to the upper end of head 202 so as to supply power fluid at a substantially constant pressure to flow path 204 formed axially within head 202 concentric with and below tubing 32. Now referring to Figure 9, switching valve 206 may be positioned within bore 208 formed axially within head 202 and parallel to flow path 204 so as to protrude into chamber 52 as shown at 210 when in the lowermost position, and reversably movable to an uppermost position 212 as depicted by solid lines. When valve 206 is in the uppermost position, recess 214 formed around a portion of valve stem 216 is positioned such that spent power fluid may return from tube 50 up through axially disposed flow path 218, through laterally disposed flow path 220 into path 208 via recess 214, thence into flow path 222 in communication with return tubing 200. Should it be desired to return power fluid through

OMPI production tubing 30, flow path 222 may be furnished with 'a suitable check valve not shown, and connected so as to communicate with tubing 30 instead of with tubing 200 to thereby allow flow from path 222 into tubing 30 but no return flow. While chamber 52 is filling with liquid, valve 206 is held in the uppermost position by the hydrostatic pressure of spent power fluid acting against an upper enlarged end of stem 216 as at shoulder 224, the top end 226 of stem 216 being vented at that time. When fluid force acting against end 226 exceeds the fluid force acting against shoulder 224, valve 206 must move to the lowermost position such that shoulder 224 abuts shoulder 228 and recess 214 connects flow path 230 with path 220 and path 222 is sealed by stem 216 above recess 214. Valve 232 is constructed the same as valve 162 previously described except that valve 232 vents pressure when in the lowermost position and repressures when in the uppermost position. When valve 232 is in the lowermost position as depicted in Figure 9, fluid pressure acting against end 226 may be vented through lateral flow path 234 into valve 232 through recess 236 and thence out vent 238 to the well bore. A check valve may be installed in vent 238 to prevent well fluid from entering the vent path. When valve 232 is shifted to the uppermost position, vent path 238 is closed by the valve stem and recess 236 places flow path 234 in communication with flow path 240 which in turn is in communication with pressurized fluid flow path 204.

Operation of alternate head 202 may now be described, the remainder of the pump operating as described above. As gas and vapor are vented through valve 232, liquid rises within pump chamber 52 until it is filled whereupon it causes valve 232 to move to the uppermost position as described above for valve 162, thence causing power fluid to flow from path 204 through path 240, recess 236 and path 234 into chamber 225 to act against end 226 of valve •stem 216 to overcome hydrostatic pressure against shoulder 224 and to cause stem 216 to move to the lowermost position such that path 222 is sealed by stem 216 and simultaneously paths 220 and 230 are placed in communication via recess 214. Then pressurized power fluid may flow from path 204 into tube 50 so as to actuate the plunger as described above. As upper cap 80 approaches the top of the stroke, the cap contacts the lower end of stem 216 as at 210 and pushes the stem to the uppermost position as at 212, whereupon, power fluid is allowed to return from tube 50 through recess 214 and path 222 and up the tubing to the wellhead. As the plunger starts to descend, a vacuum is created in chamber 52 which causes valve 232 to return to the lowermost position which causes recess 236 to vent pressure from chamber 225 through paths 234 and 238 such that hydrostatic pressure of spent power fluid may once again act on shoulder 224 to maintain valve 206 in the uppermost position in preparation for a subsequent pump cycle. Because the pressure area against cap 80 is far greater than the pressure area against end 226 of stem 206, plunger 74 will easily move stem 216 upwardly and expel fluid from chamber 225 through path 234, recess 236, path 240 and back into path 204. The return stroke speed of the plunger may be adjusted to the fastest reasonable speed consistant with proper operation by sizing ports 92 to restrict the flow of oil or by regulating the return flow of spent power fluid as by sizing ports 88 or by placing a flow restrictor at any point along the spent power fluid return path including placing flow restrictors at the source of pressurized power fluid. For some well conditions it may be desired to use only a gas chamber with no oil, for powering the return stroke of the plunger. Any suitable conventional flow restrictors may be utilized, depending upon the position of installation and the flow and fluid

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OMPI v . WIPO requirements. The pump stroke speed may be■independently -regulated by adjusting the volume output at the source of fluid pressure mounted near the wellhead. The pump stroke need be no faster than is necessary to pump liquid from the well at the rate the well is capable of producing to thereby reduce the size of the power unit required and to reduce the amount of power consumed to pump the well. It may therefore be understood how to regulate the pump and return strokes independently of one another so as to use the minimum energy required to pump a given well.

New and timely methods, means and apparatus for pumping liquids from deep oil wells and the like may now be understood by study of these disclosures and review of the attached drawings. It is now obvious that the present invention is well suited to attain the desired objectives and provide novel advantages for pumping oil and water from deep wells so as to conserve energy, to reduce maintenance requirements, to reduce costs, to extend equipment life and to recover hydrocarbon deposits otherwise not feasible to recover.

Claims

I claim:

1. A method for operating a pump comprising: placing a flow restrictor in a path for venting gas from the pump chamber; the flow restrictor being sensitive to the mass ^• flow rate of fluid flowing through the vent path such that when the mass flow rate exceeds a predetermined value, the vent path is caused to close and a pump stroke is caused to begin.

2. The method of claim 1 further comprising: the predetermined value being exceeded when the flowing fluid changes from vapor to liquid.

3. The method of claim 1 wherein initiation of the pump stroke comprises: the actuation of a pilot valve caused by the flow restrictor so as to open a power valve which in turn admits pressurized fluid to the pump as may be necessary to cause a pump stroke.

4. The method of claim 3 further comprising: causing the power valve to close substantially at the end of the pump stroke.

5. Means for operating a pump comprising: a flow restrictor mounted in a path for venting gas from the pump chamber; the flow restrictor being sensitive to the mass flow rate of fluid flowing through the vent path such that when the mass flow rate exceeds a predetermined value, the vent path is caused to close and a pump stroke is caused to begin.

6. The means of claim 5 further comprising: the predetermined value being exceeded when the flowing fluid changes from vapor to liquid.

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YA-y. WIPO 7. The means of claim 5 further comprising a pilot -valve arranged for actuation by the flow restrictor so as to open a power valve which in turn admits pressurized fluid to the pump as may be necessary to cause a pump stroke.

8. The means of claim 5 further comprising: a power valve arranged to close substantially at the end of the pump stroke.

9. An apparatus for operating a pump comprising: a flow restrictor mounted in a path for venting gas from a pump chamber; the flow restrictor being sensitive to the mass flow rate of fluid flowing through the vent path such that when the mass flow rate exceeds a predetermined value, the vent path is caused to close and a pump stroke is caused to begin.

10. The apparatus of claim 9 further comprising: the predetermined value being exceeded when the flowing fluid changes from vapor to liquid.

11. The apparatus of claim 9 wherein means for initiation of the pump stroke comprise a pilot valve actuated by the flow restrictor so as to open a power valve which in turn admits pressurized fluid to the pump as may be necessary to cause a pump stroke.

12. The apparatus of claim 7 further comprising: the power valve being arranged to close substantially at the end of the pump stroke.

13. The apparatus of claim 9 wherein the flow restrictor comprises: a disc mounted concentrically within a vent path of greater diameter than the disc so as to form an annular flow path around the disc and thereby cause a differential flowing pressure to form across the "disc when fluid is being vented.

14. The apparatus of claim 13 further comprising: the disc being mounted on a stem which in turn is slidably

^• mounted within the vent path, the stem having means to resist axial movement from a first position to a second position, when no more than a predetermined differential pressure acts across the disc.

15. The apparatus of claim 14 further comprising: the stem having means to cause the vent path to close upon movement of the stem to the second position.

16. The apparatus of claim 14 further comprising: the stem having means to cause actuation of a power valve so as to cause a pump stroke upon movement of the stem to the second position.

17. The apparatus of claim 12 further comprising means to: return the stem and disc to the first position; open the vent path and reverse actuation of the power valve so as to be in position to begin a subsequent pump cycle.

18. In a hydraulic circuit, a valve comprising a differential piston having: a first pressure area on a large end; a second pressure area on a small end; a third pressure area on a surface joining the diameter of the large end with the diameter of the small end, said third pressure area connected with an open vent path; a fourth pressure area on a cylindrical surface around the diameter of the small end and connecting the second and third pressure areas; suitable fluid seals as required to form seals between each of the pressure areas when the piston is in a closed position; means to adjust the relative pressure acting against the first area such that pressure acting against the second area will cause the piston to -move to an open position so as to disengage the seal between the second and fourth areas, so as to allow fluid to flow between the second area and the fourth area.

19. The invention of claim 18 further comprising: means to adjust the pressure acting against the first area so as to move the piston to the closed position so as to engage the seal between the second and fourth areas, so as to stop the flow between the first area and the fourth area.

20. The invention of claim 19 further comprising: a sealing surface for cooperation with the seal between the second and fourth areas being formed on an annular piston which in turn is slidably sealed within a cylindrical surface around the periphery of the annular piston such that the annular piston may be reversably moved to engage the seal between the second and fourth pressure areas when the differential piston has moved to the closed position.

21. The invention of claim 20 wherein: the cooperating sealing surface on the annular piston seals against the differential piston only when the pressure against the second area equals or exceeds the pressure against the fourth area.

22. The invention of claim 18 or 19 wherein means to adjust the pressure acting against the first pressure area comprise: a two way valve that may be operated to admit pressure from the second pressure area to the first area and alternately, to vent pressure from the first area.

23. A method for pumping liquids containing hard particles such as sand or the like, comprising: forcing a plunger into a pump chamber through an annular seal ring for sealing between the plunger and the pump chamber wall; said plunger having a surface for sealing cooperation with the seal ring that is harder than the sand; the seal ring having a surface for sealing cooperation with the plunger harder than said plunger surface, such that pressurization of the liquid is effected without sand cutting of the sealing surfaces.

24. Means for pumping liquids containing hard particles such as sand or the like, comprising: a plunger arranged for forcing into a pump chamber through an annular seal ring for sealing between the plunger and the pump chamber wall; said plunger having a surface for sealing cooperation with the seal ring that is harder than the sand; the seal ring having a surface for sealing cooperation with the plunger harder than said plunger surface, such that pressurization of the liquid may be effected without sand cutting of the sealing surfaces.

25. An apparatus for pumping liquids containing hard particles such as sand or the like, comprising: a plunger arranged for forcing into a pump chamber through an annular seal ring for sealing betwen the plunger and the pump chamber wall; said plunger having a surface for sealing cooperation with the seal ring, that is harder than the sand; the seal ring having a surface for sealing cooperation with the plunger, harder than said plunger surface, such that pressurization of the liquid may be effected without sand cutting of the sealing surfaces.

26. Means for pumping liquids containing sand from a well comprising: a pump chamber having intake ports near the lower end thereof; the chamber having a bottom wall contoured so as to direct sand that may settle out of the fluid in said chamber, out through the intake ports. 27. The invention of claim 26 wherein: the lower end wall of the pump chamber is formed by the upper end of a plunger.

28. The invention of claim 23 wherein: first motion of the plunger occurs before sealing contact around the plunger is effected to thereby cause a temporary outflow through the intake ports so as to wash out any sand that may have settled at the bottom of the pump chamber.

29. Means for pumping liquid from a well comprising; a tubular member formed around a pump chamber; an upper centrally disposed tube within the pump chamber sealably attached to an upper end of a centrally disposed fixed piston; a lower centrally disposed tube sealably attached to a lower end of said fixed piston; an annular plunger positioned within the pump chamber so as to allow for slidable sealing means between the outer surface of the plunger and an inner surface of the tubular member; the fixed piston having an outer diameter larger than the outer diameters of the tubes; the fixed pistons' outer periphery having means for slidable sealing contact with an inner diameter of the plunger; the plunger having a reduced bore near each end thereof provided with means for slidable sealing contact with the tubes; means to inject fluid pressure alternately above and below the fixed piston within the plunger so as to selectively reciprocate the plunger up and down within the pump chamber so as to cause the pump to operate.

30. The invention of claim 29 wherein: cooperating sealing surfaces between the plunger and the tubular member are harder than any particles contained in the fluid to be pumped; the sealing surface cooperating with

- E OMPI _ the plunger sealing surface being harder than the plunger -sealing surface.

31. The invention of claim 29 wherein: the sealing surfaces between the plunger and the tubular member are • not in sealing engagement when the plunger is near a lowermost position of the plunger so as to allow for communication between the well bore and the pump chamber.

32. The invention of claim 31 wherein: cooperating sealing surfaces between the plunger and the centrally disposed tube are harder than any particles contained in the fluid to be pumped and one of said surfaces is harder than the other.

33. The invention of claim 29 further comprising: the fixed piston and the tubes attached to the ends thereof being preloaded in tension so as to prevent buckling of the tubes upon operation of the pump.

34. The invention of claim 29 further comprising: at least one of said tubes being utilized to convey fluid to within the plunger.

35. The invention of claim 29 further comprising: clearance between the outer surface of the plunger and the inner surface of the tubular member being sufficient to prevent contact between the plunger and the tubular member upon operation of the pump.

36. The invention of claim 29 or 35 wherein: the slidable sealing means between the plunger and the tubular member is sufficiently flexible to allow for limited eccentric movement of the plunger with respect to the tubular member such that normal flexing of the tubular

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OMPI > ^~ V/1PO member during installation or operation will not prevent -normal operation of the pump.

37. The invention of claim 29 or 35 further comprising: radial clearance between the plunger and the * tubular member sufficiently greater than clearance between the tubes and the plunger ends such that the tubes serve to guide the plunger ends without allowing contact between the plunger and the tubular member.

38. A downhole well pump comprising means to: receive fluid and entrained sediment from the well bore and automatically drain sediment from the pump chamber so as to prevent pumping of the sediment toward the wellhead.

39. A downhole well pump comprising means within the pump to: receive pressurized power fluid into the pump from an external source sufficient to operate the pump; receive well liquid, gas and vapor from the well bore into a pump chamber; vent gas and vapor from the pump chamber; sense when the pump chamber is substantially filled with liquid and close the vent; automatically admit power fluid into such operating chambers as is necessary to operate the pump.

40. The invention of claim 39 further comprising: a gas chamber for retaining a compressed gas as required to cause a return stroke of the pump; the power fluid being of sufficient pressure and volume to power the pump stroke and to further compress said compressed gas so as to store sufficient energy as required to cause a return stroke of the pump powered by expansion of the gas to the degree of compression as before the pump stroke began. 41. The invention of claim 40 wherein: flow of the -return fluid is restricted so as to limit the speed of the stroke as may be desired.

42. The invention of claim 39 wherein: the flow of the • power oil is restricted so as to limit the speed of the stroke as may be desired.

43. The invention of claim 40 further comprising: a gas chamber for retaining a compressed gas as required to drive a return stroke of the pump; the power fluid being of sufficient pressure and volume to power the pump stroke and to further compress said compressed gas so as to store sufficient energy as required to drive a return stroke of the pump by expansion of the gas to the degree of compression as before the pump stroke began.

44. The invention of claim 39 further comprising means within the downhole pump to cause an automatic return stroke of the pump sufficient to allow for successive cycles.

45. The invention of claim 39 wherein means to automatically admit power fluid comprises a hydraulically operated power valve positioned so as to control flow within a power fluid conduit connected with such chambers as is necessary to oerate the pump.

46. The invention of claim 45 further comprising: means to cause the power valve to open when the vent is closed; means to cause the power valve to close when the vent is open.

47. The invention of claim 39 wherein the power fluid reciprocates in a conduit connected between the external power source and the pump, during operation of the pump. 48. The invention of claim 39 wherein the power fluid flows in a conduit connected between the external power source and the pump, without reciprocation of the power fluid.

49. The invention of claim 39 further comprising means to return power fluid from the pump to the external power source, separate from the the power fluid conduit.

50. The invention of claim 49 wherein means to return the power fluid comprise: an outlet valve positioned in a conduit for connecting the operating chambers with a power valve; the power valve being positioned so as to selectively admit power fluid to the operating chambers; means to open the outlet valve and close the power valve as the power stroke substantially ends; means to close the outlet valve and open the power valve as the pump chamber becomes substantially filled with liquid.

51. A system within a submersible pump for controlling operation of the pump comprising: a power valve for controlling the flow of power fluid from an external source to a power chamber within the pump; an outlet valve for controlling the flow of spent power fluid from the power chamber; one or more check valves for allowing liquid to be pumped from the pump chamber; a vent path from the pump chamber connected so as to allow escape of gas and vapor from the pump chamber before a pump stroke begins; a sensor mounted so as to sense when the pump chamber is filled with liquid; a suitable valve connected so as to close the vent path and cause the power valve to open, upon the pump chamber being substantially filled with liquid.

« 52. The system of claim 51 further comprising: a pilot -valve positioned and connected so as to cause the power valve to close as the pump nears the end of a pump stroke; the outlet valve positioned and connected so as to open upon closing of the power valve.

53. The system of claim 51 or 52 further comprising: the vent being suitably arranged and connected so as to open substantially as the power valve closes.

54. The system of claim 51 or 52 further comprising: the outlet valve being suitably arranged and connected so as to close when the power valve is opened.

55. The system of claim 54 further comprising: a return stroke of the pump being powered by a resilient spring or the like.

56. A method for pumping a well with a reciprocating pump comprising: adjusting the return stroke of the pump to the fastest reasonable speed; adjusting the pump stroke of the pump to a slower speed sufficient to pump the well at the production rate that the well is capable of sustaining.

57. The method of claim 56 further comprising: the pump being hydraulically powered.

58. The method of claim 56 further comprising: the pump being powered by mechanical means.

59. The method of claim 56 further comprising: the pump being powered by electrical means.

60. Means for pumping a well with a reciprocating pump comprising; means for adjusting the return stroke of the pump to the fastest reasonable speed; means for adjusting -the pump stroke of the pump to a slower speed sufficient to pump the well at the production rate that the well is capable of sustaining.

61. An apparatus for pumping a well with a reciprocating pump comprising means for adjusting speed of a pump stroke and means for independently adjusting a return stroke to a different speed.

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