GB2512375A

GB2512375A - Extraction of hydrocarbons from carbonaceous materials

Info

Publication number: GB2512375A
Application number: GB1305724.5A
Authority: GB
Inventors: Cyril Palmer
Original assignee: SONOCO OIL SERVICES Ltd
Current assignee: SONOCO OIL SERVICES Ltd
Priority date: 2013-03-28
Filing date: 2013-03-28
Publication date: 2014-10-01
Also published as: GB201305724D0

Abstract

A method and apparatus are disclosed for extracting hydrocarbons from carbonaceous materials. The method comprises the steps of: driving a low frequency acoustic source 20 immersed within a fluid comprising the carbonaceous material, e.g. in a settling tank 10, at a frequency of between 5 and 200Hz, whereby the acoustic waves facilitate separation of the hydrocarbons from other materials within the fluid; and extracting the hydrocarbons that are at least partially separated from the fluid. The acoustic source may be a projector arranged within the tank and comprising a plurality of flexible plates configured, when driven, to generate an acoustic wave at the above frequency.

Description

Extraction of hydrocarbons from carbonaceous materials HELD OF THE iNVENTION The present invention relates to the field of recovery of hydrocarbons from complex organic mixtures such as occur naturally and in particular the recovery of hydrocarbons from carbonaceous materials such as tar sands, oil shale petroleum residues or the like.

BACKGROUNI) OF THE INVENTION Hydrocarbons such as oil occur naturally in many forms and various techniques have been developed to extract the hydrocarbons from the complex organic mixtures they are found within. Tar sands for example, occur naturally in much of North America and particularly in Alberta in Canada, these tar sands hold considerable amounts of hydrocarbons but their extraction is complex, energy intensive and potentially damaging to the enviromnent.

A conventional way of removing the hydrocarbons from the tar or oil sands is in a hot water treatment process, whereby the crushed sands are mixed with hot water and transferred to a separation vessel where at least some of the hydrocarbons, principally in the form of bitumen, are released from the sands by the hot water and rise to the surface of the fluid forming a froth that can be skimmed off This froth is then sent to a secondary extraction process in which solvents may be used to provide Thrther separation.

CA 2179948 and US 4765885 both disclose the extraction of bitumen from crushed tar sands using solvents and high frequency acoustic waves to enhance the extraction. The crushed tar sands have been prc-treated to remove an initial proportion of the sand.

The use of solvents has its own environmental and cost impacts.

In the field of oil extraction from oil wells, the amount of oil that is extracted from a well can be relatively small compared to the amount of oil present in the deposits.

With increasing oil prices and reducing resources the ability to extract a greater percentage of the deposits is becoming increasingly important.

It would be desirable to be able to increase the amount of hydrocarbons extracted from carbonaceous deposits.

SUMMARY OF THE INVENTION

Viewed from a first aspect, the present invention provides a method for extracting hydrocarbons from carbonaceous materials comprising the steps of: driving a low frequency acoustic source immersed within a fluid comprising the carbonaceous material at a frequency of between 5 and 200Hz, whereby the acoustic waves facilitate separation of the hydrocarbons from other materials within the fluid; extracting the hydrocarbons that are at least partially separated from the fluid.

The present invention has found that the application of low frequency acoustic waves in the frequency range of 5 Hz to 200 Hz increases the amount of hydrocarbons that can be extracted from carbonaceous materials. This frequency of acoustic waves has been found to reduce The surface tension of the hydrocarbons facilitating their release from solids within the fluid. Furthermore, the iimnersion of the source wiThin the Ed d mixture allows thc acoustic energy to be distributed throughout the fluid in a uniform and efficient manner making the transmission of the waves throughout the fluid significantly more effective.

A low frequency of acoustic wave has been found to improve the extraction significantly, the improvement depending on the carbonaceous material in which the hydrocarbons are found. In particular, where the carbonaceous material contains a large amount of sands then a frequency of between 10 and 30 Hz has been found to be particularly effective, whereas for clays 30 to 70 Hz works better and for granites frequencies of between 70 and 100Hz are effective.

In some embodiments the carbonaceous material comprises tar sands and the method comprises an initial step of crushing the tar sands and mixing with hot water to form the fluid.

One type of carbonaceous material where the extraction of hydrocarbons is particularly challenging is tar sands. These contain grains of silaceous material such as sand impregnated with oil. Hot water and/or solvents have been used traditionally to release the hydrocarbons from the grains. The use of the low frequency acoustic energy has been found to increase the release of the hydrocarbons, by reducing the surface tension of the hydrocarbons thereby freeing them from the individual grains. This allows the use of far lower temperatures than has been conventionally used in these hot water extraction techniques.

hi some embodiments the method comprises a fttrther secondary separation step of further treating the at least partially separated hydrocarbons with a solvent.

Further separation of the hydrocarbons may be performed with a secondary separation step where solvents are used to fhcilitate further separation of the hydrocarbons from the other materials present in the fluid.

In some embodiments the step of extracting the at least partially separated hydrocarbons comprises skimming the hydrocarbons from the surface of the fluid.

Although the separated hydrocarbons may be removed in a number of ways in some embodiments a settling tank arrangement is used such that they rise to the surface and can be skimmed off.

In some embodiments, the method comprises an additional step of adding hydrogen peroxide to the fluid prior to driving the low frequency acoustic source.

It has been found in some instances that the extraction of the hydrocarbons can be further improved by the addition of hydrogen peroxide. Hydrogen peroxide acts as a frothing agent that helps the hydrocarbons to rise to the surface, In some embodiments the fluid is within a sealed separation tank with the acoustic source located within the tank during the step of driving the acoustic source.

The method has been found to he particularly effective if the acoustic source is immersed in the fluid within a sealed container. hi this way the container is pressurised by the acoustic energy and a more uniform distribution of the energy throughout the fluid can be achieved.

In other embodiments the fluid is within an oil well and said method comprises an initial step of inserting said acoustic source into a shaft within the oil well.

The quantity of hydrocarbons that can be extracted in-situ from naturally occurring deposits has been found to be increased considerably by the immersion of a low frequency acoustic source into the well. The effect is thought to be similar to that occurring after seismic activity. The use of a low frequency acoustic source provides a controllable and safe level of energy that can be confined to the relevant regions and therefore have a more predictable effect than other methods such as fracldng where shock waves are sent throughout the surrounding ground.

In some embodiments said oil well comprises a water injection oil well wherein water is injected into an injector well to maintain the pressure within the oil field and help sweep the oil from the surrounding ground to the production wells, and said fluid comprises said water.

Oil well production may be maintained in oilflelds by the use of water injection whereby water is injected into an injector well to replace the fluids extracted so as to retain the down hole pressure without which a good flow rate to the production wells throughout the oil reservoir would not be possible. By taking advantage of this existing industry practice the oil, additional amounts of which have been released thanks to the acoustic waves generated by the acoustic source, is swept into the adjacent production wells to be pumped to the surface. In this arrangement the injected water provides the base for the fluid that the acoustic source is immersed in.

In some embodiments, the acoustic source comprises a modular projector comprising a plurality of flexible plates.

One particularly effective way of providing the acoustic energy is with the use of a modular projector such as that disclosed in US2009/0268554. The frequency generated by the modular projector and the energy imparted depends on the size of the projector and this type of modular projector has been found to scale well with this application. Inthis way acoustic waves of a suitable power and frequency can be generated by building a projector of a suitable size and arranging the required number of modules together.

In some embodiments said plurality of flexible plates are held within a flexible easing such that said projector is isolated from the fluid.

It may be advantageous to isolate the plates from the fluid to protect them from the corrosive and damaging properties of the fluid.

In some embodiments, said flexible casing is filled with oil, such that the plurality of flexible plates are surrounded by oil.

In order for the projector to be able to transmit the acoustic waves efficiently to the fluid, while itself remaining isolated and protected from the corrosive environment of the carbonaceous material, the use of a flexible casing and the immersion of the plates in oil has been found to be effective.

S

A second aspect of the present invention provides an apparatus for extracting hydrocarbons from carbonaceous materials comprising: a settling tank comprising an inlet for receiving a fluid comprising the carbonaceous material; a projector arranged within the lank, said projector comprising a plurality of flexible plates configured when driven to generate an acoustic wave at a frequency of between 5 aiid 200Hz, whereby the acoustic waves facilitate separation of the hydrocarbons from other materials within the fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described further, by way of example only, with reference to embodiments thereof as illustrated in the accompanying drawings, in which: Figure 1 shows a settling tank comprising an acoustic source according to an embodiment of the present invention; Figure 2 shows a system for extracting hydrocarbons from tar sands according to an embodiment of the present invention; Figure 3 shows the acoustic source used in embodiments of the present invention; Figure 4 shows a shaft of an oil well with an acoustic source therein according to an embodiment of the present invention; Figure 5 shows a flow diagram indicating steps in a method for extracting hydrocarbons from oil sands; and Figure 6 shows steps in a method for facilitating extraction of hydrocarbons from an oil well.

DESCRIPTION OF EMBODIMENTS

Figure 1 shows a settling tank 10 having an inlet 12 for receiving a fluid consisting of a mixture of hot water and crushed tar sands and a second inlet 14 for receiving hydrogen peroxide. Settling tank 10 also has an outlet 16 for outputting hydrocarbons that have been at least partially extracted from the crush tar sands and have floated to the top. There is an acoustic source 20 suspended within the tank for applying acoustic waves to the fluid mixture. There is an outlet 22 at the bottom of the tank from which waste products or tailings arc output.

Tank 10 receives a mixture of crushed tar sands and hot water via inlet 12 and the acoustic source 20 is driven such that the settling tank 10 is pressurised with the acoustic waves. The waves are of a low frequency of between 5 and 200 Hz the actual frequency selected depending on the nature of the tar sands in the fluid, In this example, a frequency of 20 l-Tz is used and this low frequency sound wave lowers the surface tension of the hydrocarbons and releases them from the sands, They then float to the surface of the fluid where they can be extracted by skimming off at outlet 16.

Generally the process talces about an hour, the skimming off being performed at tins point.

The acoustic waves from acoustic source 20 increases the speed and amount of hydrocarbons released from the tar sands such that when this process is compared to systems where there is no acoustic source more hydrocarbons can be extracted in a shorter time and using cooler water. The hydrocarbon froth that floats to the top is still impure containing some solids, water and the hydrocarbons and further extraction of the hydrocarbons from this skininied off mixture will be performed in secondary processes. Gencrally the froth contains about 30% water, 10% solids mainly clays, with the remaining proportion being hydrocarbons.

In some cases hydrogen peroxide is added by inlet 14 and this also improves and speeds up the process of extraction.

Once the hydrocarbons have been extracted and the process is finished, outlet 22 is opened and the mixture remaining in the settling tank is output for disposal, whereupon new fluid is input via inlet 12 and the process starts again.

Figure 2 shows settling tank 10 within a larger hydrocarbon extraction system.

In this system mined oil sands 30 are dumped into a roller crusher 32 which performs an initial crushing of these sands. The crushed sands are then funnelled onto a belt 34 and transported into a rotary breaker 36 wherein they are broken up further. They are then transported along conditioning pipeline 38 where they are mixed with hot water and air and following this they are input to the settling tunIc 10 of Figure 1. This settling tank 10 has the acoustic source 20 within it.

The fluid within settling tank 1 0 is left for about an hour, the actual time selected depending on the temperature of the water used, and during this time the acoustic source is driven such that the fluid is filled with acoustic waves 20. The hydrocarbons that are released from the tar sands float to the surface where they can be skimmed off via outlet 16 to a secondary extraction tanlc 40. This tank sees the mixing of the hydrocarbons with solvent to further purify them. The solvent is output via output 42 for recycling and the further refined hydrocarbons aTe output via output 44 for further processing.

The output from settling tank 10 or the tailings are output via output 22 for disposal.

Figure 3 shows the acoustic source 20that is used within embodiments of the present invention. The acoustic source of Figure 3 has two circular ceramic plates 50 and 51 that are each affixed to aluminium plates 52 and 53. The plates are held together at their perimeter in a way that allows each plate to bend freely. The gap between the plates is large enough such that the plates do not touch each other at the maximum vibration amplitude. Although only one set of plates is shown in this example, in reality there will be several sets depending on the frequency and power desired. The assembly is encased in flexible plastic 55 that insulates the assembly from the fluid but does not substantially restrict plate vibrations. Electrical connections are made to the aluminium plates and to the ceramic plates but these arc not shown.

The diameter of the plates is between S and 20cm and the distance the between the sets of plates is between 25 and 100mm depending on the desired frequency of operation. The sets of plates are typically arranged in stacks the numbcr of plates used depending on the required power and frequency, for example there may be between 10 and 100 sets depending on the size of the settling tank. Typical driving voltages are up to 1000 volts. Although they are generally arranged in stacks the sets plates can be arranged side by side or they can be arranged in several stacks that are arranged side by side with each other.

The resonant frequency of the sets of plates or bender can be changed by changing the diameter plate thickness and ceramic thickness as will be clear to a skilled person.

Figure 4 shows an example of an oil well hole 70 having an acoustic source 20 according to Figure 3 located therein. The oil well hole 70 has a pipe lining 72 with holes 74 that go through to the surrounding rock. There is an injector well 73 also shown, which in many cases may be an old production well into which water is pumped. The figure is schematic and this injector well 73 may be at some distance from the production well with hole 70. Both wells must access the same oil reservoir, such that water injected into injector well 73 affects the pressure in the oil reservoir.

The injected water will maintain the pressure within the oil reservoir and help sweep the oil into the production well or oil well hole 70 where it is extracted.

In this embodiment a pumping system is used to extract the hydrocarbons. The pumping system has a sucker rod 76 which goes up and down and has a valve 78 at one end. The acoustic source 20 is suspended in the hole and transmits acoustic waves into the water! hydrocarbon mix and out into the surrounding ground 80 which is hydrocarbon rich. Although the acoustic source is shown as being suspended in the hole 70 of the production well, it can be suspended in the water injection well 73, or indeed in any shaft within the oil reservoir region provided that the acoustic waves generated by the acoustic source travel Through the ground of the oil reservoir acting to release hydrocarbons.

The hydrocarboii water mix swept into the hole 70 from the surrounding ground is evacuated from the hole. The acoustic waves from acoustic source 20 act to reduce the surface tension of the hydrocarbons within the surrounding ground causing them to be released and thereby substantially increasing the yield of the oil well.

In the case illustrated the oil well is a water injection oil well where water is pumped into an injector well 73 to replace the fluids extracted and maintain the pressure in the oil reservoir and help sweep the oil from the reservoir to the production wells.

The acoustic source 20 can be inserted or run into the hole (RIH) using either a crane or a mobile rig. Most mature oil fields have a small mobile rig as there is a continuous cycle of maintenance needed, thus, the equipment required for inserting and removing the acoustic source will in many eases already be available.

Figure 5 shows a flow diagram illustrating steps in a method for removing the hydrocarbons from oil sands. Initially the crushed oil sands and warm water mixture are input into a settling tank and an acoustic source within the settling tank is driven to generate low frequency acoustic waves. The resulting mixture is left for some time to settle and ten tile top layer is skimmed off The top layer contains at least partially separated hydrocarbons that have floated to the top.

S Figure 6 shows steps in a method according to an embodiment of the present invention where the acoustic source is used in an oil well. The acoustic source is inserted into the oil well and driven such that low frequency waves are generated.

These waves help release hydrocarbons from the ground surrounding the well such that the amount of hydrocarbons that are extracted from the well increase when the acoustic source is driven.

Various ftirther aspects and features of the present invention are defined in the appended claims. Various modifications can be made to the embodiments herein before described without departing from the scope of the present invention.

Claims

1 0

2. A method according to claim 1, wherein the frequency is between 10 and 30 Hz.

3. A method according to claim 1, whereinthe frequency is between 30 and 70Hz.

4. A method according to claim 1, wherein the frequency is between 70 and 100 Hz.

5. A method according to any preceding claim, wherein the carbonaceous material comprises tar sands and the method comprises an initial step of: crushing the tar sands and mixing with hot water to form the fluid.

6. A method according to claim 5, wherein the method comprises a further secondary separation step, of further treating the at least partialiy separated hydrocarbons with a solvent.

7. A method according to any preceding claim, wherein the step of extracting the hydrocarbons that are at least partially separated from the fluid comprises skimming the surface of the fluid.

8. A method according to any preceding claim, wherein the method comprises an additional step of adding hydrogen peroxide to the fluid prior to driving the low frequency acoustic source.

9. A method according to any preceding claim, wherein the fluid is within a sealed separation tank with the acoustic source located within the tank during the step of driving the acoustic source.

10. A method according to claim 1, wherein the fluid is within an oil well and said method comprises an initial step of inserting said acoustic source into a shaft within the oil well.

11. A method according to claim 10, wherein said oil well comprises a water injection oil well wherein water is injected into an injector well to maintain the pressure within the oil field and help sweep the oil from the surrounding ground to the production wells, and said fluid comprises said water.

12. A method according to any preceding claim, wherein the acoustic source comprises a modular projector comprising a plurality of flexible plates.

13. A method according to any preceding claim, wherein the plurality of flexible plates are held within a flexible casing such that said projector is isolated from the fluid..

14. A method according to any preceding claim, wherein said flexible casing is filled with oil, such that the plurality of flexible plates are surrounded by oil.

15. An apparatus for extracting hydrocarbons front carbonaceous. materials comprising: a settling tank comprising an inlet for receiving a fluid comprising the carbonaceous material: a projector arranged within the tank, said projector comprising a plurality of flexible plates configured when driven to generate an acoustic wave at a frequency of between S and 200Hz, whereby the acoustic waves facilitate separation of the hydrocarbons from other materials within the fluid.

16. An apparatus according to claim 15, wherein the modular projector is suspended within the tank such that when filled with the fluid the projector is surrounded by the fluid.

17. An apparatus according to claim 15 or 16, wherein said projector is a modular projector, comprising a plurality of flexible plates, the number of flexible plates being selected to provide the desired power and frequency of acoustic waves generated.

18. An apparatus according to any one of claims 15 to 17, wherein the phira]ity of flexible plates are held within a flexible casing such that said projector is isolated from the fluid.

19. An apparatus according to any one of claims 15 to 18, wherein said flexible casing is filled with oil, such that the plurality of flexible plates arc surrounded by oil.

20. An apparatus according to any one of claims 15 to 19 comprising an outlet towards an upper surface of said settling tank for outputting hydrocarbons that are at least partially separated from the fluid and that have floated to the top of the fluid.

21. An apparatus substantially as hereinbefore described with reference to the appended Figures.

22. A method substantially as hereinbefore described with reference to the appended Figures.