Artificial lift system for hydrocarbon wells using oleophilic materials

Abstract

A spool assembly alternately lowers an oleophilic absorbent material into a hydrocarbon-bearing fluid column in a wellbore and winds the material onto the spool, releasing the hydrocarbon-bearing fluid into a tank at the surface.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This is a U.S. Non-provisional patent application and claims priority to U.S. Provisional Application No. 63 / 673,776, filed Jul. 21, 2024.FIELD

[0002] The disclosure relates generally to producing hydrocarbons from a wellbore, and more particularly to producing a liquid phase hydrocarbon from a subterranean wellbore. An exemplary method comprises moving an absorbent assembly, including an oleophilic material, into a wellbore having a fluid column, absorbing the hydrocarbons, and lifting the hydrocarbons out of the wellbore.BACKGROUND

[0003] This disclosure relates to the artificial lift of fluid out of wellbores in the oil and gas industry. A wellbore is drilled into a reservoir or formation. The wellbore extends through a target or production zone from which fluids flow into the wellbore. In a cased or lined wellbore, the fluids flow through perforations in the casing or liner. Often, hydrocarbons and other formation fluids, such as water, will flow into the wellbore but lack naturally occurring pressure to force flow to the surface. Consequently, an artificial lift system is installed to lift the fluids in the lower wellbore to the surface.

[0004] At older and depleted reservoirs, the currently used artificial lift systems are no longer economical. There are high numbers of wells abandoned or waiting for maintenance in the US alone. These wells could be brought back into economical production with the use of the low-cost artificial lift system disclosed herein.

[0005] Currently used artificial lift systems pump the fluids in the wellbore to the surface, regardless of the content of the fluids. The reservoir fluid is typically mixed, containing water as well as hydrocarbons. The water is often contaminated with salts and other minerals and must be disposed of after being produced. The mixed fluid, once produced to the surface, must be separated into hydrocarbons, for storage or transport, and water for disposal. Sometimes a reservoir is “water driven,” with a high Water Oil Ratio (WOR), requiring disposal of large quantities of water. Water disposal can be a costly operation, between $1 and $5 per barrel, depending on the method of extraction and disposal. The disclosed system provides a method for producing less water than a typical lift system.

[0006] In the US, 20% of the oil production comes from so-called “stripper wells,” wells which produce less than 15 Barrels of Oil Per Day (BOPD). Many of these wells produce less than 2 BOPD. The maintenance and running costs of the currently used artificial lift system systems is too high to make these tripper wells economically feasible.

[0007] There are several forms of artificial lift systems currently in use, like Sucker Rod Pumps, Electrical Submersible Pumps, Progressing Cavity Pumps and more. All these pumps press the fluid through a tube to the surface. The moving elements are prone to wear-and-tear and must be maintained, costing time for repairs and money for spare parts and maintenance equipment. The equipment to service these artificial lift systems, including the pumps, is costly. Depleted fields and low producing wells can only bear minimal costs to remain economical.

[0008] Loop-rope-pumps use a continuously running rope of hydrocarbon-absorbing material. These pumps have not functioned well in practice, as the downward traveling part of the rope and the upward travelling part of the rope get twisted or form knots which impede functioning.

[0009] Reciprocating mechanisms with buckets or other forms of containers to lift oil from wellbores have been used. These have not functioned well in practice because the capacity of such containers is low, and because it is difficult to effectively empty the containers at the surface.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Drawings of the preferred embodiments of the present disclosure are attached hereto so that the embodiments of the present disclosure may be better and more fully understood:

[0011] FIG. 1 is a schematic front view of an exemplary artificial lift system according to aspects of the disclosure wherein the absorbent assembly is raised to the surface and wound on a spool.

[0012] FIG. 2 is a schematic side view of the exemplary system of FIG. 1 wherein the absorbent assembly is lowered into the wellbore.DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

[0013] FIGS. 1 and 2 are discussed together. FIG. 1 shows the system with the absorbent assembly at the surface, wound on the spool, while FIG. 2 shows the system with the absorbent assembly lowered into the fluid column of the wellbore for absorbing hydrocarbon-bearing fluid.Lift Assembly

[0014] In an exemplary embodiment of the disclosure, a method for producing a liquid phase hydrocarbon fluid from a wellbore is provided. The method and apparatus move a fluid absorbing assembly including a fluid absorbing material through a fluid column in the wellbore.

[0015] A well 10 has a wellbore 12 extending from the surface 8 through a subterranean production zone 16. Often a well will include a casing 14 extending for a selected distance from the surface into the wellbore. At the surface 8, a wellhead assembly 18 controls the well system and can include various valves, safety valves, tubing, tanks, etc., as is known in the art. In its simplest form, often the case with minimally producing wells with low bottom hole pressure, the wellhead assembly can be as an above-ground tubing acting as an extension of the casing 14.

[0016] The wellbore 12 contains a fluid column 32 which will typically have a hydrocarbon-bearing layer 34 above a heavier water-bearing layer 36.

[0017] A drive assembly 20, including a motor 24, spool 26, and controller 42, is operable to reciprocate the absorbent assembly 22 between the fluid column in the wellbore and the surface. The drive assembly 20 lowers (or allows to be lowered) an absorbent assembly 22 containing or comprising one or more absorbent materials 23 into the fluid column.

[0018] The absorbent assembly 22 is connected to a drive assembly 20. The drive assembly 20 includes a motor 24 for rotating a lift spool 26 or pulley around which a lift wire 28 or cord can be wound and unwound. The term “cord” as used herein includes wires, ropes, cords, and other lengths of flexible material suitable for reciprocating into and out of a wellbore. The cord can be a synthetic material which is light and strong with good wear performance.

[0019] As seen in the schematic, the motor 24 can have a drive shaft 25 in line with the spool shaft. In practice, the motor 24 can be mounted to the exterior of the surface unit 38 with the drive shaft extending through the wall of the surface unit and into connection with the spool shaft. Alternately, the motor could be mounted in the surface unit, preferably protected from hydrocarbon and fluid by a shielding enclosure.

[0020] Beneath the absorbent assembly 22, a weight assembly 30 can be installed to help pull the absorbent assembly down into the wellbore. He wellbore can be lined, cased, contain tubing or open hole. The weight assembly can alternatively be integrated into the absorbent assembly.

[0021] The absorbent assembly 22 is immersed into the fluid column 32 in the wellbore. The assembly is lowered into the fluid column a selected depth. For example, the assembly can be lowered into a hydrocarbon fluid layer 34 on top of the column, or further into a water-bearing layer 36. The absorbent assembly selectively absorbs or picks up the hydrocarbon fluids.

[0022] The drive assembly 20 subsequently pulls the cord 28 with the attached absorbent assembly 22 to the surface 8. The absorbed fluids stay in the absorbing assembly 22 as it enters the surface unit 38. In the surface unit 38, the absorbed fluids are removed from the absorbent assembly into a tank. For example, the assembly can be passed over, between, or wrapped around one or more rollers, spools or scrapers. Alternately, the assembly can be placed in a centrifuge which removes the fluids by centrifugal force. In some embodiments, as the assembly is wound, at speed, around a spool, pulley or roller, centrifugal force acts to throw the fluids from the assembly. The fluid can be extracted from the absorbent assembly by centrifugal forces or compression of the absorbent assembly. The separated fluid flows through an outlet 40 of the surface unit 38 for storage or further treatment.

[0023] The process is repeated, with the assembly reciprocated down and up the wellbore. The reciprocating process is controlled by a programmable control unit 42 which acts on and controls the drive assembly.

[0024] In some embodiments, the control assembly 42 is used to selectively bring the assembly into contact only with an upper portion of the fluid-filled wellbore, such that the absorbent assembly only or primarily contacts the hydrocarbons at the top of the fluid column. The controller 42 can be located in a selected location with wired or wireless communication with the motor. As seen, the controller can simply be mounted on the exterior of the surface unit 38 for ease of access. The controller 42 can include a graphical user interface or other control panel such that the user can manually operate the equipment, program the associated controller computer to operate the equipment, etc.

[0025] In other embodiments, the absorbent assembly is lowered through the hydrocarbon layer 34 and into the water layer 36 in the wellbore. After the absorbent assembly is immersed in the hydrocarbon layer of the fluid column, a hydrocarbon-film on the surface of the absorbent assembly makes the assembly hydrophobic. When the absorbent assembly is lowered further into the fluid column and is immersed in the water below the hydrocarbons, the assembly repels the water or absorbs relatively little water. In this manner, the hydrocarbons are skimmed off the top of the fluid column in the wellbore or selectively produced from the wellbore.

[0026] It is anticipated that the lift process in, for example, a 500 feet deep perforation zone in a wellbore with a properly formed oil column, will lift more than six barrels of fluid per day depending on the Water Oil Ratio, API and ID of the casing or tubing.The Absorbent Assembly

[0027] In some embodiments, the absorbent assembly 22 is designed to selectively soak up or pick up hydrocarbon liquids. In such cases, the absorbent assembly can comprise a rope or cord 28, one or more slugs or masses of oleophilic absorbent material 23 or materials suspended on the cord or in a tool containing the absorbent material or materials suspended on the cord.

[0028] The absorbent assembly 22 includes substances that are oleophilic. As used herein, oleophilic means: of or relating to a substance that has an affinity for hydrocarbon fluids, such as oil. In addition, the selected substances can be hydrophobic, meaning that they repel or do not have an affinity for water or water-based fluids. Some in the industry have been known to use the term lipophilic interchangeably with oleophilic.

[0029] The oleophilic substances or materials in the absorbent assembly selectively absorb hydrocarbons. Here, the term “absorb” includes absorption of the hydrocarbons into the material, and / or sticking of the hydrocarbon fluids to the oleophilic material.

[0030] The oleophilic absorbent material can be a single substance, a mix of substances, or layers of substances. The oleophilic absorbent material is oleophilic to attract, soak up, or pick up the hydrocarbons preferentially. In some embodiments, the materials are also hydrophobic to assist in returning a greater ratio of hydrocarbon fluids to the surface. The materials can be natural or man-made. For example, the absorbent materials can be selected from the group comprising: polypropylene, poly-blend materials, acrylic, nylon, polyester, treated cotton fiber or flakes, flax fiber, ground corn-cob, paper mill waste, wool, sponge, para-aramids, such as Kevlar (tradename), High Modulus PolyEthylene fiber, such as Dyneema (tradename), polypropylene and polyester textured filaments, microfibers and chamois.

[0031] The absorbent assembly 22 can be comprised of natural fibers or synthetic fibers bound, woven or braided together. The absorbent material can be carried in a container such as a permeable sack, sock or sleeve. The absorbent material can be carried in one or more tools.

[0032] The absorbing material of the absorbent assembly can be mixed, layered or coated with wear-resistant materials to prolong the life of the assembly.

[0033] The absorbent assembly can comprise a woven cord of material or materials. The absorbent assembly can comprise one or more strands of cord. The strands can be oleophilic material or a mix of materials specific to the needs of the fluids in the wellbore. The selected materials can be woven or braided to a cord and may have a circular, oval or triangular cross-sectional shape.

[0034] In some embodiments, the absorbent assembly 22 is relatively long and flexible. The flexible assembly is able to be wound on a spool or roller during lifting and lowering into the wellbore. Further, such an assembly can be compressible, able to be squeezed or compressed, to remove fluids. The assembly in some cases will be dozens or hundreds of feet long, designed to extend along the length of the wellbore having the fluid column. Above the assembly can be, in some cases, a rope, wire, etc., which is not absorbent. Similarly, a non-absorbent rope, wire, etc., can be positioned below the assembly for, for example, suspension of a weight assembly.Control Unit

[0035] The control unit 42 controls the drive assembly 20 to lower the absorbent assembly 22 into the wellbore 12 and to retrieve the hydrocarbon-saturated absorbent assembly to the surface unit 38 for extraction of hydrocarbons. The maximum depth of the reciprocating of the absorbent assembly in the wellbore and the speed of the reciprocating are adjustable with the programmable control unit of the drive assembly. The apparatus is thus programmable for a wide variety of wellbores, fluid levels, and fluid compositions. The method and apparatus are largely independent of depth and fluid column composition. The programmable control unit and drive assembly can be independently powered or powered by the grid.

[0036] The control unit can be programmed to operated in various ways. In one embodiment, the control unit controls the drive assembly to lower the assembly to a selected depth, maintain the assembly at depth for a selected period of time, then retrieve the assembly to the surface. The system can run continuously or intermittently. For example, for low producing wells, the system can lower the absorbent assembly into the fluid column once every selected period of time, such as once every eight hours. This prevents operation of the lift, and associated costs.

[0037] In another embodiment, the controller works to lower the assembly progressively deeper depths as reciprocations downhole continue. That is, hydrocarbons are skimmed from the upper portion of the fluid column in the first or initial runs in, then, as the column depletes, the assembly is lowered further into the wellbore and into contact with the depleting fluid column. By increasing the depth in successive or subsequent runs, the assembly is dropped deeper into the well. This way, the fluid column can be lowered to or even below the perforation zone. The Bottom Hole Pressure (BHP) is thus reduced and the inflow increases. When the deepest point of the fluid column in the wellbore is reached, the lift depths remain at that selected lowest depth to optimize production.

[0038] The potential of depth adjustment makes this artificial lift system extremely flexible and can so be installed in existing wellbores without significant hardware adjustments. The programmable control unit controls the reciprocating process and so optimizes the production of the fluid from the subterranean. An installation in an abandoned well with some hydrocarbons present can be done without precise and large equipment. The flexibility of this artificial lift system and the programmable control unit makes the assembly a flexible solution without an expensive and complex installation.

[0039] The disclosed system eliminates the problem of loop-rope-pumps. In the disclosed method, a single cord in the wellbore reciprocates. The problem of the loop-rope-pump, namely, that the upward and downward travelling parts of the rope get twisted or hung-up, is eliminated.

[0040] Further, the disclosure provides a solutions for insufficient capacity and ineffective extraction, problems which hamper reciprocating mechanisms with buckets or containers. The absorbing assembly, with its hydrocarbon-absorbent material, can be as long, in some embodiments, as the length of the hydrocarbon column in the wellbore. For example, the assembly can be more than 300 feet long. This gives the absorbing assembly a sufficiently large capacity for lifting hydrocarbons. For example, it is expected that a assembly can lift more than six barrels per day. In addition, extracting fluid from the absorbing assembly by pressing or squeezing is simple and effective.Water Lift

[0041] In some situations, it is beneficial to selectively produce the water from a fluid column to lower the level of the column.

[0042] In some embodiments, the assembly can include one or more absorbent substances which comprise one or more hydrophilic materials. The hydrophilic materials will absorb as much water as possible when immersed in the fluid column.

[0043] In some embodiments, the hydrophilic substances are also oleophobic. The water can then be lifted to the surface and removed. The process of extraction of the water from the absorbent element is the same as in the oil-absorbing embodiments described above. The removal of the water from a wellbore can be beneficial to improve the inflow from the reservoir to the wellbore. By removing of the static pressure column, the bottom hole pressure is lowered. The reservoir pressure makes new inflow of fluid to the wellbore possible. New fluid, a mixture of hydrocarbons and water, will enter the wellbore through the perforation zone.

[0044] Hydrophilic materials include cotton, waxed cotton, cellulose sponge, viscose, yarn, etc., as is known in the art.Pre-Assembly, Maintenance

[0045] Other embodiments are pre-assembled and pre-configured for a known size and depth wellbore with a known fluid column. The assembly can be installed in a short period of time with limited installation equipment and a limited installation team. In some embodiments, the installation can be done by one person. The complexity of the installation and capital expenditures are kept low.

[0046] The maintenance of the assembly can be done manually on the surface. No complex service equipment needs to be brought to the well. The cord, absorbent assembly, and the attached or integrated weight can be replaced or serviced at the surface. The number of moving parts is limited. This simple maintenance procedure results in low operational costs. The required time for maintenance is short, so the downtime of the system is low.Conclusion

[0047] One apparatus includes an absorbent element containing materials which are lipophilic. The absorbent element is connected to a drive assembly with a cord. Beneath the absorbent element a weight can be installed to pull down the assembly downward by force of gravity. The drive assembly is configured to reciprocate the absorbing element down into the fluid column in the wellbore and back up to the surface.

[0048] A programable control unit is installed to control the reciprocating process. In the surface unit the absorbent element passes one or more rollers, spools, or the like, to squeeze the extracted fluid from the element. Alternately, the element is placed in a centrifugal machine and the liquid extracted by centrifugal force.

[0049] The process is repeated, as the element is again lowered into the wellbore to absorb additional fluid.

[0050] In the wellbore, where mixed fluids are present, the hydrocarbons will float on top of the water. The absorbing element is lowered into the hydrocarbons floating on top of the column of fluid, absorbing the hydrocarbons. The produced fluids will therefore have limited water content.

[0051] The apparatus can be placed directly on the casing and / or on the tubing of the well and the complete embodiment holds the artificial lift for fluid production out of the reservoir. The installation procedure can be done without the use of heavy equipment and the maintenance will be manually.

[0052] It is understood that the ability to inject carbon dioxide entrained in a pumpable slurry as nanobubbles, for example, creates benefits and feasibilities not available when simply pumping carbon dioxide larger bubbles (macrobubbles), which will separate from the slurry or liquid easily and before injection.

[0053] Persons of skill in the art will recognize changes, additions and deletions of particular steps of the process that can be made depending on the circumstances of the wastes, slurry preparation, injection operations, etc. The methods presented in the claims are explicitly disclosed in this application. Steps can be repeated, as those of skill in the art will understand. Steps can be rearranged, as those of skill in the art will understand.

Claims

1. A method for producing hydrocarbons to the surface from a subterranean wellbore extending through a production zone, the method comprising:repeatedly:lowering an absorbent assembly having at least one oleophilic absorbent material into a fluid column in the wellbore;absorbing hydrocarbon-bearing fluid from the fluid column with the absorbent assembly;raising the absorbent assembly to the surface;winding the absorbent assembly on a spool at the surface; andremoving the hydrocarbon-bearing fluid from the absorbent assembly at the surface.

2. The method of claim 1, wherein removing the hydrocarbon-bearing fluid further comprises compressing the absorbent assembly.

3. The method of claim 1, wherein removing the hydrocarbon-bearing fluid further comprises applying centrifugal force to the absorbent assembly.

4. The method of claim 1, wherein removing the hydrocarbon-bearing fluid further comprises wrapping the absorbent assembly around a spool.

5. The method of claim 1, wherein the at least one oleophilic absorbent material is taken from the group consisting of: polypropylene, poly-blend materials, acrylic, nylon, polyester, treated cotton fiber or flakes, flax fiber, ground corn-cob, paper mill waste, wool, sponge, para-aramids, high modulus polyethylene fiber, polypropylene and polyester textured filaments, and chamois.

6. The method of claim 1, wherein the absorbent assembly further comprises at least one hydrophilic material.

7. The method of claim 1, wherein the absorbent assembly further comprises an absorbent material housed in a permeable container.

8. The method of claim 1, further comprising: automatically, using a controller, maintaining the absorbent assembly into the fluid column in the wellbore at a selected depth for a selected period of time.

9. The method of claim 1, wherein repeatedly lowering the absorbent assembly into the fluid column further comprises: automatically, using a controller, lowering the absorbent assembly into the fluid column at sequentially lower depths on sequential trips into the fluid column.

10. The method of claim 1, wherein the fluid column in the wellbore comprises a hydrocarbon-bearing fluid layer above a water-bearing fluid layer; and further comprising: lowering the absorbent assembly into the water-bearing layer of the fluid column.

11. An apparatus for producing hydrocarbons to the surface from a subterranean wellbore extending through a production zone, a fluid column having a hydrocarbon-bearing fluid above a water-bearing fluid in the wellbore, the apparatus comprising:a spool positioned in a tank, the tank having an outlet for selectively discharging fluid from the tank;an absorbent assembly operable to be alternately wound on the spool and lowered into a fluid column in the wellbore, the absorbent assembly comprising at least one oleophilic absorbent material for absorbing the hydrocarbon-bearing fluid;a motor operable to selectively rotate the spool in opposite directions, thereby lowering the absorbent assembly into the fluid column and winding the absorbent assembly on the spool;the motor operable and spool operable to remove hydrocarbon-bearing fluid from the absorbent assembly by applying compression or centrifugal force to the absorbent assembly; anda controller for automatically controlling operation of the motor to repeatedly lower and raise the absorbent assembly by operation of the motor and spool.

12. The apparatus of claim 11, wherein removing the hydrocarbon-bearing fluid further comprises compressing the absorbent assembly.

13. The apparatus of claim 11, wherein the at least one oleophilic absorbent material is taken from the group consisting of: polypropylene, poly-blend materials, acrylic, nylon, polyester, treated cotton fiber or flakes, flax fiber, ground corn-cob, paper mill waste, wool, sponge, para-aramids, high modulus polyethylene fiber, polypropylene and polyester textured filaments, and chamois.

14. The apparatus of claim 11, wherein the absorbent assembly further comprises at least one hydrophilic material.

15. The apparatus of claim 11, wherein the absorbent assembly further comprises a permeable container, and wherein the oleophilic absorbent material is housed in the permeable container.

16. The apparatus of claim 1, wherein the controller is operable to automatically maintain the absorbent assembly in the fluid column at a selected depth for a selected period of time.

17. The apparatus of claim 1, wherein the controller is operable to automatically lower the absorbent assembly into the fluid column at sequentially lower depths on sequential trips into the fluid column.

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