Self-powered nanomotor for water lock-up release in tight gas reservoirs and method of release thereof

Abstract

The present application relates to a self-driven nanometer micromotor for water lock solution of tight gas reservoir and a method for water lock solution of tight gas reservoir, the self-driven nanometer micromotor for water lock solution of tight gas reservoir is a double-section cone structure coated with a core-shell, which is composed of, from inside to outside, a motion control section: a CaCO3 thin layer at the tip of the cone cannot react with water, controlling the generated bubbles to push the motor to directional advance; an Al4C3 reaction section: the atomic ratio of aluminum and carbon is 4:3, the crystal form is face-centered cubic structure, and the cone is the rear section of the motor, with a diameter of 450-2000 nm; a delay coating layer: a polypyrrole (PPY) copolymer film or a polyaniline (PANI) copolymer film, the copolymer film is a porous hydrophobic polymer macromolecular outer layer, coated outside the conical CaCO3-Al4C3 core structure, prolonging the contact time of the nanometer micromotor with water and promoting the motor to push deeper. The present application not only can go deep into the fissure to solve water lock, but also can significantly improve the gas production and recovery efficiency.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development technology, specifically to a self-driven nano-micro motor for improving the recovery rate of tight gas reservoirs and a method for releasing water locks in tight sandstone gas reservoirs with low permeability. Background Technology

[0002] Tight gas reservoirs in oil and gas fields refer to gas reservoir types with extremely low permeability and underdeveloped natural fractures. During the extraction process, tight gas reservoirs often experience water-locking, where water in the fluid is trapped on the surface of minerals or in pores, blocking the gas flow channels and severely affecting gas flow and production. According to relevant research, water-locking can lead to a 40% to 70% decrease in gas well productivity (data source: China Tight Gas Development White Paper 2022).

[0003] Currently, commonly used methods for water-lock removal include acidizing, thermal operations, and chemical demulsification. However, these methods generally suffer from low efficiency, complex operation, and high cost. For example, while traditional acidizing can improve fluid flow, its strong corrosiveness and limited radius of action prevent it from effectively covering the entire tight gas reservoir. Thermal operations, on the other hand, consume a large amount of energy, leading to a significant increase in extraction costs. Therefore, there is an urgent need to develop a new, efficient, and economical water-lock removal technology to meet the extraction requirements of modern tight gas reservoirs. Summary of the Invention

[0004] One objective of this invention is to provide a self-driven nano-micro motor for water lock release in tight gas reservoirs. This self-driven nano-micro motor for water lock release in tight gas reservoirs solves the problems of low efficiency, complex operation, and high cost that are common in existing water lock release methods. Another objective of this invention is to provide an unlocking method for this self-driven nano-micro motor for water lock release in tight gas reservoirs.

[0005] The technical solution adopted by this invention to solve its technical problem is: this self-driven nano-micro motor for water-lock breaking in tight gas reservoirs is a core-shell encapsulated double-segment cone structure, which comprises, from the inside out:

[0006] Motion control segment: The thin layer of CaCO3 at the tip of the vertebral body cannot react with water, and the generated bubbles control the motor to propel it in a directional manner;

[0007] Al4C3 reaction section: aluminum to carbon atom ratio of 4:3, crystal form is face-centered cubic structure, which is the cone of the motor rear section, with a cone diameter of 450-2000 nm;

[0008] Delayed coating layer: polypyrrole (PPY) copolymer film or polyaniline (PANI) copolymer film, wherein the copolymer film is a porous hydrophobic polymer outer layer that coats the conical CaCO3-Al4C3 core structure, extending the contact time between the nano- and micro-sized motor and water, and promoting the motor to push into deeper layers.

[0009] The fabrication method of the self-driven nano-micro motor for water-lock breaking in tight gas reservoirs in the above scheme includes the following steps:

[0010] Step 1: Fabrication of self-driven nano / micro motors:

[0011] (1) Using a PC / PE or Al2O3 filter membrane with a diameter of 450-2000 nm and a pore length of 10 μm as a template, immerse it in a saturated Ca(OH)2 solution, dry it, and react it in a drying oven at 60 degrees Celsius for 12 h under CO2 atmosphere to obtain a CaCO3 thin layer.

[0012] (2) Perform chemical vapor deposition of a C thin layer on the template;

[0013] (3) Dissolve the external template with a solvent to obtain CaCO3-C conical nano-micro tubes. After drying, deposit an Al layer on the powder surface of the CaCO3-C nano-micro cones again using vapor deposition to obtain CaCO3-C-Al nano-micro cones.

[0014] (4) The CaCO3-C-Al nano-micro cone was placed in a tube furnace, and an Ar / CH4 mixture was introduced to maintain a pressure of 60±5 kPa. A three-stage temperature control was used to obtain the cone-shaped CaCO3-Al4C3 core structure.

[0015] Stage 1: 20℃→600℃, heating rate 8℃ / min, maintain for 40 minutes to allow methane to crack and deposit;

[0016] Stage 2: 600℃→1450℃, heating rate 12℃ / min, aluminum powder evaporation and deposition for 90 minutes;

[0017] Stage 3: 1450℃→2100℃, heating rate 15℃ / min, carbonization reaction for 120 minutes to generate Al4C3;

[0018] Step 2: Surface functionalization treatment:

[0019] The conical CaCO3-Al4C3 core structure is ultrasonically dispersed in benzene solvent, and then pyrrole monomers or aniline units are added for further dispersion and full contact with the cone. An initiator is added to initiate the polymerization of pyrrole or aniline on the surface of the nano-micro cone. Polypyrrole or polyaniline is used as a protective layer. After centrifugation and drying, CaCO3-Al4C3@ppy nano-micro cones are obtained, which are self-driven nano-micro motors.

[0020] The solvent in step (3) of the above scheme is dichloromethane.

[0021] In step (4) of the above scheme, when the Ar / CH4 mixture is introduced, the flow rate ratio of Ar to CH4 is 3:1-2.

[0022] In step two of the above scheme, the initiator is benzoyl peroxide or tert-butyl peroxide.

[0023] The above-mentioned self-driven nano-micro motor unlocking method for water-locking tight gas reservoirs involves deploying the self-driven nano-micro motor into the tight gas reservoir, utilizing the gas driving force it generates to quickly penetrate the water-locked area, promoting the discharge of water and the flow of gas, thereby achieving the purpose of unlocking the water lock.

[0024] Furthermore, the self-driven nano-micro motor unlocking method described above for water-locking in tight gas reservoirs:

[0025] The self-driven nano-micro motor is suspended in an appropriate amount of oil-based fluid and injected into a tight gas reservoir through an injection well at an injection pressure of 10-20 MPa.

[0026] Driving force generation: When the self-driven nano-micro motor encounters formation water or injected water in the gas reservoir, it uses Al4C3 to react with water to generate gas. The generated gas forms bubbles on the surface of the self-driven nano-micro motor.

[0027] Self-driven motion: Due to the asymmetric release of bubbles, the self-driven nano-micro motor generates self-driving force, propelling it to move rapidly in the aqueous phase, and the bubbles are ejected along the direction of the large end.

[0028] Water lock release: The self-driven motion of the self-driven nano-micro motor penetrates the water lock area, and the gas driving force generated by it promotes the discharge of water and the flow of gas, thereby releasing the water lock and improving the recovery rate of the gas reservoir. Beneficial effects

[0029] 1. This invention designs a self-driven motor at the nano-microscale, which can not only penetrate deep into fissures to release water locks, but also significantly improve gas production and harvesting efficiency.

[0030] 2. The core innovation of this invention lies in the use of a template method to deposit a conical CaCO3-Al4C3 core structure within nano-micro pores, while simultaneously coating it with a porous hydrophobic polymer outer layer to extend the contact and reaction time of the molecular motor. This Al4C3 core reacts with water in the gas reservoir to generate gas driving force. The conical structure ensures that the generated gas can push the motor deep into the fractures, achieving rapid release of water locks. This invention will effectively improve gas flowability and provide a new solution for the economical development of tight gas reservoirs in oil and gas fields.

[0031] 3. This invention achieves high-efficiency drive: When the Al4C3 core reacts with moisture in the gas reservoir, it generates a large amount of gas, which drives the motor to move rapidly. Compared with traditional water-lock release methods, the motor of this invention can release water locks in a shorter time, significantly improving gas flow and recovery efficiency.

[0032] 4. This invention possesses excellent adaptability: The motor designed in this invention can adapt to various complex geological conditions, including extreme environments such as high temperature and high pressure. Whether in tight sandstone, shale, or other types of tight gas reservoirs, this motor can operate effectively, bringing higher economic benefits.

[0033] 5. The present invention simplifies the operation process: Compared with the complex operation steps in the prior art, the self-driven motor of the present invention has a simple preparation and application process. Through the optimized preparation process, it can be quickly generated under laboratory conditions and is convenient to use in field operations.

[0034] 6. Deep penetration capability of the present invention: Compared with traditional nanoparticles (maximum effective distance < 1.5m), the present invention achieves penetration through micropores > 15mm within 72 hours (permeability recovery rate ≥ 90%). Experimental data are as follows:

[0035] 7. The composite unblocking mechanism of this invention:

[0036] Gas-driven: CH4 generates a local pressure difference (ΔP > 2.1 MPa), which drives the liquid film to move;

[0037] Chemical dissociation: Al(OH)3 colloid reduces interfacial tension to <5mN / m;

[0038] Physical scouring: The cluster effect of nanomotors creates microturbulence.

[0039] 8. Environmental adaptability of the invention: It maintains a stable displacement efficiency of >80% in extreme formation environments with mineralization >80000mg / L and pH 3-11. Detailed Implementation

[0040] The present invention will be further described below: Example 1

[0041] This self-driven nano-micro motor for water-lock breaking in tight gas reservoirs has a core-shell encapsulated, two-segment cone structure, which, from the inside out, comprises:

[0042] Motion control segment: The thin layer of CaCO3 at the tip of the vertebral body cannot react with water, and the generated bubbles control the motor to propel it in a directional manner;

[0043] Al4C3 reaction section: aluminum to carbon atom ratio of 4:3, crystal form is face-centered cubic structure, which is the cone of the motor rear section, with a cone diameter of 450-2000 nm;

[0044] Delayed coating layer: PPY copolymer film, a porous hydrophobic polymer outer layer, is coated on the conical CaCO3-Al4C3 core structure, which prolongs the contact time between the nano- and micro-sized motor and water, and promotes the motor to push into deeper layers.

[0045] The fabrication method of this self-driven nano-micro motor for water-lock breaking in tight gas reservoirs:

[0046] Step 1: Fabrication of CaCO3-C conical nanotube / microtube motor:

[0047] Template preparation: A polycarbonate (PC) filter membrane with a diameter of 450-2000 nm and a pore length of 10 μm is used as a template. The pore size of the PC membrane is selected in the range of 0.2-1 μm to ensure that the formed nanotubes have appropriate dimensions. The nano-micro motor of this invention is named as such because the motor obtained by using this template has a diameter in the nanometer range and a length in the micrometer range.

[0048] CaCO3 Thin-Layer Deposition: A PC template is immersed in a saturated Ca(OH)2 solution for 1-6 hours. The template is then removed and dried in a 60°C oven for 6 hours. Subsequently, the dried template is placed in a CO2 atmosphere oven and reacted at 60°C for 12 hours to form a CaCO3 thin layer. The CO2 atmosphere can be maintained by placing dry ice at the bottom of the oven.

[0049] C. Thin-layer chemical vapor deposition: A PC template with a CaCO3 thin layer deposited on it is placed in a chemical vapor deposition (CVD) furnace. Template removal: After deposition, the sample is immersed in a dichloromethane solution and sonicated for 30 minutes to dissolve the PC template, obtaining CaCO3-C conical nanotubes.

[0050] Then, an Al layer was deposited on the surface of CaCO3-C conical nanotubes using vapor deposition.

[0051] Three-stage temperature control is adopted:

[0052] Using methane (CH4) as the carbon source and argon (Ar) as the carrier gas, the flow rate ratio of CH4 to Ar was controlled at 3:1-2, and the gas pressure was maintained at 60±5 kPa.

[0053] Phase 1: Increase the temperature from room temperature to 600°C at a rate of 8°C / min and maintain it for 40 minutes to allow methane to crack and deposit.

[0054] Phase 2: Heat to 1450°C at a rate of 12°C / min and maintain for 90 minutes to perform aluminum powder evaporation deposition.

[0055] Stage 3: The temperature is increased to 2100℃ at a rate of 15℃ / min and maintained for 120 minutes, resulting in a carbonization reaction to produce Al4C3.

[0056] Step 2: Surface functionalization treatment:

[0057] Dispersion: The prepared Al4C3 framework (i.e., the conical CaCO3-Al4C3 core structure) was ultrasonically dispersed in 100 mL of benzene solvent for 30 minutes to form a uniform suspension.

[0058] Polymerization: 0.5 mL of pyrrole monomer was added to the suspension, and ultrasonic dispersion was continued for 15 minutes. Then, 0.1 g of benzoyl peroxide and 0.1 g of tert-butyl peroxide were added as initiators to initiate pyrrole polymerization. The reaction was carried out in an ice-water bath for 24 hours, yielding a hydrophobic and porous PPY outer layer structure.

[0059] Purification: After the reaction was completed, the supernatant was removed by centrifugation at 10,000 rpm for 10 minutes. The precipitate was then dried in a vacuum drying oven at 60°C for 12 hours to obtain CaO-Al4C3@ppy nanocones, i.e., self-driven nano-micro motors.

[0060] This self-driven nanomotor unlocking method for water-locking in tight gas reservoirs:

[0061] Motor deployment: The prepared self-driven nano- and micro-sized motors are suspended in an appropriate amount of carrier fluid (oil-based fluid) and injected into the tight gas reservoir through an injection well. The injection pressure is determined based on the formation pressure of the gas reservoir, typically 10-20 MPa.

[0062] Driving force generation: When the motor encounters formation water or injected water in the gas reservoir, it utilizes Al4C3 to react with the water and generate gas. The generation of these gases forms bubbles on the surface of the motor.

[0063] Self-driven motion: Due to the asymmetric release of bubbles, the motor generates a self-driving force, propelling them rapidly in the aqueous phase. The motor's speed can be controlled by adjusting its size, shape, and surface properties. For example, tapered nanotubes operate faster than circular tubes because the asymmetric tapered structure allows bubbles to be ejected more efficiently along the larger end.

[0064] Water lock release: The self-driven motion of the motor can effectively penetrate the water-locked area, utilizing the gas driving force it generates to promote the discharge of water and the flow of gas, thereby releasing the water lock and improving the recovery rate of the gas reservoir. The motor can also interact with formation rocks or fluids through functionalized coatings (such as polypyrrole) on its surface, further improving the oil displacement effect. For example, polypyrrole is a conductive polymer with high electrical conductivity, easy synthesis, and good environmental stability; it can increase the corrosion potential of metals and protect them from corrosion. Example 2

[0065] This self-driven nano-micro motor for water-lock breaking in tight gas reservoirs has a core-shell encapsulated, two-segment cone structure, which, from the inside out, comprises:

[0066] Motion control segment: The thin layer of CaCO3 at the tip of the vertebral body cannot react with water, and the generated bubbles control the motor to propel it in a directional manner;

[0067] Al4C3 reaction section: aluminum to carbon atom ratio of 4:3, crystal form is face-centered cubic structure, which is the cone of the motor rear section, with a cone diameter of 450-2000 nm;

[0068] Delayed coating layer: PANI copolymer film, a porous hydrophobic polymer outer layer, is coated on the conical CaCO3-Al4C3 core structure, which prolongs the contact time between the micro-nano motor and water, and promotes the motor to push into deeper layers.

[0069] The fabrication method of this self-driven micromotor for water-lock breaking in tight gas reservoirs:

[0070] Step 1: Preparation of CaCO3-C conical nanotubes

[0071] Template preparation: Al₂O₃ filter membranes with small pores of 450-2000 nm in diameter and pore length of 10 μm were used as templates. This template size was chosen to control the final size and morphology of the nanotubes.

[0072] CaCO3 thin-layer deposition: Immerse the Al2O3 template in a saturated Ca(OH)2 solution and let it stand for 1-6 hours to allow the CaCO3 to settle. 2+ OH⁻ forms a Ca(OH)₂ precipitate on the template surface. The template is then removed and dried. During drying, Ca(OH)₂ partially dehydrates and transforms into CaO.

[0073] CO2 Reaction: The dried template was placed in a drying oven under a CO2 atmosphere and reacted at 60°C for 12 hours. CO2 reacts with CaO to produce CaCO3, and simultaneously reacts with the remaining Ca(OH)2 to produce CaCO3 and H2O. Finally, a thin layer of CaCO3 is formed on the template surface. The reaction equations are: CaO + CO2 → CaCO3 Ca(OH)2 + CO2 → CaCO3 + H2O

[0074] C thin-layer deposition: A carbon thin layer is deposited on the surface of a CaCO3 thin layer using chemical vapor deposition (CVD). The template is placed in a CVD furnace, a carbon source gas (such as methane) is introduced, and deposition is carried out at 800-1000℃ for 1-2 hours to form a uniform C thin layer.

[0075] Template Removal: The template with deposited CaCO3 and C thin layers was immersed in a sodium hydroxide solution and sonicated for 30 minutes to dissolve the Al2O3 template. Then, residual solvent was removed by centrifugation to obtain CaCO3-C tapered nanotubes / microtubes.

[0076] Preparation of Al4C3-coated CaCO3-C micro / nano cones:

[0077] A layer of Al was deposited on the surface of CaCO3-C micro / nano cones using chemical vapor deposition.

[0078] Introduce an Ar / CH4 mixture (flow rate ratio 3:1-2) and maintain a pressure of 60±5 kPa.

[0079] Three-stage temperature control:

[0080] Stage 1: Increase the temperature from 20°C to 600°C at a rate of 8°C / min and maintain it for 40 minutes to allow methane to crack and deposit.

[0081] Stage 2: The temperature is increased from 600℃ to 1450℃ at a rate of 12℃ / min and maintained for 90 minutes, allowing aluminum powder to evaporate and deposit.

[0082] Stage 3: The temperature is increased from 1450℃ to 2100℃ at a rate of 15℃ / min and maintained for 120 minutes, resulting in a carbonization reaction that produces Al4C3.

[0083] Cooling: After the reaction is complete, the mixture is allowed to cool naturally to room temperature to obtain CaCO3-Al4C3 nano-micro cones.

[0084] Step 2: Surface functionalization treatment:

[0085] Dispersion: The prepared Al4C3 framework sample was ultrasonically dispersed in 100 mL of benzene solvent for 30 minutes to form a uniform suspension.

[0086] Polymerization: 0.5 mL of aniline monomer was added to the suspension, and ultrasonic dispersion was continued for 15 minutes. Then, 0.2 g of benzoyl peroxide was added as an initiator to initiate the polymerization of aniline. The reaction was carried out in an ice-water bath for 24 hours. A hydrophobic porous polyaniline functional coating was formed, yielding CaO-Al2C3@PANI nano-micro cones.

[0087] This self-driven nano-micro motor unlocking method for water lock removal in tight gas reservoirs is the same as the unlocking method in Example 1.

[0088] Comparative experiment:

[0089] To verify the effectiveness of the present invention, multiple batches of comparative experiments were conducted to verify the effect of different nano- and micro-cones on the molecular motor drying agent.

[0090] Experimental instruments: Model AE300.SH emulsifier (Shanghai Onni Instrument Co., Ltd.); MCR-3 microwave chemical reactor (Gongyi Kerui Instrument Co., Ltd.); microscope (model N117M, equipped with a 5MP digital camera, Beijing Nuowei Optics Co., Ltd. / China); incubator; stirrer.

[0091] Experimental steps:

[0092] 1. In a tight sandstone gas reservoir with a salinity of 4500 mg / L, a micron-sized supercritical carbon dioxide suspension with a concentration of 100 mg / L was prepared and injected into the reservoir using a plunger pump at an injection rate of 3 m³ / h.

[0093] 2. 48 hours after injection, the daily gas production of the gas well increased from 18,000 cubic meters to 35,000 cubic meters, an increase of 94%. At the same time, the permeability recovered from the original 0.08 mD to 0.69 mD, an increase of 8.63 times.

[0094] 3. After 96 hours of continuous injection, the gas well production stabilized at 39,000 cubic meters per day, an increase of 116% compared to before injection. CT scan results showed that the injected fluid had penetrated about 1.5 meters along the main fracture, forming a high-permeability channel with a diameter of 1-3 mm.

[0095] The CaCO3 substrate, used as the support substrate for the motor, not only improves the overall structural strength but also provides an abundant CO2 source for Al4C3, which is beneficial for reducing the salinity of tight gas reservoirs in oil and gas fields. The heat and gas released when the drying agent reacts with water are conducive to the formation of new channels.

Claims

1. A self-driven nano-micro motor for water-lock breaking in tight gas reservoirs, characterized in that: This self-driven nano-micro motor for water-lock breaking in tight gas reservoirs has a core-shell encapsulated, two-segment conical structure, which, from the inside out, comprises: Motion control section: The thin layer of CaCO3 at the tip of the cone does not react with water, and the generated bubbles drive the motor for directional propulsion. Al4C3 reaction section: aluminum to carbon atomic ratio 4:3, crystal form is face-centered cubic structure, which is the cone of the motor section, with a cone diameter of 450-2000nm; Delayed coating layer: polypyrrole (PPY) homopolymer film or polyaniline (PANI) homopolymer film, wherein the homopolymer film is a porous hydrophobic polymer outer layer that coats the conical CaCO3-Al4C3 core structure, extending the contact time between the nano-micro motor and water, and promoting the motor to push into deeper layers.

2. The self-driven nano-micro motor for water-lock breaking in tight gas reservoirs according to claim 1, characterized in that: The method for fabricating the self-driven nano-micro motor for water-lock breaking in tight gas reservoirs includes the following steps: Step 1: Fabrication of self-driven nano / micro motors: (1) Using a PC / PE or Al2O3 filter membrane with a diameter of 450-2000 nm and a pore length of 10 μm as a template, immerse it in a saturated Ca(OH)2 solution, dry it, and react it in a drying oven at 60 degrees Celsius for 12 h under CO2 atmosphere to obtain a CaCO3 thin layer. (2) Perform chemical vapor deposition of a C thin layer on the template; (3) Dissolve the external template with a solvent to obtain CaCO3-C conical nano-micro tubes. After drying, deposit an Al layer on the powder surface of the CaCO3-C nano-micro cones again using vapor deposition to obtain CaCO3-C-Al nano-micro cones. (4) The CaCO3-C-Al nano-micro cone was placed in a tube furnace, and an Ar / CH4 mixture was introduced to maintain a pressure of 60±5 kPa. A three-stage temperature control was used to obtain the cone-shaped CaCO3-Al4C3 core structure. Stage 1: 20℃→600℃, heating rate 8℃ / min, maintain for 40 minutes to allow methane to crack and deposit; Stage 2: 600℃→1450℃, heating rate 12℃ / min, aluminum powder evaporation and deposition for 90 minutes; Stage 3: 1450℃→2100℃, heating rate 15℃ / min, carbonization reaction for 120 minutes to generate Al4C3; Step 2: Surface functionalization treatment: The conical CaCO3-Al4C3 core structure is ultrasonically dispersed in benzene solvent, and then pyrrole monomer or aniline monomer is added and dispersed again to ensure full contact with the cone. An initiator is added to initiate the polymerization of pyrrole or aniline on the surface of the nano-micro cone. Polypyrrole or polyaniline is used as a protective layer. After centrifugation and drying, CaCO3-Al4C3@ppy nano-micro cone is obtained, which is a self-driven nano-micro motor.

3. The self-driven nano-micro motor for water-lock breaking in tight gas reservoirs according to claim 2, characterized in that: The solvent in step (3) is dichloromethane.

4. The self-driven nano-micro motor for water-lock breaking in tight gas reservoirs according to claim 3, characterized in that: In step (4), when the Ar / CH4 mixture is introduced, the flow rate ratio of Ar to CH4 is 3:1-2.

5. A self-driven nano-micro motor unlocking method for water-locking in tight gas reservoirs as described in claim 4, characterized in that: The self-driven nano-micro motor is deployed into the tight gas reservoir, and the gas driving force it generates is used to quickly penetrate into the water-locked area, promote the discharge of water and the flow of gas, and achieve the purpose of releasing the water lock.