Coal rock gas well drilling fluid borehole stabilizer, preparation method and application thereof

Abstract

This invention belongs to the field of drilling fluid technology, specifically relating to a wellbore stabilizer for coal and gas wells, its preparation method, and its application. The wellbore stabilizer for coal and gas wells, by weight, comprises the following raw material components: 5-10 parts of 2-acrylamide-2-methylpropanesulfonic acid, 1-5 parts of N,N-dimethylacrylamide, 0.1-1 parts of dimethyldiallyl ammonium chloride, 0.05-0.1 parts of N,N-methylenebisacrylamide, 0.1-1 parts of octylphenol polyoxyethylene ether, 10-20 parts of soda ash, 0.05-0.2 parts of ammonium persulfate, 15-20 parts of styrene, 0.1-1 parts of emulsifier, 15-20 parts of acid-soluble framework material, 15-20 parts of deformable polymer material, 15-20 parts of polyamine shale inhibitor, 45-55 parts of anhydrous ethanol, and 45-55 parts of deionized water. This wellbore stabilizer rapidly forms an isolating outer film on the surface and internal pores of mudstone and coal, achieving complete water repellency and water blocking, thereby effectively inhibiting the development of microcracks inside the rock, effectively ensuring the overall structural strength of the formation, and also having a temperature resistance of up to 150℃.

Description

Technical Field

[0001] This invention belongs to the field of drilling fluid technology, specifically relating to a wellbore stabilizer for coal and rock gas wells, its preparation method, and its application. Background Technology

[0002] Wellbore stability in weak formations during coal gas well drilling has always been a major concern, directly impacting wellbore safety and drilling / completion cycles. With increasing national demand for natural gas resources, the development of unconventional natural gas resources will be strengthened. Taking the Jizhong Depression in the Bohai Bay Basin of China as an example, the mudstone formations near coal gas well reservoirs are highly water-sensitive, loose in texture, and highly heterogeneous, with fragmented sandstone-mudstone junctions. The coal reservoirs are deep, and the bottomhole temperature is high. Furthermore, the coal formations contain clay minerals, and the coal body exhibits well-developed cleavage and microfractures. Wellbore instability is caused by two main factors: firstly, the ingress of fluids along cleavage or microfractures into the coal body causes localized hydration of clay minerals, weakening intergranular bonding; secondly, the coal body is brittle and easily broken, making it prone to downhole collapse due to drill string impacts.

[0003] Currently, common drilling fluid systems for coal and gas wells employ conventional polymer macromolecular particles to seal formation pores, increasing drilling fluid salinity and column pressure to improve wellbore stability. However, conventional polymers are prone to failure under high-temperature conditions and cannot effectively seal pores in mudstone and coal formations. High-salinity drilling fluids penetrate deep into the formation, failing to guarantee overall formation inhibition, and the drilling fluid column pressure window is difficult to accurately control in practical field applications, often leading to downhole complexity. Therefore, further improvements to wellbore stabilizing materials for drilling fluids are necessary.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a wellbore stabilizer for drilling fluid in coal and rock gas wells, its preparation method, and its application. This wellbore stabilizer achieves thorough water repellency and water blocking by rapidly forming an isolating outer film on the surface and internal pores of mudstone and coal, thereby effectively inhibiting the development of microcracks inside the rock, effectively ensuring the overall structural strength of the formation, and also having a temperature resistance of up to 150℃.

[0006] To overcome the shortcomings of the prior art, the present invention provides the following technical solution:

[0007] A wellbore stabilizer for drilling fluid used in coal and rock gas wells, comprising the following raw material components by weight: 5-10 parts of 2-acrylamide-2-methylpropanesulfonic acid, 1-5 parts of N,N-dimethylacrylamide, 0.1-1 parts of dimethyldiallylammonium chloride, 0.05-0.1 parts of N,N-methylenebisacrylamide, 0.1-1 parts of octylphenol polyoxyethylene ether, 10-20 parts of soda ash, 0.05-0.2 parts of ammonium persulfate, 15-20 parts of styrene, 0.1-1 parts of emulsifier, 15-30 parts of acid-soluble skeleton material, 15-20 parts of deformable polymer material, 15-20 parts of polyamine shale inhibitor, 45-55 parts of anhydrous ethanol, and 45-55 parts of deionized water.

[0008] Further, by weight, it includes the following raw material components: 8 parts of 2-acrylamide-2-methylpropanesulfonic acid, 3 parts of N,N-dimethylacrylamide, 0.3 parts of dimethyldiallylammonium chloride, 0.1 parts of N,N-methylenebisacrylamide, 0.5 parts of octylphenol polyoxyethylene ether, 15 parts of soda ash, 0.1 parts of ammonium persulfate, 20 parts of styrene, 0.5 parts of emulsifier, 20 parts of acid-soluble skeleton material, 15 parts of deformable polymer material, 15 parts of polyamine shale inhibitor, 45 parts of anhydrous ethanol, and 55 parts of deionized water.

[0009] Furthermore, the acid-soluble skeleton material is selected from calcium carbonate particles or marble particles, or a combination thereof.

[0010] Furthermore, the calcium carbonate particles or marble particles have a mesh size of 400, 800, or 1000.

[0011] Furthermore, the deformable polymer material is selected from any one of styrene-butadiene-styrene block copolymers, styrene-isoprene-styrene block copolymers, styrene-ethylene-butene-styrene block copolymers, and styrene-ethylene-propylene-styrene block copolymers.

[0012] Furthermore, the polyamine shale inhibitor is selected from any one of chain polyamine shale inhibitors, hyperbranched polyamine shale inhibitors, polyquaternary amine shale inhibitors, and aromatic amine shale inhibitors.

[0013] Furthermore, the emulsifier is selected from any one of dodecyl dimethyl ammonium chloride, dodecyl dimethyl benzyl ammonium chloride, dodecyl trimethyl ammonium chloride, and sodium dodecyl sulfate.

[0014] In addition, the present invention also provides a method for preparing the wellbore stabilizer for drilling fluid used in coal and rock gas wells as described above, comprising the following steps:

[0015] S1. Mix 2-acrylamido-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, dimethyldiallylammonium chloride, N,N-methylenebisacrylamide, and octylphenol polyoxyethylene ether, and stir until homogeneous to obtain mixture A.

[0016] S2. Mix anhydrous ethanol and deionized water and stir until homogeneous to obtain mixture B;

[0017] S3. Add mixture A to mixture B and stir well. Then add soda ash to adjust the pH value to weakly alkaline to obtain mixture C.

[0018] S4. Add styrene and emulsifier to mixture C, stir well, and then add ammonium persulfate to carry out the polymerization reaction to obtain polymer D;

[0019] S5. After mixing polymer D, acid-soluble skeleton material, deformable polymer material, and polyamine shale inhibitor, stir evenly to obtain the wellbore stabilizer for drilling fluid in coal and rock gas wells.

[0020] Further, in step S4, the conditions for the polymerization reaction are: reaction temperature 75-85℃, reaction pressure 0.8-1.2MPa, and reaction time 30-35min.

[0021] In addition, the present invention also provides a drilling fluid, including the above-mentioned drilling fluid wellbore stabilizer for coal and rock gas wells or the drilling fluid wellbore stabilizer for coal and rock gas wells prepared by the above-mentioned preparation method.

[0022] Compared with the prior art, the technical solution of the present invention has at least the following technical effects:

[0023] (1) The wellbore stabilizer for drilling fluid in coal gas wells of the present invention utilizes plugging particles of different sizes and deformable plugging particles to establish a micro-nano-scale multi-scale plugging technology near micro-fractures, combined with shale porosity inhibition technology to reduce the risk of drilling fluid intrusion; at the same time, it improves the intergranular cementation of shale by mainly using polyamine shale inhibitors inside the micro-fractures, maintains stress balance, thereby increasing the effective stress near the wellbore from the inside out and strengthening the wellbore stability; thus, it reduces the risk of wellbore instability during drilling in weakly cemented coal and mudstone formations of coal gas wells.

[0024] (2) The well wall stabilizer for drilling fluid in coal and rock gas wells of the present invention can rely on intermolecular interactions and special film structure to achieve thorough water-repellent and water-blocking purpose by rapidly isolating the outer film on the surface and internal pores of mudstone and coal, thereby effectively inhibiting the development of microcracks in the rock and effectively ensuring the overall structural strength of the formation.

[0025] (3) The wellbore stabilizer for drilling fluid in coal and rock gas wells of the present invention has a temperature resistance of up to 150°C. After 16 hours of high-temperature aging, the basic parameters of drilling fluid such as API filtration loss, viscosity, and dynamic shear force change by less than 15%. The micro-nano particles are not easily degraded under high temperature conditions and can be applied to most downhole conditions of coal and rock gas wells. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Those skilled in the art should understand that the embodiments described are merely illustrative of the invention and should not be considered as specific limitations thereof. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Process parameters not specifically specified in the following embodiments are generally performed under conventional conditions.

[0027] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0028] According to a first aspect of the present invention, a wellbore stabilizer for drilling fluid in coal and gas wells is provided, comprising, by weight, the following raw material components: 5-10 parts (e.g., 5, 6, 7, 8, 9, 10 parts) of 2-acrylamide-2-methylpropanesulfonic acid, 1-5 parts (e.g., 1, 2, 3, 4, 5 parts) of N,N-dimethylacrylamide, 0.1-1 part (e.g., 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 part) of N,N-methylenebisacrylamide, and 0.05-... 0.1 parts (e.g., 0.05 parts, 0.06 parts, 0.07 parts, 0.08 parts, 0.09 parts, 0.1 parts), 0.1-1 parts (e.g., 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 part) of octylphenol polyoxyethylene ether, 10-20 parts (e.g., 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts) of soda ash, and 0.05-0.2 parts (e.g., 0.05 parts, 0.06 parts, 0.07 parts, 0.08 parts, 0.09 parts) of ammonium persulfate. 0.1 parts, 0.12 parts, 0.14 parts, 0.16 parts, 0.18 parts, 0.2 parts), 15-20 parts of styrene (e.g., 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts), 0.1-1 part of emulsifier (e.g., 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 part), 15-30 parts of acid-soluble matrix material (e.g., 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, 25 parts, 26 parts, 27 parts, 28 parts, 29 parts). The following are the ingredients: 15-20 parts of deformable polymer material (e.g., 15, 16, 17, 18, 19, 20 parts), 15-20 parts of polyamine shale inhibitor (e.g., 15, 16, 17, 18, 19, 20 parts), 45-55 parts of anhydrous ethanol (e.g., 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55 parts), and 45-55 parts of deionized water (e.g., 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55 parts).

[0029] This invention is based on the synthesis of nano-plugging materials, supplemented with acid-soluble framework materials, deformable polymers, polyamine shale inhibitors, and other key materials, to formulate a wellbore stabilizer for coal and gas well drilling fluids. This wellbore stabilizer utilizes plugging particles of different sizes and deformable plugging particles to establish a micro-nano-scale multi-scale plugging technology near micro-fractures, combined with shale porosity inhibition technology to reduce the risk of drilling fluid intrusion. Simultaneously, within the micro-fractures, polyamine shale inhibitors primarily enhance the intergranular cementation of shale, maintaining stress balance, thereby increasing the effective stress near the wellbore from the inside out and strengthening wellbore stability. This reduces the risk of wellbore instability during drilling in weakly cemented coal and mudstone formations in coal and gas wells. Furthermore, relying on intermolecular interactions and a special layered structure, it achieves thorough water repellency and water blocking through a rapidly isolating outer film on the surface and within the pores of mudstone and coal, effectively inhibiting the development of micro-cracks within the rock and ensuring the overall structural strength of the formation.

[0030] The weight portions described in this invention mainly include the disclosed numerical range, any value (including integers and decimals) within the disclosed range, or an interval between any two values, or multiple discontinuous intervals. It also includes values ​​or numerical ranges whose effects are expected to be similar to the endpoints of the numerical range, such as 5-10 parts. This does not only include 5, 6, 7, 8, 9, 10 parts, or any interval between any two parts. Other numerical ranges, not listed individually, are all included in this invention. Therefore, this invention also includes sub-ranges of any directly disclosed numerical range or any specific value within that range.

[0031] To further adapt this invention to wellbore stabilizers for drilling fluids used in coal and gas wells, the present invention investigated the influence of different proportions of various components on their effectiveness, and obtained a more optimal component ratio as follows: by weight, the components include the following raw materials: 8 parts of 2-acrylamide-2-methylpropanesulfonic acid, 3 parts of N,N-dimethylacrylamide, 0.3 parts of dimethyldiallyl ammonium chloride, 0.1 parts of N,N-methylenebisacrylamide, 0.5 parts of octylphenol polyoxyethylene ether, 15 parts of soda ash, 0.1 parts of ammonium persulfate, 20 parts of styrene, 0.5 parts of emulsifier, 20 parts of acid-soluble skeleton material, 15 parts of deformable polymer material, 15 parts of polyamine shale inhibitor, 45 parts of anhydrous ethanol, and 55 parts of deionized water.

[0032] In the aforementioned drilling fluid wellbore stabilizer for coal and rock gas wells, as a preferred embodiment, the acid-soluble skeleton material is selected from calcium carbonate particles or marble particles, or a combination thereof. More preferably, the calcium carbonate particles or marble particles have a mesh size of 400, 800, or 1000. Using these three mesh sizes in combination results in a denser mud cake and less water loss.

[0033] In the above-mentioned drilling fluid wellbore stabilizer for coal and gas wells, as a preferred embodiment, the deformable polymer material is selected from any one of styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene-ethylene-butene-styrene block copolymer (SEBS), and styrene-ethylene-propylene-styrene block copolymer (SEPS).

[0034] In the aforementioned drilling fluid wellbore stabilizers for coal and gas wells, as a preferred embodiment, the polyamine shale inhibitor is selected from any one of chain-like polyamine shale inhibitors, hyperbranched polyamine shale inhibitors, polyquaternary amine shale inhibitors, and aromatic amine shale inhibitors. Specifically, the chain-like polyamine shale inhibitor is selected from Sinopec Bosheng's product, model POLYAMINE; the hyperbranched polyamine shale inhibitor is selected from Shandong Deshunyuan's product, model AP-1; the polyquaternary amine shale inhibitor is selected from Shark Oil's product, model HYPERHIB; and the aromatic amine shale inhibitor is selected from Hengju Biotechnology's product, model HJP-103.

[0035] In the above-mentioned drilling fluid wellbore stabilizer for coal and rock gas wells, as a preferred embodiment, the emulsifier is selected from any one of dodecyl dimethyl ammonium chloride, dodecyl dimethyl benzyl ammonium chloride, dodecyl trimethyl ammonium chloride, and sodium dodecyl sulfate.

[0036] According to a second aspect of the present invention, a method for preparing a wellbore stabilizer for drilling fluid used in coal and rock gas wells as described above is provided, comprising the following steps:

[0037] S1. Mix 2-acrylamido-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, dimethyldiallylammonium chloride, N,N-methylenebisacrylamide, and octylphenol polyoxyethylene ether, and stir until homogeneous to obtain mixture A.

[0038] S2. Mix anhydrous ethanol and deionized water and stir until homogeneous to obtain mixture B;

[0039] S3. Add mixture A to mixture B and stir well. Then add soda ash to adjust the pH value to weakly alkaline (pH value of 7-8.5) to obtain mixture C.

[0040] S4. Add styrene and emulsifier to mixture C, stir well, and then add ammonium persulfate to carry out the polymerization reaction to obtain polymer D;

[0041] S5. After mixing polymer D, acid-soluble skeleton material, deformable polymer material, and polyamine shale inhibitor, stir evenly to obtain the wellbore stabilizer for drilling fluid in coal and rock gas wells.

[0042] Reaction principle:

[0043] Initiation stage: Ammonium persulfate decomposes at 80℃ to generate sulfate radicals (·SO4). - This triggers free radical polymerization.

[0044] Chain growth: Free radicals attack the double bonds of monomers (acrylamide, allyl, styrene, etc.), forming a chain growth.

[0045] Crosslinking reaction: The bisacrylamide structure of MBA connects different polymer chains to form a three-dimensional network. Electrostatic interaction: AMPS(-SO3) - It forms a polyionic complex with DMDAAC(+N(CH3)2), affecting chain conformation and phase separation.

[0046] Expected structure: Hydrophobic segments of styrene and DMAA form a physically cross-linked and microphase-separated structure. OP-10 micelles encapsulate the hydrophobic components, forming core-shell microparticles. Molecular weight is 8000-30000.

[0047] In the above preparation method, as a preferred embodiment, in step S4, the conditions of the polymerization reaction are: reaction temperature 75-85℃ (e.g., 75℃, 80℃, 85℃), reaction pressure 0.8-1.2MPa (e.g., 0.8MPa, 0.9MPa, 1.0MPa, 1.1MPa, 1.2MPa), and reaction time 30-35min (e.g., 30min, 31min, 32min, 33min, 34min, 35min).

[0048] According to a third aspect of the present invention, a drilling fluid is provided, comprising the above-described drilling fluid wellbore stabilizer for coal and rock gas wells or the drilling fluid wellbore stabilizer for coal and rock gas wells prepared by the above-described preparation method.

[0049] The present invention will now be described in detail with reference to embodiments thereof. These examples are provided by way of explanation and not by way of limitation. In fact, those skilled in the art will recognize that modifications and variations can be made to the present invention without departing from its scope or spirit. For example, a feature shown or described as part of one embodiment may be used in another embodiment to produce yet another embodiment. Therefore, it is desirable that the present invention encompass such modifications and variations that fall within the scope of the appended claims and their equivalents.

[0050] In the embodiments of the present invention, unless otherwise specified, the experimental methods used are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0051] Example 1

[0052] This embodiment provides a wellbore stabilizer for drilling fluid in coal and rock gas wells. The raw material components and preparation method are as follows:

[0053] (1) Mix 8 parts of 2-acrylamide-2-methylpropanesulfonic acid, 3 parts of N,N-dimethylacrylamide, 0.3 parts of dimethyldiallylammonium chloride, 0.1 parts of N,N-methylenebisacrylamide, and 0.5 parts of octylphenol polyoxyethylene ether, and add them to a stirring vessel. Stir thoroughly at room temperature to obtain a preliminary sample of nano-sealing material.

[0054] (2) Add the initial sample of nano-blocking material to a mixture of 45 parts anhydrous ethanol and 55 parts deionized water, and stir thoroughly in a stirred tank at room temperature to obtain a mixed solution of the initial sample of nano-blocking material.

[0055] (3) After thoroughly mixing the initial sample of nano-sealing material, add 15 parts of soda ash to adjust the pH of the mixed solution to weak alkalinity. Add 20 parts of styrene and 0.5 parts of sodium dodecyl sulfate to the mixed solution and stir thoroughly in the reactor to form a stable emulsion. Then add 0.1 parts of ammonium persulfate to the reactor, purge with nitrogen and adjust the temperature inside the reactor to 80 degrees Celsius. Maintain the pressure inside the reactor at 1 MPa and continue the reaction for 30 minutes to obtain the nano-sealing material, which is a milky white liquid.

[0056] (4) Under room temperature conditions, the nano-sealing material obtained above, 20 parts of calcium carbonate particles with a mass ratio of 400 mesh: 800 mesh: 1000 mesh = 1:1:1, 15 parts of styrene-ethylene-butene-styrene block copolymer, and 15 parts of chain polyamine shale inhibitor are mixed evenly in a mixing and stirring device to obtain a gray viscous liquid, which is the wellbore stabilizer for drilling fluid in coal gas wells in this embodiment.

[0057] Example 2

[0058] This embodiment provides a wellbore stabilizer for drilling fluid in coal and rock gas wells. The raw material components and preparation method are as follows:

[0059] (1) Mix 8 parts of 2-acrylamide-2-methylpropanesulfonic acid, 3 parts of N,N-dimethylacrylamide, 0.3 parts of dimethyldiallylammonium chloride, 0.1 parts of N,N-methylenebisacrylamide, and 0.5 parts of octylphenol polyoxyethylene ether, and add them to a stirring vessel. Stir thoroughly at room temperature to obtain a preliminary sample of nano-sealing material.

[0060] (2) Add the initial sample of nano-blocking material to a mixture of 45 parts anhydrous ethanol and 55 parts deionized water, and stir thoroughly in a stirred tank at room temperature to obtain a mixed solution of the initial sample of nano-blocking material.

[0061] (3) After thoroughly mixing the initial sample of nano-sealing material, add 15 parts of soda ash to adjust the pH of the mixed solution to weak alkalinity. Add 20 parts of styrene and 1 part of dodecyl dimethyl ammonium chloride to the mixed solution and stir thoroughly in the reactor to form a stable emulsion. Then add 0.1 parts of ammonium persulfate to the reactor, purge with nitrogen and adjust the temperature inside the reactor to 80 degrees Celsius. Maintain the pressure inside the reactor at 1 MPa and continue the reaction for 30 minutes to obtain the nano-sealing material, which is a milky white liquid.

[0062] (4) Under room temperature conditions, the nano-sealing material obtained above, 15 parts of calcium carbonate particles with a mass ratio of 400 mesh: 800 mesh: 1000 mesh = 1:1:1, 10 parts of 1000 mesh marble particles, 15 parts of styrene-ethylene-propylene-styrene block copolymer, and 15 parts of polyquaternary shale inhibitor are mixed evenly in a mixing and stirring device to obtain a white viscous liquid, which is the wellbore stabilizer for drilling fluid in coal gas wells in this embodiment.

[0063] Experimental Example 1

[0064] The basic performance of the drilling fluid wall stabilizer for coal and rock gas wells prepared in Example 1 was evaluated: the temperature resistance of the wall stabilizer was evaluated by measuring the changes in the basic performance parameters of the formulation before and after high-temperature aging and rolling at 150°C.

[0065] The test method was as follows: Drilling fluid base slurry was prepared as follows: 800ml water + 32g bentonite + 1.6g Na2CO3. This base slurry was the basic formulation of the drilling fluid used in the field. 16g (2% addition) and 24g (3% addition) of the wellbore stabilizer from Example 1 were added under high-speed stirring. The basic properties of the system were tested. After rolling in a roller furnace at 150℃ for 16 hours and then completely cooled, the system was stirred at medium speed for 30 minutes. The basic properties of the aged drilling fluid system were then tested. The smaller the change in basic performance parameters before and after aging, the better the temperature resistance. The test results are shown in Table 1.

[0066] Table 1

[0067]

[0068] Table 1 shows that the addition of the wellbore stabilizer from Example 1 enhances the compactness and film-forming sealing ability of the mud cake, thereby significantly reducing medium-pressure filtration loss. The change rate of basic performance parameters of the test system before and after aging is less than 15%, which can stabilize the basic properties of the drilling fluid under simulated downhole conditions. As the dosage of the wellbore stabilizer from Example 1 increases, parameters such as system viscosity, dynamic shear force, and filtration loss tend to stabilize, and a dosage of 2% is determined to be the optimal dosage.

[0069] Experimental Example 2

[0070] An evaluation experiment was conducted on the drilling fluid wall stabilizer for coal and rock gas wells prepared in Example 1 to assess its sand bed plugging ability. The plugging capacity of the wall stabilizer was evaluated by measuring the penetration depth of the base slurry + wall stabilizer formulation into quartz sand beds of different mesh sizes. A lower penetration depth indicates a better plugging effect.

[0071] The test method was as follows: A drilling fluid base slurry was prepared using 800ml of clean water + 32g of bentonite + 1.6g of Na₂CO₃. This base slurry was the basic formulation for the drilling fluid used in the field. 16g of the wellbore stabilizer from Example 1 was added under high-speed stirring. The penetration depth of the base slurry system containing the wellbore stabilizer from Example 1 into 20-40 mesh, 40-80 mesh, 80-100 mesh, and 100-120 mesh quartz sand beds was tested within 480 minutes. A lower penetration depth into the sand bed indicates a stronger sealing ability of the wellbore stabilizer. The test results are shown in Table 2.

[0072] Table 2

[0073]

[0074]

[0075] Table 2 shows that the addition of the wellbore stabilizer in Example 1 helps to enhance the compactness and plugging ability of the base slurry in the sand bed, thereby significantly reducing the depth of the base slurry intrusion into the sand bed. The denser the sand bed, the stronger the plugging ability of the base slurry system.

[0076] Experimental Example 3

[0077] The linear expansion evaluation experiment of bentonite samples was carried out on the drilling fluid wall stabilizer for coal and rock gas wells prepared in Example 1: The inhibition performance of Example 1 was verified by measuring the readings of bentonite samples after soaking in water and water + well wall stabilizer of Example 1 for 24 hours. The test results are shown in Table 3.

[0078] Table 3

[0079] test solution Sample expansion reading, mm Sample expansion reduction rate, mm Clear water 15.77 / Water + 2% Example 1 8.04 49.02％

[0080] Table 3 shows that the addition of the wellbore stabilizer in Example 1 significantly reduced the swelling of the bentonite sample and greatly improved its inhibition performance. This demonstrates that the wellbore stabilizer can effectively enhance formation inhibition performance.

[0081] Test Example 4

[0082] A rolling recovery rate evaluation experiment was conducted on the drilling fluid wall stabilizer for coal and rock gas wells prepared in Example 1: Coal and mudstone cuttings from the Taiyuan Formation at 2450m and 2520m of the Xintan 1 well in the Baxian Depression of the Jizhong Depression in the Bohai Bay Basin were weighed and soaked in clean water and clean water + 2% of the solution in Example 1, respectively. After hot rolling at 150℃ for 16h, the cuttings recovery rate data were tested, and the cuttings recovery rate data are shown in Table 4 below.

[0083] Table 4

[0084]

[0085] The cuttings recovery rate data in Table 4 show that the water + Example 1 wellbore stabilizer formulation has better inhibition performance compared to water alone. After hot rolling at 150℃, two groups of coal and mudstone formations from different strata showed higher recovery rates in the water + 2% Example 1 wellbore stabilizer formulation, proving that this wellbore stabilizer can improve wellbore stability in coal and mudstone formations under simulated downhole conditions.

[0086] The foregoing has described and evaluated some embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. This does not affect the essential content of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the present invention, still fall within the protection scope of the present invention.

Claims

1. A wellbore stabilizer for drilling fluid used in coal and rock gas wells, characterized in that, By weight, it comprises the following raw material components: 5-10 parts of 2-acrylamide-2-methylpropanesulfonic acid, 1-5 parts of N,N-dimethylacrylamide, 0.1-1 parts of dimethyldiallylammonium chloride, 0.05-0.1 parts of N,N-methylenebisacrylamide, 0.1-1 parts of octylphenol polyoxyethylene ether, 10-20 parts of soda ash, 0.05-0.2 parts of ammonium persulfate, 15-20 parts of styrene, 0.1-1 parts of emulsifier, 15-30 parts of acid-soluble skeleton material, 15-20 parts of deformable polymer material, 15-20 parts of polyamine shale inhibitor, 45-55 parts of anhydrous ethanol, and 45-55 parts of deionized water.

2. The wellbore stabilizer for drilling fluid in coal and rock gas wells according to claim 1, characterized in that, By weight, it comprises the following raw material components: 8 parts 2-acrylamide-2-methylpropanesulfonic acid, 3 parts N,N-dimethylacrylamide, 0.3 parts dimethyldiallylammonium chloride, 0.1 parts N,N-methylenebisacrylamide, 0.5 parts octylphenol polyoxyethylene ether, 15 parts soda ash, 0.1 parts ammonium persulfate, 20 parts styrene, 0.5 parts emulsifier, 20 parts acid-soluble skeleton material, 15 parts deformable polymer material, 15 parts polyamine shale inhibitor, 45 parts anhydrous ethanol, and 55 parts deionized water.

3. The wellbore stabilizer for drilling fluid in coal and rock gas wells according to claim 1, characterized in that, The acid-soluble skeleton material is selected from calcium carbonate particles or marble particles, or a combination thereof.

4. The wellbore stabilizer for drilling fluid in coal and rock gas wells according to claim 3, characterized in that, The calcium carbonate particles or marble particles have a mesh size of 400, 800, or 1000.

5. The wellbore stabilizer for drilling fluid in coal and rock gas wells according to claim 1, characterized in that, The deformable polymer material is selected from any one of styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, styrene-ethylene-butene-styrene block copolymer, and styrene-ethylene-propylene-styrene block copolymer.

6. The wellbore stabilizer for drilling fluid in coal and rock gas wells according to claim 1, characterized in that, The polyamine shale inhibitor is selected from any one of the following: chain polyamine shale inhibitors, hyperbranched polyamine shale inhibitors, polyquaternary amine shale inhibitors, and aromatic amine shale inhibitors.

7. The wellbore stabilizer for drilling fluid in coal and rock gas wells according to claim 1, characterized in that, The emulsifier is selected from any one of dodecyl dimethyl ammonium chloride, dodecyl dimethyl benzyl ammonium chloride, dodecyl trimethyl ammonium chloride, and sodium dodecyl sulfate.

8. A method for preparing a wellbore stabilizer for drilling fluid in coal and rock gas wells as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Mix 2-acrylamido-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, dimethyldiallylammonium chloride, N,N-methylenebisacrylamide, and octylphenol polyoxyethylene ether, and stir until homogeneous to obtain mixture A. S2. Mix anhydrous ethanol and deionized water and stir until homogeneous to obtain mixture B; S3. Add mixture A to mixture B and stir well. Then add soda ash to adjust the pH value to weakly alkaline to obtain mixture C. S4. Add styrene and emulsifier to mixture C, stir well, and then add ammonium persulfate to carry out the polymerization reaction to obtain polymer D; S5. After mixing polymer D, acid-soluble skeleton material, deformable polymer material, and polyamine shale inhibitor, stir evenly to obtain the wellbore stabilizer for drilling fluid in coal and rock gas wells.

9. The preparation method according to claim 8, characterized in that, In step S4, the polymerization reaction conditions are: reaction temperature 75-85℃, reaction pressure 0.8-1.2MPa, and reaction time 30-35min.

10. A drilling fluid, characterized in that, This includes the wellbore stabilizer for drilling fluid used in coal and rock gas wells as described in any one of claims 1-7, or the wellbore stabilizer for drilling fluid used in coal and rock gas wells prepared by the method of claim 8 or 9.

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