High-performance leak-proof plugging gel for fractured formation and preparation method of high-performance leak-proof plugging gel

Abstract

The invention provides a high-performance leak-proof plugging gel for fractured formations and a preparation method thereof, and belongs to the technical field of oil and gas field drilling fluids. The gel is prepared from a copolymerization reaction monomer, fibers, a surfactant and other components, and has high pressure bearing capacity, good temperature and salt resistance, excellent mechanical property and environmental response capacity. The intelligent plugging device can effectively plug a fractured formation leakage channel, adapts to a high-temperature, high-pressure and high-salt environment, and realizes intelligent plugging. The preparation method is simple and small in environmental pollution. The effectiveness and the practicability of the method are verified through specific embodiments, an effective solution is provided for oil and gas drilling fractured formation leaking stoppage, and the method has important industrial application value and market prospects.

Description

Technical Field

[0001] The invention discloses a high-performance leak-proof and plugging gel for fractured formations and a preparation method thereof, and relates to the technical field of oil and gas field drilling fluids. Background Art

[0002] In oil and gas drilling projects, the problem of well leakage has always been a major challenge faced by engineering and technical personnel. Well leakage not only leads to drilling fluid loss and increases drilling costs, but may also cause serious safety accidents such as well wall collapse and drill stuck, seriously affecting the smooth progress of drilling operations. In mining operations, we often face the problem of loose cementation of sandstone and conglomerate in the formation. These formations have weak pressure bearing capacity and relatively developed pores, so they are prone to complex situations such as well leakage. During the drilling process, the positive and negative pressures of the wellbore are constantly changing. In this case, the formation is easily compressed, thereby forming artificially induced cracks, which increases the complexity of the leakage problem. In addition, in some areas, the quicksand layer is relatively developed. Once leakage occurs, it may cause the well wall to become unstable, thereby increasing the risk of sand bridge drill stuck. Although the currently used anti-leakage and plugging treatment agent can physically block the leakage channel through particle size matching and increase the leakage pressure of the formation, it is not effective for formations with artificially induced cracks and quicksand layers, and has little effect on improving the pressure bearing capacity of the formation and stabilizing the well wall. Existing plugging materials usually have deficiencies in pressure bearing capacity, temperature and salt resistance, etc. In high temperature, high pressure and high salt environments, the performance of these materials is often difficult to meet actual needs. Specifically:

[0003] 1. Insufficient pressure bearing capacity: Existing materials are prone to cracking or deformation under high pressure and cannot effectively block the leakage channels of fractured formations.

[0004] 2. Poor temperature resistance: In high temperature environments, the stability and mechanical properties of existing materials will decrease significantly, affecting their plugging effects.

[0005] 3. Weak salt resistance: In high-salt environments, existing materials are not able to resist salt invasion, which can easily lead to deterioration of drilling fluid performance and increase the risk of water loss and well wall collapse.

[0006] In view of the shortcomings of the prior art, the present invention provides a new type of high-performance leak-proof and plugging gel and a preparation method thereof. The gel of the present invention has the following innovative features:

[0007] 1. Excellent mechanical properties: Through specific chemical composition and structural design, the gel of the present invention has high pressure bearing capacity and good mechanical properties, and can effectively block the leakage channel of fractured formations.

[0008] 2. Good environmental responsiveness: The gel of the present invention can intelligently respond to different formation environments and automatically adjust its performance to adapt to extreme conditions such as high temperature, high pressure and high salinity.

[0009] 3. High temperature and salt resistance: Through special chemical design and material selection, the gel of the present invention can still maintain stable performance in high temperature and high salt environments, avoiding performance degradation caused by environmental changes.

[0010] 4. Simple preparation method: The gel preparation method of the present invention is simple and feasible, easy to scale up production, and has little impact on the environment.

[0011] Through these innovations, the leak-proof and plugging gel of the present invention is expected to play an important role in oil and gas drilling projects, improve the performance of drilling fluids, reduce drilling risks, and improve drilling efficiency. Summary of the invention

[0012] The present invention aims to solve the problem of leakage in fractured formations during oil and gas drilling, and in particular, to provide a new type of high-performance leak-proof and plugging gel and its preparation method in view of the deficiencies of existing plugging materials in terms of pressure bearing capacity, temperature resistance and salt resistance. The gel of the present invention can adapt to high temperature, high pressure and high salt environments, and at the same time has excellent mechanical properties and environmental response capabilities, thereby achieving more effective plugging.

[0013] The technical solution of the present invention mainly includes the following aspects:

[0014] 1. New gel formula: The leak-proof and plugging gel of the present invention adopts a specific chemical composition, including copolymerization monomers, ultrafine plant fibers, surfactants, initiators, cosolvents, promoters, polymer powders, saline solution and water. The synergistic effect of these components gives the gel excellent comprehensive properties.

[0015] 2. Innovative design of copolymer monomers: The copolymer monomers are composed of hydrophilic monomers, hydrophobic monomers and functional group molecules. By precisely controlling the mass ratio of each component, the high pressure bearing capacity and good environmental adaptability of the gel can be achieved.

[0016] 3. Application of ultrafine plant fibers: In the present invention, ultrafine plant fibers are effectively integrated into the gel system through interaction with polymer powder, thereby significantly improving the mechanical properties and environmental adaptability of the gel. These fibers form a three-dimensional network structure in the gel matrix, which enhances the strength and toughness of the gel. As an adhesive, polymer powder enhances the interaction between the fiber and the gel through physical or chemical bonding, and may participate in the chemical cross-linking reaction to form a stable three-dimensional cross-linked network. In addition, the water absorption and swelling properties of ultrafine plant fibers help to plug tiny pores and reduce the loss of drilling fluid. The environmental responsiveness of polymer powder enables the gel to intelligently adjust its performance to adapt to different formation conditions. This combination method not only improves the stability of the gel, especially in high temperature, high pressure and high salt environments, but also optimizes the preparation process of the gel, achieving effective plugging in fractured formations and stable maintenance of drilling fluid performance.

[0017] 4. High temperature and high salt resistance: Through special chemical design, the gel of the present invention can still maintain stable performance in high temperature and high salt environments, effectively avoiding performance degradation caused by environmental changes.

[0018] 5. Simple preparation method: The gel preparation method of the present invention is simple and feasible, easy to scale up production, and has little impact on the environment.

[0019] The technical solution of the present invention is as follows:

[0020] A gel plugging agent for fractured formations, comprising the following raw materials in percentage by mass:

[0021] The copolymerization monomers are composed of hydrophilic monomers, hydrophobic monomers and functional group molecules, and the mass ratio of the three is 6:3:1. The hydrophilic monomers include but are not limited to acrylamide, acrylic acid, etc., the hydrophobic monomers include octadecyl methacrylate, etc., and the functional group molecules include scleroglucan, chitosan, etc.;

[0022] The dosage of the ultrafine plant fiber is 15-25%, characterized in that the ultrafine plant fiber is a mixture of 150-mesh wood fiber and 200-mesh wood fiber, wherein the 150-mesh wood fiber and the 200-mesh wood fiber are both wood fibers with a sieve residue of ≤10%, and the mixed weight ratio is 150-mesh wood fiber: 200-mesh wood fiber = 30:70;

[0023] Surfactant: The dosage is 2.0-4.0%, which acts as a stabilizer to promote the hydrophobic interaction between the hydrophilic monomer and the hydrophobic monomer and enhance the stability of the gel. Including but not limited to sodium tetrapropylene benzene sulfonate, sodium lauryl sulfate, etc.;

[0024] Initiator: The dosage is 1.0-2.0%, used to start the polymerization process of copolymerization monomers. Including but not limited to potassium persulfate, ammonium persulfate, etc.;

[0025] Cosolvent: The dosage is 1.5-2.0%, which accelerates the dissolution of initiators and promoters. Including but not limited to sulfates and / or nitrogen-containing compounds;

[0026] Accelerator: The dosage is 0.1-0.5% to accelerate the polymerization reaction. Including but not limited to 1,2-bis(dimethylamino)ethane, tetraethylenepentamine, etc.;

[0027] Polymer powder: The dosage is 0.2-0.6, which promotes the formation of gel network and increases the adhesion of gel;

[0028] Saline solution: The dosage is 0.5-5% to provide the electrolyte environment required for gelation.

[0029] The preparation method of the supramolecular gel plugging agent for fractured formations of the present invention comprises the following steps:

[0030] (1) A hydrophilic monomer and a hydrophobic monomer are mixed to form a mixed solution A.

[0031] (2) Add functional group molecules and surfactants to form a mixed solution B.

[0032] (3) Add initiator and cosolvent to form mixed solution C.

[0033] (4) Add accelerator and saline solution to form mixed solution D.

[0034] (5) Mix the mixed solution D with the ultrafine plant fiber and the polymer powder, and stir until they are evenly dispersed to obtain a mixed solution E.

[0035] (6) After nitrogen is introduced (to ensure that there is no oxygen interference during the polymerization reaction), the reaction is allowed to stand for a period of time at a specific temperature to obtain a supramolecular gel.

[0036] (7) After the reaction is completed, the obtained supramolecular gel is dried under certain conditions and then crushed to obtain a supramolecular gel plugging agent with a desired particle size or powder form to obtain the final product.

[0037] Preferably, the hydrophilic monomer is a combination of three or more of methacrylic acid (MAA), acrylic acid (AA), maleic acid (MA), 2-hydroxyethyl methacrylate (HEMA), methacrylic acid (MAA), and butyl acrylate (BA).

[0038] Preferably, the hydrophobic monomer is a combination of three or more of styrene (ST), butadiene (BD), isoprene (IP), isobutyl methacrylate (IBMA), isooctyl methacrylate (IOMA), and cyclohexyl methacrylate (CHMA).

[0039] Preferably, the functional group molecule is a combination of three or more of polyhydroxybutyrate (PHB), polylaurylamide (PA12), tragacanth gum, carboxymethyl cellulose (CMC), and polyvinyl pyrrolidone (PVP).

[0040] Preferably, the co-solvent is a combination of anhydrous calcium sulfate and ammonium chloride.

[0041] Preferably, the initiator is one or a combination of two or more of dibenzoyl peroxide (BPO), cyclohexanone peroxide, hydrogen peroxide, potassium persulfate, ammonium persulfate, and azobisisobutyl ester.

[0042] Preferably, the accelerator is one or a combination of two or more of 1,2-bis(dimethylamino)ethane, tetraethylenepentamine, aluminum trichloride, and tetramethylthiourea.

[0043] Preferably, the fiber is specifically: one or a combination of polypropylene fiber and polyvinyl alcohol fiber.

[0044] Preferably, the length of the fiber is 3-5 mm; the diameter of the fiber is 10-20 μm.

[0045] Preferably, the accelerator is one or a combination of two or more of 1,2-bis(dimethylamino)ethane, tetraethylenepentamine, aluminum trichloride, and tetramethylthiourea.

[0046] Preferably, the polymer powder is one or a combination of two of polyvinyl alcohol (PVA), polymethyl methacrylate (PMMA), and polyacrylamide (PAM).

[0047] Preferably, the particle size of the polymer powder is in the range of 200 to 1000 μm.

[0048] Preferably, in step (6), the temperature of the static reaction is 55-70° C., and the static reaction time is 6-8 hours. DETAILED DESCRIPTION

[0049] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the 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 article.

[0050] To make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be clearly and completely described below. If the specific conditions are not specified in the embodiments, they are carried out according to the normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially. The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0051] Example 1

[0052] A supramolecular gel plugging agent for fractured strata comprises the following raw materials in percentage by mass: 20% copolymerization monomer; 15% ultrafine plant fiber; 1.0% surfactant; 0.1% initiator; 0.1% cosolvent; 0.05% promoter; 1% polymer powder; 0.5% salt water solution; and the balance is water.

[0053] The copolymerization monomer is a combination of a hydrophilic monomer, a hydrophobic monomer and a functional group molecule, wherein the mass ratio of the hydrophilic monomer, the hydrophobic monomer and the functional group molecule is 6:3:1; the hydrophilic monomer is a combination of methacrylic acid, acrylic acid and maleic acid, wherein the mass ratio of methacrylic acid, acrylic acid and maleic acid is 4:5:1; the hydrophobic monomer is a combination of styrene, butadiene and isoprene, wherein the mass ratio of styrene, butadiene and isoprene is 7:2:1; the functional group molecule is a combination of tragacanth gum, carboxymethyl cellulose and polyvinyl pyrrolidone, wherein the mass ratio of tragacanth gum, carboxymethyl cellulose and polyvinyl pyrrolidone is 6:3:1.

[0054] The surfactant is a combination of sodium tetrapropylene benzene sulfonate and sodium lauryl sulfate, and the mass ratio of sodium tetrapropylene benzene sulfonate to sodium lauryl sulfate is 1:1.

[0055] The initiator is a combination of cyclohexanone peroxide and hydrogen peroxide, and the mass ratio of cyclohexanone peroxide to hydrogen peroxide is 1:4.

[0056] The co-solvent is a combination of anhydrous calcium sulfate and ammonium chloride in a mass ratio of 1:1.

[0057] The accelerator is a combination of 1,2-bis(dimethylamino)ethane and tetraethylenepentamine, and the mass ratio of 1,2-bis(dimethylamino)ethane to tetraethylenepentamine is 3:2.

[0058] The cellulose is a combination of polyvinyl alcohol fiber and polyester fiber, and the mass ratio of the polyvinyl alcohol fiber to the polyester fiber is 1:1.

[0059] Polyvinyl alcohol is selected as the polymer powder.

[0060] The saline solution is a sodium chloride solution with a concentration of 2.0 mol / L.

[0061] The preparation method of the supramolecular gel plugging agent for fractured formations comprises the following steps:

[0062] (1) adding the hydrophilic monomer and the hydrophobic monomer in the copolymerization monomer into water, stirring at a stirring speed of 500 rpm at 30° C. for 25 minutes to obtain a mixed solution A;

[0063] (2) adding functional group molecules and surfactants to the mixed solution A, stirring at a temperature of 30° C. and a stirring speed of 500 rpm for 30 minutes to obtain a mixed solution B;

[0064] (3) adding the initiator and the co-solvent to the mixed solution B, stirring at a stirring temperature of 40° C. and a stirring speed of 500 rpm for 30 minutes until the initiators and the co-solvents are completely dissolved to obtain a mixed solution C;

[0065] (4) adding an accelerator and a saline solution to the mixed solution C, stirring the mixture at 50° C. and 500 rpm for 30 minutes to obtain a mixed solution D;

[0066] (5) Mixing the mixed solution D with the ultrafine plant fiber and the polymer powder, stirring at 40° C. and 500 rpm for 30 minutes until the mixture is uniformly dispersed, to obtain a mixed solution E.

[0067] (6) The mixed solution E was placed in a three-necked flask, nitrogen was introduced, and the mixture was vacuumed. The mixture was then allowed to stand at 50°C for 6 hours until it was fully polymerized to obtain a supramolecular gel. The supramolecular gel was vacuum dried at 60°C for 24 hours and then crushed to obtain a supramolecular gel plugging agent for fractured formations, which was recorded as sample S1.

[0068] Example 2

[0069] A supramolecular gel plugging agent for fractured strata comprises the following raw materials in percentage by mass: 20% copolymerization monomer; 15% ultrafine plant fiber; 1.0% surfactant; 0.1% initiator; 0.1% cosolvent; 0.05% promoter; 1% polymer powder; 0.5% salt water solution; and the balance is water.

[0070] The copolymerization monomer is a combination of a hydrophilic monomer, a hydrophobic monomer and a functional group molecule, wherein the mass ratio of the hydrophilic monomer, the hydrophobic monomer and the functional group molecule is 6:3:1; the hydrophilic monomer is a combination of methacrylic acid, acrylic acid and butyl acrylate, wherein the mass ratio of methacrylic acid, acrylic acid and butyl acrylate is 4:5:1; the hydrophobic monomer is a combination of phenyl methacrylate, dodecyl methacrylate and isoprene, wherein the mass ratio of phenyl methacrylate, dodecyl methacrylate and isoprene is 7:2:1; the functional group molecule is a combination of polyimide, carboxymethyl cellulose and polyvinyl pyrrolidone, wherein the mass ratio of polyimide, carboxymethyl cellulose and polyvinyl pyrrolidone is 6:3:1.

[0071] The surfactant is a combination of sodium tetrapropylene benzene sulfonate and sodium lauryl sulfate, and the mass ratio of sodium tetrapropylene benzene sulfonate to sodium lauryl sulfate is 1:1.

[0072] The initiator is a combination of cyclohexanone peroxide and hydrogen peroxide, and the mass ratio of cyclohexanone peroxide to hydrogen peroxide is 1:4.

[0073] The co-solvent is a combination of anhydrous calcium sulfate and ammonium chloride in a mass ratio of 1:1.

[0074] The accelerator is a combination of 1,2-bis(dimethylamino)ethane and tetraethylenepentamine, and the mass ratio of 1,2-bis(dimethylamino)ethane to tetraethylenepentamine is 3:2.

[0075] The cellulose is a combination of polyvinyl alcohol fiber and polyester fiber, and the mass ratio of the polyvinyl alcohol fiber to the polyester fiber is 1:1.

[0076] Polyvinyl alcohol is selected as the polymer powder.

[0077] The saline solution is a sodium chloride solution with a concentration of 2.0 mol / L.

[0078] The preparation method of the supramolecular gel plugging agent for fractured formations is as described in Example 1, and the prepared supramolecular gel plugging agent is recorded as sample S2.

[0079] Example 3

[0080] A supramolecular gel plugging agent for fractured strata comprises the following raw materials in percentage by mass: 20% copolymerization monomer; 15% ultrafine plant fiber; 1.0% surfactant; 0.1% initiator; 0.1% cosolvent; 0.05% promoter; 1% polymer powder; 0.5% salt water solution; and the balance is water.

[0081] The copolymerization monomer is a combination of a hydrophilic monomer, a hydrophobic monomer and a functional group molecule, wherein the mass ratio of the hydrophilic monomer, the hydrophobic monomer and the functional group molecule is 6:3:1; the hydrophilic monomer is a combination of butyl acrylate, acrylic acid and ethylene glycol methacrylate, wherein the mass ratio of butyl acrylate, acrylic acid and ethylene glycol methacrylate is 4:5:1; the hydrophobic monomer is a combination of cyclohexyl methacrylate, isooctyl methacrylate and methyl methacrylate, wherein the mass ratio of cyclohexyl methacrylate, isooctyl methacrylate and methyl methacrylate is 7:2:1; the functional group molecule is a combination of polypropylene oxide, tragacanth gum and polyvinyl pyrrolidone, wherein the mass ratio of polypropylene oxide, tragacanth gum and polyvinyl pyrrolidone is 6:3:1.

[0082] The surfactant is a combination of myristic acid and sorbitan laurate, and the mass ratio of myristic acid to sorbitan laurate is 1:1.

[0083] The initiator is a combination of potassium persulfate and ammonium persulfate, and the mass ratio of potassium persulfate to ammonium persulfate is 1:4.

[0084] The co-solvent is a combination of anhydrous calcium sulfate and ammonium chloride in a mass ratio of 1:1.

[0085] The accelerator is a combination of tetramethylthiourea and cobalt acetylacetonate, and the mass ratio of tetramethylthiourea to cobalt acetylacetonate is 3:2.

[0086] The cellulose is selected from a mixture of 150-mesh wood fiber and 200-mesh wood fiber, and the mixed weight ratio is 150-mesh wood fiber: 200-mesh wood fiber = 30:70.

[0087] Polyvinyl alcohol is selected as the polymer powder.

[0088] The saline solution is a sodium chloride solution with a concentration of 2.0 mol / L.

[0089] The preparation method of the supramolecular gel plugging agent for fractured formations is as described in Example 1. The prepared supramolecular gel plugging agent is recorded as sample S3.

[0090] Example 4

[0091] A supramolecular gel plugging agent for fractured strata comprises the following raw materials in percentage by mass: 20% copolymerization monomer; 15% ultrafine plant fiber; 1.0% surfactant; 0.1% initiator; 0.1% cosolvent; 0.05% promoter; 1% polymer powder; 0.5% salt water solution; and the balance is water.

[0092] The copolymerization reaction monomer is a combination of a hydrophilic monomer, a hydrophobic monomer and a functional group molecule, wherein the mass ratio of the hydrophilic monomer, the hydrophobic monomer and the functional group molecule is 6:3:1; the hydrophilic monomer is a combination of butyl acrylate, N-vinyl pyrrolidone and ethylene glycol methacrylate, wherein the mass ratio of butyl acrylate, N-vinyl pyrrolidone and ethylene glycol methacrylate is 4:5:1; the hydrophobic monomer is a combination of cyclohexyl methacrylate, phenyl methacrylate and methyl methacrylate, wherein the mass ratio of cyclohexyl methacrylate, phenyl methacrylate and methyl methacrylate is 7:2:1; the functional group molecule is a combination of polyoxypropylene, polyimide and polyvinyl pyrrolidone, wherein the mass ratio of polyoxypropylene, polyimide and polyvinyl pyrrolidone is 6:3:1.

[0093] The surfactant is a combination of myristic acid and sorbitan laurate, and the mass ratio of myristic acid to sorbitan laurate is 1:1.

[0094] The initiator is a combination of potassium persulfate and ammonium persulfate, and the mass ratio of potassium persulfate to ammonium persulfate is 1:4.

[0095] The co-solvent is a combination of anhydrous calcium sulfate and ammonium chloride in a mass ratio of 1:1.

[0096] The accelerator is a combination of tetramethylthiourea and cobalt acetylacetonate, and the mass ratio of tetramethylthiourea to cobalt acetylacetonate is 3:2.

[0097] The cellulose is selected from a mixture of 150-mesh wood fiber and 200-mesh wood fiber, and the mixed weight ratio is 150-mesh wood fiber: 200-mesh wood fiber = 30:70.

[0098] Polyvinyl alcohol is selected as the polymer powder.

[0099] The saline solution is a sodium chloride solution with a concentration of 2.0 mol / L.

[0100] The preparation method of the supramolecular gel plugging agent for fractured formations is as described in Example 1. The prepared supramolecular gel plugging agent is recorded as sample S4.

[0101] Comparative Example 1

[0102] A supramolecular gel plugging agent for fractured formations, the raw material composition is as described in Example 1, except that: the formulation ratios of the components are different.

[0103] The specific component ratios are: 25% copolymerization monomer; 20% ultrafine plant fiber; 1.5% surfactant; 0.2% initiator; 0.2% cosolvent; 0.1% promoter; 1.5% polymer powder; 1.5% saline solution; and the balance is water.

[0104] The preparation method of the supramolecular gel plugging agent is as described in Example 1, and the obtained product is recorded as D1.

[0105] Comparative Example 2

[0106] A supramolecular gel plugging agent for fractured formations, the raw material composition is as described in Example 1, except that the mass ratio of the hydrophilic monomer, the hydrophobic monomer and the functional group molecule is 4:4:2.

[0107] The specific component ratios are: 25% copolymerization monomer; 20% ultrafine plant fiber; 1.5% surfactant; 0.2% initiator; 0.2% cosolvent; 0.1% promoter; 1.5% polymer powder; 1.5% saline solution; and the balance is water.

[0108] The preparation method of the supramolecular gel plugging agent is as described in Example 1, and the obtained product is recorded as D2.

[0109] Comparative Example 3

[0110] A supramolecular gel plugging agent for fractured formations, the raw material composition of which is as described in Example 1, except that no polymer powder is added.

[0111] The specific component ratios are: 20% copolymerization monomer; 15% ultrafine plant fiber; 1.0% surfactant; 0.1% initiator; 0.1% cosolvent; 0.05% promoter; 0.5% saline solution; and the balance is water.

[0112] The preparation method of the supramolecular gel plugging agent is as described in Example 1, and the obtained product is recorded as D3.

[0113] Comparative Example 4

[0114] A supramolecular gel plugging agent for fractured strata, the raw material composition of which is as described in Example 1, except that: no ultrafine plant fiber is added.

[0115] The specific component ratios are: 20% copolymerization monomer; 1.0% surfactant; 0.1% initiator; 0.1% cosolvent; 0.05% promoter; 1.5% polymer powder; 0.5% saline solution; and the balance is water.

[0116] The preparation method of the supramolecular gel plugging agent is as described in Example 1, and the obtained product is recorded as D4.

[0117] Comparative Example 5

[0118] A supramolecular gel plugging agent for fractured formations, the raw material composition is as described in Example 1, except that no co-solvent is added.

[0119] The specific component ratios are: 20% copolymerization monomer; 15% ultrafine plant fiber; 1.0% surfactant; 0.1% initiator; 0.05% promoter; 1% polymer powder; 0.5% saline solution; and the balance is water.

[0120] The preparation method of the supramolecular gel plugging agent is as described in Example 1, and the obtained product is recorded as D5.

[0121] Comparative Example 6

[0122] A supramolecular gel plugging agent for fractured formations, the raw material composition is as described in Example 1, except that: no surfactant is added.

[0123] The specific component ratios are: 20% copolymerization monomer; 15% ultrafine plant fiber; 0.1% initiator; 0.1% cosolvent; 0.05% promoter; 1% polymer powder; 0.5% saline solution; and the balance is water.

[0124] The preparation method of the supramolecular gel plugging agent is as described in Example 1, and the obtained product is recorded as D6.

[0125] Comparative Example 7

[0126] A supramolecular gel plugging agent for fractured formations, the raw material composition is as described in Example 1, except that no accelerant is added.

[0127] The specific component ratios are: 20% copolymerization monomer; 15% ultrafine plant fiber; 0.1% initiator; 0.1% cosolvent; 1% polymer powder; 0.5% saline solution; and the balance is water.

[0128] The preparation method of the supramolecular gel plugging agent is as described in Example 1, and the obtained product is recorded as D7.

[0129] Table 1 High temperature and high pressure plugging performance results of the embodiments and comparative examples

[0130]

[0131] Table 2 Initial apparent viscosity and initial elastic modulus and high temperature stability of the embodiments and comparative examples

[0132]

[0133] In summary, compared with the same series of drilling fluids, whether J or D series, the gel plugging agent obtained in Example 1 has higher initial strength, viscoelasticity, high temperature stability and high temperature and high pressure plugging performance.

Claims

1. A high-performance leak-proof and plugging gel for fractured formations and a preparation method thereof, characterized in that: It is composed of the following components by weight percentage: Copolymerization monomer 20-30%; Ultrafine plant fiber 15-25%; Surfactant 0.5-6.0%; Initiator 0.1-2.0%; Cosolvent 0.1-2.0%; Accelerator 0.05-0.5%; Polymer powder 1-5%; Saline solution 0.5-5%; The balance is water; The copolymerization monomer is a combination of a hydrophilic monomer, a hydrophobic monomer and a functional group molecule; the mass ratio of the hydrophilic monomer, the hydrophobic monomer and the functional group molecule in the copolymerization monomer is 5-7:2-4:

1.

2. According to the leak-proof and plugging gel of claim 1, the hydrophilic monomer is a combination of three or more of methacrylic acid (MAA), acrylic acid (AA), maleic acid (MA), 2-hydroxyethyl methacrylate (HEMA), methacrylic acid (MAA), butyl acrylate (BA), N-vinyl pyrrolidone (VP), N-methylacrylamide (NMAA), ethylene glycol methacrylate (PEGMA), and 2-acrylamido-2-methylpropanesulfonic acid (AMPS).

3. The leak-proof and plugging gel according to claim 1, wherein the hydrophobic monomer is a combination of three or more of styrene (ST), ethylenediene (BD), isoprene (IP), isobutyl methacrylate (IBMA), isooctyl methacrylate (IOMA), cyclohexyl methacrylate (CHMA), phenyl methacrylate (BzMA), dodecyl methacrylate (DDMA), trifluoropropyl methacrylate (TFEMA), and methyl methacrylate (MMA).

4. According to the leak-proof and plugging gel of claim 1, the functional group molecules are a combination of three or more of polyhydroxybutyrate (PHB), polydodecylamide (PA12), tragacanth gum, carboxymethyl cellulose (CMC), polyvinyl pyrrolidone (PVP), polypropylene oxide (PPO), polyimide (PI), and polyurea (PU).

5. The leak-proof and plugging gel according to claim 1, wherein the surfactant is one or a combination of two or more of sodium tetrapropylenesulfonate, sodium lauryl sulfate, fatty alcohol polyoxyethylene ether, myristic acid, sorbitan laurate, and betaine.

6. The leak-proof and plugging gel according to claim 1, wherein the cosolvent is a sulfate and / or a nitrogen-containing compound, the sulfate is anhydrous sodium sulfate or anhydrous calcium sulfate, and the nitrogen-containing compound is urea or ammonium chloride.

7. The leak-proof and plugging gel according to claim 1, wherein the initiator is one or a combination of two or more of dibenzoyl peroxide (BPO), cyclohexanone peroxide, hydrogen peroxide, potassium persulfate, ammonium persulfate, azobisisobutyl ester, dimethyl azobisisobutyrate, azobisisobutylimidazoline hydrochloride, and sodium sulfite.

8. The leak-proof and plugging gel according to claim 1, wherein the accelerator is one or a combination of two or more of 1,2-bis(dimethylamino)ethane, tetraethylenepentamine, aluminum chloride, tetramethylthiourea, cobalt acetylacetonate, acetylacetone, N,N-dialkyl aromatic amine, triethylamine, tetrahydroquinoline, p-tert-butylphenol, and ferrocene.

9. The leak-proof and plugging gel according to claim 1, wherein the fiber is a combination of one or more of polyethylene fiber, polypropylene fiber, polyvinyl alcohol fiber, polyester fiber, polyacrylonitrile fiber, nylon fiber and lignin fiber.

10. The leak-proof and plugging gel according to claim 1, wherein the polymer powder is one or a combination of two of polyvinyl alcohol (PVA), polymethyl methacrylate (PMMA), polyacrylamide (PAM), polyethylene oxide (PEO), and polycarbonate (PC).

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