A high-strength consolidation plugging agent

Abstract

The present invention relates to the technical field of drilling plugging agents, and more specifically, it relates to a high-strength consolidation plugging agent. The agent comprises the following components by weight: 30-68 parts of a polymer matrix, 15-36 parts of a composite gel, 8-16 parts of a coagulant, 5-12 parts of an initiator, 7-12 parts of a nanomaterial, 6-21 parts of a toughening agent, 6-13 parts of a cross-linking agent, and 2-8 parts of a flame retardant; the polymer matrix is ​​copolymerized with ethyl acrylate and butyl acrylate as main monomers, methoxyethyl acrylate as a functional monomer, and monobutyl itaconate as a vulcanization point monomer; the mass ratio of the ethyl acrylate, butyl acrylate, methoxyethyl acrylate, and monobutyl itaconate is 2-3:1-2:1-3:1. The agent has a controllable curing time, is suitable for fractured and cavitary leakage layers, has a high plugging success rate, and can effectively improve the pressure bearing capacity of the formation. The agent has good temperature resistance and is suitable for plugging construction in high-temperature environments.

Description

Technical Field

[0001] The invention relates to the technical field of drilling plugging agents, and more particularly to a high-strength solidified plugging agent. Background Art

[0002] Lost circulation is a major engineering issue hindering safe and efficient drilling. The loss of expensive drilling fluid into the formation and the significant non-productive time required to re-establish circulation significantly increase drilling costs. If lost circulation is not addressed, it can lead to complex accidents such as poor well control, poor wellbore cleaning, blockage, and stuck pipe. Selecting appropriate preventive measures during the drilling design phase can significantly reduce lost circulation. However, if preventive measures are unavoidable, effective measures to control lost circulation are necessary.

[0003] A range of plugging materials have been developed to address various types of drilling fluid loss. Based on their plugging mechanisms, they can be broadly categorized into three categories: curable plugging materials (such as cement and polymer gels), conventional lost circulation materials (LCMs) (such as granules and mineral fibers), and blends of curable and LCMs (such as gels and LCM composites). While the development of these plugging materials provides effective solutions to address drilling fluid loss, they still present a degree of uncertainty and unpredictability in complex formations.

[0004] In the existing technology, the plugging methods lack scientificity and specificity, resulting in the same plugging material showing large differences in plugging effects in different formations, unstable temperature resistance, insufficient pressure bearing capacity and retention capacity, and other problems. These problems lead to a low success rate of wellbore plugging.

[0005] The problems and defects of the existing technology are as follows: (1) High-strength solidified plugging agents are prone to premature solidification or strength loss in high-temperature environments, affecting their plugging effect in deep or high-temperature formations; (2) The plugging agent is incompatible with the synthetic-based drilling fluid system, resulting in a decrease in the performance of the drilling fluid and affecting the plugging effect. Summary of the Invention

[0006] The present invention provides a high-strength, consolidating plugging agent with a controllable curing time. It is suitable for use in fractured and karst leaking zones, has a high plugging success rate, and can effectively increase the pressure-bearing capacity of the formation. It also has good temperature resistance and is suitable for plugging leaks in high-temperature environments.

[0007] In a first aspect, the present invention provides a high-strength solidified plugging agent, comprising the following components by weight: 30-68 parts of a polymer matrix, 15-36 parts of a composite gel, 8-16 parts of a coagulant, 5-12 parts of an initiator, 7-12 parts of a nanomaterial, 6-21 parts of a toughening agent, 6-13 parts of a cross-linking agent, and 2-8 parts of a flame retardant; the polymer matrix is ​​prepared by copolymerizing ethyl acrylate and butyl acrylate as main monomers, methoxyethyl acrylate as a functional monomer, and monobutyl itaconate as a vulcanization point monomer; the mass ratio of ethyl acrylate, butyl acrylate, methoxyethyl acrylate, and monobutyl itaconate is 2-3:1-2:1-3:1.

[0008] Preferably, the composite gel is synthesized by using octadecyl methacrylate, acrylamide, and sodium bisulfite as main monomers, adding a nonionic emulsifier and peroxide, and the mass ratio of octadecyl methacrylate, acrylamide, sodium bisulfite, nonionic emulsifier and peroxide is 1-5:2-4:1-2:1:1-3.

[0009] Preferably, the nonionic emulsifier is one or more of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, fatty acid polyoxyethylene ether and castor oil polyoxyethylene ether.

[0010] Preferably, the coagulant is one or more of polyacrylamide, polyacrylonitrile, polyester resin and furan resin.

[0011] Preferably, the initiator is one or more of potassium persulfate, ammonium persulfate, dicumyl peroxide, benzoyl peroxide, azobisisobutyronitrile and tert-butyl peroxide.

[0012] Preferably, the nanomaterial is one or both of nano-silicon dioxide and nano-carbon fiber.

[0013] Preferably, the toughening agent is one or more of polypropylene fiber, polyamide fiber, polyester fiber and polyacrylonitrile fiber.

[0014] Preferably, the crosslinking agent is one or more of methylenebisacrylamide, N, N'-methylenebisacrylamide, tetraethyl orthosilicate, trimethoxysilane and borax.

[0015] Preferably, the flame retardant is one or more of melamine, nanoclay, carbon nanotube antimony trioxide, magnesium hydroxide and aluminum hydroxide.

[0016] In a second aspect, the present invention provides a method for preparing a high-strength consolidating plugging agent, comprising the following steps:

[0017] (1) Add the nanomaterial suspension to the polymer matrix and composite gel to obtain a solution, then add the toughening agent to the solution, seal the solution and magnetically stir it in a constant temperature water bath for 2-3 hours to obtain gel solution A;

[0018] (2) Add the flame retardant and cross-linking agent to the gel solution A, seal the solution and stir it magnetically in a constant temperature water bath for 3-4 hours to obtain the gel solution B;

[0019] (3) Add the initiator and coagulant into deionized water, mix and dissolve them, then add them into gel solution B, and solidify them at 60-80°C for 1-3 hours to obtain a high-strength solidified plugging agent.

[0020] In summary, the present invention has the following beneficial effects:

[0021] 1. The polymer matrix of the present invention is prepared by copolymerization of ethyl acrylate and butyl acrylate as main monomers, methoxyethyl acrylate as functional monomer, and monobutyl itaconate as vulcanization point monomer. Ethyl acrylate and butyl acrylate are main monomers. As soft monomers, their long alkyl chain structures give the polymer chain segments good flexibility and ductility, which can lower the glass transition temperature and promote the adaptability of the plugging agent in cracks. Ethyl acrylate has the function of a water-soluble monomer and is covalently bonded to the surface of the emulsion particles, reducing the desorption problem caused by physical adsorption, thereby improving the storage stability of the emulsion and the dispersibility of the polymerization process. Ethyl acrylate and butyl acrylate lay a flexible base to ensure film-forming properties and environmental adaptability. The methoxyethyl ester group (-OCH2CH2O-) in methoxyethyl acrylate increases the polymer's hydrophilicity and chemical activity, enhancing the adhesion of the plugging agent to the substrate. It also participates in subsequent cross-linking reactions through ether bonds or hydroxyl groups, further improving the polymer's solvent and water resistance. The hydrophilic methoxyethyl ester group promotes wetting between the plugging agent and the crack surface, reducing interfacial defects and improving plugging efficiency. The double bond in the monobutyl itaconate molecule copolymerizes with other vinyl monomers to introduce carboxyl groups into the polymer backbone. Subsequently, the carboxyl groups can form a three-dimensional network structure through ionic bonds, hydrogen bonds, or reactions with cross-linkers (such as metal ions). The cross-linked structure restricts water and solvent penetration, preventing swelling or degradation of the plugging layer. The hydrophilic groups in the polymer matrix absorb water and swell, filling micro-cracks and locking in the expanded volume through the cross-linked structure.

[0022] 2. The composite gel of this invention is synthesized using octadecyl methacrylate, acrylamide, and sodium bisulfite as primary monomers, along with a nonionic emulsifier and peroxide. Each component plays a key role in the plugging agent, and the components exhibit synergistic effects. The long alkyl side chains (C18) in octadecyl methacrylate impart significant hydrophobicity to the polymer, effectively improving the gel's high-temperature resistance (tolerance above 240°C). The crystallinity of these side chains forms physical crosslinks during polymerization, enhancing the mechanical stability of the gel network. Furthermore, the controllable polymerization of octadecyl methacrylate allows for precise control of the molecular weight distribution, optimizing the gel's rheological properties to meet the plugging requirements of various leakage channels. Acrylamide, a hydrophilic monomer, forms a polyacrylamide backbone through free radical polymerization, providing high water absorption and thickening capacity, significantly increasing the gel's viscosity. The mechanism of action of nonionic emulsifiers in gel systems is mainly reflected in that they stabilize the latex particles by adsorbing a protective layer, thereby preventing aggregation and coagulation between the latex particles. The hydrophilic groups of nonionic emulsifiers form hydrogen bonds with water molecules, thereby forming a thicker hydration layer on the surface of the latex particles, producing a steric hindrance effect, preventing the latex particles from approaching each other and agglomerating, thereby improving the stability of the emulsion.

[0023] 3. The polymer matrix of the present invention interacts with the composite gel to achieve synergistic effects. Octadecyl methacrylate in the composite gel acts as a hydrophobic monomer, which can provide hydrophobicity, enhance the stability, hydrolysis resistance and biocompatibility of the hydrogel, and form composite gels with different cross-linked structures by copolymerizing with hydrophilic monomers such as acrylamide. Acrylamide, as a hydrophilic monomer, can form a hydrophobic association-microcrystal-covalent-ionic multiple cross-linked network with octadecyl methacrylate, thereby significantly improving the mechanical properties of the hydrogel. Acrylamide can also be copolymerized with other monomers such as methoxyethyl acrylate to form polymers with specific functions. Sodium bisulfite, as an initiator, can form a composite initiation system with potassium persulfate to promote free radical polymerization, thereby promoting the polymerization reaction of acrylamide and octadecyl methacrylate.

[0024] 4. The high-strength consolidation-type plugging agent prepared by the present invention has a high compressive strength after solidification, can effectively seal cracks and improve the pressure-bearing capacity of the formation. High-strength consolidation-type plugging agents usually have good temperature resistance and are suitable for plugging construction in high-temperature environments. The density of the high-strength consolidation-type plugging agent can be adjusted in a wide range (1.3-1.9 g / cm³), and it can maintain good fluidity when entering the cracks, facilitating penetration into the cracks. It has a controllable solidification time and is suitable for fractured and karst leakage layers. It has a high plugging success rate and can effectively improve the pressure-bearing capacity of the formation. It has good temperature resistance and is suitable for plugging construction in high-temperature environments.

[0025] It should be understood that the above general description and the following detailed description are merely exemplary and explanatory and are not intended to limit the scope of protection of the present invention. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below with reference to the examples. It is particularly noted that if no specific conditions are specified in the following examples, the reactions were carried out according to conventional conditions or the conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following examples can be obtained from common commercial sources.

[0027] Example 1

[0028] A high-strength consolidation plugging agent comprises the following components by weight: 30 parts of a polymer matrix, 15 parts of a composite gel, 8 parts of a coagulant, 5 parts of an initiator, 7 parts of a nanomaterial, 6 parts of a toughening agent, 6 parts of a cross-linking agent, and 2 parts of a flame retardant; the polymer matrix is ​​prepared by copolymerizing ethyl acrylate and butyl acrylate as main monomers, methoxyethyl acrylate as a functional monomer, and monobutyl itaconate as a vulcanization point monomer; the mass ratio of ethyl acrylate, butyl acrylate, methoxyethyl acrylate, and monobutyl itaconate is 2:1:1:1.

[0029] The composite gel is synthesized by using octadecyl methacrylate, acrylamide and sodium bisulfite as main monomers, adding a non-ionic emulsifier and peroxide, and the mass ratio of octadecyl methacrylate, acrylamide, sodium bisulfite, non-ionic emulsifier and peroxide is 1:2:1:1:1; the non-ionic emulsifier is fatty alcohol polyoxyethylene ether.

[0030] The coagulant is polyacrylamide; the initiator is potassium persulfate; the nanomaterial is nano-silicon dioxide; the toughening agent is polypropylene fiber; the cross-linking agent is methylene bisacrylamide; and the flame retardant is melamine.

[0031] A method for preparing a high-strength consolidation type plugging agent comprises the following steps:

[0032] (1) Add the nanomaterial suspension to the polymer matrix and composite gel to obtain a solution, then add the toughening agent to the solution, seal the solution and magnetically stir it in a constant temperature water bath for 2 hours to obtain gel solution A;

[0033] (2) Add the flame retardant and cross-linking agent to the gel solution A, seal the solution and stir it magnetically in a constant temperature water bath for 3 hours to obtain the gel solution B;

[0034] (3) The initiator and coagulant were added to deionized water, mixed and dissolved, and then added to the gel solution B. The mixture was cured at 60°C for 1 hour to obtain a high-strength solidified plugging agent.

[0035] Example 2

[0036] A high-strength consolidation plugging agent comprises the following components by weight: 49 parts of a polymer matrix, 25 parts of a composite gel, 12 parts of a coagulant, 10 parts of an initiator, 10 parts of a nanomaterial, 14 parts of a toughening agent, 10 parts of a cross-linking agent, and 5 parts of a flame retardant; the polymer matrix is ​​prepared by copolymerizing ethyl acrylate and butyl acrylate as main monomers, methoxyethyl acrylate as a functional monomer, and monobutyl itaconate as a vulcanization point monomer; the mass ratio of ethyl acrylate, butyl acrylate, methoxyethyl acrylate, and monobutyl itaconate is 3:2:2:1.

[0037] The composite gel is synthesized by using octadecyl methacrylate, acrylamide and sodium bisulfite as main monomers, adding a non-ionic emulsifier and peroxide, and the mass ratio of octadecyl methacrylate, acrylamide, sodium bisulfite, non-ionic emulsifier and peroxide is 3:2:1:1:1; the non-ionic emulsifier is fatty alcohol polyoxyethylene ether.

[0038] The coagulant is polyacrylamide; the initiator is potassium persulfate; the nanomaterial is nano-silicon dioxide; the toughening agent is polypropylene fiber; the cross-linking agent is methylene bisacrylamide; and the flame retardant is melamine.

[0039] A method for preparing a high-strength consolidation type plugging agent comprises the following steps:

[0040] (1) Add the nanomaterial suspension to the polymer matrix and composite gel to obtain a solution, then add the toughening agent to the solution, seal it in a constant temperature water bath and magnetically stir it for 2.5 hours to obtain gel solution A;

[0041] (2) Add the flame retardant and cross-linking agent to the gel solution A, seal the solution and stir it magnetically in a constant temperature water bath for 3.5 hours to obtain the gel solution B;

[0042] (3) The initiator and coagulant were added to deionized water, mixed and dissolved, and then added to the gel solution B. The mixture was cured at 70°C for 2 hours to obtain a high-strength solidified plugging agent.

[0043] Example 3

[0044] A high-strength consolidation plugging agent comprises the following components by weight: 68 parts of a polymer matrix, 36 parts of a composite gel, 16 parts of a coagulant, 12 parts of an initiator, 12 parts of a nanomaterial, 21 parts of a toughening agent, 13 parts of a cross-linking agent, and 8 parts of a flame retardant; the polymer matrix is ​​prepared by copolymerizing ethyl acrylate and butyl acrylate as main monomers, methoxyethyl acrylate as a functional monomer, and monobutyl itaconate as a vulcanization point monomer; the mass ratio of ethyl acrylate, butyl acrylate, methoxyethyl acrylate, and monobutyl itaconate is 3:2:3:1.

[0045] The composite gel is synthesized by using octadecyl methacrylate, acrylamide and sodium bisulfite as main monomers, adding a non-ionic emulsifier and peroxide, and the mass ratio of octadecyl methacrylate, acrylamide, sodium bisulfite, non-ionic emulsifier and peroxide is 5:4:2:1:3; the non-ionic emulsifier is fatty alcohol polyoxyethylene ether.

[0046] The coagulant is polyacrylamide; the initiator is potassium persulfate; the nanomaterial is nano-silicon dioxide; the toughening agent is polypropylene fiber; the cross-linking agent is methylene bisacrylamide; and the flame retardant is melamine.

[0047] A method for preparing a high-strength consolidation type plugging agent comprises the following steps:

[0048] (1) Add the nanomaterial suspension to the polymer matrix and composite gel to obtain a solution, then add the toughening agent to the solution, seal the solution and magnetically stir it in a constant temperature water bath for 3 hours to obtain gel solution A;

[0049] (2) Add the flame retardant and cross-linking agent to the gel solution A, seal the solution and stir it magnetically in a constant temperature water bath for 4 hours to obtain the gel solution B;

[0050] (3) The initiator and coagulant were added to deionized water, mixed and dissolved, and then added to the gel solution B. The mixture was cured at 80°C for 3 hours to obtain a high-strength solidified plugging agent.

[0051] Comparative Example 1

[0052] The same preparation method as in Example 1 was used for the preparation, except that no polymer matrix was added.

[0053] Comparative Example 2

[0054] The preparation method was the same as that of Example 1, except that no composite gel was added.

[0055] Comparative Example 3

[0056] The same preparation method as in Example 1 was used, except that no coagulant was added.

[0057] Performance testing:

[0058] 1. Pressure-bearing and plugging capacity: according to industry standards The specific process of the high-temperature and high-pressure dynamic plugging simulation experiment is as follows:

[0059] Select test modules with a seam width of 3-5mm and a seam width of 8-10mm, install them into the test module containers respectively, and seal them; open the upper cover of the plugging liquid container, add the high-strength consolidation plugging agent to be tested, and seal the upper cover; set the heating temperature to 180℃, and the system will automatically heat to the required temperature and maintain a constant temperature; use a mechanical booster pump to increase pressure to simulate the overburden pressure of the formation. When the pressure is 0.5MPa, 1.0MPa, 3.0MPa, 5.0MPa, 7.0MPa, 10.0MPa, 15.0MPa, 20.0MPa, etc., keep the pressure stable for no less than 5 minutes, conduct a forward plugging experiment, and record the changes in the pressure value.

[0060] 2. According to national standards Determine the curing and bonding ability of high-strength consolidation plugging agents by the method specified in;

[0061] The pressure-bearing sealing capabilities of the high-strength, consolidated plugging agents prepared in Examples 1-3 and Comparative Examples 1-3 (selecting a seam width of 8-10 mm) were tested, along with their curing and bonding abilities. During the testing, it was observed that each plugging agent fully solidified within approximately 15 minutes. The test results are shown in Table 1.

[0062] Table 1

[0063]

[0064] As can be seen from Table 1, the high-strength consolidated plugging agents prepared in Examples 1-3 have better performance than those prepared in Comparative Examples 1-3, especially the high-strength consolidated plugging agent prepared in Example 1 has the characteristics of good temperature resistance, rapid strength development, and no pollution to the reservoir. The pressure bearing capacity is greater than 21 MPa and the curing and bonding capacity is greater than 12 MPa, which shows that the high-strength consolidated plugging agent can effectively seal the fractured leakage layer, improve the pressure bearing capacity of the formation, and ensure the safety of drilling operations.

[0065] The foregoing description is merely an exemplary embodiment of the present invention, and the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A high-strength consolidation plugging agent, characterized in that: The invention comprises the following components by weight: 30-68 parts of a polymer matrix, 15-36 parts of a composite gel, 8-16 parts of a coagulant, 5-12 parts of an initiator, 7-12 parts of a nanomaterial, 6-21 parts of a toughening agent, 6-13 parts of a cross-linking agent, and 2-8 parts of a flame retardant; the polymer matrix is ​​prepared by copolymerizing ethyl acrylate and butyl acrylate as main monomers, methoxyethyl acrylate as a functional monomer, and monobutyl itaconate as a vulcanization point monomer; the mass ratio of ethyl acrylate, butyl acrylate, methoxyethyl acrylate, and monobutyl itaconate is 2-3:1-2:1-3:1; The composite gel is synthesized by using octadecyl methacrylate, acrylamide, and sodium bisulfite as main monomers, adding a nonionic emulsifier and peroxide, wherein the mass ratio of octadecyl methacrylate, acrylamide, sodium bisulfite, nonionic emulsifier and peroxide is 1-5:2-4:1-2:1:1-3; The coagulant is one or more of polyacrylamide, polyacrylonitrile, polyester resin and furan resin; The nanomaterial is one or both of nano silicon dioxide and nano carbon fiber.

2. The high-strength consolidation plugging agent according to claim 1, characterized in that: The nonionic emulsifier is one or more of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, fatty acid polyoxyethylene ether and castor oil polyoxyethylene ether.

3. The high-strength consolidation plugging agent according to claim 1, characterized in that: The initiator is one or more of potassium persulfate, ammonium persulfate, dicumyl peroxide, benzoyl peroxide, azobisisobutyronitrile and tert-butyl peroxide.

4. The high-strength consolidation plugging agent according to claim 1, characterized in that: The toughening agent is one or more of polypropylene fiber, polyamide fiber, polyester fiber and polyacrylonitrile fiber.

5. The high-strength consolidation plugging agent according to claim 1, characterized in that: The crosslinking agent is one or more of N, N'-methylenebisacrylamide, tetraethyl orthosilicate, trimethoxysilane and borax.

6. The high-strength consolidation plugging agent according to claim 1, characterized in that: The flame retardant is one or more of melamine, nanoclay, carbon nanotube antimony trioxide, magnesium hydroxide and aluminum hydroxide.

7. The method for preparing the high-strength consolidation plugging agent according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) Add the nanomaterial suspension to the polymer matrix and composite gel to obtain a solution, then add the toughening agent to the solution, seal the solution and magnetically stir it in a constant temperature water bath for 2-3 hours to obtain gel solution A; (2) Add the flame retardant and cross-linking agent to the gel solution A, seal the solution and stir it magnetically in a constant temperature water bath for 3-4 hours to obtain the gel solution B; (3) Add the initiator and coagulant into deionized water, mix and dissolve them, then add them into gel solution B, and solidify them at 60-80°C for 1-3 hours to obtain a high-strength solidified plugging agent.

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