A waterproof locking agent for fracturing

Abstract

The present invention belongs to the technical field of fracturing, and specifically relates to a waterproof lock agent for fracturing, wherein the waterproof lock agent comprises component A and component B, wherein component A is an emulsion of an acrylate / methacrylic acid copolymer containing an epoxy group, and component B comprises an enhancer, a promoter and distilled water. When component A is added to component B to prepare a waterproof lock agent and applied, the promoter of component B promotes the ring opening of the epoxy group in component A and the cross-linking reaction of the sulfonamide group in the enhancer, thereby enhancing the strength and density of the film attached to the rock surface and forming a film with a cross-linked structure. At the same time, the enhancer in component B contains a fluoroalkyl group, which has hydrophobic and oleophobic properties, reduces the strong water wettability of the rock surface, and reduces the surface tension of the invading fluid. By utilizing the film-forming properties of component A and the cross-linking enhancement effect of component B, the waterproof lock agent generates a dense hydrophobic and oleophobic film on the rock surface, which can significantly improve its waterproof lock performance.

Description

Technical Field

[0001] The invention belongs to the technical field of fracturing, and in particular relates to a waterproof locking agent for fracturing. Background Art

[0002] Low permeability, ultra-low permeability and tight oil and gas reservoirs have the characteristics of dense rocks, small pore throats and large oil and gas flow resistance. During the drilling process, the entry of foreign fluids can easily cause water lock damage, greatly reducing the relative permeability of the reservoir and seriously affecting production capacity. Therefore, the research on efficient water lock technology for low permeability, ultra-low permeability and tight oil and gas reservoirs is of great practical significance to the field of oil and gas fracturing technology.

[0003] At present, the main waterproofing measures include increasing the pressure difference, injecting nitrogen, adding waterproofing agents, etc. The best effect is to add waterproofing agents. By adding waterproofing agents, the surface tension of the drilling fluid is reduced, the return pressure of the drilling fluid in the pore throat is significantly reduced, the drainage rate is increased, and the damage to the oil and gas reservoir is reduced.

[0004] In the patent number "CN202110199037.1" and the name "Waterproofing locking agent for fracturing and its preparation method", 1.5%-2.5% of sodium p-perfluorononenyloxybenzenesulfonate, 0.15%-0.5% of perfluorooctane sulfonyl polyoxyethylene ether, 0.7%-1.5% of sodium dodecylbenzene sulfonate, 5%-8% of formate, and 0.25%-0.5% of chloride salt are synergistically compounded. The obtained waterproofing locking agent has a good waterproofing locking effect, but poor stability.

[0005] Patent No. "CN202110790794.6" and the name "A low permeability oil and gas reservoir waterproof lock agent and its preparation method and application" provides a low permeability oil and gas reservoir waterproof lock agent, which is composed of the following raw materials in mass percentage: 10-50% ternary copolymer block silicone oil, 0.3-1.5% glacial acetic acid, 0.1-0.5% defoamer, and the balance is water. The molecular structure of the ternary copolymer block silicone oil is composed of siloxane segments, polyetheramine segments and polyether segments. The above-mentioned waterproof lock agent effectively reduces the surface tension of water and reduces the damage of water lock, but the hydrophobic film formed on the rock formation is easy to fall off, which not only affects the waterproof lock effect, but also causes pore throat blockage. Summary of the invention

[0006] In order to solve the problems existing in the prior art, the present invention provides a waterproof locking agent for fracturing, which not only has excellent waterproof locking effect, but also has good salt resistance and strong stability; the waterproof locking agent for fracturing comprises component A and component B, wherein component A is an emulsion of acrylate / methacrylic acid copolymer containing epoxy groups, and component B comprises a reinforcing agent, a accelerator and distilled water.

[0007] The preparation method of component A comprises the following steps:

[0008] S11, adding an emulsifier and a buffer into distilled water and stirring for 10 to 20 minutes, and then adding monomers 2-butyl acrylate, methacrylic acid and glycidyl methacrylate and stirring for 20 to 30 minutes to obtain a uniform emulsion;

[0009] S12, adding the emulsion into a reactor, introducing nitrogen to remove oxygen, then heating to 70-85°C, adding an initiator, stirring and reacting for 4-6 hours, cooling to room temperature after the reaction is completed, adjusting the pH to neutral, and obtaining component A.

[0010] Preferably, the emulsifier is one or more of sodium dodecylbenzene sulfonate and sodium dodecyl sulfate, and the added amount is 1.5-2.5% of the mass of distilled water.

[0011] Preferably, the buffer is sodium bicarbonate, and the added amount is 0.3-0.6% of the mass of distilled water.

[0012] Preferably, the mass ratio of 2-butyl acrylate, methacrylic acid and glycidyl methacrylate in the monomer is 2 to 3:1.5 to 2:1.

[0013] Preferably, the total mass of the monomers is 50-60% of the mass of distilled water.

[0014] Preferably, the initiator is potassium persulfate, and the added amount is 0.2-0.5% of the total weight of the monomers.

[0015] Preferably, the stirring reaction rate is 200-300 r / min.

[0016] The double bonds in glycidyl methacrylate can be free radically polymerized with the double bonds in 2-butyl acrylate and methacrylic acid, but the epoxy groups in glycidyl methacrylate will not be destroyed. Therefore, component A is an emulsion of acrylate / methacrylic acid copolymer containing epoxy groups. During the copolymerization process, continuous stirring is performed to prevent agglomeration from affecting the properties of the copolymer and to make the emulsion more uniform.

[0017] The preparation method of component B comprises the following steps:

[0018] S21: adding the enhancer to the solvent and stirring for 10 to 20 minutes, and then adding the accelerator and stirring for 10 to 20 minutes to obtain component B.

[0019] Preferably, the enhancer is one or more of N-ethylperfluorooctanesulfonamidoethyl acrylate, N-ethyl-N-(2-hydroxyethyl)perfluorooctanesulfonamide, and N-ethylperfluorooctanesulfonamide.

[0020] Preferably, the accelerator is one or more of bis(dimethylaminoethyl)ether and dodecyldimethyl tertiary amine.

[0021] Preferably, the mass ratio of the enhancer, the accelerator and the solvent in the component B is 12-18:1.5-3:90-100.

[0022] Preferably, the solvent is distilled water or methanol or an aqueous solution of methanol.

[0023] The method for using the waterproof locking agent for fracturing is as follows: before use, component A is added to component B and stirred evenly to form the waterproof locking agent.

[0024] Preferably, the mass ratio of component A to component B is 15-20:5-7.

[0025] Component A of the waterproof lock agent is an emulsion of acrylate / methacrylic acid copolymer containing epoxy groups, which has excellent film-forming properties and can adhere to the rock surface to form a film; when component A is added to component B to make a waterproof lock agent and applied, the accelerator of component B promotes the ring opening of the epoxy group in component A and the cross-linking reaction of the sulfonamide group in the enhancer, enhancing the strength and density of the film attached to the rock surface and forming a cross-linked film. At the same time, the enhancer in component B contains fluoroalkyl groups, which have hydrophobic and oleophobic properties, reduce the strong water wettability of the rock surface, and reduce the surface tension of the invading fluid. By utilizing the film-forming properties of component A and the cross-linking enhancement effect of component B, the waterproof lock agent forms a dense hydrophobic and oleophobic film on the rock surface, which can significantly improve its waterproof lock performance.

[0026] Due to the adoption of the above technical solution, the technical effects achieved by the present invention are:

[0027] 1. The waterproof lock agent prepared by the present invention can form a dense cross-linked film on the surface of the rock formation, which has strong stability and is not easy to fall off and cause pore throat blockage, greatly reducing the resistance of the fluid on the rock surface, reducing water lock damage, and improving the permeability recovery rate.

[0028] 2. The waterproof lock agent prepared by the present invention has excellent salt resistance.

[0029] 3. The waterproofing agent prepared by the present invention is a nano-scale droplet particle with an average particle size of 20 to 40 nm, while the pore throat diameters of low permeability oil and gas reservoirs are mostly micrometer-level or even nanometer-level. Therefore, the waterproofing agent can enter the core pores and effectively improve the wettability of the core pore surface, making it impossible for water molecules to enter the core pore throats, reducing the water saturation in the reservoir, and thus reducing the degree of water lock damage. DETAILED DESCRIPTION

[0030] The present invention is further described below in conjunction with specific embodiments.

[0031] Example 1: A waterproof lock agent for fracturing includes component A and component B, wherein component A is an emulsion of an acrylate / methacrylic acid copolymer containing epoxy groups, and component B includes a reinforcing agent, an accelerator and distilled water.

[0032] The preparation method of component A comprises the following steps:

[0033] S11, adding an emulsifier and a buffer into distilled water and stirring for 15 minutes, and then adding monomers 2-butyl acrylate, methacrylic acid and glycidyl methacrylate and stirring for 25 minutes to obtain a uniform emulsion;

[0034] S12, adding the emulsion into a reactor, introducing nitrogen to deoxygenate, then heating to 82°C, adding an initiator, stirring and reacting for 5 hours, cooling to room temperature after the reaction is completed, adjusting the pH to neutral, and obtaining component A.

[0035] The emulsifier is sodium dodecylbenzene sulfonate, and the added amount is 2% of the mass of distilled water.

[0036] The buffer is sodium bicarbonate, and the amount added is 0.5% of the mass of distilled water.

[0037] The mass ratio of 2-butyl acrylate, methacrylic acid and glycidyl methacrylate in the monomer is 2.4:1.7:1.

[0038] The initiator is potassium persulfate, and the added amount is 0.4% of the total weight of the monomers.

[0039] The total mass of the monomers is 55% of the mass of distilled water.

[0040] The stirring reaction rate is 250 r / min.

[0041] The preparation method of component B comprises the following steps:

[0042] S21: adding the enhancer to methanol and stirring for 15 min, then adding the accelerator and stirring for 20 min at a stirring rate of 120 r / min to obtain component B.

[0043] The reinforcing agent is N-ethyl perfluorooctane sulfonamido ethyl acrylate, and the accelerator is dodecyl dimethyl tertiary amine.

[0044] The mass ratio of the enhancer, the accelerator and the methanol in the component B is 16:2:95.

[0045] The method for using the waterproof locking agent for fracturing is as follows: before use, component A is added to component B and stirred evenly to form the waterproof locking agent.

[0046] The mass ratio of component A to component B is 17:6.

[0047] Example 2: A waterproof lock agent for fracturing includes component A and component B, wherein component A is an emulsion of an acrylate / methacrylic acid copolymer containing epoxy groups, and component B includes a reinforcing agent, an accelerator and distilled water.

[0048] The preparation method of component A comprises the following steps:

[0049] S11, adding an emulsifier and a buffer into distilled water and stirring for 10 minutes, and then adding monomers 2-butyl acrylate, methacrylic acid and glycidyl methacrylate and stirring for 20 minutes to obtain a uniform emulsion;

[0050] S12, adding the emulsion into a reactor, introducing nitrogen to remove oxygen, then heating to 70°C, adding an initiator, stirring and reacting for 4 hours, cooling to room temperature after the reaction is completed, adjusting the pH to neutral, and obtaining component A.

[0051] The emulsifier is sodium dodecylbenzene sulfonate, and the added amount is 1.5% of the mass of distilled water.

[0052] The buffer is sodium bicarbonate, and the added amount is 0.3% of the mass of distilled water.

[0053] The mass ratio of 2-butyl acrylate, methacrylic acid and glycidyl methacrylate in the monomer is 2:1.5:1.

[0054] The initiator is potassium persulfate, and the added amount is 0.2% of the total weight of the monomers.

[0055] The total mass of the monomers is 50% of the mass of distilled water.

[0056] The stirring reaction rate is 200 r / min.

[0057] The preparation method of component B comprises the following steps:

[0058] S21: adding the enhancer to methanol and stirring for 10 min, then adding the accelerator and stirring for 10 min at a stirring rate of 120 r / min to obtain component B.

[0059] The reinforcing agent is N-ethyl perfluorooctane sulfonamido ethyl acrylate, and the accelerator is dodecyl dimethyl tertiary amine.

[0060] The mass ratio of the enhancer, the accelerator and the methanol in the component B is 12:1.5:90.

[0061] The method for using the waterproof locking agent for fracturing is as follows: before use, component A is added to component B and stirred evenly to form the waterproof locking agent.

[0062] The mass ratio of component A to component B is 15:5.

[0063] Example 3: A waterproof lock agent for fracturing includes component A and component B, wherein component A is an emulsion of an acrylate / methacrylic acid copolymer containing epoxy groups, and component B includes a reinforcing agent, a accelerator and distilled water.

[0064] The preparation method of component A comprises the following steps:

[0065] S11, adding an emulsifier and a buffer into distilled water and stirring for 20 minutes, and then adding monomers 2-butyl acrylate, methacrylic acid and glycidyl methacrylate and stirring for 30 minutes to obtain a uniform emulsion;

[0066] S12, adding the emulsion into a reactor, introducing nitrogen to remove oxygen, then heating to 85°C, adding an initiator, stirring and reacting for 6 hours, cooling to room temperature after the reaction is completed, adjusting the pH to neutral, and obtaining component A.

[0067] The emulsifier is sodium dodecylbenzene sulfonate, and the added amount is 2.5% of the mass of distilled water.

[0068] The buffer is sodium bicarbonate, and the added amount is 0.6% of the mass of distilled water.

[0069] The mass ratio of 2-butyl acrylate, methacrylic acid and glycidyl methacrylate in the monomer is 3:2:1.

[0070] The initiator is potassium persulfate, and the added amount is 0.5% of the total weight of the monomers.

[0071] The total mass of the monomers is 60% of the mass of distilled water.

[0072] The stirring reaction speed is 300 r / min.

[0073] The preparation method of component B comprises the following steps:

[0074] S21: adding the enhancer to methanol and stirring for 20 min, then adding the accelerator and stirring for 15 min at a stirring rate of 120 r / min to obtain component B.

[0075] The reinforcing agent is N-ethyl perfluorooctane sulfonamido ethyl acrylate, and the accelerator is dodecyl dimethyl tertiary amine.

[0076] The mass ratio of the enhancer, the accelerator and the methanol in the component B is 18:3:100.

[0077] The method for using the waterproof locking agent for fracturing is as follows: before use, component A is added to component B and stirred evenly to form the waterproof locking agent.

[0078] The mass ratio of component A to component B is 20:7.

[0079] Example 4: This example is different from Example 1 in that the enhancer is N-ethyl-N-(2-hydroxyethyl) perfluorooctane sulfonamide, the promoter is bis(dimethylamino)ethyl ether, the solvent is 60 wt % methanol aqueous solution, and the rest is consistent with Example 1.

[0080] Example 5: This example is different from Example 1 in that the enhancer is N-ethyl perfluorooctane sulfonamide, the promoter is bis(dimethylamino)ethyl ether, and the solvent is 60 wt % methanol aqueous solution.

[0081] Comparative Example 1

[0082] Representative Example 1 was selected as Comparative Example 1, except for the glycidyl methacrylate in step S11, and the rest was the same as Example 1.

[0083] Comparative Example 2

[0084] Representative Example 1 was selected as Comparative Example 2, except for the accelerator in step S21, and the rest was the same as Example 1.

[0085] Comparative Example 3

[0086] Representative Example 1 was selected, and the enhancer in step S21 was removed, while the rest was consistent with Example 1, as Comparative Example 3.

[0087] The waterproof lock agent prepared in Examples 1-5 was added to clean water for various performance tests, as shown in Table 1; the waterproof lock agent prepared in Examples 1-5 was added to 5wt% NaCl solution for performance tests, as shown in Table 2; the added amount was 0.35wt%.

[0088] Table 1 is the performance test of Examples 1-5 in clean water

[0089]

[0090] Table 2 is the performance test of Examples 1-5 in 5wt% NaCl solution

[0091]

[0092] It can be seen from Table 1 that the waterproof lock agent prepared in Examples 1-5 has a small surface tension, a large contact angle, a permeability recovery rate higher than 70%, and a low water lock damage rate, indicating that the waterproof lock agent prepared in Examples 1-5 has a good waterproof lock effect; it can be seen from Table 2 that the waterproof lock agent prepared by the present invention still has excellent waterproof lock performance in salt water, indicating that it has strong salt resistance.

[0093] The waterproof lock agent prepared in Comparative Examples 1-3 was added to clean water for various performance tests, as shown in Table 3; the waterproof lock agent prepared in Comparative Examples 1-3 was added to 5wt% NaCl solution for performance tests, as shown in Table 2; the added amount was 0.35wt%.

[0094] Table 3 is the performance test of Example 1 and Comparative Examples 1-3 in clean water

[0095]

[0096] Table 4 shows the performance test of Example 1 and Comparative Examples 1-3 in 5wt% NaCl solution

[0097]

[0098] As can be seen from Table 3 and Table 4, the performance of the waterproof lock agent prepared in Comparative Examples 1-3 is relatively reduced in both clear water and salt water. Comparative Example 1 removes the glycidyl methacrylate in step S11, and component A lacks epoxy groups, so it cannot open the ring to form a dense cross-linked structure when acting on the surface of the rock formation, so the hydrophobicity is reduced and the salt resistance effect is greatly discounted. No promoter is added to Comparative Example 2, and the epoxy group is less open, so the cross-linked structure generated by the reaction with the enhancer is less, and the waterproof lock effect is worse than the embodiment, but better than Comparative Example 1. No enhancer is added to Comparative Example 3, and the enhancer contains fluorocarbon long chains and sulfonamide groups. The hydrophobic effect of the fluorocarbon long chain is stronger. Under the action of the promoter, the epoxy group and the sulfonamide group in the enhancer can generate more and denser cross-linked structures, so the hydrophobic effect of Comparative Example 3 is worse than that of the embodiment and Comparative Examples 1 and 2, and the waterproof lock effect is also greatly reduced. However, compared with Comparative Example 1, Comparative Example 3 contains epoxy groups. Under the action of the promoter, some cross-linked structures are also generated between the molecules of Component A. The generated hydrophobic protective layer is denser than that of Comparative Example 1. Therefore, the permeability recovery rate of Comparative Example 3 is slightly higher than that of Comparative Example 1, and the water lock damage rate is lower than that of Comparative Example 1.

[0099] At the same time, it can be seen from Table 3 and Table 4 that the salt tolerance effects of Comparative Examples 2 and 3 are lower than that of Example 1, but are also better than that of Comparative Example 1.

[0100] Detection method:

[0101] Surface tension: Determined in accordance with GB / T 5549-2010 "Surface tension of surfactants by the liquid film pulling method".

[0102] Contact angle: measured in accordance with SY / T5153-2017 “Method for determination of wettability of reservoir rocks”.

[0103] Permeability recovery rate: gas test the permeability Kg1 of the core in a dry state, then add the core into a clear water solution of a waterproof lock agent or a brine solution of a waterproof lock agent, use nitrogen to displace the two cores to equilibrium at the same pressure, measure the gas test permeability Kg2 and residual water saturation of the core, calculate the ratio of the permeability after gas drive to the permeability in the dry state, which is the core permeability recovery rate; the permeability is measured in accordance with SY / T 6370-1998 "Core Gas Permeability Tester".

[0104] Water lock damage rate: Determined in accordance with Q / SY 1832-2015 “Experimental evaluation method for water lock damage in tight gas reservoirs”.

[0105] Unless otherwise specified, the ratios and percentages described in the present invention are all weight ratios and weight percentages; and the raw materials are all commercially available.

[0106] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A waterproof locking agent for fracturing, characterized in that: The waterproof lock agent comprises component A and component B, wherein component A is an emulsion of an acrylate / methacrylic acid copolymer containing epoxy groups, and component B comprises a reinforcing agent, a accelerator and distilled water; The mass ratio of component A to component B is 15-20:5-7; The preparation method of component A comprises the following steps: S11, adding an emulsifier and a buffer into distilled water and stirring for 10 to 20 minutes, and then adding monomers 2-butyl acrylate, methacrylic acid and glycidyl methacrylate and stirring for 20 to 30 minutes to obtain a uniform emulsion; S12, adding the emulsion to a reactor, introducing nitrogen to remove oxygen, then heating to 70-85° C., adding an initiator, stirring and reacting for 4-6 hours, cooling to room temperature after the reaction, adjusting the pH to neutral, and obtaining component A; The preparation method of component B comprises the following steps: S21: adding the enhancer to the solvent and stirring for 10 to 20 minutes, and then adding the accelerator and stirring for 10 to 20 minutes to obtain component B; The enhancer in S21 is one or more of N-ethyl perfluorooctane sulfonamido ethyl acrylate, N-ethyl-N-(2-hydroxyethyl) perfluorooctane sulfonamide, and N-ethyl perfluorooctane sulfonamide; The accelerator in S21 is one or more of bis(dimethylaminoethyl)ether and dodecyldimethyl tertiary amine.

2. A waterproof locking agent for fracturing according to claim 1, characterized in that: The emulsifier in S11 is one or more of sodium dodecylbenzene sulfonate and sodium dodecyl sulfate, and the added amount is 1.5-2.5% of the mass of distilled water.

3. A waterproof locking agent for fracturing according to claim 1, characterized in that: The buffer in S11 is sodium bicarbonate, and the amount added is 0.3-0.6% of the mass of distilled water.

4. A waterproof locking agent for fracturing according to claim 1, characterized in that: The mass ratio of 2-butyl acrylate, methacrylic acid and glycidyl methacrylate in the monomer of S11 is 2-3:1.5-2:

1.

5. A waterproof locking agent for fracturing according to claim 1, characterized in that: The initiator in S12 is potassium persulfate, and the added amount is 0.2-0.5% of the total weight of the monomers.

6. A waterproof locking agent for fracturing according to claim 1, characterized in that: The total mass of monomers in the emulsion in S12 is 50-60% of the mass of distilled water.

7. A waterproof locking agent for fracturing according to claim 1, characterized in that: The stirring reaction rate in S12 is 200-300 r / min.

8. The waterproof locking agent for fracturing according to claim 1, characterized in that: The mass ratio of the reinforcing agent, the accelerator and the solvent in the component B in S21 is 12-18:1.5-3:90-100.

9. The waterproof locking agent for fracturing according to claim 1, characterized in that: The solvent is distilled water or methanol or an aqueous solution of methanol.

10. A method for using the waterproof locking agent for fracturing as claimed in claim 1, characterized in that: The method for using the waterproof locking agent for fracturing is as follows: before use, component A is added to component B and stirred evenly to form the waterproof locking agent.

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