High-temperature-resistant and salt-resistant gel plugging agent, preparation method and application thereof

Abstract

This invention provides a high-temperature and salt-resistant gel sealing agent, its preparation method, and its application. The gel sealing agent, by weight, comprises: 8-12 parts polyvinyl alcohol, 9-11 parts acrylic acid, 9-11 parts acrylamide, 2-5 parts sodium styrene sulfonate, 0.4-0.8 parts N,N-dimethylbisacrylamide, 0.4-0.8 parts polymer crosslinking agent PA, 0.01-0.06 parts initiator, and water. The polymer crosslinking agent is prepared from polysuccinimide and hydrazine hydrate. This gel sealing agent exhibits good sealing performance under high-temperature and high-salt conditions.

Description

Technical Field

[0001] This invention belongs to the field of drilling technology, specifically relating to a high-temperature and salt-resistant gel plugging agent, its preparation method, and its application. Background Technology

[0002] With rapid industrialization and increasing energy demand, deep, high-temperature, and high-salinity oil and gas reservoirs are key areas for future exploration and development. However, due to the development of micro-fractures and fractures in deep formations, drilling fluids can easily penetrate into the rock mass along these micro-fractures and fractures, causing mechanical and hydraulic fracturing and promoting hydration, leading to frequent wellbore instability accidents and resulting in huge economic losses. Therefore, it is necessary to effectively seal the pores, micro-fractures, and fractures in the formation to reduce the intrusion of free water from the drilling fluid into the formation, reduce the pressure transmission to the formation, improve the formation's pressure-bearing capacity, and achieve the goal of stabilizing the wellbore and preventing collapse.

[0003] Gel-based plugging agents exhibit enhanced deformation-adaptive plugging performance in formations, particularly in pores, micro-fractures, and fractures. However, most existing gel-based plugging agents for drilling fluids have poor temperature resistance and cannot simultaneously achieve salt resistance, resulting in poor plugging effects in high-temperature and high-salt formations. Therefore, there is an urgent need to develop a drilling fluid treatment agent that can meet the requirements of high-temperature and salt resistance to improve drilling fluid plugging performance. Consequently, research on a high-temperature and salt-resistant gel plugging agent and its preparation method has significant practical implications. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a high-temperature and salt-resistant gel plugging agent PPAA and its preparation method, which can play a good plugging role under high temperature and high salt conditions.

[0005] To achieve the above objectives, the present invention provides a gel sealing agent PPAA, whose raw material composition, calculated by mass parts, includes:

[0006] 8-12 parts polyvinyl alcohol, 9-11 parts acrylic acid, 9-11 parts acrylamide, 2-5 parts sodium styrene sulfonate, 0.4-0.8 parts N,N-dimethylbisacrylamide, 0.4-0.8 parts polymer crosslinking agent PA, 0.01-0.06 parts initiator and water;

[0007] The polymer crosslinking agent PA is prepared from polysuccinimide and hydrazine hydrate.

[0008] According to a specific embodiment of the present invention, preferably, the initiator is one or a combination of two of ammonium persulfate and potassium persulfate.

[0009] According to a specific embodiment of the present invention, preferably, the water content is 80-100 parts.

[0010] According to a specific embodiment of the present invention, preferably, the preparation method of the polymer crosslinking agent PA includes the following steps:

[0011] (1) Disperse 1-5 parts of polysuccinimide in 20-30 parts of water at 50-60℃ to obtain a suspension;

[0012] (2) Add 0.1-0.4 parts of hydrazine hydrate dropwise to the suspension and stir for 20-30 minutes to obtain a mixture;

[0013] (3) Add 7-8 portions of 2M alkaline solution dropwise to the mixture, and after 20-30 minutes, adjust the pH to 7;

[0014] (4) The reaction mixture is slowly precipitated in an excess of unsuitable solvent and filtered. The precipitate is washed with unsuitable solvent and dried under vacuum at 40-60°C to constant weight to obtain the polymer crosslinking agent PA.

[0015] According to a specific embodiment of the present invention, preferably, in the above-mentioned method for preparing the polymer crosslinking agent PA, the alkaline solution is one or a combination of sodium hydroxide solution and potassium hydroxide solution.

[0016] According to a specific embodiment of the present invention, preferably, in the above-mentioned method for preparing the polymer crosslinking agent PA, the undesirable solvent is one or a combination of two or more of acetone, methanol and ethanol.

[0017] According to a specific embodiment of the present invention, preferably, the preparation method of the polymer crosslinking agent PA includes the following steps:

[0018] (1) Disperse 1-5 parts of polysuccinimide in 20 parts of water at 50°C to obtain a suspension;

[0019] (2) Add 0.1-0.4 parts of hydrazine hydrate dropwise to the suspension and stir for 30 minutes to obtain a mixture;

[0020] (3) Add 7-8 portions of 2M sodium hydroxide solution dropwise to the mixture, and after 0.5 hours, adjust the pH to 7;

[0021] (4) The reaction mixture was slowly precipitated in excess acetone and filtered. The precipitate was washed with acetone and dried under vacuum at 40°C to constant weight to obtain the polymer crosslinking agent PA.

[0022] According to a specific embodiment of the present invention, preferably, in the above-mentioned method for preparing polymer crosslinking agent PA, the pH adjuster used to adjust the pH value is one or a combination of hydrochloric acid and sulfuric acid.

[0023] According to a specific embodiment of the present invention, preferably, in step (2) of the above-mentioned method for preparing polymer crosslinking agent PA, hydrazine hydrate is added dropwise to the mixture under stirring.

[0024] This invention also provides a method for preparing the above-mentioned gel sealing agent PPAA, which includes the following steps:

[0025] (1) Polyvinyl alcohol, acrylic acid, acrylamide, sodium styrene sulfonate, N,N-dimethylbisacrylamide and polymer crosslinking agent PA are mixed with water to obtain a mixture;

[0026] (2) Heat the mixture to 60-70°C and deoxygenate it with a protective gas for 20-30 minutes;

[0027] (3) Add an initiator to the mixture and react for 2-4 hours;

[0028] (4) The reaction product is taken out, washed with solvent, dried and pulverized to obtain the gel sealing agent PPAA.

[0029] According to a specific embodiment of the present invention, preferably, in the above-mentioned method for preparing the gel sealing agent, the solvent is one or a combination of two or more of acetone, methanol and ethanol.

[0030] According to a specific embodiment of the present invention, the preparation method of the above-mentioned gel blocking agent PPAA can be carried out according to the following specific steps:

[0031] (1) Weigh 8-12 parts of polyvinyl alcohol, 9-11 parts of acrylic acid, 9-11 parts of acrylamide, 2-5 parts of sodium styrene sulfonate, 0.4-0.8 parts of N,N-dimethylbisacrylamide and 0.4-0.8 parts of polymer crosslinking agent PA, and add them to a flask containing 105 parts of water, and stir until fully dispersed;

[0032] (2) Heat the water in the flask to 60-70℃, keep stirring and heating, and remove oxygen with nitrogen for 30 minutes;

[0033] (3) Add 0.01-0.06 parts of ammonium persulfate initiator to the flask and maintain the reaction for 2-4 hours;

[0034] (4) Take out the viscous reaction product, wash it with acetone 2-3 times, dry and pulverize it to obtain the high temperature and salt resistant gel sealing agent PPAA.

[0035] This invention also provides the application of the above-mentioned gel plugging agent in the preparation of drilling fluid.

[0036] According to a specific embodiment of the present invention, preferably, the drilling fluid is a drilling fluid used in deep wells, high-temperature or high-salt environments; the content of the gel plugging agent in the drilling fluid is 1-3% by mass percentage.

[0037] The high-temperature and salt-resistant gel plugging agent PPAA provided by this invention can play a good plugging role under high temperature and high salt conditions. The molecular chain of the above-mentioned gel plugging agent PPAA contains strong hydrophilic amide groups, sulfonic acid groups and other groups. The sulfonic acid groups have good thermal stability and are not sensitive to salt. The cyclic groups enhance the rigidity of the molecular chain, and cross-linking through macromolecular cross-linking agents further improves the temperature and salt resistance of the gel plugging agent. It can be adsorbed on the surface of drilling fluid clay through adsorption groups such as amide groups to enhance the clay adhesion. It can form two layers of high-performance mud cake inside and outside the well wall. The outer mud cake can form a dense protective film between the mud cake and the formation, effectively preventing water from entering the formation. At the same time, it has good plugging ability. It can seal the micropores in the mud cake and the pores in the formation during the formation of the mud cake in the drilling fluid, improve the density of the mud cake, reduce filtration loss, and enhance the plugging performance of the drilling fluid under high temperature and high salt conditions. Detailed Implementation

[0038] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0039] Preparation Example 1

[0040] This preparation example provides a gel blocking agent, which is prepared by the following steps:

[0041] (1) Weigh 2 parts by weight of polysuccinimide and disperse it into 20 parts of water at 50°C. Stir magnetically to obtain a uniform suspension.

[0042] (2) Weigh 0.25 parts by mass of hydrazine hydrate and add it dropwise to the suspension while stirring. Stir for 30 minutes.

[0043] (3) Add 8 parts of sodium hydroxide solution (2M) dropwise to the system. After 0.5h, adjust the pH to 7 with 2M HCl.

[0044] (4) The reaction mixture was slowly precipitated in excess acetone and filtered. The precipitate was washed three times with acetone and dried under vacuum at 40°C to constant weight to obtain polymer crosslinking agent PA-1.

[0045] (5) Weigh 10 parts of polyvinyl alcohol, 11 parts of acrylic acid, 11 parts of acrylamide, 3 parts of sodium styrene sulfonate, 0.65 parts of N,N-dimethylbisacrylamide and 0.65 parts of polymer crosslinking agent PA-1, and add them to a flask containing 105 parts of water, and stir until fully dispersed.

[0046] (6) Heat the water in the flask to 60°C, keep stirring and heating, and deoxygenate with nitrogen for 30 minutes;

[0047] (7) Add 0.05 parts of ammonium persulfate initiator to the flask and maintain the reaction for 3 hours;

[0048] (8) Take out the viscous reaction product, wash it with acetone 2-3 times, dry and pulverize it to obtain the high temperature and salt resistant gel sealing agent A1.

[0049] Preparation Example 2

[0050] This preparation example provides a gel blocking agent, which is prepared by the following steps:

[0051] (1) Prepare polymer crosslinking agent PA-1 according to the steps in preparation 1;

[0052] (2) Weigh 8 parts of polyvinyl alcohol, 10 parts of acrylic acid, 10 parts of acrylamide, 3 parts of sodium styrene sulfonate, 0.65 parts of N,N-dimethylbisacrylamide and 0.65 parts of polymer crosslinking agent PA-1, and add them to a flask containing 105 parts of water, and stir until fully dispersed.

[0053] (3) Heat the water in the flask to 60°C, keep stirring and heating, and deoxygenate with nitrogen for 30 minutes;

[0054] (4) Add 0.05 parts of ammonium persulfate initiator to the flask and maintain the reaction for 3 hours;

[0055] (5) Take out the viscous reaction product, wash it with acetone 2-3 times, dry and pulverize it to obtain the high temperature and salt resistant gel sealing agent A2.

[0056] Preparation Example 3

[0057] This preparation example provides a gel blocking agent, which is prepared by the following steps:

[0058] (1) Weigh 3 parts by mass of polysuccinimide and disperse it into 20 parts of water at 50°C. Stir magnetically to obtain a uniform suspension.

[0059] (2) Weigh 0.25 parts by mass of hydrazine hydrate and add it dropwise to the suspension while stirring. Stir for 30 minutes.

[0060] (3) Add 7 portions of sodium hydroxide solution (2M) dropwise to the system. After 0.5 hours, adjust the pH to 7 with 2M HCl.

[0061] (4) The reaction mixture was slowly precipitated in excess acetone and filtered. The precipitate was washed three times with acetone and dried under vacuum at 40°C to constant weight to obtain polymer crosslinking agent PA-2.

[0062] (5) Weigh 8 parts of polyvinyl alcohol, 11 parts of acrylic acid, 11 parts of acrylamide, 5 parts of sodium styrene sulfonate, 0.8 parts of N,N-dimethylbisacrylamide and 0.8 parts of polymer crosslinking agent PA-2, and add them to a flask containing 105 parts of water, and stir until fully dispersed.

[0063] (6) Heat the water in the flask to 60°C, keep stirring and heating, and deoxygenate with nitrogen for 30 minutes;

[0064] (7) Add 0.06 parts of ammonium persulfate initiator to the flask and maintain the reaction for 3 hours;

[0065] (8) Take out the viscous reaction product, wash it with acetone 2-3 times, dry and pulverize it to obtain the high temperature and salt resistant gel sealing agent A3.

[0066] Example 1

[0067] Drilling fluid C1 is prepared as follows: Add 4 parts by weight of sodium-based bentonite to 100 parts by weight of water, stir at high speed for 20 minutes, and let it stand at room temperature for 24 hours. Then stir the bentonite slurry for another 20 minutes and add 1 part of A1.

[0068] Example 2

[0069] Drilling fluid C2 is prepared as follows: Add 4 parts by weight of sodium-based bentonite to 100 parts by weight of water, stir at high speed for 20 minutes, and let it stand at room temperature for 24 hours. Then stir the bentonite slurry for another 20 minutes and add 2 parts by weight of A1.

[0070] Example 3

[0071] Prepare drilling fluid C3 as follows: Add 4 parts by weight of sodium-based bentonite to 100 parts by weight of water, stir at high speed for 20 minutes, and let it stand at room temperature for 24 hours. Then stir the bentonite slurry for another 20 minutes and add 3 parts by weight of A1.

[0072] Example 4

[0073] Prepare drilling fluid C4 as follows: Add 4 parts by weight of sodium-based bentonite to 100 parts by weight of water, stir at high speed for 20 minutes, and let it stand at room temperature for 24 hours. Then stir the bentonite slurry for another 20 minutes and add 3 parts of A2.

[0074] Example 5

[0075] Prepare drilling fluid C5 as follows: Add 4 parts by weight of sodium-based bentonite to 100 parts by weight of water, stir at high speed for 20 minutes, and let it stand at room temperature for 24 hours. Then stir the bentonite slurry for another 20 minutes and add 3 parts of A3.

[0076] Comparative Example 1

[0077] Prepare drilling fluid BC1 as follows: Add 4 parts by weight of sodium-based bentonite to 100 parts by weight of water, stir at high speed for 20 minutes, let it stand at room temperature for 24 hours, stir the bentonite slurry again for 20 minutes, without adding any treatment agent.

[0078] Comparative Example 2

[0079] Prepare drilling fluid BC2 as follows: Add 4 parts by weight of sodium-based bentonite to 100 parts by weight of water, stir at high speed for 20 minutes, let it stand at room temperature for 24 hours, stir the bentonite slurry again for 20 minutes, and add 3 parts by weight of sulfonated asphalt.

[0080] Comparative Example 3

[0081] Prepare drilling fluid BC3 as follows: Add 4 parts by weight of sodium-based bentonite to 100 parts by weight of water, stir at high speed for 20 minutes, let it stand at room temperature for 24 hours, stir the bentonite slurry for another 20 minutes, and add 3 parts by weight of polyacrylamide.

[0082] Test Example 1

[0083] Test method:

[0084] Take 400 mL of the above drilling fluids Cl-C5 and BC1-BC3 respectively, add 15 wt% NaCl, stir at 5000 rpm for 20 min, then put them into an aging tank, place them in a roller furnace, and roll them at 190℃ for 16 h. After cooling to room temperature, stir at 5000 rpm for 20 min. Then, according to GB / T16783.1-2006, determine the apparent viscosity (AV, mPa.s), plastic viscosity (PV, mPa.s), dynamic shear force (YP, Pa), sand bed penetration depth (80-100 mesh, cm), and high-temperature and high-pressure sand disc filtration loss reduction rate (%, 190℃) of the above drilling fluids. The results are shown in Table 1.

[0085] As can be seen from the data in Table 1, when 3% of the high-temperature and salt-resistant gel plugging agent of the present invention is added to the drilling fluid, under the high-temperature and high-salt conditions of 190℃ and 15wt% NaCl, the sand bed penetration depth in the sand bed plugging experiment is only 1.1cm, and the high-temperature and high-pressure sand disc filtration loss reduction rate can reach 81.2%, which greatly improves the plugging performance of the drilling fluid and is far superior to sulfonated asphalt and polyacrylamide.

[0086] Table 1 Drilling Fluid Performance Tests

[0087]

[0088] Test Example 2

[0089] Test method:

[0090] Take 400 mL of the above drilling fluids Cl-C5 and BC1-BC3 respectively, add 30 wt% NaCl, stir at 5000 rpm for 20 min, then put them into an aging tank, place them in a roller furnace, and roll them at 220℃ for 16 h. After cooling to room temperature, stir at 5000 rpm for 20 min. Then, according to GB / T16783.1-2006, determine the apparent viscosity (AV, mPa.s), plastic viscosity (PV, mPa.s), dynamic shear force (YP, Pa), sand bed penetration depth (80-100 mesh, cm), and high-temperature and high-pressure sand disc filtration loss reduction rate (%, 220℃) of the above drilling fluids. The results are shown in Table 2.

[0091] Table 2 Drilling Fluid Performance Tests

[0092]

[0093] As can be seen from the data in Table 2, when 3% of the high-temperature and salt-resistant gel plugging agent of the present invention is added to the drilling fluid, under the high-temperature and high-salt conditions of 220℃ and 30wt% NaCl, the sand bed penetration depth in the sand bed plugging experiment is 2.3cm, and the high-temperature and high-pressure sand disc filtration loss reduction rate can reach 76.8%, which greatly improves the plugging performance of the drilling fluid and is superior to sulfonated asphalt and polyacrylamide.

[0094] In summary, the high-temperature and salt-resistant gel plugging agent of the present invention can effectively improve the plugging performance of drilling fluid under high temperature and high salt conditions, meeting the needs of deep and ultra-deep well drilling.

[0095] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0096] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0097] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A gel sealing agent, comprising, by weight parts: 8-12 parts polyvinyl alcohol, 9-11 parts acrylic acid, 9-11 parts acrylamide, 2-5 parts sodium styrene sulfonate, 0.4-0.8 parts N,N'-methylenebisacrylamide, 0.4-0.8 parts polymer crosslinking agent, 0.01-0.06 parts initiator and water; The preparation method of the polymer crosslinking agent includes the following steps: (1) Disperse 1-5 parts of polysuccinimide into 20-30 parts of water at 50-60℃ to obtain a suspension; (2) Add 0.1-0.4 parts of hydrazine hydrate dropwise to the suspension and stir for 20-30 minutes to obtain a mixture; (3) Add 7-8 portions of 2M alkaline solution dropwise to the mixture, and after 20-30 minutes, adjust the pH to 7; (4) The reaction mixture is slowly precipitated in an excess of unsuitable solvent and filtered. The precipitate is washed with unsuitable solvent and dried under vacuum at 40-60°C to constant weight to obtain the polymer crosslinking agent.

2. The gel plug according to claim 1, wherein, The initiator is one or a combination of two of ammonium persulfate and potassium persulfate; the water content is 80-100 parts.

3. The gel plug according to claim 1, wherein, The alkaline solution is one or a combination of sodium hydroxide solution and potassium hydroxide solution; the unsuitable solvent is one or a combination of acetone, methanol and ethanol.

4. The gel sealing agent according to claim 1, wherein, The pH adjuster used to adjust the pH value is one or a combination of hydrochloric acid and sulfuric acid.

5. The gel plug according to claim 1, wherein, In step (2), hydrazine hydrate is added dropwise to the mixture while being stirred.

6. A method for preparing the gel blocking agent according to any one of claims 1-5, comprising the following steps: (1) Polyvinyl alcohol, acrylic acid, acrylamide, sodium styrene sulfonate, N,N'-methylenebisacrylamide and polymer crosslinking agent are mixed with water to obtain a mixture; (2) Heat the mixture to 60-70°C and deoxygenate it with a protective gas for 20-30 min; (3) Add an initiator to the mixture and react for 2-4 hours; (4) Take out the reaction product, wash it with solvent, dry and pulverize it to obtain the gel sealing agent.

7. The production method according to claim 6, wherein The solvent is one or a combination of two or more of acetone, methanol and ethanol.

8. The use of the gel plugging agent according to any one of claims 1-5 in the preparation of drilling fluid.

9. Use according to claim 8, wherein, The drilling fluid is used in deep wells, high-temperature or high-salt environments; The content of the gel plugging agent in the drilling fluid is 1-3% by mass percentage.

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