Temporary plugging reservoir protective agent for oil gas drilling fluid and preparation method of temporary plugging reservoir protective agent

Abstract

The invention relates to a reservoir temporary plugging protective agent for oil and gas drilling fluid and a preparation method thereof, and belongs to the technical field of oil and gas drilling and production. According to the invention, isopropylacrylamide, an anionic monomer 2-acrylamido-2-methyl-1-propanesulfonic acid and a hydrophobic monomer butyl methacrylate are subjected to free radical polymerization according to a certain proportion, so that the reservoir protective agent for the oil and gas drilling fluid is successfully prepared; hydrophilic acylamino (-CO-NH-) and hydrophobic isopropyl (-CH (CH3) 2) functional groups in molecules of the obtained reservoir protective agent have the lowest critical solution temperature in an aqueous solution, and when the temperature is gradually increased, a process of converting from a stretching state to a curled state is carried out, so that plugging and self-plugging removal of the reservoir are realized; the introduction of butyl methacrylate promotes the enhancement of the hydrophobic effect of the copolymer, effectively reduces the phase transition temperature of the polymer to adapt to the temperature of the reservoir, and can realize the effect on reservoirs at different temperatures by adjusting the dosage of the polymer.

Description

Technical Field

[0001] The invention relates to a temporary plugging reservoir protective agent for oil and gas drilling fluid and a preparation method thereof, belonging to the technical field of oil and gas drilling and production. Background Art

[0002] With the continuous growth of global energy demand and the gradual decline of traditional fossil fuel resources, the development of marine oil and gas resources has become an important part of the global energy strategy. Marine oil and gas resources are abundant, especially in deep-sea areas, where the potential oil and gas reserves are huge and of great strategic significance. The development of marine oil and gas drilling technology not only provides a new way for global energy supply, but also plays a vital role in ensuring national energy security. However, marine oil and gas drilling faces extremely complex geological and environmental conditions. Problems such as high pressure, high temperature, and seawater corrosion damage in the well bring many challenges to drilling operations. Especially in deep-sea drilling, how to effectively protect oil and gas reservoirs and avoid reservoir damage caused by drilling fluid intrusion has become a major problem in drilling operations. In order to ensure the smooth progress of drilling and the efficient extraction of oil and gas resources, the research and development of high-performance drilling fluids and reservoir protection agents is particularly important.

[0003] During offshore oil and gas drilling, reservoir protection faces many challenges, including drilling fluid invasion leading to pore blockage and reservoir contamination, increased drilling fluid loss causing clay hydration expansion, chemical compatibility issues between drilling fluid and reservoir rocks and formation fluids leading to the formation of insoluble precipitates, mechanical damage to the reservoir by drilling tools causing microcracks and breakage, and poor wellbore stability leading to formation collapse and wellbore shrinkage. These factors together affect the seepage capacity of oil and gas and reservoir integrity.

[0004] During offshore oil and gas drilling, the drilling fluid's pressure is often higher than the reservoir pressure. Combined with the reservoir rock's pore structure and formation integrity, drilling fluid easily penetrates the reservoir. This penetration can damage the reservoir, impacting subsequent oil or gas recovery operations. During offshore drilling, wellbore stability issues are primarily due to reduced formation strength caused by poor lithology, high clay content, and water sensitivity.

[0005] Patent document CN101942294A discloses a marine oil and gas drilling fluid that has the dual functions of protecting oil and gas reservoirs and the environment. This fluid is formulated by combining potassium polyacrylonitrile, sulfonated phenolic resin, oil-soluble resin, and ultrafine calcium carbonate to enhance the drilling fluid's plugging effectiveness and minimize damage to the reservoir caused by drilling fluid intrusion. The fluid is simple to prepare and is environmentally friendly. Currently, there is limited research on plugging agents for marine oil and gas drilling fluids, and existing plugging agents have limited effectiveness in inhibiting clay hydration. Therefore, developing plugging agents for marine oil and gas drilling fluids is of great significance.

[0006] Patent document CN105331339A discloses a drilling fluid for marine oil and gas drilling. Through the synergistic inhibition of sodium silicate and polyol, the linear expansion rate of shale is reduced, which can effectively solve the problem of wellbore instability caused by shale hydration during the drilling process.

[0007] In general, hydration inhibitors are currently mainly suitable for shale formations, and no reservoir protection agent with both hydration inhibition and drilling fluid loss reduction effects has been proposed for oil and gas drilling.

[0008] Therefore, developing reservoir protection agents with drilling plugging effects and clay hydration inhibition effects is one of the key research directions in the field of marine oil and gas drilling and production technology. Summary of the Invention

[0009] In response to the shortcomings of the existing technology, the present invention provides a temporary plugging reservoir protection agent for oil and gas drilling fluid and a preparation method thereof. After being added to the drilling fluid, the reservoir protection agent of the present invention can significantly reduce the filtration loss of the drilling fluid, reduce the reservoir permeability, and effectively reduce the damage to the reservoir caused by drilling fluid intrusion. When the reservoir temperature drops, the polymer can be redissolved in the drilling fluid, realizing the self-unplugging function, restoring the reservoir permeability, and effectively protecting the reservoir. At the same time, it can inhibit the hydration dispersion of clay, reduce the development of formation cracks, and help ensure the stability of the well wall during marine oil and gas drilling. The reservoir protection agent of the present invention has both plugging and clay hydration inhibition properties, and the preparation method is simple.

[0010] The technical solutions of the present invention are as follows: A temporary plugging reservoir protective agent for oil and gas drilling fluid, which is prepared by free radical polymerization of isopropyl acrylamide, 2-acrylamido-2-methyl-1-propane sulfonic acid and butyl methacrylate, and has the structure shown in the following formula I: Ⅰ In formula I, x:y:z=1:(0.05-0.1):0.01.

[0011] The second object of the present invention is to provide a method for preparing the temporary plugging reservoir protective agent for oil and gas drilling fluid.

[0012] The preparation method of the reservoir protective agent for oil and gas drilling fluid comprises the following steps: (1) Mix isopropyl acrylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid and dimethylformamide (DMF), heat and stir, and mix well to obtain a monomer solution; (2) Add butyl methacrylate to the monomer solution, heat and stir, mix evenly, and obtain a mixed solution; (3) Nitrogen is introduced into the mixed solution, heated to 60-80°C, an initiator is added, and the mixture is kept warm for reaction; the mixture is then purified, dried, and crushed to obtain a temporary plugging reservoir protective agent for oil and gas drilling fluid.

[0013] Preferably, according to the present invention, in step (1), the ratio of the total mass of isopropylacrylamide and 2-acrylamido-2-methyl-1-propanesulfonic acid to the volume of DMF is 0.1-0.5 g:1 mL.

[0014] Preferably, according to the present invention, in step (1), the mass ratio of isopropyl acrylamide to 2-acrylamido-2-methyl-1-propanesulfonic acid is (25-35): (0.1-2).

[0015] According to the preferred embodiment of the present invention, in step (1), the heating and stirring temperature is 35-45°C, the stirring rate is 200-400 rpm, and the stirring time is 5-10 minutes.

[0016] Preferably, according to the present invention, in step (2), the stirring temperature is 35-45° C., the stirring rate is 200-300 rpm, and the stirring time is 10-20 minutes.

[0017] According to the preferred embodiment of the present invention, in step (2), the molar ratio of isopropyl acrylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid and butyl methacrylate in the mixed solution is 1:0.05-0.1:0.01.

[0018] According to the preferred embodiment of the present invention, in step (3), the time for introducing nitrogen is 25-40 minutes, and the nitrogen is introduced to exhaust the air in the reaction system.

[0019] According to the preferred embodiment of the present invention, in step (3), the initiator is azobisisobutyronitrile, and the initiator is added to the system in the form of an initiator DMF solution.

[0020] According to the preferred embodiment of the present invention, in step (3), the mass of the initiator is 0.01% to 0.015% of the total mass of isopropyl acrylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid and butyl methacrylate.

[0021] Preferably, according to the present invention, in step (3), the insulation reaction temperature is 60-80°C, the reaction time is 6-8 hours, and the stirring rate during the reaction is 200-400 rpm.

[0022] According to the preferred embodiment of the present invention, in step (3), the drying temperature is 50-60° C., and the drying time is 18-24 hours.

[0023] According to the present invention, the application of the above-mentioned reservoir protective agent for oil and gas drilling fluid in oil and gas drilling fluid prevents drilling fluid from invading the reservoir and inhibits clay hydration. The mass concentration of the reservoir protective agent for marine oil and gas drilling fluid in the drilling fluid is 2-3wt%.

[0024] The technical features and beneficial effects of the present invention are as follows: 1. The present invention utilizes isopropyl acrylamide, anionic monomer 2-acrylamido-2-methyl-1-propane sulfonic acid, and hydrophobic monomer butyl methacrylate to polymerize in a certain proportion to successfully prepare a reservoir protective agent for oil and gas drilling fluid. The hydrophilic amide group (—CO—NH—) and hydrophobic isopropyl group (—CH(CH3)2) functional groups in the obtained reservoir protective agent molecules have a minimum critical solubility temperature in aqueous solution. When the temperature gradually increases, they will undergo a process of transition from an extended state to a curled state, achieving reservoir plugging and self-unplugging. The introduction of butyl methacrylate promotes the enhancement of the hydrophobic effect of the copolymer, effectively lowering the phase transition temperature of the polymer to adapt to the reservoir temperature. By adjusting its added amount, the effect on reservoirs of different temperatures can be achieved. At the same time, the introduction of AMPS monomer improves the salt resistance of the polymer.

[0025] 2. The reservoir protection agent for oil and gas drilling fluids of the present invention can reduce the degree of clay hydration and has a stronger inhibitory ability than polyamine and potassium chloride. The inhibitor of the present invention has good compatibility with drilling fluids, improves the plugging efficiency of drilling fluids, significantly reduces reservoir permeability, reduces the degree of clay hydration and dispersion, and synergistically maintains the stability of the formation wall during drilling.

[0026] 3. The reservoir protective agent for oil and gas drilling fluid of the present invention has both plugging performance and clay hydration inhibition performance. Only one additive is added to achieve multiple effects, reducing the types of additives and having little impact on the performance of the oil and gas drilling fluid. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of the reservoir protective agent for oil and gas drilling fluid prepared in Example 1.

[0028] Figure 2 This is the Zeta potential tested in Experimental Example 2.

[0029] Figure 3 This is a graph of the linear expansion rate of the core in Experimental Example 4 in pure water, polyamine inhibitor solution, and the reservoir protection agent solution prepared in Example 1. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to specific embodiments, but is not limited thereto.

[0031] Meanwhile, the experimental methods described in the following examples, unless otherwise specified, are conventional methods; the reagents, materials and equipment, unless otherwise specified, can be obtained from commercial channels.

[0032] Example 1 The preparation method of the temporary plugging reservoir protective agent for oil and gas drilling fluid comprises the following steps: (1) Add 27.64 g of isopropyl acrylamide and 0.53 g of AMPS into a three-necked flask containing 165 mL of DMF solvent, stir at a stirring rate of 300 r / min and a temperature of 40°C for 5 minutes, and mix well to obtain a monomer solution.

[0033] (2) Add 1.83 g of butyl methacrylate to the monomer solution, and stir at a stirring rate of 300 r / min and a temperature of 40°C for 15 minutes to obtain a mixed solution; (3) Let nitrogen flow through the solution for 30 minutes to expel all the air from the mixture.

[0034] (4) Weigh 0.03 g of azobisisobutyronitrile initiator and dissolve it in 5 mL of DMF solvent. Heat the mixed solution in the three-necked flask to 70 °C and set the magnetic stirring to 200 rpm. Slowly add the initiator under stirring conditions and continue the reaction at a stirring rate of 200 r / min and a temperature of 70 °C for 8 hours. (5) After the reaction is completed, the solution is poured into excess anhydrous ethanol, and the resulting precipitate is dried at 60°C for 24 hours and crushed to obtain a temporary plugging reservoir protective agent for oil and gas drilling fluid.

[0035] The reservoir protection agent synthesized in this example was analyzed by nuclear magnetic resonance hydrogen spectrum using a German BRUKER-AVANCE III HD 500MHz nuclear magnetic resonance spectrometer. 10 mg of the dried sample was weighed and dissolved in deuterated chloroform, and the nuclear magnetic resonance tube containing the sample was placed in the spectrometer for analysis. The results are shown in Figure 2. Figure 1 As shown. Figure 1It can be seen that the chemical shift (δ) = 7.97 ppm is the proton peak of the secondary amide (-NH-), (δ) = 7.26 ppm is the deuterated chloroform solvent peak, (δ) = 6.25-6.22 ppm is the proton peak of the sulfonate group (-SO3H), (δ) = 2.94 ppm is the proton peak of the tertiary carbon (-CH-), (δ) = 2.86 ppm is the proton peak of the methylene (-CH2-) connected to the tertiary carbon and oxygen, (δ) = 2.23-2.09 ppm is the proton peak of the methylene (-CH2-) in the main chain, (δ) = 2.09 ppm is the proton peak of the methyl (-CH3) close to the sulfonate group, (δ) = 1.78-1.16 ppm is the proton peak of the methyl group (-CH3) in the main chain, and (δ) = 0.91 is the proton peak of the remaining methyl group (-CH3) in the main chain. Therefore, it is confirmed that the target product was successfully prepared.

[0036] Example 2 A method for preparing a temporary plugging reservoir protective agent for oil and gas drilling fluid comprises the following steps: (1) Add 27.16 g of isopropyl acrylamide and 1.04 g of AMPS into a three-necked flask containing 165 mL of DMF solvent, stir at a stirring rate of 300 r / min and a temperature of 40°C for 5 minutes, and mix well to obtain a monomer solution; (2) Add 1.8 g of butyl methacrylate to the monomer solution and stir at a stirring rate of 300 r / min and a temperature of 40°C for 15 minutes to obtain a mixed solution; (3) Let nitrogen flow for 30 minutes to expel all the air from the mixed solution; (4) Weigh 0.03 g of azobisisobutyronitrile initiator and dissolve it in 5 mL of DMF solvent; heat the mixed solution in the three-necked flask to 70 °C, set the magnetic stirring to 200 rpm, and slowly add the initiator under stirring conditions; continue to react at a stirring rate of 200 r / min and a temperature of 70 °C for 8 hours; (5) After the reaction is completed, the solution is poured into excess anhydrous ethanol, and the resulting precipitate is dried at 60°C for 24 hours and crushed to obtain a reservoir protective agent for oil and gas drilling fluid.

[0037] Comparative Example 1 The method for preparing the temporary plugging reservoir protective agent for oil and gas drilling fluid is the same as that described in Example 1, except that: No AMPS was added in step (1).

[0038] Comparative Example 2 This comparative example uses 800-mesh ultrafine calcium carbonate as a plugging agent for oil and gas drilling fluid, which is provided by Guangxi Lingyun Ultrafine Calcium Carbonate Co., Ltd.

[0039] Comparative Example 3 This comparative example uses sulfonated asphalt as a plugging agent, which is provided by Shandong Zhengyang New Material Technology Co., Ltd.

[0040] Test Example 1 The oil and gas drilling fluid prepared in Example 1 was tested for compatibility with a temporary plugging reservoir protective agent.

[0041] The temporary plugging reservoir protective agent for oil and gas drilling fluid prepared in Example 1 was used to prepare a marine deepwater drilling fluid base slurry, and the formula was: seawater + 4wt% bentonite + 0.35wt% Na2CO3 + 2wt% reservoir protective agent prepared in Example 1; at the same time, a blank drilling fluid without the reservoir protective agent was prepared as a comparison.

[0042] Conventional performance tests were conducted on the two prepared drilling fluid base slurries to evaluate the compatibility of the temporary plugging reservoir protection agent for oil and gas drilling fluids prepared according to the present invention with water-based drilling fluids. The rheological parameters and API fluid loss of the drilling fluids were tested in accordance with the national standard "GB / T 29170-2012 Laboratory Testing of Drilling Fluids for the Petroleum and Natural Gas Industry." The results are shown in Table 1.

[0043] Table 1 Rheological filtration test of Example 1 and blank drilling fluid As can be seen from Table 1, under the influence of the temporary plugging reservoir protective agent for oil and gas drilling fluid of the present invention, the viscosity of the base slurry increases, and the drilling fluid has good compatibility. After addition, the filtration loss reduction performance of the drilling fluid is significantly improved, which is conducive to the formation of a low-permeability mud cake in the formation, and the damage of the drilling fluid to the reservoir is reduced by blocking the mass transfer between the drilling fluid and the formation.

[0044] Test Example 2 The Zeta potential of the temporary plugging reservoir protective agents for oil and gas drilling fluids prepared in Example 1, Example 2 and Comparative Example 1 in bentonite slurry was tested to evaluate the dispersibility of the plugging agents.

[0045] Weigh 400mL of 4wt% bentonite slurry, add 8g of reservoir protection agent to the base slurry, stir at 7000r / min on a high-speed stirrer for 20min to obtain the sample to be tested. Dilute it with deionized water to a certain multiple, and place the diluted sample into the sample cell of the Zeta potential tester for testing. The test results are shown in Figure 2 .

[0046] Depend on Figure 2 It can be seen that the introduction of AMPS monomer into the polymer increases the dispersion performance of the reservoir protection agent in the base mud and ensures its plugging performance in the drilling fluid.

[0047] Test Example 3 The reservoir protection agents prepared in Example 1 and Example 2 and Comparative Examples 2 and 3 were subjected to core plugging experimental tests.

[0048] The specific steps are as follows: (1) Weigh 4 cups of 500 ml of 4 wt% bentonite slurry, add 10 g of the reservoir protection agent prepared in Example 1 and Example 2, the 800 mesh ultrafine calcium carbonate of Comparative Example 2, and the sulfonated asphalt of Comparative Example 3, respectively, and stir evenly; (2) Pure water was injected into the core at 2 mL / min at 25°C to measure the permeability K1 of the artificial core. (2) Prepared bentonite slurry was displaced into the cores to measure the permeability K2 of the artificial cores. The core plugging rate was calculated as follows: QUOTE ×100% (4) Pure water at 4°C was injected into the plugged core at a rate of 2 mL / min to measure the water permeability K3 of the artificial core. The core unplugging rate was calculated as follows: QUOTE ×100% Core plugging experiments were conducted using the reservoir protection agents prepared in Examples 1 and 2, as well as Comparative Examples 2 and 3, according to the aforementioned experimental method. The test results are shown in Table 2. As can be seen from Table 2, the reservoir protection agent of the present invention is superior to ultrafine calcium carbonate and sulfonated asphalt in core plugging effectiveness. Furthermore, the agent can self-unplug as the reservoir temperature changes, restoring reservoir permeability and minimizing reservoir damage.

[0049] Table 2 Blocking and unblocking tests of different samples Test Example 4 The hydration inhibition performance of the reservoir protection agents prepared in Example 1 and Example 2 was tested, and a commonly used hydration inhibitor polyamine product (provided by Shandong Juxin Chemical Co., Ltd.) was used as a comparison.

[0050] The specific test steps are as follows: Measure 130 mL of pure water, add polyamine inhibitor and the reservoir protective agent prepared in Example 1 to prepare an aqueous solution with a mass concentration of 1 wt%. Take 10.0 g of bentonite dried at 105 ° C and put it in a test barrel. Compact it on a hydraulic press at a pressure of 10 MPa for 5 minutes to obtain an artificial bentonite core. After the core is taken out, add a polyamine inhibitor with a mass concentration of 1 wt%, an aqueous solution of the reservoir protective agent prepared in Example 1 and pure water to a linear expansion instrument at room temperature and pressure, and measure the linear expansion height. The linear expansion rate of pure water, polyamine inhibitor and reservoir protective agent prepared in Example 1 was tested, and the results are as follows Figure 3 Compared with pure water, the expansion rate of the core in Example 1 after 16 hours was significantly reduced, and the effect was better than that of similar products such as polyamine, indicating that the prepared reservoir protective agent can effectively play a role in inhibiting hydration.

[0051] Test Example 5 The rolling recovery test is a common method for evaluating the dispersion properties of rocks. It is a dynamic experiment that simulates the shear rate of the annular space downhole. Measure 6 parts of 350mL of water, add potassium chloride to one part to prepare a potassium chloride solution with a mass concentration of 3wt%, and the other four parts are configured into a polyamine solution with a mass concentration of 1wt%, and a reservoir protection agent solution prepared by Example 1, Comparative Example 2 and Comparative Example 3 with a mass concentration of 1wt% to obtain the test solution. Weigh 20g of 6-10 mesh rock chips respectively, put them into a roller aging furnace filled with the above-mentioned test solution, roll them at room temperature for 16h, take them out, wash the rock chips with standard brine, sieve them with a 40-mesh standard sieve, dry them and weigh them, and record the ratio to the initial rock chip mass as the rock chip recovery rate. The results are shown in Table 3.

[0052] Table 3 Standard rock sample rolling recovery test data Under the action of the reservoir protection agent prepared in Example 1 of the present invention, the recovery rate of the rock sample increased from 21% to 88.6%, reflecting the hydration and dispersion inhibitory effect of the example on the rock sample.

Claims

1. A temporary plugging reservoir protective agent for oil and gas drilling fluid, characterized in that: The temporary plugging reservoir protective agent for oil and gas drilling fluid is prepared by free radical polymerization of isopropyl acrylamide, 2-acrylamido-2-methyl-1-propane sulfonic acid and butyl methacrylate, and has a structure shown in the following formula I: Ⅰ In formula I, x:y:z=1:(0.05-0.1):0.

01.

2. The method for preparing the reservoir protective agent for oil and gas drilling fluid according to claim 1, characterized in that: The steps are as follows: (1) Mix isopropyl acrylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid and dimethylformamide (DMF), heat and stir, and mix well to obtain a monomer solution; (2) Add butyl methacrylate to the monomer solution, heat and stir, mix evenly, and obtain a mixed solution; (3) Nitrogen is introduced into the mixed solution, heated to 60-80°C, an initiator is added, and the mixture is kept warm for reaction; the mixture is then purified, dried, and crushed to obtain a temporary plugging reservoir protective agent for oil and gas drilling fluid.

3. The preparation method according to claim 2, characterized in that In step (1), the ratio of the total mass of isopropylacrylamide and 2-acrylamido-2-methyl-1-propanesulfonic acid to the volume of DMF is 0.1-0.5 g:1 mL.

4. The preparation method according to claim 2, characterized in that In step (1), the mass ratio of isopropyl acrylamide to 2-acrylamido-2-methyl-1-propanesulfonic acid is (25-35): (0.1-2).

5. The preparation method according to claim 2, characterized in that In step (1), the heating and stirring temperature is 35-45°C, the stirring rate is 200-400 rpm, and the stirring time is 5-10 minutes.

6. The preparation method according to claim 2, characterized in that In step (2), the stirring temperature is 35-45°C, the stirring rate is 200-300 rpm, and the stirring time is 10-20 minutes.

7. The preparation method according to claim 2, characterized in that In step (2), the molar ratio of isopropyl acrylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid and butyl methacrylate in the mixed solution is 1:0.05-0.1:0.

01.

8. The preparation method according to claim 2, characterized in that In step (3), the time for introducing nitrogen is 25-40 minutes, and the air in the reaction system is exhausted by introducing nitrogen. The initiator is azobisisobutyronitrile, and the initiator is added to the system in the form of an initiator DMF solution. The mass of the initiator is 0.01% to 0.015% of the total mass of isopropyl acrylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid and butyl methacrylate.

9. The preparation method according to claim 2, characterized in that In step (3), the heat preservation reaction temperature is 60~80℃, and the reaction time is 6~8 hours; the stirring rate during the reaction is 200~400 rpm, the drying temperature is 50~60℃, and the drying time is 18~24 hours.

10. Use of the reservoir protective agent for oil and gas drilling fluid according to claim 1 in oil and gas drilling fluid, characterized in that: Prevent drilling fluid from invading the reservoir and inhibit clay hydration. The mass concentration of reservoir protective agent for oil and gas drilling fluid in the drilling fluid is 2~3wt%.

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