High-Temperature Response Environmentally Friendly Gel Blocking Agent and Its Preparation Method
A high-temperature responsive and environmentally friendly gel plugging agent prepared by using nanocellulose crystals and monomeric acrylamide solves the problems of fast gelation speed and insufficient strength in high-temperature oil reservoirs, achieving efficient plugging and environmental friendliness.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XINJIANG UNIVERSITY
- Filing Date
- 2023-07-11
- Publication Date
- 2026-06-30
AI Technical Summary
Existing gel plugging agents gel rapidly in high-temperature oil reservoir environments, leading to enema-like phenomena. They also contain toxic cross-linking agents, making it difficult to effectively block gas migration, and their long-term stability is poor.
Using physically coated nanocellulose crystals and monomeric acrylamide as raw materials, a high-temperature responsive environmentally friendly gel blocker is prepared by a one-pot method, avoiding the use of crosslinking agents and initiators, controlling gelation time, and improving temperature and salt resistance.
It achieves effective gas channeling blocking in high-temperature environments, possesses excellent temperature and salt resistance and environmental friendliness, high ductility, and high blocking rate, and solves the problem of insufficient strength of existing gel plugging agents at high temperatures.
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Figure CN116854858B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of gel plugging agent technology, specifically a high-temperature responsive environmentally friendly gel plugging agent and its preparation method. Background Technology
[0002] Carbon dioxide enhanced oil recovery (COD) technology achieves both economic benefits and carbon sequestration. However, this technology is still susceptible to gas channeling caused by reservoir fractures. Gas channeling reduces oil recovery, and sealing reservoir fractures is a crucial means of preventing gas channeling. Polymer gels exhibit strong self-adaptability to pores and fractures of varying sizes in the reservoir environment and are widely used in oil and gas fields to prevent carbon dioxide channeling.
[0003] As oilfield extraction depths increase, downhole temperatures and pressures also rise, with high temperature, high pressure, and high salinity becoming major characteristics of current oilfields. Currently, common plugging agents for high temperature resistance, salinity resistance, and high strength are primarily based on polyacrylamide polymers. Polyacrylamide hydrogels using peroxide initiators often gel rapidly at low temperatures, and the gelation rate is even faster in high-temperature reservoir environments. The gel may gel before the solution is even injected into the desired formation, leading to a "gastrointestinal" phenomenon. To improve its temperature resistance, crosslinking agents are added to polyacrylamide or grafted polyacrylamide solutions. Gel plugging agents obtained through this method are mostly gels, which are relatively soft and prone to dehydration and shrinkage at high temperatures, exhibiting poor long-term stability and thus making it difficult to achieve long-term gas channeling prevention. Furthermore, the phenolic crosslinking agents added to the gel system have a certain degree of toxicity, which can cause harm to the environment and human health.
[0004] Therefore, preparing a gel plugging agent that can simultaneously meet the requirements of temperature resistance, salt resistance, high toughness, environmental friendliness, controllable gelation time, and good economy is a huge challenge. Summary of the Invention
[0005] This invention provides a high-temperature responsive environmentally friendly gel plugging agent and its preparation method, overcoming the shortcomings of the prior art. It can effectively solve the problems that existing gel plugging agents are difficult to apply effectively to higher reservoir temperatures and have weak gel strength.
[0006] One of the technical solutions of the present invention is achieved through the following measures: a high-temperature responsive environmentally friendly gel plugging agent, wherein the raw materials include, by mass percentage, 2.04% to 2.18% physically coated nanocellulose crystals, 20% monomeric acrylamide, and the balance water.
[0007] The following are further optimizations and / or improvements to one of the above-mentioned technical solutions:
[0008] The above-mentioned high-temperature responsive environmentally friendly gel plugging agent is obtained by the following method:
[0009] The first step is to add the required amount of physically coated nanocellulose crystals to the required amount of water under stirring conditions, and then add the required amount of monomeric acrylamide until it is completely dissolved to obtain a mixed solution.
[0010] The second step is to introduce nitrogen gas into the mixed solution to remove dissolved oxygen from the mixed solution system.
[0011] The third step involves drying the deoxygenated mixed solution at high temperature to obtain a high-temperature responsive environmentally friendly gel plugging agent.
[0012] In the first step above, the physically coated nanocellulose crystals are added to the required amount of water at a speed of 800 r / min to 1000 r / min and stirred for 20 min to 25 min. Then, the monomer acrylamide is added and stirring is continued for 20 min to 25 min.
[0013] In the second step above, the nitrogen gas is introduced at a rate of 30 mL / min to 35 mL / min for a time of 20 min to 25 min.
[0014] In the third step above, the high-temperature drying temperature is 100℃ to 130℃.
[0015] The above-mentioned physically coated nanocellulose crystals were obtained by the following method:
[0016] S1, add the required amount of nanocellulose crystals to water until completely dispersed, then add the required amount of polyvinylpyrrolidone until completely dissolved to obtain a mixture;
[0017] S2 involves freezing, thawing, and sonicating the mixture until a homogeneous solution is formed, resulting in physically coated nanocellulose crystals.
[0018] In step S1 above, the mass ratio of polyvinylpyrrolidone to nanocellulose crystals is 0.44:(2.20 to 2.24).
[0019] In step S2 above, the mixture is placed in an environment of -20°C to -25°C and frozen for 6.0h to 6.5h. After freezing, it is thawed and then sonicated for 30min to 35min until a homogeneous solution is formed.
[0020] The second technical solution of the present invention is achieved through the following measures: a method for preparing a high-temperature responsive environmentally friendly gel plugging agent, which is carried out according to the following method:
[0021] The first step is to add the required amount of physically coated nanocellulose crystals to the required amount of water under stirring conditions, and then add the required amount of monomeric acrylamide until it is completely dissolved to obtain a mixed solution.
[0022] The second step is to introduce nitrogen gas into the mixed solution to remove dissolved oxygen from the mixed solution system.
[0023] The third step involves drying the deoxygenated mixed solution at high temperature to obtain a high-temperature responsive environmentally friendly gel plugging agent.
[0024] Compared with existing high-temperature resistant gel plugging agents, the high-temperature responsive environmentally friendly gel plugging agent of this invention has a simple and efficient preparation process, does not require the addition of crosslinking agents and initiators, and is green, environmentally friendly and economical. By changing the raw material formulation, the gelation time can be controlled, and its excellent temperature and salt resistance can effectively block gas channeling in high-temperature oil reservoir environments. Attached Figure Description
[0025] Figure 1 The tensile stress-strain curves are for the high-temperature responsive environmentally friendly gel plugging agents prepared in Examples 12 to 16 of this invention.
[0026] Figure 2 The diagram shows the salt resistance of the high-temperature responsive environmentally friendly gel plugging agent prepared in Example 14 of the present invention; wherein, (a) the stability of Example 14 of the present invention at 120°C for 0 to 40 days; (b) the stability of Example 14 of the present invention in sodium chloride solution at 120°C for 0 to 40 days; and (c) the stability of Example 14 of the present invention in calcium chloride solution at 120°C for 0 to 40 days. Detailed Implementation
[0027] This invention is not limited to the following embodiments, and specific implementation methods can be determined according to the technical solutions and actual conditions of this invention. Unless otherwise specified, all chemical reagents and chemicals mentioned in this invention are well-known and commonly used chemical reagents and chemicals in the prior art; unless otherwise specified, all percentages in this invention are mass percentages; unless otherwise specified, all solutions in this invention are aqueous solutions with water as the solvent, for example, hydrochloric acid solution is an aqueous solution of hydrochloric acid; room temperature in this invention generally refers to a temperature between 15°C and 25°C, generally defined as 25°C.
[0028] The present invention will be further described below with reference to embodiments:
[0029] Example 1: The high-temperature responsive environmentally friendly gel plugger comprises, by weight percentage, 2.04% to 2.18% physically coated nanocellulose crystals, 20% monomeric acrylamide, and the balance water.
[0030] In this invention, the purity of the raw material monomer acrylamide is 99%.
[0031] Example 2: As an optimization of the above examples, a high-temperature responsive environmentally friendly gel plugging agent was obtained by the following method:
[0032] The first step is to add the required amount of physically coated nanocellulose crystals to the required amount of water under stirring conditions, and then add the required amount of monomeric acrylamide until it is completely dissolved to obtain a mixed solution.
[0033] The second step is to introduce nitrogen gas into the mixed solution to remove dissolved oxygen from the mixed solution system.
[0034] The third step involves drying the deoxygenated mixed solution at high temperature to obtain a high-temperature responsive environmentally friendly gel plugging agent.
[0035] Example 3: As an optimization of the above example, in the first step, the physically coated nanocellulose crystals are added to the required amount of water at a speed of 800 r / min to 1000 r / min and stirred for 20 min to 25 min. Then, the monomer acrylamide is added and stirring is continued for 20 min to 25 min.
[0036] Example 4: As an optimization of the above example, in the second step, the nitrogen gas flow rate is 30 mL / min to 35 mL / min, and the time is 20 min to 25 min.
[0037] Example 5: As an optimization of the above example, in the third step, the high-temperature drying temperature is 100°C to 130°C.
[0038] Example 6: As an optimization of the above examples, the physically coated nanocellulose crystals were obtained according to the following method:
[0039] S1, add the required amount of nanocellulose crystals to water until completely dispersed, then add the required amount of polyvinylpyrrolidone until completely dissolved to obtain a mixture;
[0040] S2 involves freezing, thawing, and sonicating the mixture until a homogeneous solution is formed, resulting in physically coated nanocellulose crystals.
[0041] In this invention, the molecular weight of polyvinylpyrrolidone is 40,000.
[0042] Example 7: As an optimization of the above example, in step S1, the mass ratio of polyvinylpyrrolidone to nanocellulose crystals is 0.44:(2.20 to 2.24).
[0043] Example 8: As an optimization of the above example, in step S2, the mixture is placed in an environment of -20°C to -25°C and frozen for 6.0h to 6.5h. After freezing, it is thawed and then sonicated for 30min to 35min until a homogeneous solution is formed.
[0044] Compared with the prior art, the advantages of this invention are:
[0045] First, the raw material system of the high-temperature responsive environmentally friendly gel plugging agent of the present invention is simple, containing only monomeric acrylamide and physically coated nanocellulose crystals, without the need for chemical crosslinking agents and initiators;
[0046] Secondly, the preparation process of the high-temperature responsive environmentally friendly gel plugging agent of the present invention is simple. Under the stimulation of a high-temperature environment, the high-temperature responsive environmentally friendly gel plugging agent is formed in one pot.
[0047] Third, the temperature-responsive, environmentally friendly gel plugging agent of this invention exhibits a fracture strain exceeding 9000%, demonstrating excellent performance and effectively preventing gas channeling.
[0048] Example 9:
[0049] This high-temperature responsive environmentally friendly gel plugger contains, by weight percentage, 2.04% physically coated nanocellulose crystals, 20% monomeric acrylamide, and the balance water;
[0050] The physically coated nanocellulose crystals were obtained using the following method:
[0051] S1, add the required amount of nanocellulose crystals to water until completely dispersed, then add the required amount of polyvinylpyrrolidone until completely dissolved to obtain a mixture; wherein, the mass ratio of polyvinylpyrrolidone to nanocellulose crystals is 0.44:2.20;
[0052] S2, the mixture is placed in an environment of -20℃ and frozen for 6.0h. After freezing and thawing, it is sonicated in an ultrasonic machine for 30min until a uniform solution is formed, and then the physically coated nanocellulose crystals are obtained, denoted as PC.
[0053] This high-temperature responsive, environmentally friendly gel plugging agent is obtained by the following method:
[0054] First, at a speed of 800 r / min, add the required amount of physically coated nanocellulose crystals to the required amount of water and stir for 20 min, then add the required amount of monomeric acrylamide and stir for 20 min until completely dissolved to obtain a mixed solution.
[0055] The second step is to purge the mixed solution with nitrogen gas at a rate of 30 mL / min for 20 min to remove dissolved oxygen from the mixed solution system.
[0056] The third step involves drying the deoxygenated mixed solution in a constant temperature oven at 100°C to obtain a high-temperature responsive environmentally friendly gel plugging agent.
[0057] Example 10:
[0058] This high-temperature responsive environmentally friendly gel plugger contains, by weight percentage, 2.18% physically coated nanocellulose crystals, 20% monomeric acrylamide, and the balance water;
[0059] The physically coated nanocellulose crystals were obtained using the following method:
[0060] S1, add the required amount of nanocellulose crystals to water until completely dispersed, then add the required amount of polyvinylpyrrolidone until completely dissolved to obtain a mixture; wherein, the mass ratio of polyvinylpyrrolidone to nanocellulose crystals is 0.44:2.24;
[0061] S2, the mixture is placed in an environment of -25℃ and frozen for 6.5h. After freezing and thawing, it is sonicated in an ultrasonic machine for 35min until a uniform solution is formed, and then the physically coated nanocellulose crystals are obtained, denoted as PC.
[0062] This high-temperature responsive, environmentally friendly gel plugging agent is obtained by the following method:
[0063] First, at a speed of 1000 r / min, add the required amount of physically coated nanocellulose crystals to the required amount of water and stir for 25 min, then add the required amount of monomeric acrylamide and stir for 25 min until completely dissolved to obtain a mixed solution.
[0064] The second step is to purge the mixed solution with nitrogen gas at a rate of 35 mL / min for 25 min to remove dissolved oxygen from the mixed solution system.
[0065] The third step involves drying the deoxygenated mixed solution in a constant temperature oven at 130°C to obtain a high-temperature responsive environmentally friendly gel plugging agent.
[0066] Example 11:
[0067] This high-temperature responsive environmentally friendly gel plugger comprises, by weight percentage, 2.04% to 2.18% physically coated nanocellulose crystals, 20% monomeric acrylamide, and the balance water;
[0068] The physically coated nanocellulose crystals were obtained using the following method:
[0069] S1, add the required amount of nanocellulose crystals to water until completely dispersed, then add the required amount of polyvinylpyrrolidone until completely dissolved to obtain a mixture; wherein, the mass ratio of polyvinylpyrrolidone to nanocellulose crystals is 0.44:2.22;
[0070] S2. The mixture is placed in an environment of -20℃ and frozen for 6 hours. After freezing and thawing, it is ultrasonicated in an ultrasonic machine for 30 minutes until a uniform solution is formed. The physically coated nanocellulose crystals are then obtained and denoted as PC.
[0071] This high-temperature responsive, environmentally friendly gel plugging agent is obtained by the following method:
[0072] First, at a speed of 800 r / min, add the required amount of physically coated nanocellulose crystals to the required amount of water and stir for 22 min, then add the required amount of monomeric acrylamide and stir for 20 min until completely dissolved to obtain a mixed solution.
[0073] The second step is to purge the mixed solution with nitrogen gas at a rate of 30 mL / min for 20 min to remove dissolved oxygen from the mixed solution system.
[0074] The third step involves drying the deoxygenated mixed solution in a constant temperature oven at 120°C to obtain a high-temperature responsive environmentally friendly gel plugging agent.
[0075] The method for preparing a high-temperature responsive environmentally friendly gel plugging agent provided by this invention is green and environmentally friendly, requiring no chemical cross-linking agents or initiators. It prepares a high-temperature responsive environmentally friendly gel plugging agent in a one-pot process, which can effectively block gas channeling in high-temperature environments, thereby improving crude oil recovery. At the same time, it solves the problem that existing gel plugging agents are difficult to apply effectively to high reservoir temperatures and have weak gel strength.
[0076] Example 12: Compared with Example 11, the difference in this example is that the raw materials of this high-temperature responsive environmentally friendly gel plugging agent include, by mass percentage, 2.04% physically coated nanocellulose crystals, 20% acrylamide monomer, and the balance water. The high-temperature responsive environmentally friendly gel plugging agent prepared in this example is denoted as PCH-2.04%.
[0077] Example 13: Compared with Example 11, the difference in this example is that the raw materials of this high-temperature responsive environmentally friendly gel plugging agent, by mass percentage, include 2.07% physically coated nanocellulose crystals, 20% monomeric acrylamide, and the balance water. The high-temperature responsive environmentally friendly gel plugging agent prepared in this example is denoted as PCH-2.07%.
[0078] Example 14: Compared with Example 11, the difference in this example is that the raw materials of this high-temperature responsive environmentally friendly gel plugging agent, by mass percentage, include 2.11% physically coated nanocellulose crystals, 20% acrylamide monomer, and the balance water. The high-temperature responsive environmentally friendly gel plugging agent prepared in this example is denoted as PCH-2.11%.
[0079] Example 15: Compared with Example 11, the difference in this example is that the raw materials of this high-temperature responsive environmentally friendly gel plugging agent, by mass percentage, include 2.14% physically coated nanocellulose crystals, 20% acrylamide monomer, and the balance water. The high-temperature responsive environmentally friendly gel plugging agent prepared in this example is denoted as PCH-2.14%.
[0080] Example 16: Compared with Example 11, the difference in this example is that the raw materials of this high-temperature responsive environmentally friendly gel plugging agent, by mass percentage, include 2.18% physically coated nanocellulose crystals, 20% acrylamide monomer, and the balance water. The high-temperature responsive environmentally friendly gel plugging agent prepared in this example is denoted as PCH-2.18%.
[0081] Example 17: The mechanical properties of the high-temperature responsive environmentally friendly gel plugging agents prepared in Examples 12 to 16 of this invention were tested using a universal testing machine. The mechanical property results are as follows: Figure 1 As shown, by Figure 1 It can be seen that the high-temperature responsive environmentally friendly gel plugging agents prepared in Examples 12 to 16 of the present invention have good extensibility. When the PC content is 2.11%, that is, PCH-2.11% prepared in Example 14 of the present invention, it exhibits amazing extensibility, with an elongation at break of 9522% and a fracture stress of 134.60 kPa.
[0082] Example 18: The gelation time of the high-temperature responsive environmentally friendly gel plugger prepared in Example 14 of the present invention was tested. Specific tests included gelation time tests of gel systems containing different acrylamide concentrations at different temperatures and gelation time tests of gel systems containing different concentrations of physically coated nanocellulose crystals (PC) at different temperatures.
[0083] The gelation time of gel systems containing different acrylamide concentrations at different temperatures was tested as follows: The mass percentage concentration of the physically coated nanocellulose crystals (PC) from Example 14 of this invention was kept constant at 2.11%, and the mass percentage concentration of monomeric acrylamide was set to 5%, 10%, 1%, 20%, 25%, and 30%, respectively. The mixed solutions obtained by mixing the physically coated nanocellulose crystals (PC) with monomeric acrylamide of different mass percentage concentrations were deoxygenated with nitrogen, and then placed in constant temperature ovens at 100℃, 110℃, 120℃, and 130℃, respectively, and the gelation was observed and recorded. The gelation time test results of gel systems containing different acrylamide concentrations at different temperatures are shown in Table 1. As can be seen from Table 1, at temperatures of 100℃ to 130℃, gelation times of 31 min to 1 h 55 min can be obtained by adjusting the acrylamide concentration, achieving controllable gelation time.
[0084] The gelation time of gel systems containing different concentrations of physically coated cellulose nanocrystals (PC) at different temperatures was tested. The specific experiments were as follows: The mass percentage concentration of acrylamide, the raw material in Example 14 of this invention, was kept constant at 20%. The mass percentage concentrations of physically coated cellulose nanocrystals (PC) were set to 2.03%, 2.05%, 2.07%, 2.09%, 2.11%, and 2.13%, respectively. Mixed solutions obtained by mixing physically coated cellulose nanocrystals (PC) with monomeric acrylamide at different mass percentage concentrations were subjected to nitrogen deoxygenation. Then, they were placed in constant temperature ovens at 100℃, 110℃, 120℃, and 130℃, and the gelation process was observed and recorded. The gelation time results of gel systems containing different PC concentrations at different temperatures are shown in Table 2. Table 2 shows that at temperatures ranging from 100℃ to 130℃, gelation times from 31 min to 1 h 5 min can be obtained by adjusting the concentration of cellulose nanocrystals, achieving controllable gelation time.
[0085] Example 19: Temperature and salt resistance tests were conducted on the high-temperature responsive environmentally friendly gel plugging agent prepared in Example 14 of this invention. The water in the high-temperature responsive environmentally friendly gel plugging agent system prepared in Example 14 of this invention was replaced with 3 mol / L sodium chloride solution and 3 mol / L calcium chloride solution. The gelation behavior at 120℃ and the stability after gelation were observed. The stability test results are as follows: Figure 2 As shown, by Figure 2As can be seen from the temperature and salt resistance tests, the PCH-2.11% prepared in Example 14 of this invention did not exhibit significant liquid precipitation or flow on the gel surface during the 40-day anti-aging test. This is because the introduction of rigid groups in the nanocellulose crystals increased the thermal stability of the gel system and raised the thermal degradation temperature of the gel. Simultaneously, no significant liquid precipitation or flow on the gel surface was observed in sodium chloride solution or calcium chloride solution, indicating that the high-temperature responsive environmentally friendly gel blocker of this invention not only possesses excellent temperature resistance but also exhibits salt resistance at high temperatures.
[0086] Example 20: The sealing performance of the high-temperature responsive environmentally friendly gel plugging agents prepared in Examples 12 to 16 of this invention was tested. Specific experiments are as follows:
[0087] (1) Preparation of sand filling pipe
[0088] Quartz sand of 40 to 80 mesh was used to fill the sand-filling tube. 300-mesh screens were installed at both ends of the bottom of the sand-filling tube to prevent sand leakage. Water was injected into the core at an injection rate of 0.5 mL / min, and the permeability K1 before plugging the sand-filling tube was measured. Sand-filling tube model parameters: core length 30.3 cm, diameter 2.7 cm;
[0089] (2) Inject the aqueous solutions prepared in the above embodiments before gelation.
[0090] At room temperature, the aqueous solution of Examples 12 to 16 before gelation was injected into the core tube, and then the sand-filled tube was placed in a constant temperature oven at 100°C for 4 hours.
[0091] (3) Displacement
[0092] Remove the sand-filled tube and connect it to the displacement system device. Inject CO2 at a flow rate of 0.5 ml / min until bubbles are generated at the outlet end immersed in water and the pressure remains constant. Stop the CO2 injection, record the reading on the pressure gauge, and calculate the permeability K2 after plugging, as well as the breakthrough pressure gradient, residual resistance coefficient, and plugging efficiency.
[0093] The sealing effect is shown in Table 3. As can be seen from Table 3, at a temperature of 100℃, the gas driving permeability after sealing is significantly reduced (from 22.1 to 42.4) compared with the permeability before sealing (707.4 to 738.1). Furthermore, the PCH-2.04%, PCH-2.07%, PCH-2.11%, and PCH-2.14% prepared in the embodiments of the present invention all showed a sealing rate of more than 94% in the indoor displacement system device, indicating that the high-temperature responsive environmentally friendly gel plugging agent of the present invention has excellent anti-gas channeling performance.
[0094] Example 21: To investigate the adaptability of the high-temperature responsive environmentally friendly gel plugging agent of the present invention to reservoir environments with higher temperatures, PCH-2.11% prepared in Example 14 of the present invention, which exhibited the best plugging performance at 100℃, was selected for plugging experiments at 110℃, 120℃, and 130℃. The test results are shown in Table 4. As can be seen from Table 4, under high-temperature stimulation of 110 to 130℃, the gel solution of the high-temperature responsive environmentally friendly gel plugging agent of the present invention can form a gel in situ within the porous channels, with a plugging rate exceeding 97%, indicating that the high-temperature responsive environmentally friendly gel plugging agent of the present invention exhibits excellent anti-gas channeling performance under high-temperature environments.
[0095] In summary, the preparation process of the high-temperature responsive environmentally friendly gel plugging agent of this invention is simple and efficient, requiring no addition of crosslinking agents and initiators. It is green, environmentally friendly, and economical. By changing the raw material formulation, the gelation time can be controlled. At the same time, its excellent temperature and salt resistance can effectively block gas channeling in high-temperature oil reservoir environments.
[0096] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.
[0097]
Claims
1. A high-temperature responsive environmentally friendly gel plugging agent, characterized in that... The raw materials, by mass percentage, comprise 2.04% to 2.18% physically coated nanocellulose crystals, 20% acrylamide monomer, and the balance water, and are obtained by the following method: The first step involves adding the required amount of physically coated cellulose nanocrystals to the required amount of water under stirring conditions, followed by the required amount of acrylamide monomer, until completely dissolved to obtain a mixed solution. The physically coated cellulose nanocrystals are obtained as follows: S1, add the required amount of nanocellulose crystals to water until completely dispersed, then add the required amount of polyvinylpyrrolidone until completely dissolved to obtain a mixture; S2, after freezing, thawing and sonicating the mixture until a homogeneous solution is formed, the physically coated nanocellulose crystals are obtained; The second step is to introduce nitrogen gas into the mixed solution to remove dissolved oxygen from the mixed solution system. The third step involves drying the deoxygenated mixed solution at high temperature to obtain a high-temperature responsive environmentally friendly gel plugging agent.
2. The high-temperature responsive environmentally friendly gel plugging agent according to claim 1, characterized in that... In the first step, the physically coated nanocellulose crystals are added to the required amount of water at a speed of 800 r / min to 1000 r / min and stirred for 20 min to 25 min. Then, the monomer acrylamide is added and stirring is continued for 20 min to 25 min.
3. The high-temperature responsive environmentally friendly gel plugging agent according to claim 1 or 2, characterized in that... In the second step, the nitrogen gas is introduced at a rate of 30 mL / min to 35 mL / min for a time of 20 min to 25 min.
4. The high-temperature responsive environmentally friendly gel plugging agent according to claim 3, characterized in that... In the third step, the high-temperature drying temperature is 100℃ to 130℃.
5. The high-temperature responsive environmentally friendly gel plugging agent according to claim 1, 2, or 4, characterized in that... In step S1, the mass ratio of polyvinylpyrrolidone to nanocellulose crystals is 0.44:2.20 to 2.
24.
6. The high-temperature responsive environmentally friendly gel plugging agent according to claim 5, characterized in that... In step S2, the mixture is placed in an environment of -20°C to -25°C and frozen for 6.0h to 6.5h. After freezing, it is thawed and then sonicated for 30min to 35min until a homogeneous solution is formed.
7. The method for preparing the high-temperature responsive environmentally friendly gel plugging agent according to any one of claims 1 to 6, characterized in that... Perform it as follows: The first step is to add the required amount of physically coated nanocellulose crystals to the required amount of water under stirring conditions, and then add the required amount of monomeric acrylamide until it is completely dissolved to obtain a mixed solution. The second step is to introduce nitrogen gas into the mixed solution to remove dissolved oxygen from the mixed solution system. The third step involves drying the deoxygenated mixed solution at high temperature to obtain a high-temperature responsive environmentally friendly gel plugging agent.