Modified graphene graft polymer as well as preparation method and application thereof
Patent Information
- Application Number
- CN202411128898.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-16
- Publication Date
- 2026-03-03
Smart Images
Figure CN121591968A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of oilfield development technology, specifically to a modified graphene-grafted polymer, its preparation method, and its application. Background Technology
[0002] During oil and gas drilling, when encountering microfractures and nanopores in the rock formation, drilling fluid (filtrate) preferentially penetrates the formation along bedding planes and microfractures under the influence of hydraulic pressure, capillary force, and chemical potential difference, leading to wellbore instability. Therefore, the key to maintaining wellbore stability is to prevent pore pressure transmission, which requires enhancing the sealing properties of the drilling fluid against micropores and microfractures in the rock formation. Traditional drilling fluid plugging agents have relatively large particle sizes (millimeters and micrometers), making it difficult to effectively seal nanopores in the rock formation. Driven by hydraulic pressure, capillary force, and chemical potential difference, drilling fluid (filtrate) can still slowly infiltrate the formation through nanopores and microfractures, affecting wellbore stability.
[0003] To address the unique microporous structure of formations, researchers both domestically and internationally have explored adding nanoparticles to drilling fluids to enhance their sealing performance against nanoscale micropores and microfractures. For example, nano-silica can effectively embed itself into the throats of shale micropores, forming a dense inner and outer mud cake around the wellbore, thus reducing shale permeability. Ferric oxide nano-plugging agents obtained through thermal decomposition can significantly improve the sealing performance of drilling fluids and exhibit good magnetic field response behavior and salt resistance. However, the sealing effectiveness of these plugging agents requires further improvement. Summary of the Invention
[0004] Traditional plugging agents primarily achieve physical plugging through the size effect of their nanoparticles. The inventors of this invention discovered that modified graphene-grafted polymers, prepared by surface modification and graft polymerization of graphene, can adapt to different formation temperatures. Furthermore, when the minimum co-solution temperature of the modified graphene-grafted polymer is below the temperature of the bottom layer containing the wellbore, the plugging effect on the wellbore is good, further improving wellbore stability. This leads to the present invention.
[0005] The first aspect of the present invention provides a modified graphene graft polymer, wherein the modified graphene graft polymer comprises a polymer portion, a linking group and a graphene portion, wherein the polymer portion is connected to the graphene through the linking group, the polymer portion comprises structural unit A as shown in formula (A) and structural unit B as shown in formula (B), and the molar ratio of structural unit A to structural unit B in the polymer portion is (1-10):1;
[0006]
[0007] Wherein, R1 and R2 are each independently selected from hydrogen or C1-C3 alkyl groups, and R3 is selected from hydroxyl or...
[0008]
[0009] A second aspect of the present invention provides a method for preparing a modified graphene-grafted polymer, wherein the preparation method includes the following steps:
[0010] (1) Graphene and silane coupling agent are contacted to obtain silane coupling agent-grafted graphene.
[0011] (2) Silane coupling agent-grafted graphene, N-isopropylacrylamide and monomer B are polymerized in the presence of an initiator;
[0012] The structure of monomer B is shown in formula (B');
[0013]
[0014] Wherein, R'1 and R'2 are each independently selected from hydrogen or C1-C3 alkyl groups, and R'3 is selected from hydroxyl or...
[0015]
[0016] The third aspect of the present invention provides a modified graphene graft polymer prepared by the method described in the second aspect of the present invention.
[0017] A fourth aspect of the present invention provides a drilling fluid, wherein the drilling fluid contains the modified graphene graft polymer described in any one of the first and third aspects of the present invention.
[0018] The fifth aspect of the present invention provides the application of the modified graphene-grafted polymer described in any one of the first and third aspects of the present invention in oil and gas drilling.
[0019] Through the above technical solution, the modified graphene graft polymer provided by the present invention can adapt to different formation temperatures when used as a plugging agent, with low drilling fluid filtration loss, good plugging effect, and the sealing and plugging characteristics of nanoparticles. It also has strong non-permeability and can prevent gas and liquid penetration. Detailed Implementation
[0020] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0021] The first aspect of the present invention provides a modified graphene graft polymer, wherein the modified graphene graft polymer comprises a polymer portion, a linking group and a graphene portion, wherein the polymer portion is connected to the graphene through the linking group, the polymer portion comprises structural unit A as shown in formula (A) and structural unit B as shown in formula (B), and the molar ratio of structural unit A to structural unit B in the polymer portion is (1-10):1;
[0022]
[0023] Wherein, R1 and R2 are each independently selected from hydrogen or C1-C3 alkyl groups, and R3 is selected from hydroxyl or...
[0024]
[0025] The inventors of this invention discovered in their research that the sealing effect on the wellbore can be further improved by at least controlling the phase transition temperature of the graphene surface polymer. The modified graphene-grafted polymer prepared by the inventors through surface modification and graft polymerization of graphene can adapt to different formation temperatures. Furthermore, when the minimum co-solution temperature of the modified graphene-grafted polymer is below the temperature of the bottom layer containing the wellbore, the sealing effect on the wellbore is good, further improving wellbore stability.
[0026] Preferably, when the graphene portion is provided by graphene oxide, the modified graphene graft polymer formed by it and the structural units A and B has a better sealing effect on the well wall.
[0027] Preferably, the oxygen content in the XPS test results of the graphene is not less than 5 wt%.
[0028] More preferably, the oxygen content in the graphene, as determined by XPS testing, is 5-30 wt%.
[0029] In this invention, the inventors discovered that when the oxygen content in the graphene is less than 5 wt%, the particle size of the resulting modified graphene graft polymer is the same as that of the ungrafted graphene material, indicating a low degree of grafting; when the oxygen content in the graphene is greater than 30 wt%, the particle size of the resulting modified graphene graft polymer is large, making it prone to agglomeration and sedimentation.
[0030] To achieve better graft polymerization results and to ensure that the prepared modified graphene graft polymer has better wellbore sealing performance, preferably, R1 and R2 are each independently selected from hydrogen or methyl, and R3 is hydroxyl.
[0031] To achieve better graft polymerization results and improve the wellbore sealing performance of the prepared modified graphene graft polymer, preferably, R1 and R2 are both hydrogen, and R3 is hydrogen.
[0032] In this invention, the linking group is provided by a silane coupling agent. The silane coupling agent is a conventionally used coupling agent in the art, for example, it may be at least one of vinyltriethoxysilane (A151), vinyltrimethoxysilane (A171), vinyltris(β-methoxyethoxy)silane (A172), γ-aminopropyltriethoxysilane (KH550), γ-glycidoxypropyltrimethoxysilane (KH560), and γ-methacryloyloxypropyltrimethoxysilane (KH570). The structure of the linking group is a conventionally used structure in the art, for example, it may be the structure shown in formula (1):
[0033]
[0034] R4 is selected from -CH=CH2, -NH2 or n is an integer between 0 and 6.
[0035] In this invention, preferably, R4 is n is an integer between 2 and 4.
[0036] In this invention, preferably, R4 is -CH=CH2 and n=0.
[0037] In this invention, preferably, R4 is -NH2 and n is an integer from 2 to 4.
[0038] In this invention, preferably, R4 is n is an integer between 2 and 4.
[0039] To obtain better graft polymerization effect and to make the prepared modified graphene graft polymer have better wellbore sealing effect, preferably, the graphene portion accounts for 5-30 wt% of the total weight of the modified graphene graft polymer (for example, it can be 5 wt%, 7 wt%, 10 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%, 20 wt%, 22 wt%, 24 wt%, 26 wt%, 28 wt%, 30 wt%, and any range and any value within the range of the above values), more preferably 5-20 wt%, further preferably 12-20 wt%, and even more preferably 13-18%.
[0040] To obtain better grafting polymerization effect and make the prepared modified graphene grafted polymer have better well wall sealing effect, preferably, the molar ratio of structural unit A to structural unit B in the polymer part is (1-10):1, more preferably (9±0.5):1, or (7±0.5):3, or (1±0.5):1.
[0041] To achieve better graft polymerization results and to ensure that the prepared modified graphene graft polymer has better wellbore sealing performance, preferably, the polymer portion is a block copolymer.
[0042] In this invention, the particle size of the modified graphene graft polymer can be adjusted as needed. For example, the particle size of the modified graphene graft polymer can be 50-500 nm, and the determination method is laser particle size distribution.
[0043] A second aspect of the present invention provides a method for preparing a modified graphene-grafted polymer, wherein the preparation method includes the following steps:
[0044] (1) Graphene and silane coupling agent are contacted to obtain silane coupling agent-grafted graphene.
[0045] (2) Silane coupling agent-grafted graphene, N-isopropylacrylamide and monomer B are polymerized in the presence of an initiator;
[0046] The structure of monomer B is shown in formula (B');
[0047]
[0048] Wherein, R'1 and R'2 are each independently selected from hydrogen or C1-C3 alkyl groups, and R'3 is selected from hydroxyl or...
[0049]
[0050] To achieve better graft polymerization results and to ensure that the prepared modified graphene graft polymer has better wellbore sealing performance, preferably, R'1 and R'2 are each independently selected from hydrogen or methyl, and R'3 is hydroxyl.
[0051] To achieve better graft polymerization results and improve the wellbore sealing performance of the prepared modified graphene graft polymer, preferably, R'1 and R'2 are both hydrogen, and R'3 is hydrogen.
[0052] To obtain better graft polymerization effect and to make the prepared modified graphene graft polymer have better wellbore sealing effect, preferably, the mass ratio of graphene to N-isopropylacrylamide is 1:(0.1-30), for example, it can be 0.1:1, 0.5:1, 1:1, 1:2, 1:4, 1:6, 1:8, 1:10, 1:12, 1:14, 1:16, 1:18, 1:20, 1:22, 1:24, 1:26, 1:28, 1:30, and any range and any value within the range of the above values, preferably 1:(1-12).
[0053] To obtain better graft polymerization effect and make the prepared modified graphene graft polymer have better well wall sealing effect, preferably, the molar ratio of N-isopropylacrylamide to monomer B is (1-10):1; more preferably, it is (9±0.5):1, or (7±0.5):3, or (1±0.5):1.
[0054] To achieve better grafting polymerization and to ensure that the prepared modified graphene graft polymer has better wellbore sealing effect, preferably, the weight ratio of graphene to silane coupling agent is (1-60):1, more preferably (10-40):1. For example, it can be any range and any value within the range of 10, 15, 20, 25, 30, 35, 40, and any of the above values.
[0055] In this invention, the silane coupling agent is as described in the first aspect of the invention, and will not be repeated here. To further improve the wellbore sealing effect of the modified graphene-grafted polymer, the coupling agent is preferably γ-methacryloyloxypropyltrimethoxysilane (KH570).
[0056] In this invention, the mass ratio of the initiator (N-isopropylacrylamide + monomer B) is 1:(200-500), for example, it can be 1:200, 1:250, 1:30, 1:350, 1:400, 1:450, 1:500, and any range and any value within the range of the above values.
[0057] In this invention, the initiator is a conventionally used initiator in the art, such as at least one selected from persulfates and azo compounds. In this invention, the azo compounds refer to compounds containing nitrogen-nitrogen double bonds in their molecular structure, such as azobisisobutyronitrile, azobisisoheptanenitrile, and azoisobutylcyanoformamide; the persulfate can be potassium persulfate, sodium persulfate, ammonium persulfate, etc.
[0058] In this invention, preferably, the graphene is graphene oxide.
[0059] In this invention, preferably, the oxygen content in the XPS test results of the graphene is not less than 5 wt%.
[0060] More preferably, the oxygen content in the XPS test results of the graphene is 5-30 wt%.
[0061] In this invention, preferably, the contact temperature in step (1) is 60-90°C, more preferably 80-90°C.
[0062] Preferably, the contact time in step (1) is 2-10 hours, more preferably 5-7 hours.
[0063] Preferably, in step (2), the polymerization reaction conditions include a temperature of 40-95°C, more preferably 75-85°C. The polymerization reaction time can be determined according to the monomer conversion rate, and the reaction is terminated when the desired monomer conversion rate is reached. In this invention, preferably, the polymerization reaction time is 5-15 hours, and the monomer conversion rate is preferably above 80%, more preferably above 90%.
[0064] According to a preferred embodiment of the present invention, the polymerization reaction is carried out as follows: a first polymerization reaction is performed by contacting graphene grafted with a silane coupling agent, monomer B, and an initiator; then, N-isopropylacrylamide is added to the first polymerization reaction system to carry out a second polymerization reaction. The temperatures of the first and second polymerization reactions are each independently 40-95°C, preferably 75-85°C. The durations of the first and second polymerization reactions are each independently 2.5-7.5 h. More preferably, the duration of the first polymerization reaction is 2.5-3.5 h. More preferably, the duration of the second polymerization reaction is 5.5-6.5 h.
[0065] In this invention, in order to make the graphene and silane coupling agent more fully contacted in step (1), the mixture can be stirred before contact, and the stirring can be carried out by ultrasonic vibration.
[0066] In this invention, in order to make the silane coupling agent-grafted graphene, N-isopropylacrylamide and monomer B more fully contacted in step (2), the mixture can be stirred before contact, and the stirring can be carried out by ultrasonic vibration.
[0067] The third aspect of the present invention provides a graphene-grafted polymer prepared by the method described in the second aspect of the present invention.
[0068] A fourth aspect of the present invention provides a drilling fluid, wherein the drilling fluid contains the modified graphene graft polymer described in any one of the first and third aspects of the present invention.
[0069] In this invention, the drilling fluid further comprises a drilling fluid-based slurry. The drilling fluid-based slurry may contain bentonite and a treatment agent. The weight of solids in the drilling fluid-based slurry accounts for 2-20% of the total weight of the drilling fluid-based slurry, more preferably 2-10%.
[0070] In this invention, the modified graphene graft polymer accounts for 1-10% of the total weight of the drilling fluid, for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, and any range and any value within the range of the above values.
[0071] In this invention, the weight ratio of bentonite to alkyl-containing sulfonate can be (1-20):1, more preferably (1-8):1.
[0072] In this invention, the treatment agent may be a viscosity reducer (e.g., alkyl-containing sulfonates), thickener (e.g., clay), preservative, pH adjuster (e.g., calcium oxide and sodium hydroxide), bactericide (e.g., calcium oxide and sodium hypochlorite), or suspending agent (e.g., silica gel and dolomite) commonly used in the art.
[0073] The alkyl-containing sulfonate can be at least one of iron-chromium lignin sulfonate, alkylbenzene sulfonate, alkyl sulfonate and alkylnaphthalene sulfonate, for example, it can be at least one of potassium alkylbenzene sulfonate, sodium alkylbenzene sulfonate, calcium alkylbenzene sulfonate, potassium alkyl sulfonate, calcium alkyl sulfonate, sodium alkyl sulfonate, potassium alkylnaphthalene sulfonate, sodium alkylnaphthalene sulfonate and calcium alkylnaphthalene sulfonate; wherein, the alkyl group in the alkyl-containing sulfonate can also be selected from C6-C40 alkyl groups.
[0074] The modified graphene-grafted polymer described in this invention can be used as a plugging agent to improve the stability of the wellbore during oil and gas drilling.
[0075] The fifth aspect of the present invention provides the application of the modified graphene-grafted polymer described in any one of the first and third aspects of the present invention in oil and gas drilling.
[0076] The modified graphene-grafted polymer described in this invention can be used as a plugging agent in drilling fluid to improve the stability of the wellbore during oil and gas drilling.
[0077] The present invention will be described in detail below through embodiments. Unless otherwise specified, the methods used in the following embodiments are conventional methods in the art, and the reagents used are conventional reagents that are commercially available.
[0078] Unless otherwise specified, all materials and reagents used in the embodiments of this invention are commercially available. Experimental methods not specifically described in the embodiments are generally performed under standard conditions or as recommended by the manufacturer.
[0079] In the following examples and comparative examples, NIPAM refers to N-isopropylacrylamide, and AA refers to acrylic acid.
[0080] Weight content determination of each structural unit: The unreacted N-isopropylacrylamide and monomer B in the system after the reaction were measured by NMR analyzer and then calculated.
[0081] In the following examples and comparative examples, the graphene content in the modified graphene graft polymer is close to the amount of feed.
[0082] The silane coupling agent KH570 was purchased from Yunsheng Chemical (Shandong) Co., Ltd., product number KH570.
[0083] The LCST test method: The transmittance of the modified graphene grafted polymer at different temperatures was determined using a UV-1750 ultraviolet-visible spectrophotometer manufactured by Shimadzu International Trading (Shanghai) Co., Ltd. After plotting the transmittance-temperature change curve, the inflection point of the curve corresponds to the LCST temperature of the modified graphene grafted polymer.
[0084] Unless otherwise specified, the graphene oxide used in the following examples and comparative examples was purchased from Changzhou Sixth Element Materials Technology Co., Ltd. The oxygen content in the XPS test results was 28 wt%, and the sum of the contents of carbon and other elements besides oxygen in the XPS test results was 7 wt%.
[0085] In the modified graphene graft polymers prepared in the following examples, the molar ratio of structural unit A to B is close to the feed ratio of N-isopropylacrylamide and monomer B.
[0086] Example 1
[0087] 2g of graphene oxide was weighed and dispersed in deionized water, and ultrasonically dispersed for 30 min. Separately, 0.1g of silane coupling agent KH570 was dissolved in deionized water. The two mixtures were thoroughly mixed, and ultrasonic treatment was continued for 1 h. The mixture was then transferred to a synthesis reactor and ultrasonically reacted at 85℃ for 6 h. After the reaction was complete, the product was centrifuged to obtain the silane coupling agent-graphene material. 1.44g of AA (controlling the molar ratio of NIPAM to AA to be 90:10) was weighed and dissolved in water. The prepared silane coupling agent-graphene material was then added, and the mixture was ultrasonically dispersed for 30 min. 0.05g of potassium persulfate was added to the ultrasonically dispersed system, and the mixture was rapidly stirred to ensure homogeneity. After reacting at 80℃ for 3 h, 20.34g of NIPAM was added to the system, and the reaction was continued at 80℃ for another 6 h. After the reaction was complete, the product was centrifuged to obtain the modified graphene graft polymer, whose lowest eutectic temperature (LCST) was 60℃.
[0088] Example 2
[0089] 2.5 g of graphene oxide was weighed and dispersed in deionized water, and ultrasonically dispersed for 30 min. Separately, 0.1 g of silane coupling agent KH570 was dissolved in deionized water. The two mixtures were thoroughly mixed, and ultrasonic treatment was continued for 1 h. The mixture was then transferred to a synthesis reactor and ultrasonically reacted at 85 °C for 6 h. After the reaction was complete, the product was centrifuged to obtain the silane coupling agent-graphene material. 4.32 g of AA (controlling the molar ratio of NIPAM to AA to be 70:30) was weighed and dissolved in water. The prepared silane coupling agent-graphene material was then added, and the mixture was ultrasonically dispersed for 30 min. 0.05 g of potassium persulfate was added to the ultrasonically dispersed system, and the mixture was rapidly stirred to homogenize. The reaction was carried out at 80 °C for 3 h. Then, 15.82 g of NIPAM was added to the system, and the reaction was continued at 80 °C for 6 h. After the reaction was complete, the product was centrifuged to obtain the modified graphene graft polymer, with a LCST of 90 °C.
[0090] Example 3
[0091] 3g of graphene oxide was weighed and dispersed in deionized water, and ultrasonically dispersed for 30 min. Separately, 0.1g of silane coupling agent KH570 was dissolved in deionized water. The two mixtures were thoroughly mixed, and ultrasonic treatment was continued for 1 h. The mixture was then transferred to a synthesis reactor and ultrasonically vibrated at 85℃ for 6 h. After the reaction was complete, the product was centrifuged to obtain the silane coupling agent-graphene material. 7.2g of AA (controlling the molar ratio of NIPAM to AA to be 50:50) was weighed and dissolved in water. The prepared silane coupling agent-graphene material was then added, and the mixture was ultrasonically dispersed for 30 min. 0.05g of potassium persulfate was added to the ultrasonically dispersed system, and the mixture was rapidly stirred to homogenize. The reaction was carried out at 80℃ for 3 h. Then, 11.3g of NIPAM was added to the system, and the reaction was continued at 80℃ for another 6 h. After the reaction was complete, the product was centrifuged to obtain the modified graphene graft polymer, with a LCST of 160℃.
[0092] Examples 4-5
[0093] The method of Example 3 is followed, except that acrylic acid (AA) is replaced with other monomers, and the types and amounts of monomers added, as well as LCST, are shown in Table 1.
[0094] Table 1
[0095] Monomer B NIPAM: Monomer B (mol) LCST (°C) Example 4 methacrylic acid 1:1 156 Example 5 2-Acrylamido-2-methyl-1-propanesulfonic acid 1:1 151
[0096] Comparative Example 1
[0097] Following the method of Example 3, except that NIPAM was not added, but 11.3g of AA was added to obtain a modified graphene graft polymer with no LCST transition temperature.
[0098] Comparative Example 2
[0099] Following the method of Example 3, except that the molar ratio of NIPAM and AA was 1:9, a modified graphene graft polymer was obtained, which had no LCST transition temperature.
[0100] Test Example 1
[0101] The content of structural units in the polymer was determined based on the feeding of NIPAM and AA, as shown in Table 2 below.
[0102] Table 2
[0103]
[0104] Application Examples 1-5
[0105] Take 350 ml of distilled water, add 14 g of bentonite, stir at high speed for 20 min, let stand and cure for 24 h, add 3.5 g of iron-chromium lignin sulfonate and 7 g of evaluation soil, stir at low speed for 20 min, stir at high speed for 10 min to make the base slurry. Add 1 g of the modified graphene graft polymer prepared in each example to the base slurry.
[0106] Comparative application examples 1-2
[0107] The method is the same as in the application example, except that the modified graphene graft polymers prepared in each comparative ratio are added.
[0108] Comparative Application Example A
[0109] Preparation of Polymer A: The method of Example 3 was followed, except that the step of preparing the silane coupling agent-graphene material was omitted. The LCST of the obtained Polymer A was 160°C.
[0110] The method is the same as in Application Example 1, except that graphene and polymer A of the same mass as in Example 3 are added respectively.
[0111] Test Example 2
[0112] After the drilling fluids of the application examples and comparative application examples were hot-rolled for 16 hours at the corresponding LCST temperature (or 160°C if there was no LCST) of the samples prepared in each example and comparative example, the API filtration loss and high-temperature high-pressure filtration loss were evaluated. The results are shown in Table 3. The test method refers to GB / T 16783.1-2014.
[0113] Drilling fluid without any of the polymers mentioned above was used as a blank control sample, and its API filtration loss and high-temperature high-pressure filtration loss were also tested.
[0114] Table 3
[0115]
[0116]
[0117] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.
Claims
1. A modified graphene-grafted polymer, characterized in that, The modified graphene graft polymer comprises a polymer portion, a linking group, and a graphene portion, wherein the polymer portion is connected to the graphene through the linking group, and the polymer portion includes structural unit A as shown in formula (A) and structural unit B as shown in formula (B), wherein the molar ratio of structural unit A to structural unit B in the polymer portion is (1-10):
1. Wherein, R1 and R2 are each independently selected from hydrogen or C1-C3 alkyl groups, and R3 is selected from hydroxyl or...
2. The modified graphene-grafted polymer according to claim 1, wherein, The graphene portion accounts for 5-30 wt% of the total weight of the modified graphene graft polymer, preferably 5-20 wt%, and more preferably 12-20 wt%. And / or, the graphene portion is provided by graphene oxide; Preferably, the oxygen content in the XPS test results of the graphene is not less than 5 wt%. More preferably, the oxygen content in the graphene, as determined by XPS testing, is 5-30 wt%.
3. The modified graphene graft polymer according to claim 1 or 2, wherein R1 and R2 are each independently selected from hydrogen or methyl, and R3 is hydroxyl; Preferably, R1 and R2 are both hydrogen, and R3 is...
4. The modified graphene-grafted polymer according to claim 1 or 2, wherein, The molar ratio of structural unit A to structural unit B in the polymer portion is (9±0.5):1, or (7±0.5):3, or (1±0.5):1; And / or, the polymer portion is a block copolymer.
5. A method for preparing a modified graphene-grafted polymer, characterized in that, The preparation method includes the following steps: (1) Graphene and silane coupling agent are contacted to obtain silane coupling agent-grafted graphene. (2) Silane coupling agent-grafted graphene, N-isopropylacrylamide and monomer B are polymerized in the presence of an initiator; The structure of monomer B is shown in formula (B'); Wherein, R'1 and R'2 are each independently selected from hydrogen or C1-C3 alkyl groups, and R'3 is selected from hydroxyl or...
6. The method according to claim 5, wherein, The mass ratio of graphene to N-isopropylacrylamide is 1:(0.1-30), preferably 1:(1-12); Preferably, the molar ratio of N-isopropylacrylamide to monomer B is (1-10):1; more preferably (9±0.5):1, or (7±0.5):3, or (1±0.5):1; Preferably, the weight ratio of the graphene to the silane coupling agent is (1-60):1, more preferably (10-40):
1.
7. The method according to claim 5 or 6, wherein, The initiator (N-isopropylacrylamide + monomer B) has a mass ratio of 1:(200-500); Preferably, the graphene is graphene oxide; Preferably, the oxygen content in the XPS test results of the graphene is not less than 5 wt%; More preferably, the oxygen content in the graphene, as determined by XPS testing, is 5-30 wt%.
8. The method according to claim 5 or 6, wherein, The contact temperature described in step (1) is 60-90℃; Preferably, the contact time in step (1) is 2-10 hours; Preferably, in step (2), the conditions for the polymerization reaction include: a temperature of 40-95°C and a time of 5-15h.
9. The modified graphene graft polymer prepared by the method according to any one of claims 5-8.
10. A drilling fluid, characterized in that, The drilling fluid contains the modified graphene graft polymer as described in any one of claims 1-4 and 9.
11. The application of the modified graphene-grafted polymer according to any one of claims 1-4 and 9 in oil and gas drilling.