Zwitterionic polymerization grafted graphene oxide blocking agent and water-based drilling fluid

Abstract

The invention relates to the field of oilfield chemistry, and discloses a zwitterionic polymerization grafted graphene oxide blocking agent and a water-based drilling fluid, a preparation method of zwitterionic polymerization grafted graphene oxide comprises the following steps: after ultrasonic dispersion of graphene oxide, reacting with a silane coupling agent-absolute ethyl alcohol mixed solution to prepare aminated graphene oxide; dispersing the brominated graphene oxide in methylbenzene and reacting with a surface initiator to obtain brominated graphene oxide; and under the protection of nitrogen, in a deionized water / dimethyl sulfoxide mixed solvent, atom transfer radical polymerization is carried out by using a ligand, a zwitterionic monomer and a catalyst, and finally, zwitterionic polymerization grafted graphene oxide is obtained through dialysis. The composite material has excellent plugging performance under the conditions of high temperature and high salinity, can effectively solve the problem of plugging failure of high-performance plugging anti-sloughing water-based drilling fluid, and provides a novel drilling fluid system support for drilling and development of resources such as shale gas and natural gas.

Description

Technical Field

[0001] The present invention relates to the field of oilfield chemistry, and in particular to a zwitterionic polymerized grafted graphene oxide plugging agent and a water-based drilling fluid. Background Art

[0002] Drilling operations in deep wells and high-temperature, high-pressure environments present numerous technical challenges, particularly complex downhole issues such as wellbore instability and lost circulation. Micro- and nano-scale cracks are common in formations, and these cracks can easily lead to seepage losses of drilling fluid, which can in turn cause wellbore collapse, stuck pipe, and other engineering accidents, severely impacting drilling efficiency and operational safety. Therefore, developing drilling fluid systems with excellent sealing properties, particularly water-based drilling fluids that can operate stably in high-temperature, high-mineralization environments, has become a key research direction in drilling technology.

[0003] Currently, oil-based drilling fluids are widely used in complex formations due to their excellent sealing and rheological properties. However, oil-based drilling fluids suffer from poor environmental performance and high costs, limiting their widespread use in areas with strict environmental protection requirements. Therefore, high-performance plugging and anti-collapse water-based drilling fluids are becoming an increasingly popular alternative to oil-based drilling fluids due to their superior environmental performance and low cost. However, traditional water-based drilling fluids exhibit poor stability under high-temperature and high-salinity conditions, which can easily lead to plugging agent aggregation and precipitation, compromising the plugging effectiveness and reducing the overall performance of the drilling fluid.

[0004] Two-dimensional nanographene oxide, due to its high specific surface area, excellent mechanical strength, and high-temperature resistance, has become a highly promising material for plugging micro- and nano-cracks. Graphene oxide can form a tight plugging barrier in drilling fluid systems, effectively preventing drilling fluid from entering micro- and nano-cracks and reducing fluid loss. However, conventional graphene oxide is prone to agglomeration and precipitation in high-temperature, high-mineralization environments, resulting in a decrease in plugging effectiveness and affecting the rheological stability of the drilling fluid. Therefore, how to improve the dispersion stability of graphene oxide in water-based drilling fluids so that it can maintain a good plugging effect even in extreme environments has become a core issue in current drilling fluid modification research.

[0005] To address the above problems, the present invention modifies graphene oxide through zwitterionic polymerization, effectively improving its stable dispersibility in high-temperature and high-salt environments and enhancing the plugging performance of water-based drilling fluids, thereby providing a more efficient and environmentally friendly technical solution for drilling in complex formations. Summary of the Invention

[0006] The present invention relates to a zwitterionic polymerized grafted graphene oxide plugging agent and its application in water-based drilling fluids. Specifically, the present invention provides a novel preparation method for preparing zwitterionic polymerized grafted graphene oxide and applying it as a nano-plugging agent in water-based drilling fluids, thereby significantly improving the ability of the water-based drilling fluid to plug micro- and nano-fractures in formations.

[0007] In order to achieve the above object, the first aspect of the present invention provides a method for preparing a zwitterionic polymerized grafted graphene oxide plugging agent, the method comprising: (1) dispersing graphene oxide in deionized water and treating it with an ultrasonic cleaner to obtain a graphene oxide dispersion; (2) The graphene oxide dispersion obtained in step (1) is mixed with anhydrous ethanol and added to a round-bottom flask. Under magnetic stirring, the silane coupling agent and anhydrous ethanol mixture is added to the round-bottom flask. After a first reaction time, the silane coupling agent and anhydrous ethanol mixture is added to the round-bottom flask. After a second reaction time, the mixture is centrifuged and purified, and then placed in an oven for drying for a certain period of time to obtain amino-modified graphene oxide; (3) Under magnetic stirring, the amino-modified graphene oxide obtained in step (2) is added to a round-bottom flask containing a toluene solution, and a certain amount of 2-bromoisobutyryl bromide is added. After reacting for a period of time under certain temperature conditions, the reaction is centrifuged and purified, and then placed in an oven for drying for a certain period of time to obtain brominated graphene oxide; (4) Under the conditions of nitrogen flow and magnetic stirring, the brominated graphene oxide obtained in step (3) is dispersed in a mixture of deionized water and dimethyl sulfoxide, a certain amount of ligand and zwitterion is added, and then a catalyst is added. The reaction is carried out under certain temperature conditions for a period of time. After the reaction is completed, the zwitterion-polymerized grafted graphene oxide dispersion is obtained after dialysis.

[0008] The second aspect of the present invention provides a zwitterionic polymerized grafted graphene oxide dispersion prepared by the method described in the first aspect.

[0009] The third aspect of the present invention provides the zwitterionic polymerized grafted graphene oxide dispersion described in the second aspect, which is used as a nano plugging agent in water-based drilling fluid.

[0010] The above-described technical solution achieves the following beneficial effects: By utilizing a zwitterionic polymer-grafted graphene oxide composite material, the present invention significantly enhances the ability of water-based drilling fluids to seal micro- and nano-fractures in formations. The resulting composite material exhibits excellent thermal stability, maintaining long-term structural stability in extreme drilling environments such as high temperature and high pressure, and is resistant to aggregation and degradation, overcoming the performance degradation problem of traditional materials under high-temperature conditions. DETAILED DESCRIPTION

[0011] The endpoints of the ranges and any values ​​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 endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0012] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0013] In the following examples, unless otherwise specified, the products are conventional commercial products.

[0014] Example 1: (1) 1 part by weight of graphene oxide was dispersed in 50 parts by weight of deionized water, and treated with an ultrasonic cleaner at 300 W for 30 minutes to obtain a graphene oxide dispersion; (2) 1 part by weight of the graphene oxide dispersion obtained in step (1) was added to a round-bottom flask, and a mixture of 4 parts by weight of anhydrous ethanol and 0.01 parts by weight of 3-aminopropyltriethoxysilane was added to the round-bottom flask under magnetic stirring at 300 rpm. After the reaction time was 24 hours, the mixture was centrifuged and purified, and then placed in an oven at 65°C and dried for 12 hours to obtain amino-modified graphene oxide; (3) Under the condition of magnetic stirring at 800 rpm, 1 part by weight of the amino-modified graphene oxide obtained in step (2) was added to a round-bottom flask containing 500 parts by weight of toluene solution, and 1 part by weight of 2-bromoisobutyryl bromide was added. The mixture was reacted at 105°C for 4 hours, and after centrifugal purification, it was placed in an oven at 65°C and dried for 12 hours to obtain brominated graphene oxide; (4) Under nitrogen flow and magnetic stirring at 300 rpm, 1 wt. part of brominated graphene oxide obtained in step (3) was dispersed in a mixture of 75 wt. parts of deionized water and 50 wt. parts of dimethyl sulfoxide. After adding 0.0025 wt. parts of pentamethyldiethylenetriamine and 0.15 wt. parts of [2-(methacryloyloxy)ethyl]dimethylbetaine, 0.005 wt. parts of cuprous bromide were added. The mixture was reacted at 65°C for 24 h. After the reaction was completed, the mixture was dialyzed to obtain a zwitterionic polymerized grafted graphene oxide dispersion (denoted as S1).

[0015] Example 2: (1) 1 part by weight of graphene oxide was dispersed in 40 parts by weight of deionized water, and treated with an ultrasonic cleaner at 300 W for 30 minutes to obtain a graphene oxide dispersion; (2) 1 part by weight of the graphene oxide dispersion obtained in step (1) was added to a round-bottom flask, and a mixture of 3 parts by weight of anhydrous ethanol and 0.009 parts by weight of 3-aminopropyltriethoxysilane was added to the round-bottom flask under magnetic stirring at 300 rpm. After the reaction time was 24 hours, the mixture was centrifuged and purified, and then placed in an oven at 65°C and dried for 12 hours to obtain amino-modified graphene oxide; (3) Under the condition of magnetic stirring at 800 rpm, 1 part by weight of the amino-modified graphene oxide obtained in step (2) was added to a round-bottom flask containing 480 parts by weight of toluene solution, and 0.96 parts by weight of 2-bromoisobutyryl bromide was added. The mixture was reacted at a certain temperature of 105°C for 4 hours, and after centrifugal purification, it was placed in an oven at 65°C and dried for 12 hours to obtain brominated graphene oxide; (4) Under nitrogen flow and magnetic stirring at 300 rpm, 1 weight part of brominated graphene oxide obtained in step (3) was dispersed in a mixture of 70 weight parts of deionized water and 45 weight parts of dimethyl sulfoxide. After adding 0.002 weight parts of pentamethyldiethylenetriamine and 0.1 weight parts of [2-(methacryloyloxy)ethyl]dimethylbetaine, 0.004 weight parts of cuprous bromide were added. The mixture was reacted at 65°C for 24 hours. After the reaction was completed, the mixture was dialyzed to obtain a zwitterionic polymerized grafted graphene oxide dispersion (denoted as S2).

[0016] Preparation Example 3: (1) 1 part by weight of graphene oxide was dispersed in 60 parts by weight of deionized water, and treated with an ultrasonic cleaner at 300 W for 30 minutes to obtain a graphene oxide dispersion; (2) 1 part by weight of the graphene oxide dispersion obtained in step (1) was added to a round-bottom flask, and a mixture of 5 parts by weight of anhydrous ethanol and 0.012 parts by weight of 3-aminopropyltriethoxysilane was added to the round-bottom flask under magnetic stirring at 300 rpm. After the reaction time was 24 hours, the mixture was centrifuged and purified, and then placed in an oven at 65°C and dried for 12 hours to obtain amino-modified graphene oxide; (3) Under the condition of magnetic stirring at 800 rpm, 1 part by weight of the amino-modified graphene oxide obtained in step (2) was added to a round-bottom flask containing 520 parts by weight of toluene solution, and 1.06 parts by weight of 2-bromoisobutyryl bromide was added. After the reaction was carried out at a certain temperature of 105°C for 4 hours, the mixture was centrifuged and purified, and then dried in an oven at 65°C for 12 hours to obtain brominated graphene oxide. (4) Under nitrogen flow and magnetic stirring at 300 rpm, 1 weight part of brominated graphene oxide obtained in step (3) was dispersed in a mixture of 80 weight parts of deionized water and 55 weight parts of dimethyl sulfoxide. After adding 0.003 weight parts of pentamethyldiethylenetriamine and 0.2 weight parts of [2-(methacryloyloxy)ethyl]dimethylbetaine, 0.006 weight parts of cuprous bromide were added. The mixture was reacted at 65°C for 24 hours. After the reaction was completed, the mixture was dialyzed to obtain a zwitterionic polymerized grafted graphene oxide dispersion (denoted as S3).

[0017] Comparative Example 1: (1) 1 part by weight of graphene oxide was dispersed in 60 parts by weight of deionized water, and treated with an ultrasonic cleaner at 300 W for 30 min to obtain a graphene oxide dispersion; (2) 1 part by weight of the graphene oxide dispersion obtained in step (1) was added to a round-bottom flask, and under the condition of magnetic stirring at 300 rpm, 6 parts by weight of anhydrous ethanol and 0.015 parts by weight of a mixture of 3-aminopropyltriethoxysilane were added to the round-bottom flask. After the reaction time was 24 hours, the mixture was centrifuged and purified, and then placed in an oven at 65°C and dried for 12 hours to obtain amino-modified graphene oxide; (3) Under the condition of magnetic stirring at 800 rpm, 1 part by weight of the amino-modified graphene oxide obtained in step (2) was added to a round-bottom flask containing 550 parts by weight of toluene solution, and 1.5 parts by weight of 2-bromoisobutyryl bromide was added. The mixture was reacted at a certain temperature of 105°C for 4 hours, and after centrifugal purification, it was placed in an oven at 65°C and dried for 12 hours to obtain brominated graphene oxide. (4) Under the conditions of nitrogen flow and magnetic stirring at 300 rpm, 1 weight part of brominated graphene oxide obtained in step (3) was dispersed in a mixture of 90 weight parts of deionized water and 60 weight parts of dimethyl sulfoxide, 0.004 weight parts of pentamethyldiethylenetriamine and 0.3 weight parts of [2-(methacryloyloxy)ethyl]dimethylbetaine were added, and then 0.007 weight parts of cuprous bromide were added. The mixture was reacted at 65°C for 24 hours. After the reaction was completed, the mixture was dialyzed to obtain a zwitterionic polymerized grafted graphene oxide dispersion (denoted as D1).

[0018] In order to further illustrate the effect of the highly dispersible modified graphene oxide nanosheet plugging agent prepared in the embodiment of the present invention, a specific method is used to test it below.

[0019] When conducting the test, some tests also need to be combined with water-based drilling fluid. The preparation method of the water-based drilling fluid is as follows: 100 parts by weight of tap water and 10 parts by weight of bentonite are stirred at a stirring rate of 1000 r / min for 60 minutes and then allowed to stand for 24 hours. Then, 0.6 parts by weight of flow pattern regulator are added and stirred at a stirring rate of 2000 r / min for 30 minutes. Then, 5.0 parts by weight of fluid loss reducer are stirred at a stirring rate of 2000 r / min for 20 minutes. Then, 3.0 parts by weight of plugging agent are added and stirred at a stirring rate of 2000 r / min for 10 minutes. Then, 2.0 parts by weight of slurry are added. 0.5 parts by weight of lubricant were added and stirred at a stirring rate of 1000 r / min for 10 minutes, then 4.5 parts by weight of inhibitor were added and stirred at a stirring rate of 2000 r / min for 10 minutes, then 1.0 parts by weight of pH regulator were added and stirred at a stirring rate of 1000 r / min for 10 minutes, then 0.8 parts by weight of nano-anti-high temperature plugging agent S1 were added and stirred at a stirring rate of 2000 r / min for 30 minutes, then 250 parts by weight of weighting agent were added and stirred at a stirring rate of 2000 r / min for 30 minutes to obtain water-based drilling fluid (denoted as CS).

[0020] 1. Compatibility test.

[0021] The prepared examples and comparative examples at different mass concentrations were added to the drilling fluid base slurry and aged at 150°C for 16 h. The performance parameters of the water-based drilling fluid were then measured. The results are shown in Table 1.

[0022] Table 1 Performance parameters of water-based drilling fluid;

[0023] As shown in Table 1, nanosilica plugging agents significantly increased the apparent viscosity and plastic viscosity of the drilling fluid at various addition rates, affecting the fluidity and rock-carrying capacity of the drilling fluid. Furthermore, the high-temperature, high-pressure (HTHP) fluid loss of nanosilica was relatively high (6.9–7.1 mL), indicating relatively weak plugging performance. However, the plugging agents prepared in the examples of the present invention (S1, S2, and S3) and the comparative plugging agent (D1) had minimal effects on the rheological properties of the drilling fluid within their respective addition rates. The S-series plugging agents maintained an apparent viscosity of 53.5–56.5 mPa·s, a plastic viscosity of 47.0–50.0 mPa·s, and a maximum dynamic shear force of only 7.5 Pa, all within reasonable ranges, demonstrating excellent rheological control of the drilling fluid. In addition, in terms of HTHP filtration loss, the plugging agents (S1, S2, and S3) prepared in the examples of the present invention have a minimum filtration loss of 3.6 mL, while the plugging agents of the comparative examples and nano-silica are even lower, indicating that the plugging agents prepared in the examples of the present invention have more excellent high-temperature and high-pressure plugging performance.

[0024] 2. Sealing performance test.

[0025] This experiment used outcrop cores to simulate the permeability characteristics of nanofractures in formations. The plugging performance of the plugging agent was evaluated by measuring the average fluid flow rate in the cores and calculating the core permeability based on Darcy's law. Initial permeability was measured using clean water. After adding different plugging agents to the water, the post-plugging permeability was measured. The permeability formula is K = QμL / (AΔP). The plugging efficiency of the plugging agent on the outcrop core was calculated using the formula: (initial permeability - post-plugging permeability) / initial permeability × 100%. The plugging performance was evaluated. The final results are shown in Table 2.

[0026] Table 2 Plugging rate test data table; ;

[0027] The data in Table 2 show that the plugging agents (S1, S2, and S3) prepared in the examples of the present invention exhibit excellent plugging performance at various dosages. In particular, S1 achieves a plugging rate of 93.69% at a 1.5% dosage, far exceeding both the D1 plugging agent and the nano-silica plugging agent. Furthermore, the plugging agents prepared in the examples of the present invention achieve a plugging rate of 79.30% to 83.03% at a 0.5% dosage, further increasing to 84.97% to 89.25% at a 1.0% dosage, demonstrating their ability to effectively reduce core permeability even at relatively low concentrations. However, the plugging effect of the D1 plugging agent is poor, reaching a maximum plugging rate of only 75.64% at a 1.5% dosage. This significantly lower plugging rate is indicative of the limited ability of the plugging agents prepared in the examples of the present invention to plug nanocracks. The nanosilica plugging agent had the worst plugging effect, with a maximum plugging rate of only 64.02%, indicating that it is difficult to effectively reduce core permeability and is not suitable for high-efficiency plugging systems. Therefore, the plugging agent prepared in this embodiment of the present invention achieves good plugging effectiveness at relatively low dosages (0.5% to 1.0%) and achieves optimal plugging performance at a high dosage (1.5%), making it most suitable for high-performance water-based drilling fluid systems.

[0028] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A zwitterionic polymerized graphene oxide grafted plugging agent, characterized in that: (1) dispersing graphene oxide in deionized water and treating it with an ultrasonic cleaner to obtain a graphene oxide dispersion; (2) adding the graphene oxide dispersion obtained in step (1) into a round-bottom flask, adding a silane coupling agent and anhydrous ethanol mixture into the round-bottom flask under magnetic stirring, reacting for a period of time, centrifuging and purifying, and drying in an oven for a certain period of time to obtain amino-modified graphene oxide; (3) adding the amino-modified graphene oxide obtained in step (2) into a flask containing a toluene solution under magnetic stirring. After the round-bottom flask is filled, a certain amount of surface initiator is added, and the reaction is carried out under certain temperature conditions for a period of time. After centrifugal purification, the brominated graphene oxide is placed in an oven and dried for a certain period of time to obtain brominated graphene oxide; (4) under the conditions of nitrogen and magnetic stirring, the brominated graphene oxide obtained in step (3) is dispersed in a mixed solution of deionized water and dimethyl sulfoxide, a certain amount of ligand and zwitterion is added, and then a catalyst is added. The reaction is carried out under certain temperature conditions for a period of time. After the reaction is completed, the zwitterion-polymerized grafted graphene oxide plugging agent is obtained through dialysis.

2. The zwitterionic polymerized graphene oxide grafted plugging agent according to claim 1, characterized in that: In step (1), the weight ratio of the graphene oxide: deionized water is 1: (40-60); wherein, in step (2), the weight ratio of the graphene oxide dispersion: anhydrous ethanol: silane coupling agent is 1: (3-5): (0.009-0.012); wherein, in step (3), the weight ratio of the amino-modified graphene oxide: toluene solution: surface initiator is 1: (480-520): (0.96-1.06); wherein, in step (4), the weight ratio of the brominated graphene oxide: deionized water: dimethyl sulfoxide: ligand: zwitterion: catalyst is 1: (70-80): (45-55): (0.002-0.003): (0.1-0.2): (0.004-0.006).

3. The zwitterionic polymerized graphene oxide grafted plugging agent according to any one of claims 1 to 2, characterized in that: The silane coupling agent is selected from at least one of 3-aminopropyltriethoxysilane, 3-aminoethylaminopropyltrimethoxysilane, and 3-[2-aminoethyl]-aminopropyltrimethoxysilane, preferably 3-aminopropyltriethoxysilane; the surface initiator is selected from at least one of 2-bromoisobutyryl bromide, 2-bromoisobutyryl chloride, and α-bromopropionyl bromide, preferably 2-bromoisobutyryl bromide; the ligand is selected from one of pentamethyldiethylenetriamine, tetramethylethylenediamine, and N,N,N′,N′-tetramethyl-1,2-ethylenediamine, preferably pentamethyldiethylenetriamine; the zwitterion is selected from one of [2-(methacryloyloxy)ethyl]dimethylbetaine, methacryloyloxypropyldimethylbetaine, and methacryloyloxyethyldimethylbetaine, preferably [2-(methacryloyloxy)ethyl]dimethylbetaine; the catalyst is selected from one of cuprous bromide, cuprous chloride, and cuprous iodide, preferably cuprous bromide.

4. The zwitterionic polymerized graphene oxide grafted plugging agent according to any one of claims 1 to 2, wherein in step (1), the ultrasonic treatment conditions include: The time is 30 min and the power is 300 W; In step (2), the conditions include: a magnetic stirring speed of 300 rpm, a reaction time of 24 h, a drying temperature of 65°C, and a drying time of 12 h; in step (3), the conditions include: a magnetic stirring speed of 800 rpm, a reaction temperature of 105°C, a reaction time of 4 h, a drying temperature of 65°C, and a drying time of 12 h; in step (4), the conditions include: a magnetic stirring speed of 300 rpm, a reaction temperature of 65°C, and a reaction time of 24 h.

5. A zwitterionic polymerized graphene oxide grafted plugging agent according to any one of claims 1 to 4, characterized in that: The average particle size is 332-921nm.

6. A zwitterionic polymerized grafted graphene oxide plugging agent, prepared by the method according to any one of claims 1 to 5.

7. A water-based drilling fluid, characterized in that: The drilling fluid is added with the zwitterionic polymerized grafted graphene oxide plugging agent according to any one of claims 1 to 6.

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