A drilling fluid plugging agent based on lithium saponite-graphene oxide composite material, its preparation method and application

Abstract

This invention relates to the field of drilling technology, and provides a drilling fluid plugging agent based on lithium saponite-graphene oxide composite material, its preparation method, and its application. The preparation method of the drilling fluid plugging agent based on lithium saponite-graphene oxide composite material includes: adding acetic acid solution to a graphene oxide solution and mixing, then adding a lithium saponite suspension and mixing to obtain a mixture; adding a crosslinking agent to the mixture for reaction; after the reaction is complete, centrifuging the reaction solution to obtain a supernatant, and precipitating the precipitate; adding the precipitate to a polyvinyl alcohol solution and mixing to obtain the drilling fluid plugging agent based on lithium saponite-graphene oxide composite material. The drilling fluid plugging agent based on lithium saponite-graphene oxide composite material prepared by this invention has excellent adsorption performance, can form a composite film with good mechanical properties on the rock surface, and has excellent plugging effect; it also has good dispersibility in water, good temperature resistance and lubrication properties, and is suitable for application in high-temperature deep wells.

Description

Technical Field

[0001] This invention relates to the field of drilling technology, and more specifically, to a drilling fluid plugging agent based on lithium saponite-graphene oxide composite material, its preparation method, and its application. Background Technology

[0002] Graphene is the thinnest and strongest nanomaterial known to date, possessing unique thermal, electrical, mechanical, and optical properties. Since Novoselov et al. isolated graphene from graphite using micromechanical exfoliation in 2004, this material has been widely studied and applied in materials science, chemical engineering, electrical engineering, and biosensing.

[0003] With the continuous development of oil exploration both domestically and internationally, complex oil and gas reservoirs, unconventional oil and gas reservoirs, tapping remaining oil and gas potential, and offshore oil and gas resources have gradually become key areas of oil and gas exploration. This places higher demands on drilling fluid technology, especially new drilling fluid materials. Because graphene and its derivatives give drilling fluids Newtonian fluid properties, low filtration loss, and the ability to form a solid mud cake, graphene-based materials as drilling fluid additives have received increasing attention. Based on the excellent properties of graphene, some scholars have conducted research on its application in the petroleum industry. In June 2011, James M. Tour published a patent on the application of graphene and modified graphene in drilling fluids. The patent reported the preparation process of chemically modified graphene, using hydrazine hydrate as a reducing agent to graft benzene rings onto the surface of graphene. When the chemically modified graphene is added to the drilling fluid, the nano-graphene sheets are adsorbed onto the wellbore surface during drilling, forming a thin and dense filter cake. Graphene and modified graphene materials can effectively improve the quality of filter cake and reduce drilling fluid entering the formation.

[0004] Graphene materials show promising applications in drilling fluids. As a drilling fluid filtration reducer, graphene, being a single-layer sheet material, tends to curl when salts approach its edges. However, the strong π-π interactions between graphene molecules limit this curling, thus exhibiting excellent salt resistance and broad application prospects in salt- and temperature-resistant filtration reducers. Furthermore, as a drilling fluid shale inhibitor, graphene's edges contain numerous active groups such as carboxyl and hydroxyl groups. Modification by introducing adsorption groups like amino groups can enhance the adsorption of graphene onto rocks, forming large-area, high-strength sheet-like materials that adhere to the rock surface, preventing water penetration. As a nanopore plugging agent, graphene is advantageous in shale formations with low permeability and abundant nanopores with an average pore size of around 10 nm. While typical rigid nanomaterials tend to aggregate in solution and struggle to penetrate these nanopores, flexible organic materials, with their large molecular weights, exhibit weak interactions with rock and are difficult to adsorb onto the shale surface. However, by designing molecules and introducing strong adsorption groups, the interaction between graphene and rock is increased, promoting graphene adsorption onto the rock surface. As a drilling fluid lubricant, introducing groups that interact with metal ions onto the graphene surface promotes its adsorption onto the drill string, forming a thin, flexible film. This film reduces friction between the drill string and drilling fluid, and between the drill string and rock, effectively improving the lubrication performance of the drilling fluid. Introducing hydrophobic groups onto the graphene surface further reduces the interaction forces between the drill string and drilling fluid, effectively preventing mud packing, stuck pipe, and other accidents.

[0005] Graphene materials, as drilling fluid plugging agents, possess excellent film-forming and plugging properties, as well as the ability to reduce filtration loss. However, the performance of the film during the film-forming process needs improvement, and graphene materials are prone to agglomeration and thickening in water. Therefore, improving the dispersibility of graphene in drilling fluids and the performance of the film during the film-forming process, thereby further enhancing the effectiveness of filtration loss reducing agents, is a technical problem that needs to be researched and solved. Summary of the Invention

[0006] The purpose of this invention is to provide a drilling fluid plugging agent based on lithium saponite-graphene oxide composite material, its preparation method and application, so as to solve the technical problems of poor dispersion performance of graphene in drilling fluid and unsatisfactory film performance after film formation in the prior art.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect, the present invention proposes a method for preparing a drilling fluid plugging agent based on lithium saponite-graphene oxide composite material, comprising:

[0009] Acetic acid solution was added to graphene oxide solution and mixed, followed by lithium saponite suspension to obtain a mixture. A crosslinking agent was added to the mixture to react. After the reaction was completed, the reaction solution was centrifuged to obtain the supernatant, and the precipitate was precipitated. The precipitate was added to polyvinyl alcohol solution and mixed to obtain a drilling fluid plugging agent based on lithium saponite-graphene oxide composite material.

[0010] In this invention, both lithium saponite and graphene oxide contain a large number of hydroxyl groups, which can undergo an acetal reaction with a crosslinking agent to crosslink and form a composite structure. The lithium saponite-graphene oxide composite material and polyvinyl alcohol (PVA) can self-assemble into a film under the pressure difference between the wellbore and the formation, thereby forming a sealing layer.

[0011] Adding lithium saponite to form a lithium saponite-graphene oxide composite material with graphene oxide can effectively solve the problem of poor dispersibility of graphene oxide in water, and further enhance the filtration loss reduction effect of graphene oxide.

[0012] The method for forming a sealing film layer with lithium saponite-graphene oxide composite material and polyvinyl alcohol (PVA) is a dynamic LBL self-assembly film formation method. Dynamic LBL refers to the process in which a solution containing organic or inorganic materials flows under certain pressure and deposits in the pores or on the surface of a porous support layer to form a composite layer, thereby preparing a composite film with special properties. Under external pressure, the polyelectrolyte solution permeates through the base film, covering as much of the upper surface and pore surface of the base film as possible with a thin layer of polyelectrolyte. Its uniformity is better than that of the static self-assembly method and there are fewer surface defects. Therefore, a dense and complete composite film can be obtained with only a few composite layers. The process of drilling fluid filtration at the wellbore is carried out under pressure difference, where the filtrate is lost through the formation rock. During this process, the polyelectrolytes in the drilling fluid undergo dynamic LBL self-assembly to form a film.

[0013] The drilling fluid plugging agent based on lithium saponite-graphene oxide composite material prepared in this invention is added to the drilling fluid during use and circulates into the wellbore with the drilling fluid. During the process of drilling fluid filtration in the wellbore, the lithium saponite-graphene oxide composite material and polyvinyl alcohol (PVA) self-assemble, or the lithium saponite-graphene oxide composite material, polyvinyl alcohol (PVA), and montmorillonite in the drilling fluid self-assemble to form a dense and complete film, thereby sealing the well wall.

[0014] For example, one preferred embodiment includes: adding the drilling fluid plugging agent based on lithium saponite-graphene oxide composite material of the present invention to the drilling fluid. After entering the wellbore, due to the pressure difference between the inside of the wellbore and the formation on the wellbore wall, the drilling fluid undergoes filtration, forming a filter cake. During this process, the lithium saponite-graphene oxide composite material self-assembles with polyvinyl alcohol (PVA) to form a thin film on the wellbore surface, thereby preventing the drilling fluid filtrate from entering the formation on the wellbore wall and preventing further hydration and expansion of the clay in the formation on the wellbore wall, thus avoiding the disruption of the internal stress balance of the wellbore and the occurrence of wellbore instability. In this process, lithium saponite and graphene oxide form a lithium saponite-graphene oxide composite material, which improves the dispersibility of graphene oxide in water. As the graphene oxide content increases, the effectiveness of the plugging agent naturally improves.

[0015] According to some embodiments of the present invention, the lithium saponite suspension is prepared by mixing lithium saponite and a synergist in water.

[0016] Lithium laponite is a type of layered silicate clay with strong cation exchange capacity, hydrophilicity, rheological properties, and adsorption capabilities. Lithium laponite typically consists of a double layer of Si-O tetrahedra enclosing a single layer of Mg-O octahedra, further forming disc-shaped nanoparticles. The surface charge of lithium laponite nanoparticles is anisotropic and rich in active hydroxyl groups, enabling strong interactions with other substances. However, lithium laponite nanoparticles are prone to agglomeration due to their small size, preventing the full utilization of their advantages. In this invention, lithium laponite, when combined with a synergist, exhibits a synergistic thickening effect, thereby forming a colloidal structure in the lithium laponite suspension and preventing agglomeration of the lithium laponite itself.

[0017] Furthermore, lithium saponite and the synergist underwent pre-crosslinking in the lithium saponite suspension, which not only improved the dispersion effect of lithium saponite but also facilitated further crosslinking with graphene oxide in the next step.

[0018] According to some embodiments of the present invention, the synergist includes at least one selected from carboxymethyl cellulose, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, and dodecyltrimethylammonium bromide.

[0019] In this invention, carboxymethyl cellulose is used as a synergist to prevent the aggregation of lithium saponite. Hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, and dodecyltrimethylammonium bromide are used as synergists, which have a certain synergistic effect with PVA, giving the drilling fluid plugging agent a certain degree of hydrophobicity, thereby improving the lubrication capacity of the drilling fluid.

[0020] According to some embodiments of the present invention, the mass ratio of lithium saponite and synergist mixed in water is (0.8–1.2):(1.5–1.8), for example, 0.8:1.5, 0.8:1.8, 1:1.5, 1.2:1.5, 1.2:1.8, etc. During the preparation process, it is often necessary to remove excess synergist from the lithium saponite suspension. Common methods such as centrifugation and precipitation can be used to remove excess synergist from the lithium saponite suspension.

[0021] According to some embodiments of the present invention, the temperature at which the lithium saponite and the synergist are mixed in water is 50 to 80°C, for example, 50°C, 60°C, 70°C, 80°C, etc.

[0022] According to some embodiments of the present invention, the lithium saponite and the synergist are mixed in water by stirring and / or ultrasonic dispersion.

[0023] According to some embodiments of the present invention, the concentration of the graphene oxide solution is 0.5 to 5 wt%, for example, it can be 0.5 wt%, 0.7 wt%, 1 wt%, 1.2 wt%, 1.5 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, etc.

[0024] According to some embodiments of the present invention, the concentration of the acetic acid solution is 0.2 to 0.3 mol / L.

[0025] According to some embodiments of the present invention, the mass ratio of the graphene oxide solution to the acetic acid solution is (0.1-1):(5-20), for example, it can be 1:5, 1:10, 1:15, 1:20, 1:50, 1:80, 1:100, 1:150, 1:200, etc.

[0026] According to some embodiments of the present invention, the concentration of the lithium saponite suspension is 0.5 to 1.2 wt%, for example, it can be 0.5 wt%, 0.8 wt%, 1 wt%, 1.2 wt%, etc.

[0027] According to some embodiments of the present invention, the mass ratio of the graphene oxide solution to the lithium saponite suspension is (0.8-1.2):(1-1.5), for example, it can be 0.8:1.5, 1:1.2, 1:1.25, 1:1.1, 1.2:1, 1.2:1.5, etc.

[0028] According to some embodiments of the present invention, the crosslinking agent includes at least one of glutaraldehyde and boric acid.

[0029] According to some embodiments of the present invention, the crosslinking agent is a crosslinking agent solution.

[0030] According to some embodiments of the present invention, the concentration of the crosslinking agent solution is 1 to 7 wt%, for example, it can be 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, etc.

[0031] According to some embodiments of the present invention, the amount of the crosslinking agent solution is 0.1 to 3 wt% of the mixture, for example, it can be 0.1 wt%, 0.3 wt%, 0.5 wt%, 0.7 wt%, 0.8 wt%, 1 wt%, 1.8 wt%, 2 wt%, 2.5 wt%, 3 wt%, etc.

[0032] According to some embodiments of the present invention, the reaction time is 20 to 30 minutes.

[0033] According to some embodiments of the present invention, the pH is adjusted to 7 ± 0.5 after the reaction is completed and before centrifugation.

[0034] According to some embodiments of the present invention, the precipitation includes adding ethanol to precipitate the precipitate.

[0035] According to some embodiments of the present invention, the concentration of the polyvinyl alcohol solution is 2 to 10 wt%, for example, it can be 2 wt%, 3 wt%, 3.5 wt%, 5 wt%, 8 wt%, 10 wt%, etc.

[0036] According to some embodiments of the present invention, the mass ratio of the polyvinyl alcohol solution to the graphene oxide solution is (4.5-5.5):(0.5-1.5), for example, it can be 4.5:0.5, 5.5:0.5, 5:1, 4.5:1.5, 5.4:1.5, 5.5:1.5, etc.

[0037] According to some embodiments of the present invention, the temperature at which the precipitate is added to the polyvinyl alcohol solution for mixing is 30 to 80°C, for example, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, etc.

[0038] The various solutions used in this invention, such as graphene oxide solution, acetic acid solution, polyvinyl alcohol solution, and crosslinking agent solution, are all aqueous solutions.

[0039] In a second aspect, the present invention provides a drilling fluid plugging agent based on lithium saponite-graphene oxide composite material, which is prepared by the preparation method described in the first aspect.

[0040] Thirdly, the present invention provides the application of the drilling fluid plugging agent described in the second aspect in the preparation of drilling fluid.

[0041] Fourthly, the present invention provides a drilling fluid comprising the drilling fluid plugging agent described in the second aspect.

[0042] According to some embodiments of the present invention, the drilling fluid plugging agent has a content of 0.5 to 5 wt% in the drilling fluid.

[0043] Fifthly, the present invention provides the application of the drilling fluid described in the fourth aspect in oil and gas reservoir drilling, especially in high-temperature oil and gas reservoir drilling.

[0044] The beneficial effects of this invention are at least as follows:

[0045] This invention provides a drilling fluid plugging agent based on lithium saponite-graphene oxide composite material, its preparation method, and its application. The drilling fluid plugging agent based on lithium saponite-graphene oxide composite material provided by this invention exhibits excellent adsorption properties, forming a composite film with good mechanical properties on the rock surface, resulting in excellent plugging effect. Furthermore, it demonstrates good dispersibility in water, good temperature resistance, and lubrication properties, making it suitable for application in high-temperature deep wells. Attached Figure Description

[0046] Figure 1 This is a structural photograph of the composite membrane formed by the drilling fluid plugging agent based on lithium saponite-graphene oxide composite material in Example 4. Detailed Implementation

[0047] To make the technical problem to be solved, the technical solution, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely for illustrating this patent and do not limit the scope of protection of this invention in any way.

[0048] Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art. Unless otherwise specified, the reagents used in the following embodiments are conventional biochemical reagents; the raw materials, instruments, and equipment used in the following embodiments can all be obtained commercially or by existing methods; unless otherwise specified, the reagent dosages are those used in routine experimental operations; unless otherwise specified, the experimental methods are conventional methods.

[0049] The particle size of the lithium saponite particles used in the various examples and comparative examples is 30-120 nm; the polyvinyl alcohol used is all type 1799 PVA.

[0050] Example 1

[0051] The preparation method of drilling fluid plugging agent based on lithium saponite-graphene oxide composite material includes the following steps:

[0052] (1) Preparation of lithium saponite suspension: Lithium saponite particles and carboxymethyl cellulose (CMC) with a mass ratio of 1:1.5 were added to deionized water, stirred evenly at 50°C, ultrasonically dispersed, and excess carboxymethyl cellulose was removed by centrifugation and precipitation.

[0053] (2) Preparation of lithium saponite-graphene oxide composite material: Take 10g of 1wt% graphene oxide solution, add 100g of 0.2mol / L acetic acid solution, and mix thoroughly. Then add 12g of 1wt% lithium saponite suspension, mix thoroughly, and then add 2.22g of 1wt% glutaraldehyde. React for 20min, adjust pH to 7, centrifuge the reaction solution, add 300mL of ethanol to the supernatant while stirring, precipitate the precipitate, let stand for 2h, and filter.

[0054] (3) Preparation of drilling fluid plugging agent: Add the above precipitate to 50g of 2wt% polyvinyl alcohol (PVA) aqueous solution and stir slowly at 50℃ until uniform.

[0055] Example 2

[0056] The preparation method of drilling fluid plugging agent based on lithium saponite-graphene oxide composite material includes the following steps:

[0057] (1) Preparation of lithium saponite suspension: Lithium saponite particles and hexadecyltrimethylammonium bromide in a mass ratio of 0.8:1.5 were added to deionized water, stirred evenly at 80°C, ultrasonically dispersed, and excess hexadecyltrimethylammonium bromide was removed by centrifugation and precipitation.

[0058] (2) Preparation of lithium saponite-graphene oxide composite material: Take 10g of 0.5wt% graphene oxide solution, add 200g of 0.3mol / L acetic acid solution, and mix thoroughly. Then add 12.5g of 0.5wt% lithium saponite suspension, mix thoroughly, then add 6.66g of 7wt% glutaraldehyde, react for 30min, adjust pH to 7, centrifuge the reaction solution, add 300mL of ethanol to the supernatant while stirring, precipitate the precipitate, let stand for 2h, and filter.

[0059] (3) Preparation of drilling fluid plugging agent: Add the above precipitate to 36g of 10wt% polyvinyl alcohol (PVA) aqueous solution and stir slowly at 80℃ until homogeneous.

[0060] Example 3

[0061] The preparation method of drilling fluid plugging agent based on lithium saponite-graphene oxide composite material includes the following steps:

[0062] (1) Preparation of lithium saponite suspension: Lithium saponite particles and carboxymethyl cellulose (CMC) with a mass ratio of 1.2:1.8 were added to deionized water, stirred evenly at 60°C, ultrasonically dispersed, and excess carboxymethyl cellulose was removed by centrifugation and precipitation.

[0063] (2) Preparation of lithium saponite-graphene oxide composite material: Take 10g of 0.7wt% graphene oxide solution, add 500g of 0.3mol / L acetic acid solution, and mix thoroughly. Then add 15g of 1.2wt% lithium saponite suspension, mix thoroughly, then add 5.25g of 3wt% glutaraldehyde, react for 25min, adjust pH to 7, centrifuge the reaction solution, add 300mL of ethanol to the supernatant while stirring, precipitate the precipitate, let stand for 2h, and filter.

[0064] (3) Preparation of drilling fluid plugging agent: Add the above precipitate to 90g of 3.5wt% polyvinyl alcohol (PVA) aqueous solution and stir slowly at 60℃ until homogeneous.

[0065] Example 4

[0066] The preparation method of drilling fluid plugging agent based on lithium saponite-graphene oxide composite material includes the following steps:

[0067] (1) Preparation of lithium saponite suspension: Lithium saponite particles and carboxymethyl cellulose (CMC) with a mass ratio of 1.2:1.8 were added to deionized water, stirred evenly at 60°C, ultrasonically dispersed, and excess carboxymethyl cellulose was removed by centrifugation and precipitation.

[0068] (2) Preparation of lithium saponite-graphene oxide composite material: Take 10g of 0.7wt% graphene oxide solution, add 150g of 0.3mol / L acetic acid solution, and mix thoroughly. Then add 11g of 0.8wt% lithium saponite suspension, mix thoroughly, then add 1.36g of 2wt% boric acid, react for 20min, adjust pH to 7, centrifuge the reaction solution, add 300mL of ethanol to the supernatant while stirring, precipitate the precipitate, let stand for 2h, and filter.

[0069] (3) Preparation of drilling fluid plugging agent: Add the above precipitate to 50g of 3.5wt% polyvinyl alcohol (PVA) aqueous solution and stir slowly at 60℃ until uniform.

[0070] Example 5

[0071] The preparation method of drilling fluid plugging agent based on lithium saponite-graphene oxide composite material is the same as in Example 4, except that carboxymethyl cellulose is replaced with hexadecyltrimethylammonium bromide.

[0072] Comparative Example 1

[0073] The drilling fluid plugging agent was prepared according to Example 1, except that lithium saponite suspension was not added, and lithium saponite particles of the same mass as in Example 1 were added.

[0074] Comparative Example 2

[0075] The drilling fluid plugging agent preparation method is the same as in Example 1, except that the precipitate obtained in step (2) was not added to the polyvinyl alcohol solution for mixing, and the precipitate was used as the drilling fluid plugging agent.

[0076] Comparative Example 3

[0077] The preparation method of drilling fluid plugging agent includes the following steps:

[0078] (1) Preparation of lithium saponite suspension: Lithium saponite particles and carboxymethyl cellulose (CMC) with a mass ratio of 1.2:1.8 were added to deionized water, stirred at high speed at 60°C until uniform, ultrasonically dispersed, and excess carboxymethyl cellulose was removed by centrifugation and precipitation.

[0079] (2) Preparation of drilling fluid plugging agent: 11g of 0.8wt% lithium saponite suspension was added to 50g of 3.5wt% polyvinyl alcohol (PVA) aqueous solution and stirred slowly at 60℃ until homogeneous.

[0080] Comparative Example 4

[0081] The drilling fluid plugging agent was prepared according to Example 1, except that 1.36g of 2wt% boric acid was replaced with 1.36g of 2wt% lactic acid.

[0082] Performance Testing and Evaluation

[0083] The performance parameters of the plugging agent, such as high-temperature and high-pressure filtration loss and lubrication coefficient, were experimentally evaluated. Specific methods are described in GB / T 16783.1-2014 (Field Testing of Drilling Fluids for Petroleum and Natural Gas Industry). The base slurry formulation was 4 wt% bentonite slurry + 0.15 wt% PAM + 0.3 wt% DSP-2 + 1.5 wt% SMP-2 + 0.5 wt% ammonium salt, with a plugging agent dosage of 2 wt%. The plugging agent (precipitate) dosage in Comparative Example 2 was 0.04 wt%. Experimental results are shown in Table 1.

[0084] Table 1. Experimental results of sealing wedge-shaped long cracks (2×1mm)

[0085]

[0086] The drilling fluid plugging agents based on lithium saponite-graphene oxide composite materials prepared in Examples 1, 4, and 5 showed better plugging and filtration loss reduction effects than the base slurry without plugging agent and the base slurry with only graphene oxide added. This indicates that the drilling fluid plugging agent based on lithium saponite-graphene oxide composite material provided by the present invention has a better plugging effect, which can prevent drilling fluid from penetrating into the formation, thereby reducing the hydration and swelling of clay and improving the stability of the wellbore.

[0087] The drilling fluid plugging agent based on lithium saponite-graphene oxide composite material prepared in Example 5 has a relatively lower lubrication coefficient than that in Example 4, indicating that hexadecyltrimethylammonium bromide and PVA have a certain synergistic effect, which can improve the lubrication ability of the drilling fluid.

[0088] The drilling fluid plugging agent based on lithium saponite-graphene oxide composite material prepared in Example 1 showed better plugging, filtration loss reduction, and lubrication effects than the drilling fluid plugging agent in Comparative Example 1, indicating that combining lithium saponite with an synergist is very helpful for further improving the plugging performance of the crosslinked material.

[0089] The drilling fluid plugging agent based on lithium saponite-graphene oxide composite material prepared in Example 1 showed better plugging, filtration loss reduction, and lubrication effects than the drilling fluid plugging agent in Comparative Example 2. This indicates that the lithium saponite-graphene oxide composite material (precipitate) undergoes self-assembly, and the resulting film has less than ideal performance. This also shows that PVA plays a very important role in the self-assembly process.

[0090] The drilling fluid plugging agent based on lithium saponite-graphene oxide composite material prepared in Example 4 showed better plugging, filtration reduction, and lubrication effects than the drilling fluid plugging agent in Comparative Example 3, indicating that the crosslinking modification of lithium saponite and graphene oxide plays a very important role in the self-assembly film formation effect.

[0091] The drilling fluid plugging agent based on lithium saponite-graphene oxide composite material prepared in Example 4 showed better plugging, filtration loss reduction, and lubrication effects than the drilling fluid plugging agent in Comparative Example 4, indicating that the selection of crosslinking agent is also very important.

[0092] Overall, the drilling fluid plugging agent based on lithium saponite-graphene oxide composite material provided by this invention has good plugging ability and lubrication performance.

[0093] The structure of the composite membrane formed by the drilling fluid plugging agent prepared in Example 4 is shown in [example description]. Figure 1 .Depend on Figure 1 It can be seen that the composite membrane is relatively dense. By using a DMA dynamic thermomechanical analyzer to determine the relationship between the transverse tensile stress (σ) and strain (ε) of the composite membrane, the Young's modulus of the composite membrane was calculated to be above 5 GPa. The composite membrane has good mechanical properties and can effectively improve the sealing ability of drilling fluid.

[0094] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for preparing a drilling fluid plugging agent based on lithium saponite-graphene oxide composite material, characterized in that, include: Acetic acid solution was added to graphene oxide solution and mixed, followed by lithium saponite suspension and mixed to obtain a mixture. A crosslinking agent was added to the mixture for reaction. After the reaction was completed, the reaction solution was centrifuged to obtain the supernatant and precipitate. The precipitate was added to polyvinyl alcohol solution and mixed to obtain a drilling fluid plugging agent based on lithium saponite-graphene oxide composite material. The concentration of the graphene oxide solution is 0.5~5wt%; The concentration of the acetic acid solution is 0.2~0.3 mol / L; The mass ratio of the graphene oxide solution to the acetic acid solution is (0.1~1):(5~20). The concentration of the lithium saponite suspension is 0.5~1.2 wt%; The mass ratio of the graphene oxide solution to the lithium saponite suspension is (0.8~1.2):(1~1.5). The crosslinking agent includes at least one of glutaraldehyde and boric acid.

2. The preparation method according to claim 1, characterized in that, The lithium saponite suspension is prepared by mixing lithium saponite and an synergist in water.

3. The preparation method according to claim 2, characterized in that, The synergist includes at least one of carboxymethyl cellulose, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, and dodecyltrimethylammonium bromide; And / or, the lithium saponite and synergist are mixed in water at a temperature of 50~80°C; And / or, the lithium saponite and synergist are mixed in water by stirring and / or ultrasonic dispersion.

4. The preparation method according to any one of claims 1-3, characterized in that, The crosslinking agent is a crosslinking agent solution; And / or, the reaction time is 20-30 min; And / or, the preparation method further includes: adjusting the pH to 7±0.5 after the reaction is completed and before centrifugation.

5. The preparation method according to claim 4, characterized in that, The concentration of the crosslinking agent solution is 1~7wt%, and / or the amount of the crosslinking agent solution used is 0.1~3wt% of the mixture.

6. The preparation method according to any one of claims 1-3, characterized in that, The concentration of the polyvinyl alcohol solution is 2-10 wt%; And / or, the mass ratio of the polyvinyl alcohol solution to the graphene oxide solution is (4.5~5.5):(0.5~1.5); And / or, the temperature at which the precipitate is added to the polyvinyl alcohol solution for mixing is 30~80°C.

7. A drilling fluid plugging agent based on lithium saponite-graphene oxide composite material, prepared by any one of the preparation methods described in claims 1-6.

8. The application of the drilling fluid plugging agent as described in claim 7 in the preparation of drilling fluid.

9. A drilling fluid, characterized in that, The drilling fluid includes the drilling fluid plugging agent as described in claim 7.

10. The drilling fluid according to claim 9, characterized in that, The drilling fluid plugging agent has a content of 0.5~5wt% in the drilling fluid.

11. The application of the drilling fluid according to claim 9 or 10 in oil and gas reservoir drilling.

12. The application according to claim 11, characterized in that, The application is in drilling high-temperature oil and gas reservoirs.

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