A highly dispersible modified graphene oxide nanosheet plugging agent and preparation method thereof

Abstract

The invention discloses a kind of strong dispersibility modified graphene oxide nanosheet plugging agent and preparation method thereof, and relates to the technical field of oil and gas field development. The preparation method of the plugging agent comprises the following steps: taking graphene oxide and dispersing evenly, adding sodium ethoxide and chlorinated olefin, then reacting for 6~10h, after the reaction ends, separating and purifying to obtain intermediate; taking intermediate and dispersing evenly, 3-[bis[2-(methacryloyloxy)ethyl](methyl)ammonium]propane-1-sulfonate and the first monomer added later, adding initiator and reacting for 4~8h, after the reaction ends, separating and purifying to obtain. The plugging agent of the present invention, it contains sulfonic acid group and quaternary ammonium group at the same time, so that the plugging agent not only has good dispersion stability, but also has strong adsorption performance in the reservoir, and the plugging performance of the plugging agent of the present invention is stronger; at the same time, the plugging agent of the present invention is also made to have strong salt resistance.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas field development, and in particular to a strongly dispersible modified graphene oxide nanosheet plugging agent and a preparation method thereof. Background Art

[0002] my country's shale gas resources are rich and widely distributed, with broad development prospects. When water-based drilling fluids are used to drill into shale reservoirs, the hydration and expansion of shale causes the instability of the wellbore, which has caused great trouble to the drilling project in shale oil and gas production. During the drilling process, the presence of nanopores and nano-micron cracks in the shale layer makes it susceptible to erosion by the drilling fluid, which in turn leads to various complex downhole problems, including collapse, spalling, adhesion, and wellbore instability. The drilling progress will be seriously affected and the drilling cost will increase. At present, the most commonly used plugging agents include fine calcium carbonate, asphalt, walnut shell powder, and similar substances. However, these micron-sized plugging agents are larger than the nanopores in the shale formation, and they cannot prevent the drilling fluid from infiltrating into the reservoir with smaller pores. Therefore, the key to enhancing the plugging of nanopore cracks by water-based drilling fluids, preventing drilling fluids from invading nanopore cracks, and enhancing wellbore stability lies in the preparation of efficient nano-plugging materials.

[0003] Graphene is a kind of nano-sheet film material with a thickness of about 1nm, a length and width distribution of nanometer to micrometer level, and a flexible deformable one. Graphene oxide can be regarded as an oxidation product of monolayer graphene, and the surface contains a large number of functional groups such as carboxyl, hydroxyl, and epoxy. Compared with graphene, it is easier to be chemically modified and has better dispersibility in water. The plugging performance of the modified product of graphene oxide in water-based drilling fluid has aroused the research interest of scholars at home and abroad. CN118165714A discloses a preparation method, plugging agent and drilling fluid of modified graphene oxide plugging agent, and sulfonic acid groups and benzene rings are grafted on the surface of graphene oxide by 2-acrylamide-2-methylpropane sulfonic acid, styrene and azobisisobutyronitrile as monomers, thereby improving the plugging performance of graphene oxide. Under high temperature and high pressure conditions, the filtration loss of adding 0.3% modified graphene oxide plugging agent is 22mL. CN117003967B discloses a modified graphene oxide plugging agent for shale. Using graphene oxide, 2-acrylamide-2-methylpropanesulfonic acid and itaconic acid as raw materials, a plugging agent containing sulfonic acid groups and carboxylic acids at the end is prepared. Adding 4% of the modified graphene oxide plugging agent can achieve a plugging rate of 93.31%. Although modified graphene exhibits excellent plugging performance in water-based drilling fluid, the amount of the plugging agent added is relatively high, and the relative cost rises sharply. Summary of the invention

[0004] In order to solve at least one of the above problems, the present invention provides a highly dispersible modified graphene oxide nanosheet plugging agent and a preparation method thereof.

[0005] In the present invention, the basic unit of parts by mass is g, and the basic unit of parts by volume is ml.

[0006] The technical solution of the present invention is: a method for preparing a highly dispersible modified graphene oxide nanosheet plugging agent, comprising the following steps:

[0007] S1, take 1-3 parts by mass of graphene oxide and disperse it evenly, add 0.21-0.9 parts by mass of sodium ethoxide and 0.6-2.7 parts by mass of chlorinated olefin at 60-80°C, and then react for 6-10 hours. After the reaction is completed, separate and purify to obtain an intermediate;

[0008] S2. Take 1-2 parts by mass of the intermediate and disperse it evenly, then add 0.04-0.12 parts by mass of 3-[bis[2-(methacryloyloxy)ethyl](methyl)ammonium]propane-1-sulfonate and 2-6 parts by mass of the first monomer, mix evenly, add an initiator under deoxygenated conditions and react for 4-8 hours. After the reaction is completed, separate and purify to obtain the first monomer; the first monomer is a compound containing quaternary ammonium, sulfonic acid and a double bond at the same time.

[0009] One embodiment of the present invention is that the graphene oxide is prepared by the following method: take 2 parts by mass of graphite powder, add 50-60 parts by volume of concentrated sulfuric acid and 6-12 parts by volume of potassium permanganate in an ice bath, stir evenly, heat to 40-45° C. and react for 1-3 hours, after the reaction, add 50-60 parts by volume of water, react at 90-100° C. for 0.5-1 hour, after the reaction, add 2-5 parts by volume of hydrogen peroxide and ultrasonicate for 1-3 hours, and then freeze-dry to obtain.

[0010] In one embodiment of the present invention, the separation and purification steps are as follows: centrifuging the reaction product, taking the solid phase, washing it with ethanol several times and then drying it.

[0011] One embodiment of the present invention is that the chlorine-containing olefin is one of allyl chloride, 3-chloro-3-methyl-1-butene and 4-chloro-2-methyl-1-butene; the first monomer is one of 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt and N,N-dimethyl-N-acrylamidopropyl-N-propanesulfonic acid inner salt.

[0012] One embodiment of the present invention is that in S1, the continuous phase of the dispersed graphene oxide is one of tetrahydrofuran and toluene; in S2, the continuous phase of the dispersed intermediate is an aqueous solution containing 0.1~0.5wt% of a surfactant, and the surfactant is one of Tween 80, sodium dodecyl sulfate and dimethylformamide.

[0013] One embodiment of the present invention is that the initiator is a persulfate initiator.

[0014] Another object of the present invention is to disclose a strongly dispersible modified graphene oxide nanosheet plugging agent, which is prepared by any of the above methods. The prepared plugging agent has a high plugging rate and good dispersion stability in water-based drilling fluid. Beneficial Effects

[0015] The plugging agent of the present invention contains both a sulfonic acid group and a quaternary ammonium group, so that the plugging agent not only has good dispersion stability, but also has strong adsorption performance in the reservoir, which is specifically reflected in that the plugging performance of the plugging agent of the present invention is stronger; at the same time, the plugging agent of the present invention also has strong salt resistance; the added 3-[bis[2-(methacryloyloxy)ethyl](methyl)ammonium]propane-1-sulfonate can improve the plugging performance of the plugging agent. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is an electron microscope scanning image of the product obtained in Example 1, wherein: Figure 1 a is the electron microscope scanning image with a scale of 200 μm. Figure 1 b is the electron microscope scanning image with a scale of 20 μm. DETAILED DESCRIPTION

[0017] The specific implementation modes of the present invention will be described clearly and completely below with reference to examples and drawings. Obviously, the described examples are only some embodiments of the present invention, rather than all embodiments.

[0018] In the following examples, unless otherwise specified, the products described are conventional commercial products.

[0019] Example 1: S1. Put 2.0g of graphite powder into a 500mL round-bottom flask, add 50mL of concentrated H2SO4 at 0°C and stir for 5min, add 6g of KMnO4 to the mixture and stir for 5min, and stir vigorously at 45°C for 2h; then add 50ml of distilled water, keep at 95°C for 0.5h, dilute with distilled water after the reaction, add 2mL of hydrogen peroxide to remove the residue; finally, ultrasonicate for 1h, freeze-dry to obtain graphene oxide nanosheets;

[0020] S2, 0.1 g of graphene oxide nanosheets were dispersed in 120 mL of tetrahydrofuran, ultrasonicated for 30 min, 0.021 g of sodium ethoxide was added at 65 ° C, and then 0.6 g of allyl chloride was added, and the reaction was carried out for 8 h. After the reaction was completed, centrifugation was performed, washed with ethanol for 3 times, and vacuum dried at 50 ° C for 4 h to obtain an intermediate;

[0021] S3. Disperse 0.1 g of the intermediate in 100 mL of 0.25% Tween 80 solution, ultrasonically disperse for 30 min, add 0.004 g of 3-[bis[2-(methacryloyloxy)ethyl](methyl)ammonium]propane-1-sulfonate and 0.2 g of 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, ultrasonically disperse for 20 min, place in a 65°C water bath, pass nitrogen, add 0.001 g of potassium persulfate aqueous solution after 15 minutes, react for 8 h, centrifuge after the reaction, wash with ethanol 3 times, and vacuum dry at 50°C for 4 h to obtain a highly dispersible modified graphene oxide nanosheet plugging agent.

[0022] The preparation method of the strongly dispersible modified graphene oxide nanosheet plugging agent prepared in this example was dispersed in pure water, and the solution was evenly dispersed on a glass slide. The morphology was observed and photographed using a scanning electron microscope (SEM, Zeiss Gemini 300) to observe the morphology of the strongly adsorbed graphene oxide nanosheets. The results are as follows: Figure 1 As shown, Figure 1 a is the electron microscope scanning image with a scale of 200 μm. Figure 1 b is an electron microscope scanning image with a scale of 20 μm. It can be seen from the figure that there are a large number of polymer chains on the surface of the strongly adsorbed graphene oxide nanosheets.

[0023] Example 2: S1. Put 2.0g of graphite powder into a 500mL round-bottom flask, add 60mL of concentrated H2SO4 at 0°C and stir for 5min, add 8g of KMnO4 to the mixture and stir for 5min, and stir vigorously at 45°C for 2h; then add 50ml of distilled water and keep at 95°C for 0.5h. After the reaction is completed, dilute with distilled water and add 2mL of hydrogen peroxide to remove the residue; finally, use an 800W ultrasonic instrument to sonicate for 1h, and freeze-dry to obtain graphene oxide nanosheets;

[0024] S2, dispersing 0.1 g of graphene oxide nanosheets in 120 mL of toluene, ultrasonicating for 30 min, adding 0.03 g of sodium ethoxide at 65 ° C, and then adding 0.9 g of 3-chloro-3-methyl-1-butene, reacting for 8 h, centrifuging after the reaction is completed, washing with ethanol 3 times, and vacuum drying at 50 ° C for 4 h to obtain an intermediate;

[0025] S3. Disperse 0.1 g of the intermediate in 100 mL of 0.25% sodium dodecyl sulfate solution, ultrasonically disperse for 30 min, then add 0.006 g of 3-[bis[2-(methacryloyloxy)ethyl](methyl)ammonium]propane-1-sulfonate and 0.3 g of N,N-dimethyl-N-acrylamidopropyl-N-propanesulfonic acid inner salt, ultrasonically disperse for 20 min, place in a 65°C water bath, pass nitrogen, add 0.0015 g of potassium persulfate aqueous solution after 15 minutes, react for 8 h, centrifuge after the reaction, wash with ethanol 3 times, and vacuum dry at 50°C for 4 h to obtain a highly dispersible modified graphene oxide nanosheet plugging agent.

[0026] Example 3: S1. 0.1 g of graphene oxide nanosheets SGO1311 (commercial product) was dispersed in 120 mL of tetrahydrofuran, and ultrasonicated for 30 min. At 65° C., 0.021 g of sodium ethoxide and 0.6 g of allyl chloride were added, and the reaction was carried out for 8 h. After the reaction was completed, the mixture was centrifuged, washed with ethanol for 3 times, and dried under vacuum at 50° C. for 4 h to obtain an intermediate.

[0027] S2. Disperse 0.1 g of the intermediate in 100 mL of 0.25% Tween 80 solution, ultrasonically disperse for 30 min, add 0.004 g of 3-[bis[2-(methacryloyloxy)ethyl](methyl)ammonium]propane-1-sulfonate and 0.2 g of 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, ultrasonically disperse for 20 min, place in a 65°C water bath, pass nitrogen, add 0.001 g of potassium persulfate aqueous solution after 15 minutes, react for 8 h, centrifuge after the reaction, wash with ethanol 3 times, and vacuum dry at 50°C for 4 h to obtain a preparation method for a highly dispersible modified graphene oxide nanosheet plugging agent.

[0028] Comparative Example 1:

[0029] S1. Put 2.0g of graphite powder into a 500mL round-bottom flask, add 50mL of concentrated H2SO4 at 0℃ and stir for 5min, add 6g of KMnO4 to the mixture and stir for 5min, and stir vigorously at 45℃ for 2h; then add 50ml of distilled water and keep at 95℃ for 0.5h. After the reaction is completed, dilute with distilled water and add 2mL of hydrogen peroxide to remove the residue; finally, use an 800W ultrasonic instrument to sonicate for 1h, freeze-dry, and obtain graphene oxide nanosheets;

[0030] S2, dispersing 0.1 g of graphene oxide nanosheets in 120 mL of tetrahydrofuran, ultrasonicating for 30 min, adding 0.6 g of allyl chloride at 65 ° C, reacting for 8 h, centrifuging after the reaction is completed, washing with ethanol 3 times, and vacuum drying at 50 ° C for 4 h to obtain an intermediate;

[0031] S3. Disperse 0.1 g of the intermediate in 100 mL of 0.25% Tween 80 solution, ultrasonically disperse for 30 min, add 0.2 g of 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, ultrasonically disperse for 20 min, place in a 65°C water bath, pass nitrogen, add 0.001 g of potassium persulfate aqueous solution after 15 minutes, react for 8 h, centrifuge after the reaction, wash with ethanol 3 times, and vacuum dry at 50°C for 4 h to obtain a highly dispersible modified graphene oxide nanosheet plugging agent.

[0032] 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.

[0033] When conducting tests, some tests also need to be combined with water-based drilling fluid. The preparation method of water-based drilling fluid is as follows:

[0034] (1) Prehydration of bentonite slurry: At 25°C, 15 parts of bentonite were uniformly added into 300 parts of fresh water while stirring. After stirring at a speed of 2000 rpm for 30 minutes, the mixture was sealed and allowed to stand for 24 hours to obtain prehydrated bentonite slurry.

[0035] (2) In the prehydrated bentonite slurry prepared in step (1), after stirring for 5 min under a stirrer at 2500 rpm, 1.5 parts of NaOH, 1.5 parts of quicklime CaO, 10 parts of salt-resistant and high-temperature resistant fluid loss reducer JD-6, 8 parts of salt-resistant fluid loss reducer RSTF, 1 part of fluid loss reducer JNJS-220, 1 part of fluid loss reducer WNFB, 1 part of modified asphalt, 0.2 parts of polymer LS-2A, 8 parts of KCl, 0.4 parts of ultrafine barite, and 266 parts of barite were added in sequence to prepare a density of 1.6 g / cm 3 Drilling fluid. After adding each substance, stir for 10 to 15 minutes before adding another substance to obtain the base slurry.

[0036] 1. Compatibility test

[0037] Different mass concentrations of plugging agents were added to the drilling fluid base slurry and aged at 150 °C for 16 h. The performance parameters of the base slurry were then measured. The results are shown in Table 1.

[0038] Table 1 Performance parameters of water-based drilling fluid

[0039]

[0040] Note: The temperature of HTHP is 150℃ and the pressure is 3.5MPa.

[0041] As can be seen from Table 1, the plugging agent prepared in the embodiment of the present invention gradually increases the dynamic shear force of the drilling fluid with the increase of the amount added, but it is still maintained at 9~11Pa, indicating that the plugging agent has little effect on the rheological properties of the drilling fluid; at the same time, referring to Comparative Example 1, according to the dynamic shear force change trend, when the amount added is greater than 1wt%, the dynamic shear force of the drilling fluid will be greater than 11Pa, indicating that it has a relatively large effect on the rheological properties of the drilling fluid. Referring to the filtration loss, it can be seen that when the plugging agent is added at 0.75wt%, its filtration loss reduction performance is better, and when the plugging agent is increased to 1wt%, the change in filtration loss is small, indicating that the plugging agent in the embodiment of the present invention can be used to block the mud well when the amount added is 0.75wt%.

[0042] 2. Core plugging experiment

[0043] The outcrop core was used to simulate the formation nano-fracture formation, and the average flow rate of the drilling fluid system in the outcrop core was measured. The permeability K = QμL / (AΔP) of the outcrop core before and after the plugging agent was added was calculated by Darcy's formula. The plugging rate of the plugging agent on the outcrop core was calculated by the plugging rate formula: (initial permeability-permeability after plugging) / initial permeability × 100%, and its plugging performance was evaluated. The final results are shown in Table 2.

[0044] Table 2 Blockage rate test data table

[0045]

[0046] It can be seen from Table 2 that the plugging agent according to the embodiment of the present invention can effectively plug the low-permeability core, and the plugging rate can reach up to more than 93%.

[0047] 3. Dispersion stability test

[0048] The zeta potential values ​​of the strongly dispersible modified graphene oxide nanosheet plugging agents prepared in Example 1, Example 2 and Example 3 at a mass concentration of 0.75% were tested using a Zetasizer Nano-ZS particle analyzer to evaluate the dispersion stability of the plugging agents in aqueous solution.

[0049] Table 3. Zeta potential average potential values

[0050]

[0051] It can be seen from Table 3 that the plugging agent of the embodiment of the present invention has good dispersion stability.

[0052] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a highly dispersible modified graphene oxide nanosheet plugging agent, characterized in that: The following steps are involved: S1, take 1-3 parts by mass of graphene oxide and disperse it evenly, add 0.21-0.9 parts by mass of sodium ethoxide and 0.6-2.7 parts by mass of chlorinated olefin at 60-80°C, and then react for 6-10 hours. After the reaction is completed, separate and purify to obtain an intermediate; S2, take 1-2 parts by mass of the intermediate and disperse it uniformly, then add 0.04-0.12 parts by mass of 3-[bis[2-(methacryloyloxy)ethyl](methyl)ammonium]propane-1-sulfonate and 2-6 parts by mass of the first monomer, mix them uniformly, add an initiator under deoxygenation conditions and react for 4-8 hours, after the reaction is completed, separate and purify to obtain; the first monomer is a compound containing quaternary ammonium, sulfonic acid and a double bond at the same time; The chlorine-containing olefin is one of allyl chloride, 3-chloro-3-methyl-1-butene and 4-chloro-2-methyl-1-butene; the first monomer is one of 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt and N,N-dimethyl-N-acrylamidopropyl-N-propanesulfonic acid inner salt.

2. The method according to claim 1, characterized in that: The graphene oxide is prepared by the following method: taking 2 parts by mass of graphite powder, adding 50-60 parts by volume of concentrated sulfuric acid and 6-12 parts by volume of potassium permanganate in an ice bath and stirring evenly, heating to 40-45° C. and reacting for 1-3 hours, after the reaction, adding 50-60 parts by volume of water, and reacting at 90-100° C. for 0.5-1 hour, after the reaction, adding 2-5 parts by volume of hydrogen peroxide and ultrasonicating for 1-3 hours, and then freeze-drying to obtain the graphene oxide.

3. The method according to claim 1, characterized in that: In S1 and S2, the separation and purification steps are as follows: centrifuge the reaction product, take the solid phase, wash it with ethanol several times and then dry it.

4. The method according to claim 1, characterized in that: In S1, the continuous phase of the dispersed graphene oxide is one of tetrahydrofuran and toluene; in S2, the continuous phase of the dispersed intermediate is an aqueous solution containing 0.1-0.5wt% of a surfactant, and the surfactant is one of Tween 80, sodium dodecyl sulfate and dimethylformamide.

5. The method according to claim 1, characterized in that The initiator is a persulfate initiator.

6. A highly dispersible modified graphene oxide nanosheet plugging agent, prepared by the method described in any one of claims 1 to 5.

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