Preparation method for filtrate reducer and use thereof

Abstract

The present application provides a preparation method for a filtrate reducer and the use thereof. The preparation method comprises: dropwise adding a silane coupling agent containing double bonds into a graphite dispersion under an acidic condition for grafting reaction to obtain silane-coupling-agent-modified graphite, then adding a cross-linking agent into the silane-coupling-agent-modified graphite, adjusting the pH to neutrality to obtain a first intermediate solution, mixing acrylamide, a sulfonic monomer, a cationic monomer and a monomer containing a cyclic group, then adjusting the pH to neutrality to form a second intermediate solution, finally adding an initiator into the first intermediate solution, then dropwise adding the second intermediate solution for polymerization reaction to obtain the filtrate reducer. The filtrate reducer prepared by such a method has a better high-temperature-resistant filtrate loss reduction property, and better pressure bearing capacity and plugging capacity.

Description

A method for preparing a filtration loss reducing agent and its application.

[0001] This application claims priority to Chinese Patent Application No. 2024115328366, filed on October 30, 2024, entitled "A method for preparing a filtration loss reducer and its application", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application belongs to the field of petrochemicals, specifically relating to a method for preparing a filtration loss reducer and its application. Background Technology

[0003] In recent years, the depth of oil and gas exploration and development has gradually expanded from mid- to shallow formations to deep and ultra-deep formations. Achieving safe and efficient exploration and development of oil and gas in deep and ultra-deep formations is of great significance. During drilling in deep and ultra-deep formations, drilling fluid can enter the formation along fractures, causing clay minerals in the formation to hydrate and expand, which can easily lead to wellbore instability. Therefore, higher requirements are placed on the drilling fluid's filtration reduction and plugging performance.

[0004] Filtration loss reducers are important treatment agents for reducing liquid phase intrusion into formations. They are mainly divided into two categories: inorganic and organic. Their mechanisms for reducing liquid phase intrusion mainly include maintaining clay particles in a fine dispersion to form a dense mud cake, sealing the mud cake and formation pores, and increasing the viscosity of the liquid phase. CN111778003A discloses an inorganic filtration loss reducer that uses a silane coupling agent to disperse smaller hydroxide particles and bridge them to the surface of larger acidified flake graphite particles, resulting in an inorganic particle-modified elastic graphite filtration loss reducer. This filtration loss reducer is heat-resistant and highly elastic, but its surface has poor water molecule capture ability and cannot deform under high temperature or pressure differential, making it difficult to effectively seal formation fractures and pore throats.

[0005] CN114437290A discloses a low-viscosity organophosphonic acid polymer filtration reducer, which is obtained by polymerizing propylene phosphonic acid monomers and acrylamide monomers. This filtration reducer has advantages such as simple raw materials, low viscosity, and good resistance to calcium and magnesium contamination. However, its high-temperature filtration reduction performance needs improvement, and it has low pressure resistance and limited plugging ability.

[0006] The aforementioned filtration reduction agents cannot simultaneously possess good high-temperature filtration reduction properties, pressure resistance, and plugging ability, making it difficult to meet the wall-forming requirements for plugging and filtration reduction in high-temperature and high-pressure formations. Therefore, how to provide a filtration reduction agent with good high-temperature filtration reduction properties, pressure resistance, and strong plugging ability is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] This application provides a method for preparing a filtration loss reducing agent. The filtration loss reducing agent obtained by using this method has good high-temperature filtration loss reduction properties, pressure resistance, and plugging ability.

[0008] This application also provides a filtration loss reducing agent, which has good resistance to high temperature filtration loss, pressure resistance and plugging ability.

[0009] This application also provides a water-based drilling fluid, wherein the water-based drilling fluid contains the above-mentioned filtration loss reducer, and the water-based drilling fluid is...

[0010] In a first aspect, this application provides a method for preparing a filtration loss reducing agent, comprising:

[0011] 1) Under acidic conditions, a silane coupling agent containing double bonds is added dropwise to a graphite dispersion to carry out a grafting reaction to obtain silane coupling agent modified graphite. Then, a crosslinking agent is added to the silane coupling agent modified graphite to adjust the pH to neutral and obtain a first intermediate solution.

[0012] 2) Mix acrylamide, sulfonic acid monomer, cationic monomer, and monomers containing cyclic groups and large side chains, and adjust the pH to neutral to form a second intermediate solution;

[0013] 3) After adding an initiator to the first intermediate solution, the second intermediate solution is added dropwise to carry out a polymerization reaction to obtain the filtrate loss reducer.

[0014] The preparation method described above, wherein the silane coupling agent containing double bonds includes at least one selected from γ-methacryloyloxypropyltrimethoxysilane, vinyltris(methoxyethoxy)silane, and vinyltriethoxysilane; and / or,

[0015] The sulfonic acid monomer comprises at least one of 2-acrylamido-2-methylpropanesulfonic acid, sodium 3-allyloxy-1-hydroxy-1-propanesulfonate, and sodium allyl sulfonate; and / or,

[0016] The cationic monomer comprises at least one of diallyl dimethyl ammonium chloride, acryloyloxyethyltrimethyl ammonium chloride, and diallylamine; and / or

[0017] The monomer containing cyclic groups and large side chains includes at least one of vinylpyrrolidone, allyl polyoxyethylene ether, and methyl allyl polyoxyethylene ether; and / or,

[0018] The initiator includes potassium persulfate.

[0019] The graphite dispersion is prepared by the method described above, comprising the following steps:

[0020] Graphite was dispersed in water, the pH was adjusted to 3-3.5, and ultrasonic dispersion was performed to obtain the graphite dispersion.

[0021] In the preparation method described above, the mass ratio of the silane coupling agent containing double bonds to the graphite in the graphite dispersion in the grafting reaction is (1-2):(8-20).

[0022] In the preparation method described above, the mass ratio of the crosslinking agent in the first intermediate solution to the acrylamide, sulfonic acid monomer, cationic monomer, and monomer containing cyclic groups and large side chains in the second intermediate solution is (0.1-0.5):(30-31).

[0023] In the preparation method described above, the mass ratio of initiator, acrylamide, sulfonic acid monomer, cationic monomer, and monomer containing cyclic groups and large side chains in the polymerization reaction is (0.1-0.3):(14-20):(3-6):(2-8):(2-10).

[0024] In the preparation method described above, the grafting reaction is carried out at a temperature of 40-60℃ for 4-6 hours.

[0025] In the preparation method described above, the polymerization reaction is carried out at a temperature of 50-70°C for 4-8 hours.

[0026] Secondly, this application proposes a filtration loss reducing agent, which is prepared by the preparation method described in the first aspect.

[0027] Thirdly, this application proposes a water-based drilling fluid, wherein the water-based drilling fluid includes the filtration loss reducer described in the second aspect.

[0028] This application first involves adding a silane coupling agent containing double bonds dropwise to a graphite dispersion for a grafting reaction, resulting in silane coupling agent-modified graphite. Then, a crosslinking agent, acrylamide, sulfonic acid monomers, cationic monomers, and monomers containing cyclic groups and large side chains are added. Under the action of an initiator, acrylamide, sulfonic acid monomers, cationic monomers, and monomers containing cyclic groups and large side chains are introduced into the surface and pores of the silane coupling agent-modified graphite through a polymerization reaction, forming a filtration loss reducer with a macromolecular network structure. The filtration loss reducer prepared by this method exhibits strong resistance to high-temperature filtration loss, pressure resistance, and plugging ability. Under high-temperature and high-pressure conditions, the filtration loss reducer deforms, adapting to formation heterogeneity and matching different fracture shapes, effectively inhibiting filtrate intrusion into the formation. Water-based drilling fluids containing the above-mentioned filtration loss reducer exhibit good rheological properties and resistance to high-temperature and high-pressure filtration loss. Attached Figure Description

[0029] Figure 1 is a picture of the filter cake formed by high temperature and high pressure (200℃, 3.5MPa) filtration loss test after the water-based drilling fluid in Comparative Example 4 was aged at 220℃ for 16 hours.

[0030] Figure 2 is a picture of the filter cake formed by high temperature and high pressure (200℃, 3.5MPa) filtration loss test after the water-based drilling fluid in Example 10 of this application was aged at 220℃ for 16 hours. Detailed Implementation

[0031] This application provides a method for preparing a filtration loss reducing agent, comprising:

[0032] 1) Under acidic conditions, a silane coupling agent containing double bonds is added dropwise to a graphite dispersion to carry out a grafting reaction, thereby obtaining silane coupling agent modified graphite. Then, a crosslinking agent is added to the silane coupling agent modified graphite, and the pH is adjusted to neutral to obtain the first intermediate solution.

[0033] 2) Mix acrylamide, sulfonic acid monomer, cationic monomer, and monomers containing cyclic groups and large side chains, and adjust the pH to neutral to form a second intermediate solution;

[0034] 3) After adding an initiator to the first intermediate solution, the second intermediate solution is added dropwise to carry out a polymerization reaction to obtain a filtration loss reducer.

[0035] Specifically, the preparation method of the filtration loss reducing agent of this application includes: 1) under acidic conditions, adding a silane coupling agent containing double bonds dropwise to a graphite dispersion, wherein the silane coupling agent containing double bonds undergoes dehydration condensation with the activated hydroxyl groups on the graphite surface in the graphite dispersion to carry out a grafting reaction, thereby obtaining silane coupling agent modified graphite, and then adding a crosslinking agent to the silane coupling agent modified graphite to adjust the pH to neutral, thereby obtaining a first intermediate solution;

[0036] 2) After mixing acrylamide, sulfonic acid monomers, cationic monomers and monomers containing cyclic groups and large side chains, the pH is adjusted to neutral to form a second intermediate solution containing multiple polymerizable monomers.

[0037] 3) After adding the initiator to the first intermediate solution, the second intermediate solution is added dropwise to carry out the polymerization reaction. In the polymerization reaction, acrylamide, sulfonic acid monomers, cationic monomers, monomers containing cyclic groups and large side chains combine with the double bonds in the silane coupling agent modified graphite under the action of the initiator. At the same time, acrylamide, sulfonic acid monomers, cationic monomers, monomers containing cyclic groups and large side chains and crosslinking agents undergo polymerization reactions on the surface and pores of the silane coupling agent modified graphite, so that the polymer penetrates into the interior of the graphite pores to obtain the filtration loss reducer.

[0038] In some embodiments, in step 1), a grafting reaction is carried out under acidic and stirring conditions to obtain silane coupling agent modified graphite. Subsequently, a crosslinking agent is added to the silane coupling agent modified graphite, and ultrasonic treatment is performed for 30 min. The mixture can be stirred at room temperature for 2 h, and the pH is adjusted to neutral with 30% NaOH aqueous solution to obtain a first intermediate solution.

[0039] In some embodiments, in step 2), the second intermediate solution further includes water. Acrylamide, sulfonic acid monomer, cationic monomer, monomer containing cyclic groups and large side chains, and water can be stirred to uniformly mix acrylamide, sulfonic acid monomer, cationic monomer, and monomer containing cyclic groups and large side chains. The pH is then adjusted to neutral using a 30% NaOH aqueous solution to obtain the second intermediate solution.

[0040] In some embodiments, in step 3), an initiator can be added to the first intermediate solution under stirring conditions, and then the second intermediate solution is added dropwise to the first intermediate solution using a dropping funnel to carry out the polymerization reaction. After drying and pulverizing, the filtrate loss reducer is obtained.

[0041] Acrylamide, sulfonic acid monomers, cationic monomers, and monomers containing cyclic groups and large side chains are grafted onto the surface and pores of silane coupling agent-modified graphite through grafting and polymerization reactions to form a filtration loss reducer with a macromolecular network structure. The filtration loss reducer prepared by this method exhibits good resistance to high-temperature filtration loss, pressure resistance, and plugging ability. Furthermore, the preparation method is simple and suitable for widespread application.

[0042] In this application, the silane coupling agent containing double bonds includes at least one of γ-methacryloxypropyltrimethoxysilane, vinyltris(methoxyethoxy)silane, and vinyltriethoxysilane. The silane coupling agent containing double bonds reacts with graphite in the graphite dispersion to introduce double bonds on the graphite surface, thereby promoting the subsequent polymerization reaction and obtaining a filtration reducer with good resistance to high temperature filtration loss and good pressure resistance.

[0043] Furthermore, the crosslinking agent includes N,N-methylenebisacrylamide, which contains two double bonds. The crosslinking agent penetrates into the pores of the modified graphite so that the subsequent polymer can be crosslinked in the graphite pores. In the polymerization reaction, the crosslinking agent connects small molecular chains to form a macromolecular network structure, allowing the polymer to penetrate into the interior of the graphite pores, thereby giving the filtration loss reducer excellent resistance to high temperature filtration loss, pressure resistance and clogging ability.

[0044] Furthermore, the sulfonic acid monomer includes at least one of 2-acrylamide-2-methylpropanesulfonic acid, sodium 3-allyloxy-1-hydroxy-1-propanesulfonate, and sodium allyl sulfonate, which contains a sulfonic acid group. Through strong hydration and inhibition of polymer hydrolysis, the filtration loss reducer can be endowed with excellent high-temperature and salt-resistant filtration loss reduction properties.

[0045] Furthermore, the cationic monomer includes at least one of diallyl dimethyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride, and diallylamine, and its molecule contains a cationic quaternary ammonium group, which can improve the solubility and dispersibility of the filtration loss reducer in water.

[0046] Furthermore, the monomers containing cyclic groups and large side chains include at least one of vinylpyrrolidone, allyl polyoxyethylene ether, and methyl allyl polyoxyethylene ether. The monomers containing cyclic groups and large side chains contain cyclic groups and large side chains, and the filtration loss reducing agent has good temperature and salt resistance filtration loss reducing performance by inhibiting molecular chain coiling under high temperature and high salt conditions through steric hindrance.

[0047] Furthermore, the initiator includes potassium persulfate, which can effectively promote the polymerization reaction and achieve better polymerization results.

[0048] According to the technical solution of this application, the graphite dispersion is prepared by a method including the following steps:

[0049] Graphite is dispersed in water, and the pH is adjusted to 3-3.5. The acidic environment can change the charge distribution on the surface of graphite and improve the dispersibility of graphite in water. Then, ultrasonic dispersion is performed. The cavitation effect of ultrasound is used to reduce the surface energy of graphite with high energy and high vibration, so that graphite is uniformly dispersed in water to obtain a graphite dispersion.

[0050] Furthermore, glacial acetic acid was used to adjust the pH to 3-3.5, and the ultrasonic dispersion treatment time was 10-20 minutes to make the graphite more evenly dispersed in the water.

[0051] In this application, during the grafting reaction, the mass ratio of the silane coupling agent containing double bonds to the graphite in the graphite dispersion is (1-2):(8-20). An appropriate amount of silane coupling agent containing double bonds is introduced onto the surface of the graphite particles. In the subsequent polymerization reaction, more acrylamide, sulfonic acid monomers, cationic monomers, and monomers containing cyclic groups and large side chains are grafted onto the surface and pores of the graphite particles modified by the silane coupling agent, thereby obtaining a filtration reducer with good high-temperature resistance, pressure resistance, and strong sealing ability.

[0052] In some embodiments, the mass ratio of the crosslinking agent in the first intermediate solution to the acrylamide, sulfonic acid monomer, cationic monomer, and monomer containing cyclic groups and large side chains in the second intermediate solution is (0.1-0.5):(30-31). By adjusting the amount of graphite modified by silane coupling agent, the thickening properties of the filtration loss reducer in the aqueous phase are adjusted, thereby enabling the filtration loss reducer to have better resistance to high-temperature filtration loss and blocking ability.

[0053] In some embodiments, the mass ratio of initiator, acrylamide, sulfonic acid monomer, cationic monomer, and monomer containing cyclic groups and large side chains in the polymerization reaction is (0.1-0.3):(14-20):(3-6):(2-8):(2-10), so that the polymerization reaction proceeds smoothly and efficiently, thereby obtaining a filtration reducer with good high-temperature resistance and strong pressure resistance.

[0054] According to the technical solution of this application, the temperature in the grafting reaction is 40-60℃ and the time is 4-6h, so that the silane coupling agent and graphite can fully carry out the grafting reaction.

[0055] In this application, the polymerization reaction is carried out at a temperature of 50-70℃ for 4-8 hours, which can effectively improve the polymerization reaction efficiency, thereby obtaining a filtration reducer with good high-temperature resistance, strong pressure resistance and strong sealing ability.

[0056] Secondly, this application proposes a filtration loss reducing agent, which is prepared by the preparation method of the first aspect. This filtration loss reducing agent has good resistance to high temperature filtration loss, pressure resistance and sealing ability.

[0057] Thirdly, this application proposes a water-based drilling fluid comprising the filtration loss reducer of the second aspect, wherein the water-based drilling fluid has good rheological properties and resistance to high-temperature and high-pressure filtration loss.

[0058] This application is described in detail below through specific embodiments:

[0059] Example 1

[0060] The filtration loss reducer in this embodiment is prepared by a method including the following steps:

[0061] (1) Measure 100 mL of water, adjust the pH to 3.5 with glacial acetic acid, add 20 g of graphite, sonicate, stir for 15 min to obtain graphite dispersion, and heat the graphite dispersion to 50 °C.

[0062] (2) 1g KH570 was added dropwise to the graphite dispersion under stirring, and the grafting reaction was carried out at 50℃ for 6h to obtain silane coupling agent modified graphite. Then, 0.1g N,N-methylenebisacrylamide was added to the silane coupling agent modified graphite, ultrasonic treatment was carried out for 30min, cooled to 25℃, stirred and mixed for 2h, and the pH value was adjusted to 7 with 30% NaOH aqueous solution to obtain the first intermediate solution.

[0063] (3) Weigh 18g acrylamide, 4.5g 2-acrylamide-2-methylpropanesulfonic acid, 6g diallyl dimethyl ammonium chloride, and 2g vinylpyrrolidone and add them to 20g water. Adjust the pH value to 7 with 30% NaOH aqueous solution to obtain the second intermediate solution.

[0064] (4) Under stirring conditions, the first intermediate solution was heated to 60°C, the cooling water was turned on, and 0.3g of potassium persulfate was added to the first intermediate solution. Then, the second intermediate solution was added dropwise to the first intermediate solution using a dropping funnel. The polymerization reaction was carried out for 4 hours. After drying and pulverizing, the filtrate loss reducer was obtained.

[0065] Example 2

[0066] The preparation method of the filtration loss reducer in this embodiment is basically the same as that in Example 1, except that the amount of KH570 in step 2) is adjusted to 0.5g.

[0067] Example 3

[0068] The preparation method of the filtration loss reducer in this embodiment is basically the same as that in Example 1, except that the amount of N,N-methylenebisacrylamide in step 2) is adjusted to 0.3g.

[0069] Example 4

[0070] The preparation method of the filtration loss reducer in this embodiment is basically the same as that in Example 1, except that: in step 2), 0.1g of N,N-methylenebisacrylamide is added to 80g of silane coupling agent modified graphite.

[0071] Example 5

[0072] The preparation method of the filtration loss reducer in this embodiment is basically the same as that in Example 1, except that: in step 2), 0.1g of N,N-methylenebisacrylamide is added to 50g of silane coupling agent modified graphite.

[0073] Example 6

[0074] The preparation method of the filtration loss reducing agent in this embodiment is basically the same as that in Example 1, except that: in step 3), the amount of 2-acrylamido-2-methylpropanesulfonic acid is adjusted to 9g and the amount of diallyl dimethylammonium chloride is adjusted to 3g.

[0075] Example 7

[0076] The preparation method of the filtration loss reducer in this embodiment is basically the same as that in Example 1, except that the polymerization temperature is adjusted to 50°C in step 4).

[0077] Example 8

[0078] The preparation method of the filtration loss reducing agent in this embodiment is basically the same as that in Example 1, except that the amount of ammonium persulfate in step 4) is adjusted to 0.2g.

[0079] Example 9

[0080] The preparation method of the filtration loss reducer in this embodiment is basically the same as that in Example 1, except that the polymerization reaction time in step 4) is adjusted to 8 hours.

[0081] Comparative Example 1

[0082] (1) Prepare a 100 mL mixed solution of water and ethanol, wherein the volume ratio of water to ethanol is 3:1. Adjust the pH of the mixed solution to 3.5 using glacial acetic acid. Add 10 g of graphite, sonicate, and stir for 15 min to obtain a graphite dispersion. Heat the graphite dispersion to 50 °C.

[0083] (2) Dissolve 1g KH570 in 10mL ethanol, add graphite dispersion dropwise with a dropping funnel under stirring, react at 50℃ for 6h, and then dry and pulverize to obtain the filtration loss reducer.

[0084] Comparative Example 2

[0085] (1) Weigh 18g acrylamide, 4.5g 2-acrylamide-2-methylpropanesulfonic acid, 6g diallyl dimethyl ammonium chloride, and 2g vinylpyrrolidone and add them to 20g water to obtain mixed solution 1. Adjust its pH value to 7 with 30% NaOH aqueous solution.

[0086] (2) Add 0.3g of potassium persulfate to 100mL of deionized water to obtain mixed solution 2. Add mixed solution 1 dropwise to mixed solution 2 using a dropping funnel. React for 4h, then dry and pulverize to obtain the filtration loss reducer.

[0087] Comparative Example 3

[0088] Untreated graphite was used as a filtration loss reducer.

[0089] Comparative Example 4

[0090] Polyacrylamide polymer (DSP-1, Deshunyuan) was used as a filtration loss reducer.

[0091] Application Examples 1-9 and Comparative Examples 1-4

[0092] Add 16g of bentonite and 0.56g of anhydrous sodium carbonate to 400mL of water, stir at 1500r / min for 20min, scrape off the clay adhering to the container wall, and cure in a sealed container at room temperature for 24h to obtain the base slurry (as application comparative example 5). Add 2wt% of the filtration loss reducer prepared in Examples 1-9 and Comparative Examples 1-4 to 400mL of the base slurry, stir at 1500r / min for 20min, scrape off the slurry adhering to the container wall to obtain the water-based drilling fluid.

[0093] Application Example 10

[0094] The preparation method of the water-based drilling fluid in this application embodiment differs from that in Example 1 in that the amount of the filtration loss reducer is adjusted to 0.5 wt%.

[0095] The water-based drilling fluids prepared in Application Examples 1-10 and Comparative Examples 1-4 were placed in a roller aging furnace at an aging temperature of 220°C for 16 hours. Rheological and high-temperature, high-pressure filtration performance evaluations of the water-based drilling fluids before and after aging were conducted according to GB / T 16783.2, including apparent viscosity (AV), plastic viscosity (PV), dynamic shear force (YP), and high-temperature, high-pressure filtration loss (FL). HTHP The high-temperature and high-pressure filtration loss test conditions were 200℃ and 3.5MPa. The test results are shown in Figure 1 and Table 1.

[0096] As shown in Figure 1, the filter cake formed by the water-based drilling fluid using polyacrylamide polymer as a filtration reducer in Comparative Example 4 under high temperature and high pressure conditions was thick and loose, failing to provide effective sealing. As shown in Figure 2, the filter cake formed by the water-based drilling fluid with 0.5 wt% filtration reducer added in Example 10 under high temperature and high pressure conditions was thin and dense, indicating that the addition of the filtration reducer effectively prevented some of the drilling mud from entering the formation, thus preventing fracture propagation and drilling fluid water loss.

[0097] Table 1

[0098] As shown in Table 1, the water-based drilling fluids prepared using Examples 1-9 have good resistance to high temperature filtration loss, pressure bearing capacity, and plugging ability.

[0099] Compared to Application Example 2, Application Example 1 increased the amount of KH570 in the filtration loss reducer, resulting in a higher amount of polymer grafted onto the graphite particle surface. The high-temperature, high-pressure filtration loss of the water-based drilling fluid after aging decreased from 52.6 mL to 43.2 mL, indicating improved resistance to high-temperature filtration loss. This is because KH570 can undergo dehydration condensation with the activated hydroxyl groups on the graphite surface. Furthermore, in subsequent polymerization reactions, the polymer monomers can combine with the double bonds in KH570, allowing the polymer to graft onto the graphite particle surface and its pores, thus giving the filtration loss reducer excellent resistance to ultra-high-temperature filtration loss.

[0100] Compared to Application Example 3, Application Example 1 uses an appropriate amount of N,N-methylenebisacrylamide, which helps to enhance the cross-linking effect between polymers and further improve the high-temperature filtration loss reduction properties of the filtration loss reducer.

[0101] Compared to Application Examples 4 and 5, the amount of silane coupling agent modified graphite added in Application Example 1 was increased, which reduced the proportion of polymer in the filtration loss reducer. The water-based drilling fluid in Application Example 1 had better rheological properties and resistance to high temperature and high pressure filtration loss.

[0102] Compared to Application Example 1, Application Example 6 adjusted the dosage of 2-acrylamido-2-methylpropanesulfonic acid and diallyl dimethylammonium chloride, resulting in a smaller change in the high-temperature and high-pressure filtration loss of the water-based drilling fluid.

[0103] Compared to Application Example 1, Application Comparative Example 1 used only KH570 modified graphite as a filtration loss reducer, and the high-temperature, high-pressure filtration loss of the water-based drilling fluid increased from 43.2 mL to 158 mL. This is because the modified graphite has no water trapping effect and no deformation ability, making it difficult to match different formation fracture shapes to form a dense seal. Compared to Application Example 1, Application Comparative Example 2 did not add silane coupling agent to modify the graphite as a filtration loss reducer, and the high-temperature, high-pressure filtration loss of the water-based drilling fluid increased from 43.2 mL to 124 mL, while also showing significant viscosity increase. Compared to Application Example 1, Application Comparative Example 3 used untreated graphite as a filtration loss reducer, and its resistance to high-temperature filtration loss reduction was far worse than that of Application Example 1.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing a filtration loss reducing agent, wherein, include: Under acidic conditions, a silane coupling agent containing double bonds is added dropwise to a graphite dispersion to carry out a grafting reaction, thereby obtaining silane coupling agent modified graphite. Then, a crosslinking agent is added to the silane coupling agent modified graphite, and the pH is adjusted to neutral to obtain a first intermediate solution. Acrylamide, sulfonic acid monomers, cationic monomers, and monomers containing cyclic groups and large side chains are mixed and the pH is adjusted to neutral to form a second intermediate solution. After adding an initiator to the first intermediate solution, the second intermediate solution is added dropwise to carry out a polymerization reaction to obtain the filtration loss reducer; The monomer containing cyclic groups and large side chains includes at least one of vinylpyrrolidone, allyl polyoxyethylene ether, and methyl allyl polyoxyethylene ether.

2. The preparation method according to claim 1, wherein, The silane coupling agent containing double bonds includes at least one of γ-methacryloyloxypropyltrimethoxysilane, vinyltris(methoxyethoxy)silane, and vinyltriethoxysilane; and / or, The sulfonic acid monomer comprises at least one of 2-acrylamido-2-methylpropanesulfonic acid, sodium 3-allyloxy-1-hydroxy-1-propanesulfonate, and sodium allyl sulfonate; and / or, The cationic monomer comprises at least one of diallyl dimethyl ammonium chloride, acryloyloxyethyltrimethyl ammonium chloride, and diallylamine; and / or The initiator includes potassium persulfate.

3. The preparation method according to claim 1 or 2, wherein, The graphite dispersion is prepared by a method comprising the following steps: Graphite was dispersed in water, the pH was adjusted to 3-3.5, and ultrasonic dispersion was performed to obtain the graphite dispersion.

4. The preparation method according to claim 1, wherein, In the grafting reaction, the mass ratio of the silane coupling agent containing double bonds to the graphite in the graphite dispersion is (1-2):(8-20).

5. The preparation method according to claim 1, wherein, The mass ratio of the crosslinking agent in the first intermediate solution to the acrylamide, sulfonic acid monomer, cationic monomer, and monomer containing cyclic groups and large side chains in the second intermediate solution is (0.1-0.5):(30-31).

6. The preparation method according to claim 1, wherein, In the polymerization reaction, the mass ratio of initiator, acrylamide, sulfonic acid monomer, cationic monomer, and monomer containing cyclic groups and large side chains is (0.1-0.3):(14-20):(3-6):(2-8):(2-10).

7. The preparation method according to claim 1, wherein, The grafting reaction is carried out at a temperature of 40-60℃ for 4-6 hours.

8. The preparation method according to claim 1, wherein, The polymerization reaction is carried out at a temperature of 50-70℃ for 4-8 hours.

9. A filtration loss reducing agent, wherein, It is prepared by the preparation method according to any one of claims 1-8.

10. A water-based drilling fluid, wherein, Includes the filtration loss reducing agent as described in claim 9.

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