Preparation method and application of filtrate reducer

Abstract

The invention provides a preparation method and application of a filtrate reducer, and the preparation method comprises the following steps: under an acidic condition, dropwise adding a silane coupling agent containing double bonds into a graphite dispersion liquid, carrying out a grafting reaction to obtain silane coupling agent modified graphite, adding a cross-linking agent into the silane coupling agent modified graphite, adjusting the pH value to neutral, and carrying out vacuum drying to obtain the filtrate reducer. The preparation method comprises the following steps: preparing a first intermediate solution, mixing acrylamide, a sulfonic monomer, a cationic monomer and a monomer containing a cyclic group, adjusting the pH value to be neutral to form a second intermediate solution, finally adding an initiator into the first intermediate solution, dropwise adding the second intermediate solution, and carrying out a polymerization reaction to obtain the filtrate reducer. The filtrate reducer prepared by the method has better high-temperature-resistant filtrate loss reduction property, pressure bearing capacity and plugging capacity.

Description

Technical Field

[0001] The invention belongs to the field of petrochemical industry, and specifically relates to a preparation method of a fluid loss reducer and application thereof. Background Art

[0002] In recent years, the depth of oil and gas exploration and development has gradually expanded from medium-shallow layers to deep-ultra-deep layers, and it is of great significance to achieve safe and efficient exploration and development of deep-ultra-deep oil and gas. During the drilling process of deep-ultra-deep formations, the drilling fluid will enter the formation along the cracks, causing the clay minerals in the formation to hydrate and expand, which is prone to wellbore instability. Therefore, higher requirements are placed on the filtration reduction and plugging performance of the drilling fluid.

[0003] Fluid loss reducers are important treatment agents for reducing the invasion of liquid phase into formations. They are mainly divided into two categories: inorganic fluid loss reducers and organic fluid loss reducers. The mechanism of reducing liquid phase invasion mainly includes maintaining clay particles in fine dispersion to form a dense mud cake, plugging mud cake and formation pores, and increasing liquid phase viscosity. CN111778003A discloses an inorganic fluid loss reducer, which uses a silane coupling agent to disperse and bridge the surface of larger particles of acidified flake graphite to obtain an inorganic particle modified elastic graphite fluid loss reducer. The fluid loss reducer is resistant to high temperatures and has high elasticity, but its surface has poor ability to capture water molecules and cannot deform under high temperature or pressure difference, making it difficult to efficiently plug formation cracks and pore throats.

[0004] CN114437290A discloses a low-viscosity organic phosphonic acid polymer fluid loss reducer, which is obtained by polymerizing propylene phosphonic acid monomers and acrylamide monomers. The fluid loss reducer has the properties of simple synthetic raw materials, low viscosity increase, good resistance to calcium and magnesium, etc., but its high temperature resistance and fluid loss reduction performance need to be improved, its pressure bearing capacity is low, and its plugging capacity is limited.

[0005] The above-mentioned fluid loss reducers cannot simultaneously have good high temperature resistance and fluid loss reduction, pressure bearing capacity and plugging capacity, and are difficult to meet the needs of plugging, fluid loss reduction and other wall consolidation in high temperature and high pressure formations. Therefore, how to provide a fluid loss reducer with good high temperature resistance and fluid loss reduction, strong pressure bearing capacity and plugging capacity is a technical problem to be solved in this field. Summary of the invention

[0006] The invention provides a method for preparing a fluid loss reducer. The fluid loss reducer obtained by the preparation method has good high temperature resistance and fluid loss reduction performance, pressure bearing capacity and plugging capacity.

[0007] The present invention also provides a fluid loss reducer, which has good high temperature resistance, fluid loss reduction performance, pressure bearing capacity and plugging capacity.

[0008] The present invention also provides a water-based drilling fluid, wherein the water-based drilling fluid comprises the above-mentioned fluid loss reducer.

[0009] In a first aspect, the present invention provides a method for preparing a fluid loss reducer, comprising:

[0010] 1) under acidic conditions, a silane coupling agent containing a double bond is added dropwise to a graphite dispersion to carry out a grafting reaction to obtain silane coupling agent-modified graphite, and then a cross-linking agent is added to the silane coupling agent-modified graphite, and the pH is adjusted to neutral to obtain a first intermediate solution;

[0011] 2) mixing acrylamide, sulfonic acid monomer, cationic monomer and monomer containing cyclic group and large side chain, and adjusting pH to neutral to form a second intermediate solution;

[0012] 3) After adding an initiator to the first intermediate solution, the second intermediate solution is added dropwise to perform a polymerization reaction to obtain the fluid loss reducer.

[0013] The preparation method as described above, wherein the silane coupling agent containing a double bond comprises at least one of γ-methacryloxypropyltrimethoxysilane, vinyltri(methoxyethoxy)silane, and vinyltriethoxysilane; and / or,

[0014] The sulfonic acid monomer includes at least one of 2-acrylamide-2-methylpropanesulfonic acid, 3-allyloxy-1-hydroxy-1-propanesulfonic acid sodium salt, and sodium allyl sulfonate; and / or,

[0015] The cationic monomer includes at least one of diallyldimethylammonium chloride, acryloyloxyethyltrimethylammonium chloride and diallylamine; and / or,

[0016] The monomer containing a cyclic group and a large side chain includes at least one of vinyl pyrrolidone, allyl polyoxyethylene ether, and methyl allyl polyoxyethylene ether; and / or,

[0017] The initiator includes potassium persulfate.

[0018] The preparation method as described above, wherein the graphite dispersion is prepared by a method comprising the following steps:

[0019] The graphite is dispersed in water, the pH is adjusted to 3-3.5, and ultrasonic dispersion treatment is performed to obtain the graphite dispersion liquid.

[0020] In the preparation method as described above, 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).

[0021] In the preparation method as 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).

[0022] The preparation method as described above, wherein in the polymerization reaction, the mass ratio of the initiator, acrylamide, sulfonic acid monomer, cationic monomer and monomer containing a cyclic group and a large side chain is (0.1-0.3):(14-20):(3-6):(2-8):(2-10).

[0023] The preparation method as described above, wherein in the grafting reaction, the temperature is 40-60° C. and the time is 4-6 hours.

[0024] The preparation method as described above, wherein in the polymerization reaction, the temperature is 50-70°C and the time is 4-8h.

[0025] In a second aspect, the present invention provides a fluid loss reducer, which is prepared by the preparation method described in the first aspect.

[0026] In a third aspect, the present invention provides a water-based drilling fluid, wherein the water-based drilling fluid comprises the fluid loss reducer described in the second aspect.

[0027] The present invention first drops a silane coupling agent containing a double bond into a graphite dispersion for grafting reaction to obtain silane coupling agent modified graphite, then adds a crosslinking agent, acrylamide, a sulfonic acid monomer, a cationic monomer, and a monomer containing a cyclic group and a large side chain, and introduces acrylamide, a sulfonic acid monomer, a cationic monomer, and a monomer containing a cyclic group and a large side chain into the surface and pores of the silane coupling agent modified graphite through a polymerization reaction under the action of an initiator, thereby forming a fluid loss reducer with a macromolecular network structure. The fluid loss reducer prepared by the preparation method has strong high temperature resistance and fluid loss reduction, pressure bearing capacity, and plugging capacity. The fluid loss reducer deforms under high temperature and high pressure conditions, can adapt to the heterogeneity of the formation, match different fracture shapes of the formation, and effectively inhibit the intrusion of the filtrate into the formation. The water-based drilling fluid containing the above-mentioned fluid loss reducer has good rheology and resistance to high temperature and high pressure fluid loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a physical picture of the filter cake formed by carrying out a high temperature and high pressure (200°C, 3.5MPa) filtration loss test on the water-based drilling fluid in comparative example 4 of the present invention after aging at 220°C for 16 hours;

[0029] Figure 2 For the present invention Figure 2This is a physical picture of the filter cake formed by conducting a high temperature and high pressure (200°C, 3.5MPa) filtration loss test on the water-based drilling fluid in Example 10 after aging at 220°C for 16 hours. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] The present invention provides a method for preparing a fluid loss reducer, comprising:

[0032] 1) under acidic conditions, a silane coupling agent containing a double bond is added dropwise to a graphite dispersion to carry out a grafting reaction to obtain silane coupling agent-modified graphite, and then a cross-linking agent is added to the silane coupling agent-modified graphite, and the pH is adjusted to neutral to obtain a first intermediate solution;

[0033] 2) mixing acrylamide, sulfonic acid monomer, cationic monomer and monomer containing cyclic group and large side chain, and adjusting 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 perform a polymerization reaction to obtain a fluid loss reducer.

[0035] Specifically, the preparation method of the fluid loss reducer of the present invention comprises: 1) under acidic conditions, a silane coupling agent containing a double bond is added dropwise to a graphite dispersion, the silane coupling agent containing a double bond undergoes dehydration condensation with activated hydroxyl groups on the surface of graphite in the graphite dispersion, and a grafting reaction is performed to obtain silane coupling agent-modified graphite, and then a cross-linking agent is added to the silane coupling agent-modified graphite, and the pH is adjusted to neutral to obtain a first intermediate solution;

[0036] 2) mixing acrylamide, sulfonic acid monomer, cationic monomer and monomer containing cyclic group and large side chain, and adjusting pH to neutral to form a second intermediate solution containing multiple polymerizable monomers;

[0037] 3) After adding an initiator to the first intermediate solution, the second intermediate solution is added dropwise to perform a polymerization reaction. In the polymerization reaction, acrylamide, sulfonic acid monomer, cationic monomer, and monomer containing a cyclic group and a large side chain are combined with double bonds in the silane coupling agent-modified graphite under the action of the initiator. At the same time, acrylamide, sulfonic acid monomer, cationic monomer, monomer containing a cyclic group and a large side chain and a cross-linking agent are polymerized on the surface and pores of the silane coupling agent-modified graphite, so that the polymer is interspersed in the pores of the graphite to obtain a fluid 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, and then a crosslinking agent is added to the silane coupling agent-modified graphite, and ultrasonic treatment is performed for 30 minutes, and stirring can be performed at room temperature for 2 hours. The pH is adjusted to neutral with a 30% NaOH aqueous solution to obtain a first intermediate solution.

[0039] In some embodiments, in step 2), the second intermediate solution also includes water, and acrylamide, sulfonic acid monomers, cationic monomers, monomers containing cyclic groups and large side chains, and water can be stirred to uniformly mix acrylamide, sulfonic acid monomers, cationic monomers, and monomers containing cyclic groups and large side chains, and the pH is adjusted to neutral with a 30% NaOH aqueous solution to obtain a 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 perform a polymerization reaction, and then dried and pulverized to obtain a fluid loss reducer.

[0041] Through grafting reaction and polymerization reaction, acrylamide, sulfonic acid monomer, cationic monomer and monomer containing cyclic group and large side chain are grafted to the surface and pores of silane coupling agent modified graphite to form a fluid loss reducer with a macromolecular network structure. The fluid loss reducer prepared by this method has good high temperature resistance, pressure bearing capacity and plugging capacity. At the same time, the preparation method is simple to operate and is suitable for wide promotion and application.

[0042] In the present invention, the silane coupling agent containing double bonds includes at least one of γ-methacryloxypropyltrimethoxysilane, vinyltri(methoxyethoxy)silane and vinyltriethoxysilane. The silane coupling agent containing double bonds reacts with graphite in a graphite dispersion through a coupling reaction, and double bonds are introduced on the surface of the graphite to promote the subsequent polymerization reaction, so as to obtain a fluid loss reducer with good high temperature resistance and pressure bearing capacity.

[0043] Furthermore, the cross-linking agent includes N,N-methylenebisacrylamide, which contains two double bonds. The cross-linking agent penetrates into the pores of the modified graphite so that subsequent polymers can be cross-linked in the pores of the graphite. In the polymerization reaction, the cross-linking agent connects small molecule chains to form a macromolecular network structure, so that the polymer is interspersed in the pores of the graphite, thereby making the fluid loss reducer have excellent high temperature resistance, pressure bearing capacity and plugging ability.

[0044] Furthermore, the sulfonic acid monomer includes at least one of 2-acrylamide-2-methylpropane sulfonic acid, 3-allyloxy-1-hydroxy-1-propane sulfonic acid sodium salt, and sodium allyl sulfonate, which contains a sulfonic acid group and can impart excellent high temperature and salt resistance to the fluid loss reducer through strong hydration and inhibition of polymer hydrolysis.

[0045] Furthermore, the cationic monomer includes at least one of diallyldimethylammonium chloride, acryloyloxyethyltrimethylammonium chloride and diallylamine, and the molecule thereof contains a cationic quaternary ammonium group, which can improve the solubility and dispersibility of the fluid loss reducer in water.

[0046] Furthermore, the monomer containing a cyclic group and a large side chain includes at least one of vinyl pyrrolidone, allyl polyoxyethylene ether, and methyl allyl polyoxyethylene ether, and the monomer containing a cyclic group and a large side chain contains a cyclic group and a large side chain. The steric hindrance inhibits the curling of the molecular chain under high temperature and high salt conditions, so that the fluid loss reducer has better temperature and salt resistance and fluid loss reduction performance.

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

[0048] According to the technical solution of the present invention, the graphite dispersion is prepared by a method comprising 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 graphite surface and improve the dispersibility of graphite in water. Ultrasonic dispersion treatment is then performed, and the cavitation effect of ultrasound is used to reduce the surface energy of graphite with high energy and high vibration, so that the graphite is evenly dispersed in water to obtain a graphite dispersion.

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

[0051] In the present invention, 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), and an appropriate amount of the silane coupling agent containing double bonds is introduced onto the surface of the graphite particles. In the subsequent polymerization reaction, more acrylamide, sulfonic acid monomer, cationic monomer and monomer containing cyclic groups and large side chains are grafted onto the particle surface and pores of the graphite modified by the silane coupling agent, thereby obtaining a fluid loss reducer with good high temperature resistance, good pressure bearing capacity and strong plugging capacity.

[0052] In some embodiments, the mass ratio of the cross-linking agent in the first intermediate solution to the acrylamide, sulfonic acid monomer, cationic monomer, and monomer containing a cyclic group and a large side chain in the second intermediate solution is (0.1-0.5): (30-31). By adjusting the amount of silane coupling agent-modified graphite, the viscosity-increasing performance of the fluid loss reducer in the aqueous phase is adjusted, thereby making the fluid loss reducer have better high temperature resistance and fluid loss reduction properties and plugging ability.

[0053] In some embodiments, in the polymerization reaction, the mass ratio of the initiator, acrylamide, sulfonic acid monomer, cationic monomer and monomer containing a cyclic group and a large side chain 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 fluid loss reducer with good high temperature resistance and pressure resistance.

[0054] According to the technical solution of the present invention, during the grafting reaction, the temperature is 40-60° C. and the time is 4-6 hours, so that the silane coupling agent and graphite can fully undergo the grafting reaction.

[0055] In the present invention, during the polymerization reaction, the temperature is 50-70°C and the time is 4-8h, which can effectively improve the polymerization reaction efficiency, thereby obtaining a fluid loss reducer with good high temperature resistance, good pressure bearing capacity and strong plugging capacity.

[0056] In a second aspect, the present invention provides a fluid loss reducer, which is prepared by the preparation method of the first aspect. The fluid loss reducer has good high temperature resistance, pressure bearing capacity and plugging ability.

[0057] In a third aspect, the present invention provides a water-based drilling fluid, which includes the fluid loss reducer of the second aspect, and the water-based drilling fluid has good rheological properties and resistance to high temperature and high pressure fluid loss.

[0058] The present invention is described in detail below by specific embodiments:

[0059] Example 1

[0060] The fluid loss reducer of this embodiment is prepared by a method comprising the following steps:

[0061] (1) 100 mL of water was measured, the pH was adjusted to 3.5 with glacial acetic acid, 20 g of graphite was added, ultrasonic treatment was performed, and stirring was performed for 15 min to obtain a graphite dispersion, and the graphite dispersion was heated to 50° C.;

[0062] (2) adding 1 g of KH570 dropwise to the graphite dispersion under stirring, carrying out a grafting reaction at 50° C. for 6 h to obtain silane coupling agent-modified graphite, then adding 0.1 g of N,N-methylenebisacrylamide to the silane coupling agent-modified graphite, ultrasonically treating for 30 min, cooling to 25° C., stirring and mixing for 2 h, and adjusting the pH value to 7 with a 30% NaOH aqueous solution to obtain a first intermediate solution;

[0063] (3) 18 g of acrylamide, 4.5 g of 2-acrylamide-2-methylpropanesulfonic acid, 6 g of diallyldimethylammonium chloride, and 2 g of vinyl pyrrolidone were weighed and added to 20 g of water, and the pH value thereof was adjusted to 7 with a 30% NaOH aqueous solution to obtain a second intermediate solution;

[0064] (4) The first intermediate solution was heated to 60° C. under stirring conditions, condensation water was turned on, 0.3 g of potassium persulfate was added to the first intermediate solution, and then the second intermediate solution was added dropwise to the first intermediate solution using a dropping funnel to carry out polymerization reaction for 4 hours, and then dried and crushed to obtain a filtrate reducer.

[0065] Example 2

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

[0067] Example 3

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

[0069] Example 4

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

[0071] Example 5

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

[0073] Example 6

[0074] The preparation method of the fluid loss reducer in this embodiment is basically the same as that in Embodiment 1, except that in step 3), the amount of 2-acrylamido-2-methylpropanesulfonic acid is adjusted to 9 g, and the amount of diallyldimethylammonium chloride is adjusted to 3 g.

[0075] Example 7

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

[0077] Example 8

[0078] The preparation method of the fluid loss reducer in this embodiment is basically the same as that in Embodiment 1, except that: in step 4), the amount of ammonium persulfate is adjusted to 0.2 g.

[0079] Example 9

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

[0081] Comparative Example 1

[0082] (1) preparing 100 mL of a mixed solution of water and ethanol, wherein the volume ratio of water to ethanol is 3:1, adjusting the pH of the mixed solution to 3.5 using glacial acetic acid, adding 10 g of graphite, performing ultrasonic treatment, stirring for 15 min to obtain a graphite dispersion, and heating the graphite dispersion to 50° C.;

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

[0084] Comparative Example 2

[0085] (1) 18 g of acrylamide, 4.5 g of 2-acrylamide-2-methylpropanesulfonic acid, 6 g of diallyldimethylammonium chloride, and 2 g of vinyl pyrrolidone were weighed and added to 20 g of water to obtain a mixed solution 1, and the pH value of the mixed solution was adjusted to 7 with a 30% NaOH aqueous solution;

[0086] (2) In 100 mL of deionized water, 0.3 g of potassium persulfate was added to obtain a mixed solution 2, and the mixed solution 1 was added dropwise to the mixed solution 2 using a dropping funnel. The mixture was reacted for 4 hours, and then dried and crushed to obtain a filtrate reducer.

[0087] Comparative Example 3

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

[0089] Comparative Example 4

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

[0091] Application Examples 1-9 and Application Comparative Examples 1-5

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

[0093] Application Example 10

[0094] The method for preparing the water-based drilling fluid in this application example is different from the method for preparing the water-based drilling fluid in Example 1 in that the amount of the fluid loss reducer is adjusted to 0.5 wt %.

[0095] The water-based drilling fluids prepared in Example 1-10 and Comparative Example 1-5 were placed in a roller aging furnace at an aging temperature of 220°C for 16 hours. The rheological and high-temperature and high-pressure fluid loss performance of the water-based drilling fluids before and after aging were evaluated with reference to GBT16783.2, including apparent viscosity (AV), plastic viscosity (PV), dynamic shear force (YP) and high-temperature and high-pressure fluid loss (FL). HTHP ), where the high temperature and high pressure fluid loss test conditions are 200℃ and 3.5MPa, and the test results are shown in Figure 1 and Table 1.

[0096] Depend on Figure 1 It can be seen that the filter cake formed by the water-based drilling fluid using polyacrylamide polymer as a fluid loss reducer under high temperature and high pressure conditions in Comparative Example 4 is thick and loose, and cannot play an effective plugging role. Figure 2 It can be seen that the filter cake formed by the water-based drilling fluid to which 0.5 wt% of the fluid loss reducer was added under high temperature and high pressure conditions in Application Example 10 is thin and dense, indicating that the addition of the fluid loss reducer effectively prevents a portion of the mud from entering the formation, thereby preventing the expansion of cracks and water loss of the drilling fluid.

[0097] Table 1

[0098]

[0099] It can be seen from Table 1 that the water-based drilling fluids prepared using Examples 1-9 have good high temperature resistance, fluid loss reduction performance, pressure bearing capacity and plugging capacity.

[0100] Compared with Application Example 2, Application Example 1 increases the amount of KH570 in the fluid loss reducer, the amount of polymer grafted on the surface of graphite particles is increased, and the high temperature and high pressure fluid loss of the water-based drilling fluid after aging is reduced from 52.6 mL to 43.2 mL, indicating that the high temperature resistance of the fluid loss reducer is improved. This is because KH570 can undergo dehydration condensation with the activated hydroxyl groups on the surface of graphite, and further in the subsequent polymerization reaction, the polymer monomer can combine with the double bond in KH570, so that the polymer is grafted on the surface of the graphite particles and in their pores, thereby making the fluid loss reducer have good ultra-high temperature resistance and fluid loss reduction.

[0101] Compared with Application Example 3, Application Example 1 uses an appropriate amount of N,N-methylenebisacrylamide, which is beneficial to enhancing the cross-linking effect between polymers and further improving the high temperature resistance and fluid loss reduction performance of the fluid loss reducer.

[0102] Compared with Application Example 4 and Application Example 5, the amount of silane coupling agent modified graphite added in Application Example 1 is increased, so that the proportion of polymer in the fluid loss reducer is reduced, and the water-based drilling fluid in Application Example 1 has better rheology and resistance to high temperature and high pressure fluid loss.

[0103] Compared with Application Example 1, in Application Example 6, the amount of 2-acrylamido-2-methylpropanesulfonic acid and diallyldimethylammonium chloride was adjusted, and the high-temperature and high-pressure filtration loss of the water-based drilling fluid changed less.

[0104] Compared with Application Example 1, Application Comparative Example 1 only uses KH570 modified graphite as a fluid loss reducer, and the high temperature and high pressure fluid loss of the water-based drilling fluid increases from 43.2 mL to 158 mL. This is because the modified graphite has no trapping effect on water and no deformation ability, and it is difficult to match the different fracture shapes of the formation to form a dense plug. Compared with Application Example 1, the fluid loss reducer in Application Comparative Example 2 does not add silane coupling agent to modify the graphite, and the high temperature and high pressure fluid loss of the water-based drilling fluid increases from 43.2 mL to 124 mL, and the viscosity increase is more serious; Compared with Application Example 1, Application Comparative Example 3 uses untreated graphite as a fluid loss reducer, and its high temperature resistance and fluid loss reduction performance are far worse than that of Application Example 1.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a fluid loss reducer, characterized in that: include: Under acidic conditions, a silane coupling agent containing a double bond is added dropwise to a graphite dispersion to perform a grafting reaction to obtain silane coupling agent-modified graphite, and 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; After mixing acrylamide, sulfonic acid monomer, cationic monomer and monomer containing cyclic group and large side chain, 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 perform a polymerization reaction to obtain the fluid loss reducer.

2. The preparation method according to claim 1, characterized in that: The silane coupling agent containing double bonds includes at least one of γ-methacryloxypropyltrimethoxysilane, vinyltri(methoxyethoxy)silane and vinyltriethoxysilane; and / or, The sulfonic acid monomer includes at least one of 2-acrylamide-2-methylpropanesulfonic acid, 3-allyloxy-1-hydroxy-1-propanesulfonic acid sodium salt, and sodium allyl sulfonate; and / or, The cationic monomer includes at least one of diallyldimethylammonium chloride, acryloyloxyethyltrimethylammonium chloride and diallylamine; and / or, The monomer containing a cyclic group and a large side chain includes at least one of vinyl pyrrolidone, allyl polyoxyethylene ether, and methyl allyl polyoxyethylene ether; and / or, The initiator includes potassium persulfate.

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

4. The preparation method according to any one of claims 1 to 3, characterized in that 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 any one of claims 1 to 4, characterized in that: The mass ratio of the cross-linking agent in the first intermediate solution to the acrylamide, sulfonic acid monomer, cationic monomer and monomer containing cyclic group and large side chain in the second intermediate solution is (0.1-0.5): (30-31).

6. The preparation method according to any one of claims 1 to 5, characterized in that: In the polymerization reaction, the mass ratio of the initiator, acrylamide, sulfonic acid monomer, cationic monomer and monomer containing cyclic group and large side chain is (0.1-0.3): (14-20): (3-6): (2-8): (2-10).

7. The preparation method according to any one of claims 1 to 6, characterized in that: In the grafting reaction, the temperature is 40-60° C. and the time is 4-6 hours.

8. The preparation method according to any one of claims 1 to 7, characterized in that: In the polymerization reaction, the temperature is 50-70° C. and the time is 4-8 hours.

9. A fluid loss reducer, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 8.

10. A water-based drilling fluid, characterized in that: Including the fluid loss reducer as described in claim 9.

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