Modified humate-based filtrate reducer for temperature-resistant and salt-resistant water-based drilling fluid and preparation method of filtrate reducer

Abstract

The invention provides a temperature-resistant salt-resistant water-based drilling fluid filtrate reducer based on modified humate and a preparation method of the temperature-resistant salt-resistant water-based drilling fluid filtrate reducer, and belongs to the field of oilfield chemistry. A temperature-resistant salt-resistant monomer, ethylene phosphoric acid, a solubility improving monomer and an adsorbability improving monomer are grafted to humate, the solubility improving monomer is at least one of vinyl pyrrolidone, hydroxyethyl acrylate, N-vinylformamide and hydroxypropyl methacrylate; and the adsorbability improving monomer is at least one of KH570 and KH151. The filtrate reducer disclosed by the invention has excellent temperature-resistant and salt-resistant effects, shear resistance and filtrate reduction performance.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield chemistry, in particular to the technical field of drilling fluid additives, and specifically relates to a temperature-resistant and salt-resistant filtrate reducer for a base drilling fluid based on modified humate and a preparation method thereof. Background Art

[0002] In the field of oil extraction technology, drilling fluid is one of the essential key materials. Drilling fluid not only needs to have good rheological properties, but also needs to have a certain loss control ability to reduce the loss of formation fluid through the wellbore during drilling. To this end, various drilling fluid additives have been developed to enhance the loss control ability of drilling fluid. Among them, fluid loss reducer is an important type of drilling fluid additive. Its main function is to reduce the loss of drilling fluid, thereby preventing excessive loss of formation fluid and maintaining the stability of the formation.

[0003] Existing fluid loss reducers mainly interact with mineral components in the formation through physical or chemical methods, thereby forming a protective film on the well wall and reducing the loss of formation fluid. For example, some traditional fluid loss reducers react with calcium ions in the formation to form insoluble calcium salt precipitation, thereby forming a protective film on the well wall. In addition, some fluid loss reducers are adsorbed on the surface of the formation by physical adsorption, thereby reducing the loss of formation fluid. However, there are still some problems and limitations in the actual application of existing fluid loss reducers. First, the existing fluid loss reducers are insufficient in temperature and salt resistance. Under high temperature and high pressure environments, some traditional fluid loss reducers may lose their due fluid loss control ability, resulting in excessive loss of formation fluid. Secondly, the existing fluid loss reducers are also insufficient in shear resistance. During the drilling process with high shear rate, some traditional fluid loss reducers may be sheared and damaged, thereby losing their due fluid loss control ability. Finally, the existing fluid loss reducers are also insufficient in adsorption stability. Under complex formation conditions, some traditional fluid loss reducers may be lost from the formation surface due to the scouring of formation fluids, thereby reducing their fluid loss control ability. Summary of the invention

[0004] In order to solve at least one of the above problems, the object of the present invention is to provide a temperature-resistant and salt-resistant filtrate reducer for base drilling fluid based on modified humate and a preparation method thereof. The filtrate reducer of the present invention has excellent temperature and salt resistance.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A method for preparing a temperature-resistant and salt-resistant filtrate reducer for drilling fluid based on modified humate, comprising the following steps:

[0007] S1. Dissolve humate and modified monomer in a mass ratio of 1:(0.8-1.2) in deionized water, introduce inert gas to deoxygenate, add initiator, heat to 40°C-70°C under closed and continuous stirring conditions, and react for 4h-8h to obtain a grafted product solution;

[0008] The modified monomers include a temperature-resistant and salt-resistant monomer, vinyl phosphoric acid, a solubility-improving monomer, and an adsorption-improving monomer in a molar mass ratio of 1:(0.1-0.2):(0.2-0.5):(0.1-0.3);

[0009] The solubility improving monomer is a mixture of one or more of vinyl pyrrolidone, hydroxyethyl acrylate, N-vinyl formamide and hydroxypropyl methacrylate;

[0010] The adsorption improving monomer is one or a mixture of γ-methacryloxypropyltrimethoxysilane (KH-570) and vinyltriethoxysilane (KH-151);

[0011] S2. Dissolve the crosslinking agent in deionized water and pass inert gas to deoxygenate, add the crosslinking agent solution to the grafted product solution, heat to 40°C to 70°C under closed and continuous stirring conditions, and react for 1h to 2h; open the reaction container to allow the solution to contact the air, cool the reaction product to room temperature, then heat and dry it to constant weight to obtain a filtrate reducer.

[0012] As a specific embodiment of the present invention, the humate is sodium humate or potassium humate.

[0013] As a specific embodiment of the present invention, the temperature and pressure resistant monomer is a mixture of one or more of sodium 2-acrylamide-2-methylpropane sulfonate, sodium methyl propene sulfonate, sodium propene sulfonate, sodium vinyl sulfonate, and sodium p-styrene sulfonate.

[0014] As a specific implementation of the present invention, the initiator is potassium persulfate or ammonium persulfate, and the amount of the initiator added is 0.3% to 1% of the molar mass of the modified monomer.

[0015] As a specific embodiment of the present invention, the cross-linking agent is a mixture of one or more of N,N-dimethylbisacrylamide, polyethylene glycol diacrylate (PEGDA200, PEGDA400, PEGDA600 or PEGDA1000), and the molar ratio of the modified monomer to the cross-linking agent is 100:(8-12).

[0016] Drying is generally carried out below 80°C. If the temperature is too high, the drying process and the sufficient contact with oxygen may cause polymer chain breakage and affect the performance. If the temperature is too low, the drying time is too long. Therefore, as a specific embodiment of the present invention, the drying temperature is 60°C to 75°C.

[0017] A temperature-resistant and salt-resistant filtrate reducer for base drilling fluid based on modified humate is prepared by the method.

[0018] Beneficial effects:

[0019] The fluid loss reducer of the present invention has excellent temperature and salt resistance and fluid loss resistance. In the present invention, vinyl phosphate is grafted onto the humate molecular chain, and the phosphorus element can, to a certain extent, complex with the metal ions in the formation, thereby enhancing the adsorption capacity of the fluid loss reducer on the formation, thereby more effectively blocking the formation pores and reducing fluid loss; in the present invention, part of the grafted product forms a cross-linked structure within the molecule. This internal cross-linking can increase the molecular weight and molecular compactness of the fluid loss reducer, improve its shear resistance in the drilling fluid, and enable it to maintain good fluid loss reduction performance during drilling at a high shear rate; the hydroxyl functional group is introduced in the present invention to increase the hydrophilicity of the product and its compatibility with other additives, which helps to better adjust the rheological properties of the drilling fluid and indirectly reduce the fluid loss. DETAILED DESCRIPTION

[0020] The specific implementation modes of the present invention will be described clearly and completely below with reference to examples. Obviously, the examples described are only some embodiments of the present invention, rather than all embodiments.

[0021] In the following examples, sodium humate was purchased from Tianjin Huasheng Chemical Reagent Co., Ltd.

[0022] Example 1

[0023] S1. Prepare sodium humate solution and modified monomer solution

[0024] Preparation of sodium humate solution: Weigh 15 g of sodium humate (HA) and slowly add it into a three-necked flask, add 100 mL of deionized water, stir at 60°C for 1 h to fully dissolve it, and prepare a sodium humate solution.

[0025] Prepare modified monomer solution: determine the mass of modified monomer (the sum of the masses of all modified monomers) according to the mass ratio of sodium humate to modified monomer of 1:0.8, determine the mass of temperature- and salt-resistant monomer (sodium 2-acrylamide-2-methylpropane sulfonate), enhanced temperature- and salt-resistant monomer (vinyl phosphoric acid), solubility-improving monomer (vinyl pyrrolidone), and adsorption-improving monomer (KH-570) according to the molar ratio of 1:0.1:0.2:0.2, add the above-mentioned modified monomers into deionized water to prepare modified monomer solution with a concentration of 500 g / L, prepare 24 mL, and pour into a dropping funnel for later use.

[0026] S2. Grafting reaction: slowly drop the modified monomer solution into the three-necked flask, keep stirring, the stirring speed is 200r / min, after the dropwise addition is completed, nitrogen is introduced, and bubbling deoxygenation is performed for 20min. Initiator (potassium persulfate, the amount of initiator is 0.5% of the molar mass of the modified monomer) is added under nitrogen atmosphere, and the reaction container is sealed after bubbling deoxygenation for 5min, and the three-necked flask is placed in a constant temperature water bath, and magnetic stirring is continued, the temperature is set to 60°C, and the reaction time is 8h.

[0027] S3, cross-linking reaction and post-treatment: Add the cross-linking agent (N, N-dimethylbisacrylamide) into deionized water to prepare a cross-linking agent solution with a concentration of 150 g / L. Pass nitrogen gas and deoxygenate by bubbling for 5 minutes.

[0028] Open the reaction vessel of S2 grafting reaction, introduce nitrogen, bubble, dropwise add deoxygenated crosslinker solution, the molar mass ratio of modified monomer to crosslinker is 100:8, bubble and deoxygenate for 5 minutes, then seal the reaction vessel, and keep the reaction temperature unchanged (60°C). After 2 hours of reaction, take out the reaction vessel from the water bath and open it, let the solution contact the air, cool to room temperature, then heat to 60°C and dry to constant weight to obtain the final product.

[0029] Example 2

[0030] S1. Preparation of sodium humate solution and modified monomer solution

[0031] Preparation of sodium humate solution: weigh 15 g of sodium humate (HA) and slowly add it into a three-necked flask, add 100 mL of deionized water, stir at 65°C for 1 h to fully dissolve it, and prepare a sodium humate solution.

[0032] Preparation of modified monomer solution: Determine the mass of modified monomer (the sum of the masses of all modified monomers) according to the mass ratio of sodium humate to modified monomer of 1:1, determine the mass of temperature- and salt-resistant monomer (sodium p-styrene sulfonate), enhanced temperature- and salt-resistant monomer (ethylene phosphoric acid), solubility-improving monomer (hydroxyethyl acrylate), and adsorption-improving monomer (KH-151) according to the molar ratio of 1:0.2:0.5:0.3, add the above-mentioned modified monomers into deionized water to prepare modified monomer solution with a concentration of 500 g / L, prepare 30 mL, pour into a dropping funnel for later use.

[0033] S2. Grafting reaction: slowly drop the modified monomer solution into the three-necked flask, keep stirring, the stirring speed is 200r / min, after the dropwise addition is completed, bubbling deoxygenation for 30min. Initiator (ammonium persulfate, the amount of initiator is 0.8% of the molar mass of the modified monomer) is added under nitrogen atmosphere, and the reaction container is sealed after bubbling deoxygenation for 5min, and the three-necked flask is placed in a constant temperature water bath, continuous magnetic stirring, set the temperature to 65°C, and the reaction time is 7h.

[0034] S3, cross-linking reaction and post-treatment: Add the cross-linking agent (PEGDA200) into deionized water to prepare a cross-linking agent solution with a concentration of 200 g / L. Pass nitrogen gas and deoxygenate by bubbling for 10 minutes.

[0035] Open the reaction vessel of S2 grafting reaction, introduce nitrogen, bubble, dropwise add deoxygenated crosslinker solution, the molar mass ratio of modified monomer to crosslinker is 100:10, and then bubble and deoxygenate for 7 minutes and then seal the reaction vessel, the reaction temperature is unchanged (65°C). After 2 hours of reaction, take out the reaction vessel from the water bath and open it, let the solution contact the air, cool to room temperature, and then dry at 65°C to constant weight to obtain the final product.

[0036] Example 3

[0037] S1. Preparation of sodium humate solution and modified monomer solution

[0038] Preparation of sodium humate solution: weigh 15 g of sodium humate (HA) and slowly add it into a three-necked flask, add 100 mL of deionized water, stir at 50°C for 1 hour to fully dissolve it, and prepare a sodium humate solution.

[0039] Preparation of modified monomer solution: Determine the mass of modified monomer (the sum of the masses of all modified monomers) according to the mass ratio of sodium humate to modified monomer of 1:1.1, determine the mass of temperature- and salt-resistant monomer (the molar ratio of 2-acrylamide-2-methylpropane sulfonate and sodium methacrylate is 1:1), enhanced temperature- and salt-resistant monomer (sodium vinyl phosphate), solubility-improving monomer (the molar ratio of vinyl pyrrolidone and hydroxypropyl methacrylate is 1:1), and adsorption-improving monomer (the molar ratio of KH-570 and KH-151 is 1:1) according to the molar ratio of 1:0.15:0.35:0.25, add the above-mentioned modified monomers into deionized water to prepare modified monomer solution with a concentration of 500 g / L, prepare 33 mL, and pour into a dropping funnel for later use.

[0040] S2. Grafting reaction: slowly drop the modified monomer solution into the three-necked flask, keep stirring, the stirring speed is 200r / min, after the dropwise addition is completed, nitrogen is introduced, and bubbling deoxygenation is performed for 25min. Initiator (ammonium persulfate, the amount of initiator is 0.75% of the molar mass of the modified monomer) is added under nitrogen atmosphere, and the reaction container is sealed after bubbling deoxygenation for 7min, and the three-necked flask is placed in a constant temperature water bath, and magnetic stirring is continued, the temperature is set to 50°C, and the reaction time is 8h.

[0041] S3, cross-linking reaction and post-treatment: Add the cross-linking agent (PEGDA200 and PEGDA400 in a molar ratio of 3:2) into deionized water to prepare a cross-linking agent solution with a concentration of 300 g / L. Nitrogen was introduced and bubbling was performed to deoxygenate for 9 minutes.

[0042] Open the reaction vessel of S2 grafting reaction, introduce nitrogen, bubble, dropwise add deoxygenated crosslinker solution, the molar mass ratio of modified monomer to crosslinker is 100:11, and then bubble and deoxygenate for 8 minutes, then seal the reaction vessel, and keep the reaction temperature unchanged (50°C). After reacting for 1.5 hours, take out the reaction vessel from the water bath and open it, let the solution contact the air, cool to room temperature, and dry at 60°C to constant weight to obtain the final product.

[0043] Example 4

[0044] S1. Preparation of sodium humate solution and modified monomer solution

[0045] Preparation of sodium humate solution: weigh 15 g of sodium humate (HA) and slowly add it into a three-necked flask, add 100 mL of deionized water, stir at 70°C for 1 hour to fully dissolve it, and prepare a sodium humate solution.

[0046] Preparation of modified monomer solution: determine the mass of modified monomer (the sum of the masses of all modified monomers) according to the mass ratio of sodium humate to modified monomer of 1:1.1, determine the mass of temperature- and salt-resistant monomer (the molar ratio of sodium methyl methacrylate sulfonate and sodium p-styrene sulfonate is 1:1), enhanced temperature- and salt-resistant monomer (sodium vinyl phosphate), solubility-improving monomer (the molar ratio of vinyl pyrrolidone and N-vinyl formamide is 1:1), and adsorption-improving monomer (the molar ratio of KH570 and KH151 is 2:3) according to the molar ratio of 1:0.2:0.4:0.2, add the above-mentioned modified monomers into deionized water to prepare modified monomer solution with a concentration of 500 g / L, prepare 33 mL, pour into a dropping funnel for later use.

[0047] S2. Grafting reaction: slowly drop the modified monomer solution into the three-necked flask, keep stirring, the stirring speed is 200r / min, after the dropwise addition is completed, nitrogen is introduced, and bubbling deoxygenation is performed for 30min. Initiator (potassium persulfate, the amount of initiator is 0.8% of the molar mass of the modified monomer) is added under nitrogen atmosphere, and the reaction container is sealed after bubbling deoxygenation for 7min, and the three-necked flask is placed in a constant temperature water bath, and magnetic stirring is continued, the temperature is set to 70°C, and the reaction time is 4.5h.

[0048] S3, cross-linking reaction and post-treatment: Add the cross-linking agent (the molar ratio of N,N-methylenebisacrylamide and PEGDA600 is 1:1) into deionized water to prepare a cross-linking agent solution with a concentration of 220 g / L. Pass nitrogen gas and deoxygenate by bubbling for 9 minutes.

[0049] Open the reaction vessel of S2 grafting reaction, introduce nitrogen, bubble, dropwise add deoxygenated crosslinker solution, the molar mass ratio of modified monomer to crosslinker is 100:10, and then bubble and deoxygenate for 10 minutes and then seal the reaction vessel, the reaction temperature is unchanged (70°C). After 2 hours of reaction, take out the reaction vessel from the water bath and open it, let the solution contact the air, cool to room temperature, and then dry at 75°C to constant weight to obtain the final product.

[0050] Comparative Example 1

[0051] Compared with Example 1, no enhanced temperature-resistant and salt-resistant monomer is added, and other raw materials and conditions remain unchanged.

[0052] Comparative Example 2

[0053] Compared with Example 2, no solubility improving monomer was added, and other raw materials and conditions remained unchanged.

[0054] Comparative Example 3

[0055] Compared with Example 3, no adsorption improving monomer was added, and other raw materials and conditions remained unchanged.

[0056] Comparative Example 4

[0057] Compared with Example 4, no cross-linking agent is added, and other raw materials and conditions remain unchanged. After the second step grafting reaction, the reaction vessel is taken out from the water bath and opened to allow the solution to contact the air. After cooling to room temperature, it is dried at 75°C to constant weight to obtain the product of Comparative Example 4.

[0058] Comparative Example 5

[0059] Compared with Example 1, no enhanced temperature and salt resistance monomer, solubility improvement monomer, adsorption improvement monomer, or cross-linking agent is added, and only olefin sulfonate is added for modification. Other raw materials and conditions remain unchanged. After the second step of grafting reaction, the reaction vessel is taken out from the water bath and opened to allow the solution to contact the air. After cooling to room temperature, it is dried at 60°C to constant weight to obtain the product of Comparative Example 5.

[0060] Comparative Example 6

[0061] Sodium humate, unmodified.

[0062] Test Example 1

[0063] In a sample cup filled with 350 mL of distilled water, add 0.74 g of anhydrous sodium carbonate, 21.0 g of bentonite for drilling fluid test slurry, and 16.0 g of evaluation soil, stir at high speed for 20 minutes, interrupt at least twice to scrape off the sample adhering to the cup wall, and seal and cure at 25°C ± 1°C for 24 hours. This is the base slurry.

[0064] Take 350ml of base slurry, add 52.0g of sodium chloride and 5.25g of calcium chloride, 5mL of sodium hydroxide solution (10g of sodium hydroxide in 100mL of water), and stir at high speed for 20 minutes. During this time, you should stop twice to scrape off the slurry adhering to the wall of the cup. This is the salt water slurry.

[0065] Take 350ml of base slurry, add 28.0g of sample (fluid loss reducer of each comparative example or embodiment), stir at high speed for 10min, then add 52.0g of sodium chloride and 5.25g of calcium chloride, 5ml of sodium hydroxide solution (10g of sodium hydroxide in 100mL of water), stir at high speed for 20min in total, and interrupt twice to scrape off the slurry adhering to the wall of the cup. This is the sample slurry.

[0066] The brine slurry and each sample slurry were transferred to a curing tank respectively, rolled at 180℃±3℃ for 16h, taken out of the curing tank, opened after cooling, and stirred at high speed for 5min (if there are bubbles, add a few drops of defoaming agent), and the apparent viscosity of the brine slurry and the sample slurry at 50℃, the high-temperature and high-pressure filtration loss at 180℃ and the high-temperature and high-pressure filtration loss reduction rate were determined according to the provisions of 6.3 and 7.3 of GB / T 16783.1-2014 (high-temperature and high-pressure filtration loss reduction rate = (brine slurry filtration loss - sample slurry filtration loss) / brine slurry filtration loss * 100%).

[0067] The results are shown in Table 1.

[0068] Table 1 Apparent viscosity and high temperature and high pressure filtration loss of the products of the embodiments and comparative examples

[0069]

[0070]

[0071] Test Example 2

[0072] The shear resistance of the fluid loss reducers of Examples 1-4 and Comparative Examples 1-6 was evaluated using a six-speed rotational viscometer.

[0073] Prepare the sample slurry according to Test Example 1, and use a six-speed rotation viscometer to measure the reading of the sample slurry at 200 rpm, which is recorded as η1. Then stir the sample slurry in a high-speed stirrer at 10,000 rpm for 10 minutes. After the high stirring, immediately use the same instrument to measure the reading of the sample again at the same shear rate, which is recorded as η2. Calculate the viscosity change rate according to the formula: Viscosity change rate = (η1-η2) / η1×100%. The results are shown in Table 2.

[0074] Table 2 Viscosity change rate of fluid loss reducers of Examples 1-4 and Comparative Examples 1-6

[0075] project Viscosity change rate / % Example 1 14 Example 2 12 Example 3 11 Example 4 12 Comparative Example 1 15 Comparative Example 2 12 Comparative Example 3 10 Comparative Example 4 30 Comparative Example 5 36 Comparative Example 6 41

[0076] Adding an appropriate amount of cross-linking agent during the modification process can significantly improve the shear resistance of the modified humate.

[0077] Test Example 3

[0078] The effects of the fluid loss reducers of Examples 1-4 and Comparative Examples 1-6 on the Zeta potential after acting on sodium bentonite were tested using a Zeta potential meter to characterize the adsorption stability.

[0079] Prepare sodium bentonite and dry it to remove moisture (dry to constant weight at 105°C). Prepare examples 1-4 and comparative examples 1-6 fluid loss agent solutions (add 3g fluid loss agent to 100mL deionized water). Take 1g of sodium bentonite and place it in a beaker, add 100mL of fluid loss agent solution, and mix the mineral particles and the solution thoroughly. Stir the mixed system for 3h to promote the adsorption process. After 3h, centrifuge the mixed system (6000 rpm, centrifugation time is 10 minutes) to precipitate the mineral particles adsorbed with the treatment agent at the bottom, and the upper layer is the unadsorbed solution. Dilute and disperse the sodium bentonite particles adsorbed with the treatment agent obtained by centrifugation with an appropriate amount of deionized water so that the particles are evenly suspended in the solution. Ultrasonicate the diluted sample for 3 minutes to further disperse it evenly and avoid particle agglomeration affecting the measurement results. Inject the diluted and dispersed sample into the sample pool of the Zeta potential meter to avoid bubbles, and measure the Zeta potential value of the sample according to the instrument operating procedures. Repeat 3 times and take the average value as the final measurement result. The results are shown in Table 3.

[0080] Table 3 Effect of Filtrate Reducers of Examples 1-4 and Comparative Examples 1-6 on Zeta Potential of Bentonite

[0081] project Zeta potential (mV) Example 1 -31.13 Example 2 -33.38 Example 3 -32.26 Example 4 -30.84 Comparative Example 1 -30.48 Comparative Example 2 -31.63 Comparative Example 3 -27.69 Comparative Example 4 -30.37 Comparative Example 5 -26.16 Comparative Example 6 -25.47

[0082] The Zeta potential of bentonite is -24.99mV. The absolute value of the Zeta potential of the fluid loss agent modified by the adsorption improvement monomer (Examples 1-4, Comparative Examples 1-2 and Comparative Example 4) increases significantly, indicating that the adsorption improvement monomer significantly affects the adsorption of the fluid loss agent on the clay surface, and the hydration film on the clay surface thickens. Good adsorption can maintain the stability of the well wall (during drilling, the rocks around the well wall are easily unstable due to the scouring of the filtrate. The fluid loss agent has good adsorption, so it can firmly adhere to the well wall to form a dense protective film, prevent the excessive intrusion of the drilling fluid filtrate into the formation, reduce the risk of rock hydration expansion, peeling and collapse, create a stable environment for continuous and safe drilling, and reduce complex conditions such as stuck drill), and optimize the performance of the drilling fluid (strong adsorption can effectively reduce the water loss of the drilling fluid, allow the drilling fluid to maintain appropriate viscosity and fluidity, ensure that the ability to carry rock cuttings is not weakened, and can also reduce costs, reduce the frequent replenishment of new drilling fluid, and improve overall operating efficiency).

[0083] The above results show that unmodified sodium humate performs poorly in terms of temperature resistance and salt resistance, and is therefore not suitable for use as a fluid loss reducer for drilling fluids. However, after modification with olefin sulfonates, its temperature resistance and salt resistance have been enhanced to a certain extent. Furthermore, by introducing enhanced temperature and salt resistance monomers, solubility-improving monomers, adsorption-improving monomers, and cross-linking agents for composite modification, its temperature and salt resistance has been significantly improved. Under a high temperature environment of 180°C, the modified humate can effectively resist 15% monovalent salts and 1.5% divalent salts, showing its great potential in drilling fluid applications.

[0084] The present invention has been disclosed in the above preferred embodiments, but those skilled in the art should understand that these embodiments are only used to describe the present invention and should not be construed as limiting the scope of the present invention. Further improvements can be made without departing from the principles of the present invention, and these improvements should also be included in the scope of protection of the present invention.

Claims

1. A method for preparing a temperature-resistant and salt-resistant filtrate reducer for drilling fluid based on modified humate, characterized in that: The steps include: S1. Dissolve sodium humate and modified monomer in a mass ratio of 1:(0.8-1.2) in deionized water, introduce inert gas to deoxygenate, add initiator, heat to 40°C-70°C under closed and continuous stirring conditions, and react for 4h-8h to obtain a grafted product solution; The modified monomers include a temperature-resistant and salt-resistant monomer, vinyl phosphoric acid, a solubility-improving monomer, and an adsorption-improving monomer in a molar mass ratio of 1:(0.1-0.2):(0.2-0.5):(0.1-0.3); The solubility improving monomer is a mixture of one or more of vinyl pyrrolidone, hydroxyethyl acrylate, N-vinyl formamide and hydroxypropyl methacrylate; The adsorption improving monomer is γ-methacryloxypropyltrimethoxysilane or vinyltriethoxysilane; S2. Dissolve the crosslinking agent in deionized water and pass inert gas to deoxygenate, add the crosslinking agent solution to the grafting product solution, heat to 40°C to 70°C under closed and continuous stirring conditions, react for 1h to 2h, and then dry the product to obtain a filtrate reducer.

2. The method for preparing a temperature-resistant and salt-resistant filtrate reducer for base drilling fluid based on modified humate according to claim 1, characterized in that: The humate is sodium humate or potassium humate.

3. The method for preparing a temperature-resistant and salt-resistant filtrate reducer for base drilling fluid based on modified humate according to claim 1, characterized in that: The temperature and pressure resistant monomer is a mixture of one or more of sodium 2-acrylamide-2-methylpropane sulfonate, sodium methyl propene sulfonate, sodium propene sulfonate, sodium vinyl sulfonate and sodium p-styrene sulfonate.

4. The method for preparing a temperature-resistant and salt-resistant filtrate reducer for base drilling fluid based on modified humate according to claim 1, characterized in that: The initiator is potassium persulfate or ammonium persulfate, and the added amount of the initiator is 0.3% to 1% of the molar mass of the modified monomer.

5. The method for preparing a temperature-resistant and salt-resistant filtrate reducer for base drilling fluid based on modified humate according to claim 1, characterized in that: The cross-linking agent is a mixture of one or more of N,N-dimethylbisacrylamide, PEGDA200, PEGDA400, PEGDA600 and PEGDA1000, and the molar ratio of the modified monomer to the cross-linking agent is 100:(8-12).

6. The method for preparing a temperature-resistant and salt-resistant filtrate reducer for base drilling fluid based on modified humate according to claim 1, characterized in that: The drying temperature is 60°C to 75°C.

7. A temperature-resistant and salt-resistant fluid loss reducer for base drilling fluid based on modified humate, characterized in that: The invention is prepared by the method for preparing the temperature-resistant and salt-resistant filtrate reducer for drilling fluid based on modified humate according to any one of claims 1 to 6.

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