An anti-ultra-high temperature anti-salt water-based drilling fluid filtrate reducer and a preparation method thereof

Abstract

The application discloses an anti-ultra-high-temperature and anti-salt water-based drilling fluid filtrate reducer, and a structural formula of the filtrate reducer is shown in formula 1. The filtrate reducer can resist an ultra-high temperature of 260 DEG C, has excellent anti-salt effect in a high-temperature environment of 230 DEG C, and can well meet the needs of high-temperature construction.

Description

Technical Field

[0001] This invention relates to the field of oil drilling engineering technology, specifically to a high-temperature resistant and salt-water resistant drilling fluid filtration reducer and its preparation method. Background Technology

[0002] Drilling fluids possess excellent properties such as carrying and suspending rock cuttings, cooling and lubricating drill bits, stabilizing the wellbore, controlling downhole pressure, and transmitting hydrodynamic forces, earning them the nickname "the blood" of drilling. However, with increasing drilling depth and rising bottom-hole temperatures, water-based drilling fluids face significant challenges in high-temperature, high-salt environments. Under these conditions, the rheological properties, viscosity, and stability of water-based drilling fluids change, and filtration loss increases to varying degrees, severely impacting drilling efficiency and safety. Therefore, effectively controlling filtration loss in water-based drilling fluids to ensure wellbore stability and safety is a crucial issue that the drilling industry must study in depth.

[0003] As an essential treatment agent in the drilling process, the filtration loss reducer can be adsorbed on the surface of bentonite particles through physical interactions such as hydrogen bonding and electrostatic forces, forming a layered structure of "bentonite-polymer-water". This is of great significance to the rheological properties and filtration loss performance of drilling fluid.

[0004] However, existing filtration loss reducers cannot adequately meet the needs of high-temperature operations. Currently, there are two main problems: 1. Poor high-temperature resistance: Existing filtration loss reducers can only withstand temperatures up to 240℃. In harsh environments exceeding 260℃, polymeric filtration loss reducers are prone to degradation, flocculation, or desorption, weakening their protective ability against clay particles. This leads to loss of control over drilling fluid rheology and stability, rendering the treatment agent ineffective. 2. While most filtration loss reducers can withstand high temperatures, they cannot achieve salt resistance at high temperatures (T>220℃). Summary of the Invention

[0005] In order to overcome the defects in the prior art, the present invention provides an ultra-high temperature and salt water resistant drilling fluid filtration reducer and its preparation method, which can withstand ultra-high temperature of 260℃ and also has salt resistance in a high temperature environment of 230℃.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a filtration loss reducer for ultra-high temperature and salt water-based drilling fluids, the structural formula of which is shown in Formula 1:

[0008]

[0009] Wherein, v, w, x, y, and z are natural numbers;

[0010] R1 and R2 are hydrogen or alkyl; R3, R4, R5, R6 and R7 are alkyl.

[0011] Preferably, the molecular weight of the filtration loss reducing agent is 300,000 to 3,000,000.

[0012] Preferably, the filtration loss reducing agent is prepared by free radical polymerization using five monomers of formulas 2, 3, 4, 5, and 6 as raw materials:

[0013]

[0014]

[0015] R1 and R2 are hydrogen or alkyl; R3, R4, R5, R6 and R7 are alkyl.

[0016] Preferably, the mass ratio of the monomer of formula 2: monomer of formula 3: monomer of formula 4: monomer of formula 5: monomer of formula 6 is (6-9):(1-4):(3-4):(2-3):(0.1-0.5).

[0017] Secondly, the present invention provides a method for preparing the aforementioned filtration loss reducing agent, comprising the following steps:

[0018] S1. Dissolve the monomer of Formula 3 in a solvent and adjust the pH to neutral;

[0019] S2. Add the monomers described in Formulas 2, 4, 5, and 6 to the solution obtained in S1, and stir to dissolve.

[0020] S3. In an anaerobic environment, an initiator is added to the solution obtained in S2 to carry out the reaction. The reacted substance is then purified and dried to obtain the final product.

[0021] Preferably, in S1, the mass ratio of the monomer of Formula 3 to the solvent is 1:(10-50).

[0022] Preferably, in S2, the mass ratio of the monomer of formula 2: monomer of formula 3: monomer of formula 4: monomer of formula 5: monomer of formula 6 is (6-9):(1-4):(3-4):(2-3):(0.1-0.5).

[0023] Preferably, in step S3, the reaction temperature is 70–90°C and the reaction time is 5–8 hours.

[0024] Preferably, in step S3, the initiator is selected from one or more of ammonium persulfate, sodium bisulfite, and potassium persulfate.

[0025] Preferably, the initiator is ammonium persulfate and sodium bisulfite, wherein the total mass of ammonium persulfate and sodium bisulfite accounts for 0.3% to 0.4% of the total monomer mass, and the mass ratio of ammonium persulfate to sodium bisulfite is 2:1.

[0026] Preferably, the drying process is performed such that the total content of the purified solvent and the solvent described in S1 is less than 5%.

[0027] The beneficial effects of this invention are:

[0028] The filtration loss reducer of the present invention can withstand ultra-high temperature of 260°C and also has excellent salt resistance at high temperature of 230°C, which can well meet the needs of high temperature construction.

[0029] The filtration loss reducer of this invention is mainly prepared by free polymerization of five monomers. The monomer of formula 2 contains an amide group, which is an adsorption group and can improve the adsorption capacity of the polymer. The monomer of formula 3 contains a sulfonic acid group, which is a hydration group and can enhance the hydration capacity of the polymer. The monomer of formula 4 is a cationic monomer, which can reduce the electrostatic repulsion on the surface of clay particles, reduce the zeta potential, and enhance the viscosity of drilling fluid. The monomer of formula 5 has a benzene ring structure, which can improve the temperature and salt resistance of the polymer. The monomer of formula 6 is silicon dioxide modified by KH570, which can improve the overall suspension stability and thermal stability. The addition of KH-570 also introduces organosilicon groups into the side chain, further improving the temperature and salt resistance of the polymer. This can provide technical support for water-based drilling fluid systems to further drill deep and ultra-deep wells. Attached Figure Description

[0030] Figure 1 The infrared spectrum of the filtration reduction agent obtained in Example 8;

[0031] Figure 2 The images show filter cakes after aging at 260°C for 16 hours in Examples 1-3 (from left to right: Example 1, Example 2, Example 3).

[0032] Figure 3 The filter cake images are from Examples 1 to 3 after aging in 5% NaCl at 220°C for 16 hours (from left to right: Example 1, Example 2, Example 3).

[0033] Figure 4 The filter cake images are from Examples 4 to 8 after aging in 5% NaCl at 220°C for 16 hours (from left to right: Example 4, Example 5, Example 6, Example 7, Example 8).

[0034] Figure 5 The image shows the HTHP filter cake of Example 3 (the left image is the HTHP filter cake aged at 260°C, and the right image is the HTHP filter cake aged at 220°C with 5% NaCl).

[0035] Figure 6 The filter cake images for Example 8 are shown under different temperatures and salinities (left: filter cake after aging at 220°C and 10% NaCl for 16 hours; middle: filter cake after aging at 220°C and 15% NaCl for 16 hours; right: filter cake after aging at 230°C and 5% NaCl for 16 hours). Detailed Implementation

[0036] To enable those skilled in the art to better understand the technical solution of the invention, the invention will be further described in detail below with reference to specific embodiments.

[0037] In order to enable the filtration loss reducer to withstand ultra-high temperatures of 260°C and also exhibit salt resistance at high temperatures of 230°C, the present invention, in its first aspect, provides an ultra-high temperature and salt-resistant salt-based drilling fluid filtration loss reducer, the structural formula of which is shown in Formula 1:

[0038]

[0039] Where v, w, x, y, and z are natural numbers;

[0040] R1 and R2 are hydrogen or alkyl groups, such as -CH3 or (-CH2-). n Where n can be any natural number such as 1, 2, 3, ...

[0041] R3, R4, R5, R6, and R7 are alkyl groups, such as -CH3 or (-CH2-). n The n can be any natural number, such as 1, 2, 3, ...

[0042] Preferably, the molecular weight of the filtration loss reducing agent is 800,000 to 3,000,000.

[0043] Preferably, the filtration loss reducing agent of the present invention is prepared by free radical polymerization using five monomers of formulas 2, 3, 4, 5, and 6 as raw materials:

[0044]

[0045]

[0046] R1 and R2 are hydrogen or alkyl groups, such as -CH3, (-CH2-)n, where n can be any natural number such as 1, 2, 3, etc.

[0047] R3, R4, R5, R6 and R7 are alkyl groups, such as -CH3, (-CH2-)n, where n can be any natural number such as 1, 2, 3, etc.

[0048] All of the above substituents can achieve the effects described in this invention. The embodiments of this invention only select one monomer form of five compounds, which is not intended to limit the invention. Other substituents can achieve the same technical effects.

[0049] Preferably, the mass ratio of the monomer of formula 2: monomer of formula 3: monomer of formula 4: monomer of formula 5: monomer of formula 6 is (6-9):(1-4):(3-4):(2-3):(0.1-0.5).

[0050] This invention aims to synthesize a high-temperature and salt-resistant drilling fluid filtration reducer. The monomer of Formula 2 contains an amide group, which is an adsorption group and can improve the polymer's adsorption capacity. The monomer of Formula 3 contains a sulfonic acid group, which is a hydration group and can enhance the polymer's hydration capacity. The monomer of Formula 4 is a cationic monomer that can be adsorbed onto the clay surface through electrostatic interaction, neutralizing the negative charge on the clay particle surface, thereby reducing the electrostatic repulsion on the clay particle surface, lowering the Zeta potential, and increasing the drilling fluid viscosity. The monomer of Formula 5 has a benzene ring structure, which can improve the rigidity of the molecular chain and the steric hindrance effect, thereby improving the polymer's temperature and salt resistance. The monomer of Formula 6 is silica modified with KH570, exhibiting good dispersibility and improved hydrophobicity. Its nanoparticles have small particle size and large specific surface area, with surface forces, van der Waals forces, and molecular forces dominating, which facilitates more intense interactions between nanoparticles or between nanoparticles and the medium, resulting in unique properties and improving overall suspension stability and thermal stability. In addition to introducing adsorption groups, hydration groups and rigid groups into the side chains of the filtration loss reducer, the addition of KH-570 also introduces organosilicon groups into the side chains, further improving the polymer's temperature and salt resistance properties, and providing technical support for water-based drilling fluid systems to further drill deep and ultra-deep wells.

[0051] Secondly, the present invention provides a method for preparing the aforementioned filtration loss reducing agent, comprising the following steps:

[0052] S1. Dissolve the monomer of Formula 3 in a solvent and adjust the pH to neutral;

[0053] S2. Add the monomers described in Formulas 2, 4, 5, and 6 to the solution obtained in S1, and stir to dissolve.

[0054] S3. In an anaerobic environment, an initiator is added to the solution obtained in S2 to carry out the reaction. The reacted substance is then purified and dried to obtain the final product.

[0055] In S1 of this invention, the mass ratio of the monomer of Formula 3 to the solvent is 1:(10-50). The solvent can be any solvent capable of dissolving the five monomers described in this invention. In some embodiments of this invention, the solvent is water. Exemplarily, the mass ratio of the monomer of Formula 3 to the solvent is any one of 1:10, 1:17, or 1:46, or a value between two of these.

[0056] The pH adjuster described in this invention can be any conventional reagent in the art capable of adjusting pH. In an embodiment of this invention, the pH adjuster is a sodium hydroxide solution.

[0057] In S2 of this invention, the mass ratio of monomer of formula 2: monomer of formula 3: monomer of formula 4: monomer of formula 5: monomer of formula 6 is (6-9):(1-4):(3-4):(2-3):(0.1-0.5). In some embodiments of this invention, the mass ratio of monomer of formula 2: monomer of formula 3: monomer of formula 4: monomer of formula 5: monomer of formula 6 is (6.4-8.6):(1.45-4):(3.5-3.9):(2.7-3)(0.17-0.45).

[0058] In some embodiments of the present invention, the anaerobic environment specifically refers to: introducing nitrogen gas to remove oxygen in order to maintain an anaerobic environment.

[0059] In S3 of the present invention, the reaction temperature is 70-90°C and the reaction time is 5-8 hours.

[0060] In S3 of this invention, the initiator is selected from one or more of ammonium persulfate, sodium bisulfite, and potassium persulfate. In some embodiments of this invention, the initiator is ammonium persulfate and sodium bisulfite. Ammonium persulfate has higher solubility in water than potassium persulfate, resulting in higher initiation efficiency, and its cost is lower than that of potassium persulfate. Although ammonium persulfate can be used alone as an initiator, when combined with sodium bisulfite, it can form a redox system for polymerization reactions, which can lower the activation energy of free radical generation reactions and increase the polymerization rate. The total mass of ammonium persulfate and sodium bisulfite accounts for 0.3% to 0.4% of the total monomer mass, and the mass ratio of ammonium persulfate to sodium bisulfite is 2:1.

[0061] The purification described in this invention can be performed using an acetone solution.

[0062] The drying process described in this invention is such that the total content of the purified solvent and the solvent described in S1 is less than 5%.

[0063] The above is a detailed description of the present invention. The following are embodiments of the present invention.

[0064] Raw materials used in the examples:

[0065] Pure water (laboratory-made), NN dimethacrylamide (purchased from Damas-Beta), diallyl dimethylpropanesulfonic acid (purchased from Aladdin), dimethyl diallyl ammonium chloride (purchased from Aladdin), sodium p-styrene sulfonate (purchased from Damas-Beta), KH570 modified SiO2 (purchased from Exploration Platform), sodium hydroxide (purchased from GENERAL-REAGENT), ammonium persulfate (purchased from Damas-Beta), and sodium bisulfite (purchased from Chengdu Kelong Company) were all of analytical grade.

[0066] Example 1

[0067] The structural formulas of the five reactive monomers are as follows:

[0068]

[0069] The preparation method of the filtration loss reducing agent in this embodiment is as follows:

[0070] In a three-necked flask equipped with a stirrer, thermometer, and heating device, 73.164 g of pure water and 3 g of 2-acrylamido-dimethylpropanesulfonic acid were added sequentially. The pH was adjusted to 7.0 with 0.58 g of NaOH. Then, 7.902 g of N,N-dimethylacrylamide, 2.988 g of sodium p-styrenesulfonate, 3.9014 g of dimethyldiallyl ammonium chloride, and 0.45 g of KH570 modified SiO2 were added. The mixture was stirred until all monomers were dissolved. Nitrogen gas was then introduced to remove oxygen for 30 minutes. Nitrogen gas was then introduced while heating was continued until the temperature reached 90°C. 0.03768 g of ammonium persulfate and 0.01719 g of sodium bisulfite were added, and nitrogen gas was introduced again. After half an hour, the nitrogen gas introduction was stopped. The reaction was continued for 8 hours. After 8 hours, the polymer was purified in acetone solution, granulated, and then dried in a 60°C oven. The resulting white granules were the filtration loss reducer A.

[0071] Example 2

[0072] The structural formulas of the five reactive monomers are the same as in Example 1.

[0073] The preparation method of the filtration loss reducing agent in this embodiment is as follows:

[0074] Add 69.689g of pure water and 1.5g of 2-acrylamido-dimethylpropanesulfonic acid to a three-necked flask equipped with a stirrer, thermometer, and heating device. Adjust the pH to 7.0 with 0.3g of NaOH, then add 8.620g of N,N-dimethylacrylamide, 2.988g of sodium p-styrenesulfonate, 3.901g of dimethyldiallyl ammonium chloride, and 0.43g of KH570 modified SiO2. Stir until all monomers are dissolved, then purge with nitrogen for 30 minutes to remove oxygen. Continue purging with nitrogen while heating until the temperature reaches 90°C. Add 0.03589g of ammonium persulfate and 0.01637g of sodium bisulfite, and continue purging with nitrogen. Stop purging with nitrogen after half an hour. Continue the reaction for 8 hours. After 8 hours, purify the polymer in acetone solution, cut it into small pieces, granulate it, and then dry it in a 60°C oven. The white granules obtained after drying are the filtration loss reducer B.

[0075] Example 3

[0076] The structural formulas of the five reactive monomers are the same as in Example 1.

[0077] The preparation method of the filtration loss reducing agent in this embodiment is as follows:

[0078] Add 67.636g of pure water and 4g of 2-acrylamido-dimethylpropanesulfonic acid to a three-necked flask equipped with a stirrer, thermometer, and heating device. Adjust the pH to 7.0 with 0.78g of NaOH, then add 6.385g of N,N-dimethylacrylamide, 2.656g of sodium p-styrenesulfonate, 3.468g of dimethyldiallyl ammonium chloride, and 0.41g of KH570 modified SiO2. Stir until all monomers are dissolved, then purge with nitrogen for 30 minutes to remove oxygen. Continue purging with nitrogen while heating until the temperature reaches 90°C. Add 0.03484g of ammonium persulfate and 0.01589g of sodium bisulfite, and continue purging with nitrogen. Stop purging with nitrogen after half an hour. Continue the reaction for 8 hours. After 8 hours, purify the polymer in acetone solution, cut it into small pieces, granulate it, and then dry it in a 60°C oven. The white granules obtained after drying are the filtration loss reducer C.

[0079] Example 4

[0080] The structural formulas of the five reactive monomers are the same as in Example 1.

[0081] The preparation method of the filtration loss reducing agent in this embodiment is as follows:

[0082] Add 66.44g of pure water and 1.45g of 2-acrylamido-dimethylpropanesulfonic acid sequentially to a three-necked flask equipped with a stirrer, thermometer, and heating device. Adjust the pH to 7 with 0.282g of NaOH, then add 8.333g of N,N-dimethylacrylamide, 2.889g of sodium p-styrenesulfonate, 3.771g of dimethyldiallyl ammonium chloride, and 0.167g of KH570 modified SiO2. Stir until all monomers are dissolved, then purge with nitrogen for 30 minutes to remove oxygen. Continue purging with nitrogen while heating until the temperature reaches 70°C. Add 0.03422g of ammonium persulfate and 0.01561g of sodium bisulfite, and continue purging with nitrogen. Stop purging with nitrogen after half an hour. Continue the reaction for 5 hours. After 5 hours, purify the polymer in acetone solution, cut it into small pieces, granulate it, and then dry it in a 60°C oven. The white granules obtained after drying are the filtration loss reducer D.

[0083] Example 5

[0084] The structural formulas of the five reactive monomers are the same as in Example 1.

[0085] The preparation method of the filtration loss reducing agent in this embodiment is as follows:

[0086] Add 66.44g of pure water and 1.45g of 2-acrylamido-dimethylpropanesulfonic acid sequentially to a three-necked flask equipped with a stirrer, thermometer, and heating device. Adjust the pH to 7 with 0.282g of NaOH, then add 8.333g of N,N-dimethylacrylamide, 2.889g of sodium p-styrenesulfonate, 3.771g of dimethyldiallyl ammonium chloride, and 0.167g of KH570 modified SiO2. Stir until all monomers are dissolved, then purge with nitrogen for 30 minutes to remove oxygen. Continue purging with nitrogen while heating until the temperature reaches 75°C. Add 0.03422g of ammonium persulfate and 0.01561g of sodium bisulfite, and continue purging with nitrogen. Stop purging with nitrogen after half an hour. Continue the reaction for 5 hours. After 5 hours, purify the polymer in acetone solution, cut it into small pieces, granulate it, and then dry it in a 60°C oven. The white granules obtained after drying are the filtration loss reducer E.

[0087] Example 6

[0088] The structural formulas of the five reactive monomers are the same as in Example 1.

[0089] The preparation method of the filtration loss reducing agent in this embodiment is as follows:

[0090] Add 66.44g of pure water and 1.45g of 2-acrylamido-dimethylpropanesulfonic acid sequentially to a three-necked flask equipped with a stirrer, thermometer, and heating device. Adjust the pH to 7 with 0.282g of NaOH, then add 8.333g of N,N-dimethylacrylamide, 2.889g of sodium p-styrenesulfonate, 3.771g of dimethyldiallyl ammonium chloride, and 0.167g of KH570 modified SiO2. Stir until all monomers are dissolved, then purge with nitrogen for 30 minutes to remove oxygen. Continue purging with nitrogen while heating until the temperature reaches 80°C. Add 0.03422g of ammonium persulfate and 0.01561g of sodium bisulfite, and continue purging with nitrogen. Stop purging with nitrogen after half an hour. Continue the reaction for 5 hours. After 5 hours, purify the polymer in acetone solution, cut it into small pieces, granulate it, and then dry it in a 60°C oven. The white granules obtained after drying are the filtration loss reducer F.

[0091] Example 7

[0092] The structural formulas of the five reactive monomers are the same as in Example 1.

[0093] The preparation method of the filtration loss reducing agent in this embodiment is as follows:

[0094] Add 66.44g of pure water and 1.45g of 2-acrylamido-dimethylpropanesulfonic acid sequentially to a three-necked flask equipped with a stirrer, thermometer, and heating device. Adjust the pH to 7 with 0.282g of NaOH, then add 8.333g of N,N-dimethylacrylamide, 2.889g of sodium p-styrenesulfonate, 3.771g of dimethyldiallyl ammonium chloride, and 0.167g of KH570 modified SiO2. Stir until all monomers are dissolved, then purge with nitrogen for 30 minutes to remove oxygen. Continue purging with nitrogen while heating until the temperature reaches 85°C. Add 0.03422g of ammonium persulfate and 0.01561g of sodium bisulfite, and continue purging with nitrogen. Stop purging with nitrogen after half an hour. Continue the reaction for 5 hours. After 5 hours, purify the polymer in acetone solution, cut it into small pieces, granulate it, and then dry it in a 60°C oven. The white granules obtained after drying are the filtration loss reducer G.

[0095] Example 8

[0096] The structural formulas of the five reactive monomers are the same as in Example 1.

[0097] The preparation method of the filtration loss reducing agent in this embodiment is as follows:

[0098] Add 66.44g of pure water and 1.45g of 2-acrylamido-dimethylpropanesulfonic acid sequentially to a three-necked flask equipped with a stirrer, thermometer, and heating device. Adjust the pH to 7 with 0.282g of NaOH, then add 8.333g of N,N-dimethylacrylamide, 2.889g of sodium p-styrenesulfonate, 3.771g of dimethyldiallyl ammonium chloride, and 0.167g of KH570 modified SiO2. Stir until all monomers are dissolved, then purge with nitrogen for 30 minutes to remove oxygen. Continue purging with nitrogen while heating until the temperature reaches 90°C. Add 0.03422g of ammonium persulfate and 0.01561g of sodium bisulfite, and continue purging with nitrogen. Stop purging with nitrogen after half an hour. Continue the reaction for 5 hours. After 5 hours, purify the polymer in acetone solution, cut it into small pieces, granulate it, and then dry it in a 60°C oven. The white granules obtained after drying are the filtration loss reducer H.

[0099] Comparative Example 1

[0100] Add 67.63g of pure water and 4g of diallyldimethylpropanesulfonic acid to a three-necked flask equipped with a stirrer, thermometer, and heating device. Adjust the pH to 7 with 0.78g of NaOH, then add 6.385g of N,N-dimethylacrylamide, 2.656g of sodium p-styrenesulfonate, 3.468g of dimethyldiallyl ammonium chloride, and 0.41g of KH570 modified SiO2. Stir until all monomers are dissolved, then purge with nitrogen for 30 minutes to remove oxygen. Continue purging with nitrogen while heating until the temperature reaches 65°C. Add 0.03484g of ammonium persulfate and 0.01589g of sodium bisulfite, and continue purging with nitrogen. Stop purging with nitrogen after half an hour.

[0101] Result: It was found that the reactant monomers could not polymerize at this temperature, and the desired filtrate loss reducer could not be obtained.

[0102] Example 1: Performance Test of Filtration Loss Reducer on Freshwater-Based Slurry

[0103] Preparation of freshwater-based slurry: Add 400g of tap water to an enamel cup, add 16g of bentonite and 0.8g of sodium carbonate while stirring continuously, stir at 600r / min for 30min, then transfer to a high-speed stirring cup and stir at 12000r / min for 10min. Cure at room temperature for 24h to obtain freshwater-based slurry.

[0104] Experimental Procedure: Nine portions of pre-hydrated freshwater-based slurry were taken. Under continuous stirring, 1% by mass of the filtration loss reducing agent prepared in Examples 1-8 was added to eight of these portions of freshwater-based slurry. The mixture was stirred at high speed until homogeneous, and these were designated as filtration loss reducing agent A, filtration loss reducing agent B, filtration loss reducing agent C, filtration loss reducing agent D, filtration loss reducing agent E, filtration loss reducing agent F, filtration loss reducing agent G, and filtration loss reducing agent H, respectively. The freshwater-based slurry without added filtration loss reducing agent served as a control group. Rheological tests and filtration loss tests were performed on each of the freshwater-based slurries, and the results are shown in Table 1.

[0105] Table 1. Rheological properties and filtration loss test results of filtration loss reducer for freshwater-based slurry.

[0106] Freshwater-based slurry 9 5 4 26 Filtration Loss Reducer A (Fresh Water-Based Slurry) 56 48 8 2.3 Filtration Loss Reducer B - Freshwater-Based Slurry 45.5 37 8.5 1.8 Filtration Loss Reducer C - Freshwater-Based Slurry 28 16 12 1.7 Filtration Loss Reducer D Freshwater-Based Slurry 18.5 15 3.5 2.4 Filtration Loss Reducer E - Freshwater-Based Slurry 13.5 12 1.5 2.0 Filtration Loss Reducer F for Freshwater-Based Slurry 23.5 18 5.5 3.2 Filtration Loss Reducer G (Desalinated Water-Based Slurry) 27 21 6 2.8 Filtration Loss Reducer H Desalinated Slurry 39 33 6 2.6

[0107] In Table 1, AV represents apparent viscosity, PV represents plastic viscosity, YP represents dynamic shear stress, and FLAPI represents the fluid loss of drilling fluid at normal temperature and pressure. As shown in Table 1, the fluid loss reducers prepared in Examples 1-8 of this invention have good fluid loss reduction performance.

[0108] Example 2: Performance Test of Filtration Loss Reducer for Brine-Based Slurry

[0109] Preparation of brine-based slurry: Add 400g of tap water to an enamel cup, add 16g of bentonite, 0.8g of sodium carbonate, and 5% NaCl, 10% NaCl, or 15% NaCl while stirring continuously. Stir at 600r / min for 30min, then transfer to a high-speed stirring cup and stir at 12000r / min for 10min. Cure at room temperature for 24h to obtain 5% NaCl brine-based slurry, 10% NaCl brine-based slurry, or 15% NaCl brine-based slurry.

[0110] Experimental Procedure: Nine portions of pre-hydrated 5% NaCl brine-based slurry were taken. Under continuous stirring, 3% of the filtration loss reducing agents from Examples 1-8 were added to eight portions, and the mixture was stirred at high speed until homogeneous. These were designated as filtration loss reducing agent A brine-based slurry, filtration loss reducing agent B brine-based slurry, filtration loss reducing agent C brine-based slurry, filtration loss reducing agent D brine-based slurry, filtration loss reducing agent E brine-based slurry, filtration loss reducing agent F brine-based slurry, filtration loss reducing agent G brine-based slurry, and filtration loss reducing agent H brine-based slurry. The brine-based slurry without added filtration loss reducing agent served as the control group. Rheological tests and filtration loss tests were performed on each of the brine-based slurries, and the results are shown in Table 2.

[0111] Table 2. Rheological properties and filtration loss test results of brine-based slurry with filtration loss reducer.

[0112] brine-based slurry 15 10 5 64 Filtration Loss Reducer A (Brine-Based Slurry) 66.5 52 14.5 4.6 Filtration Loss Reducer B B-Based Slurry 43.5 36 7.5 3.6 Filtration Loss Reducer C Brine-Based Slurry 28 18 10 3.0 Filtration Loss Reducer D Brine-Based Slurry 67 51 16 5.6 Filtration loss reducer E brine-based slurry 40 31 11 4.4 Filtration Loss Reducer F Brine-Based Slurry 67.5 51 16.5 6.0 Filtration Loss Reducer G Brine-Based Slurry 73.5 57 16.5 6.2 Filtration loss reducer H brine-based slurry 51.5 37 14.5 4.8

[0113] As shown in Table 2, the brine-based slurry of the filtration loss reducer prepared in Examples 1-8 of this invention has good filtration loss reduction performance, indicating that the filtration loss reducer prepared in the examples has good salt resistance.

[0114] Example 3: Performance Test of High-Temperature Degradation Filter Loss Agent for Freshwater-Based Slurry

[0115] The preparation of freshwater-based slurry is the same as in Example 1.

[0116] Experimental Procedure: Nine portions of pre-hydrated freshwater-based slurry were taken. Under continuous stirring, 1% by mass of a filtration loss reducer (Examples 1-8) was added to eight of these portions of freshwater-based slurry. The mixture was stirred at high speed until homogeneous, and these were designated as filtration loss reducer A, filtration loss reducer B, filtration loss reducer C, filtration loss reducer D, filtration loss reducer E, filtration loss reducer F, filtration loss reducer G, and filtration loss reducer H. The freshwater-based slurry without added filtration loss reducer served as a control group. Each of the freshwater-based slurries was subjected to a 260°C hot rolling aging test. After the test, each freshwater-based slurry was taken out for rheological testing, filtration loss testing, and a 180°C high-temperature and high-pressure test. The results are shown in Table 3.

[0117] Table 3. Rheological properties and filtration loss test results of freshwater-based slurry after high temperature using filtration loss reducer.

[0118] Freshwater-based slurry 21 12 9 61 162 Filtration Loss Reducer A (Fresh Water-Based Slurry) 45 37 8 9.2 18 Filtration Loss Reducer B - Freshwater-Based Slurry 38.5 29 9.5 7.2 12 Filtration Loss Reducer C - Freshwater-Based Slurry 26 11 5 6.0 19 Filtration Loss Reducer D Freshwater-Based Slurry 38.5 31 7.5 11.2 32 Filtration Loss Reducer E - Freshwater-Based Slurry 42 32 10 13.6 36 Filtration Loss Reducer F for Freshwater-Based Slurry 27 25 2 9.6 26 Filtration Loss Reducer G (Fresh Water-Based Slurry) 28.5 25 3.5 7.4 27 Filtration Loss Reducer H Desalinated Slurry 32 28 4 6.8 24

[0119] As shown in Table 3, the filtration loss reducer of the present invention still has good filtration loss reduction performance under fresh water-based slurry and 260°C conditions, indicating that the filtration loss reducer has good temperature resistance.

[0120] Example 4: High-Temperature Decrease in Filtration Agent and Brine-Based Slurry Performance Test

[0121] The preparation of brine-based slurry is the same as in Example 2.

[0122] Experimental Procedure: Nine portions of pre-hydrated brine-based slurry containing 5% NaCl were taken. Under continuous stirring, 3% of a filtration loss reducer (Examples 1-8) was added to eight of these portions, and the mixture was stirred at high speed until homogeneous. These were designated as filtration loss reducer A brine-based slurry, filtration loss reducer B brine-based slurry, filtration loss reducer C brine-based slurry, filtration loss reducer D brine-based slurry, filtration loss reducer E brine-based slurry, filtration loss reducer F brine-based slurry, filtration loss reducer G brine-based slurry, and filtration loss reducer H brine-based slurry. The brine-based slurry without added filtration loss reducer served as the control group. Each brine-based slurry was subjected to a hot rolling aging test at 220℃. After the experiment, each brine-based slurry was taken out for rheological testing, filtration loss testing, and a high-temperature and high-pressure test at 180℃. The results are shown in Table 4.

[0123] Table 4. Rheological properties and filtration loss test results of brine-based slurry after high temperature using filtration loss reducer.

[0124] brine-based slurry 13 7.5 6.5 96 186 Filtration Loss Reducer A (Brine-Based Slurry) 31.5 23 8.5 5.2 21 Filtration Loss Reducer B B Saltwater-Based Slurry 22.5 18 4.5 5.0 17 Filtration Loss Reducer C Brine-Based Slurry 28 20 8 7.6 22 Filtration Loss Reducer D Brine-Based Slurry 37 15 22 9.6 29 Filtration loss reducer E brine-based slurry 32 22 10 10.4 34 Filtration Loss Reducer F Brine-Based Slurry 23 18 5 5.2 24 Filtration Loss Reducer G Brine-Based Slurry 31 23 8 5.8 25 Filtration loss reducer H brine-based slurry 20.5 17 3.5 4.4 23

[0125] As shown in Table 4, the filtration loss reducing agent of the present invention still has good filtration loss reducing performance at 220℃ and 5% NaCl, indicating that the filtration loss reducing agent has good temperature and salt resistance.

[0126] Performance tests of the filtration loss reducer at different salinities in Example 8:

[0127] Take three portions of pre-hydrated 5% NaCl brine-based slurry, 10% NaCl brine-based slurry, and 15% NaCl brine-based slurry, and add 3% of the filtration loss reducer from Example 8 to each portion under continuous stirring. Stir at high speed until homogeneous. These are denoted as filtration loss reducer H-10% NaCl brine-based slurry, filtration loss reducer H-15% NaCl brine-based slurry, and filtration loss reducer H-5% NaCl brine-based slurry. Hot rolling aging tests were conducted at 220℃ on H-10% NaCl brine-based slurry and H-15% NaCl brine-based slurry with filtration loss reducer. After the tests, the brine-based slurries were removed for rheological tests, filtration loss tests, and high-temperature and high-pressure tests at 180℃. Hot rolling aging tests were conducted at 230℃ on brine-based slurry with filtration loss reducer H-5% NaCl. After the tests, the brine-based slurry was removed for rheological tests, filtration loss tests, and high-temperature and high-pressure tests at 180℃. A brine-based slurry without filtration loss reducer was used as a control example and was subjected to hot rolling aging tests at 230℃. After the tests, the brine-based slurry was removed for rheological tests, filtration loss tests, and high-temperature and high-pressure tests at 180℃. The results of the rheological tests and filtration loss tests are shown in Table 5.

[0128] Table 5. Rheological properties and filtration loss test results of brine-based slurry with filtration loss reducer.

[0129]

[0130] As shown in Table 5, the filtration loss reducing agent of the present invention still has good filtration loss reducing performance under the conditions of 220℃ and 10% NaCl, 220℃ and 15% NaCl, and 230℃ and 5% NaCl, indicating that the filtration loss reducing agent of the present invention has good salt resistance.

[0131] Infrared spectral characterization of the filtration reduction agent in Example 5

[0132] Figure 1 The infrared spectrum of the filtration loss reducer obtained in Example 8 is shown, with a peak value at 3422 cm⁻¹. -1 and 3342cm -1 The point represents NH tensile vibration, corresponding to DMAM and AMPS respectively, at 2981 cm. -1 The characteristic peak of -CH3 is 1652 cm⁻¹. -1 The characteristic absorption peak of C=O is at 1404 cm⁻¹. -1 The bending vibration of CH in DMDAAC, 1224 cm -1and 1045cm -1 For the tensile vibration of S=O in SSS, 769cm -1 The point is the bending vibration of the benzene ring in the SSS, 1186 cm. -1 842cm -1 468cm -1 The characteristic absorption peaks of Si-O-Si indicate that the filtration loss reducer described in this invention has been successfully synthesized.

[0133] Example 6: Filter cake diagram of the filtration loss reducing agent

[0134] Figure 2 The images show filter cakes after aging at 260°C for 16 hours in Examples 1-3 (from left to right: Example 1, Example 2, Example 3). It can be seen that the filter cakes formed by the filter cakes synthesized from the five monomers are dense and can withstand temperatures up to 260°C, exhibiting excellent temperature resistance.

[0135] Figure 3 The filter cake images are from Examples 1 to 3 after aging in 5% NaCl at 220°C for 16 hours (from left to right: Example 1, Example 2, Example 3). Figure 4 The images show filter cakes after aging at 220°C and 5% NaCl for 16 hours in Examples 4-8 (from left to right: Example 4, Example 5, Example 6, Example 7, Example 8). It can be seen that after aging at 220°C, the filtration loss reducer obtained in this invention can effectively control filtration loss, and the resulting filter cake is thin and dense, indicating that the prepared filtration loss reducer has excellent salt resistance.

[0136] Figure 5 The images show the HTHP filter cake from Example 3. The left image shows the HTHP filter cake aged at 260℃ in Example 3, and the right image shows the HTHP filter cake aged at 220℃ with 5% NaCl in Example 3. It can be seen that the HTHP-formed filter cake has a suitable thickness, a smooth and uniform surface, and can effectively control filtration loss, demonstrating resistance to HTHP. In summary, this indicates that the prepared filtration loss reducer has excellent temperature and salt resistance properties.

[0137] Figure 6 The images show filter cakes from Example 8 under different temperatures and salinities. The left image shows the filter cake after aging at 220°C and 10% NaCl for 16 hours; the middle image shows the filter cake after aging at 220°C and 15% NaCl for 16 hours; and the right image shows the filter cake after aging at 230°C and 5% NaCl for 16 hours. It can be seen that the prepared filtration loss reducer can form a dense and smooth filter cake with low filtration loss under different temperatures and salinities, and can withstand 230°C and 5% NaCl.

[0138] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be considered as limitations on the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims. For those skilled in the art, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A high-temperature resistant and salt-water resistant drilling fluid filtration reducer, characterized in that, The molecular weight of the filtration loss reducing agent is 300,000 to 3,000,000; the filtration loss reducing agent is prepared by free radical polymerization using the following five monomers as raw materials: Formula 2, Formula 3, Formula 4, Formula 5, and Formula 6. Formula 2 Formula 3 Formula 4 Formula 5 The monomer of Formula 6 is silicon dioxide modified by KH570; The mass ratio of the monomer of Formula 2:Molecular 3:Molecular 4:Molecular 5:Molecular 6 is (6~9):(1~4):(3~4):(2~3):(0.1~0.5).

2. A method for preparing the filtration loss reducing agent according to claim 1, comprising the following steps: S1. Dissolve the monomer of Formula 3 in a solvent and adjust the pH to neutral; S2. Add the monomers described in Formulas 2, 4, 5, and 6 to the solution obtained in S1, and stir to dissolve. S3. In an anaerobic environment, an initiator is added to the solution obtained in S2 to carry out the reaction. The reacted substance is then purified and dried to obtain the final product. The reaction temperature is 70~90℃.

3. The preparation method according to claim 2, characterized in that, In S1, the mass ratio of the monomer of Formula 3 to the solvent is 1:(10~50).

4. The preparation method according to claim 2, characterized in that, The mass ratio of the monomer of Formula 2:Molecular 3:Molecular 4:Molecular 5:Molecular 6 is (6~9):(1~4):(3~4):(2~3):(0.1~0.5).

5. The preparation method according to claim 2, characterized in that, In S3, the reaction time is 5-8 hours.

6. The preparation method according to claim 2, characterized in that, In step S3, the initiator is selected from one or more of ammonium persulfate, sodium bisulfite, and potassium persulfate.

7. The preparation method according to claim 2, characterized in that, The initiator is ammonium persulfate and sodium bisulfite, wherein the total mass of ammonium persulfate and sodium bisulfite accounts for 0.3% to 0.4% of the total monomer mass, and the mass ratio of ammonium persulfate to sodium bisulfite is 2:1.

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