High-temperature-resistant and salt-resistant polymer filtrate reducer as well as preparation and application thereof

Abstract

The invention discloses a high-temperature-resistant and salt-resistant polymer filtrate reducer, the high-temperature-resistant and salt-resistant polymer filtrate reducer is grafted with a monomer with a polygonal ring structure, and in the process of grafting the monomer with the polygonal ring structure with the high-temperature-resistant and salt-resistant polymer filtrate reducer, an initiator is added in batches. The invention also discloses a preparation method and application thereof. The temperature-resistant and salt-resistant polymer filtrate reducer provided by the invention is used for preventing water in a drilling fluid system from permeating into a well wall to cause well wall collapse, shaft deformation and other well drilling accidents in a well drilling process, meanwhile, the rheological property of the drilling fluid system is protected from dramatic change, and the temperature-resistant and salt-resistant polymer filtrate reducer has a good temperature-resistant and salt-resistant filtrate reduction effect.

Description

Technical Field

[0001] This invention relates to a high-temperature and salt-resistant polymer filtration reducer, its preparation, and its application. Background Technology

[0002] With the ongoing exploration and development of unconventional oil and gas, deep and ultra-deep wells have gradually become the main focus of exploration and development. The well temperatures encountered during drilling are increasing, and with increasing well depth, the formations encountered are becoming more complex. Therefore, the probability of drilling fluid systems encountering salt intrusion during drilling is increasing. For example, encountering gypsum-salt layers or brine layers will release large amounts of brine. The prolonged exposure to high temperatures and high salinity will severely affect polymer-based drilling additives, causing polymer molecular chain breakage and hydrolysis, rendering the additives ineffective.

[0003] Currently, the most commonly used temperature- and salt-resistant filtration loss reducers on the market are trisulfonate and polysulfonate products. Due to severe environmental pollution, these products have been gradually banned by environmental regulations. Since trisulfonate and polysulfonate filtration loss reducers can withstand temperatures up to 180℃ and their salt resistance can reach saturation, developing filtration loss reducers that can replace trisulfonate and polysulfonate products is an important research direction. Summary of the Invention

[0004] This invention is made to further enrich the selection of filtration loss reducing agents and expand the application scope of polymer filtration loss reducing agents.

[0005] As one aspect of the present invention, a high-temperature and salt-resistant polymeric filtration reducer is disclosed, which is grafted with a monomer having a polygonal cyclic structure. During the grafting process of the high-temperature and salt-resistant polymeric filtration reducer with the monomer having a polygonal cyclic structure, an initiator is added in stages. Specifically, the monomer grafted with the polygonal cyclic structure refers to vinylpyrrolidone, hydroxybenzoic acid, or methylbenzenesulfonic acid.

[0006] Furthermore, this high-temperature and salt-resistant polymer filtration reducer is also grafted with 2-acrylamide-2-methylpropanesulfonic acid.

[0007] Furthermore, this high-temperature and salt-resistant polymer filtration reducer has a layered clay intercalation structure.

[0008] As another aspect of the present invention, a method for preparing the above-mentioned high-temperature and salt-resistant polymer filtration loss reducer is included, but is not limited to:

[0009] 10g-30g acrylic acid, 30-60g acrylamide, 30g-60g vinylpyrrolidone, 10g-30g sodium bicarbonate, and 1g-10g urea are reacted under initiator conditions.

[0010] In a specific embodiment, the initiator is 5 ml to 10 ml of 5% to 10% potassium persulfate solution, 5 ml to 10 ml of 5% to 10% sodium bisulfite solution, and 10 ml to 20 ml of 5% to 10% hydroxypropyl ether.

[0011] In a specific embodiment, the initiator is added in equal amounts in two separate applications.

[0012] As a further optimization, the high-temperature and salt-resistant polymer filtration loss reducer is intercalated with layered clay, which is selected from mica powder, montmorillonite powder and vermiculite powder. Experimental verification showed that mica has the best intercalation effect.

[0013] As another aspect of the present invention, the application of the above-mentioned high-temperature and salt-resistant polymer filtration reducer in oil and gas drilling is involved.

[0014] The high-temperature and salt-resistant polymer filtration reducer provided by this invention is used to prevent water in the drilling fluid system from seeping into the wellbore during drilling, causing wellbore collapse, wellbore deformation, and other drilling accidents. Simultaneously, it protects the rheological properties of the drilling fluid system from drastic changes. Conventional filtration reducers will severely fail in high-temperature and high-salt environments, eventually losing their filtration-reducing effect completely. The main innovation of this invention is ensuring that the performance of the filtration reducer remains unchanged in high-temperature and high-salt downhole environments, exhibiting excellent temperature and salt resistance in reducing filtration. Detailed Implementation

[0015] The experimental method of this invention refers to Chapter 5.15 of the petroleum industry standard SYT 7626-2021.

[0016] The testing method of this invention uses brine drilling fluid as the working fluid. The brine drilling fluid simulates the effect of reducing chemical loss in a high-salinity formation environment. The preparation method of the brine drilling fluid is as follows:

[0017] Add 400ml of distilled water and 0.64g of sodium carbonate to a high-speed stirring cup. After dissolving, stir at high speed and add 16g of bentonite. Stir at high speed for 20 minutes and cure for 24 hours. Then slowly add 6g of the sample and stir at high speed for 20 minutes. Finally, add 120g of sodium chloride and stir at high speed for 20 minutes.

[0018] Glossary

[0019] Brine drilling fluid: Brine drilling fluid refers to a colloidal solution formed by dispersing bentonite, a small amount of NaCO3, and NaCl in distilled water in a certain proportion. The role of bentonite is to give the solution a certain viscosity, while NaCO3 enhances the hydration of the bentonite and maintains the stability of the colloid. The addition of NaCl simulates the formation environment of saturated salt. The preparation process involves first preparing a desalinated water solution using bentonite, a small amount of NaCO3, and distilled water. After curing at room temperature for 24 hours (to ensure full hydration), a sample is added. After thorough stirring and dispersion, 30% by mass of NaCl solid particles is added to the solution to form brine drilling fluid. The main purposes of preparing brine drilling fluid are twofold: First, to simulate the drilling fluid contaminated by formation water in highly salinized formations. In drilling operations, fresh water is commonly used to prepare drilling fluid. When drilling into salt or brine layers, a large amount of salt dissolves into the drilling fluid. Salt solutions can render drilling fluid additives ineffective, leading to numerous downhole accidents. Second, replace the freshwater drilling fluid with brine drilling fluid before drilling through saltwater or salt-gypsum layers to ensure that the wellbore does not dissolve and collapse when drilling through salt-gypsum layers.

[0020] 2. High-Temperature and High-Pressure Filtration Loss: High-temperature and high-pressure filtration loss refers to the method of testing the filtration loss of drilling fluid using a high-temperature and high-pressure filtration loss meter. This experiment consists of two steps. The first step involves placing the drilling fluid sample in an aging vessel and rolling it in a high-temperature roller furnace at 180°C for 16 hours. Then, the drilling fluid sample, after being cooled to room temperature following the hot rolling, is transferred from the aging vessel to the high-temperature and high-pressure filtration loss meter to test the high-temperature and high-pressure filtration loss, which is then used as the evaluation result.

[0021] 3. High-Temperature and High-Pressure Filtration Loss Meter: This is a device specifically designed to measure filtration loss under high temperature and pressure. During testing, the drilling fluid sample is placed in the filtration loss meter's container and sealed. The pressure difference across the container is increased to 0.69 MPa, and the temperature is raised to 180°C and maintained for 1 hour. Then, maintaining the temperature at 180°C, the pressure difference across the container is increased to 3.45 MPa. The lower valve is opened, and the conditions of 180°C and 3.45 MPa are maintained for 30 minutes. Finally, the receiving valve is opened to collect the filtrate. The volume of the obtained liquid is the filtration loss.

[0022] The high-temperature aging process of this invention is as follows:

[0023] The brine drilling fluid was poured into a high-temperature aging tank, sealed, and placed in a high-temperature roller furnace, where it was heated to 180°C for 16 hours. After removing the aging tank and allowing it to cool to room temperature, the brine drilling fluid was transferred to a high-temperature, high-pressure filtration analyzer to measure the filtration loss at 180°C and a pressure difference of 3.45 MPa.

[0024] In this application, the inventors discovered that grafting groups with polygonal molecular structures onto a molecular chain can improve the temperature and salt resistance of the molecular chain. The selected monomers with polygonal structures include "vinylpyrrolidone", "hydroxybenzoic acid", and "methylbenzenesulfonic acid". In this application, these monomers with polygonal molecular structures are referred to as "reinforcing monomers".

[0025] This invention uses the filtration loss of PAC142 under the same experimental conditions as a comparison reference to demonstrate that the present invention can significantly optimize the filtration loss reduction performance under high temperature and high salt conditions.

[0026] PAC142, a thickener for drilling fluids, is a commonly used filtration loss reducer (also known as filtration loss reducer PAC142). It is a copolymer of acrylamide (adsorption group) and acrylic acid (hydration group). Since PAC142 is widely used in oil drilling engineering and is a stable polymer-based filtration loss reducer, this invention uses PAC142 as a comparative material. The filtration loss reduction performance of PAC142 under high temperature and high salt environments is used to demonstrate the temperature and salt resistance effect of this invention.

[0027] The filtration loss reduction effect of drilling fluid filtration loss reducer PAC142 in high temperature and high salinity environment is shown in Table 1.

[0028] Table 1. High-Temperature and High-Pressure Filtration Loss of Drilling Fluid Filter Loss Control Agent PAC142 in Brine Drilling Fluid

[0029] Filtration reducer Working fluid composition High-temperature, high-pressure filtration loss (ml) PAC142 Saltwater drilling fluid 98

[0030] Example 1: Grafting of dimethylaminoethyl methacrylate (DMMA)

[0031] 200 ml of distilled water was stirred at 200 rpm. Then, 20 g of acrylic acid (hydration group monomer), 40 g of acrylamide (adsorption group monomer), 40 g of dimethylaminoethyl methacrylate (reinforcing monomer), 20 g of sodium bicarbonate (for reaction with acrylic acid), 2 g of urea (to improve solubility), 5 ml of 5% potassium persulfate solution (initiator), 5 ml of 5% sodium bisulfite solution (initiator), and 10 ml of 5% hydroxypropyl ether (initiator) were added. The mixture was stirred at 200 rpm for 16 hours. The resulting viscous substance was washed with ethanol, granulated, dried at 50°C for 8 hours, and pulverized into a 200-mesh dry powder. The resulting product was obtained by grafting dimethylaminoethyl methacrylate.

[0032] The molecular formula of the obtained product is:

[0033]

[0034] Where n = 22000

[0035] The product obtained in Example 1 was subjected to high-temperature and high-pressure filtration loss testing, and the results are shown in Table 2. Grafting with dimethylaminoethyl methacrylate did not reduce the high-temperature and high-pressure filtration loss. Compared with PAC142, under the same conditions, the high-temperature and high-pressure filtration loss was similar (PAC142's high-temperature and high-pressure filtration loss was 98 ml, while Example 1's was 102 ml).

[0036] Table 2. High-temperature and high-pressure filtration loss in Example 1

[0037] Filtration reducer Working fluid composition High temperature and high pressure filtration loss, ml Product of Example 1 Saltwater drilling fluid 102

[0038] Example 2:

[0039] 200 ml of distilled water was stirred at 200 rpm. 20 g of acrylic acid, 40 g of acrylamide, 40 g of hydroxyethyl methacrylate, 20 g of sodium bicarbonate, 2 g of urea, 5 ml of 5% potassium persulfate solution, 5 ml of 5% sodium bisulfite solution, and 10 ml of 5% hydroxypropyl ether were added. The mixture was stirred at 200 rpm for 16 hours to obtain a viscous substance. The resulting viscous substance was washed with ethanol, granulated, dried at 50°C for 8 hours, and then pulverized into a 200-mesh dry powder.

[0040] The molecular formula of the obtained product is:

[0041]

[0042] Where n = 18000

[0043] The product obtained in Example 2 was subjected to high-temperature and high-pressure filtration loss testing, and the results are shown in Table 3. After grafting with hydroxyethyl methacrylate, the high-temperature and high-pressure filtration loss decreased from 98 ml to 95 ml, which was not a significant decrease.

[0044] Table 3. High-temperature and high-pressure filtration loss in Example 2

[0045] Filtration reducer Working fluid composition High temperature and high pressure filtration loss, ml Product of Example 2 Saltwater drilling fluid 95

[0046] Example 3: Grafting 2-acrylamide-2-methylpropanesulfonic acid (AMPS)

[0047] 200 ml of distilled water was stirred at 200 rpm. 20 g of acrylic acid, 40 g of acrylamide, 40 g of 2-acrylamide-2-methylpropanesulfonic acid, 20 g of sodium bicarbonate, 2 g of urea, 5 ml of 5% potassium persulfate solution, 5 ml of 5% sodium bisulfite solution, and 10 ml of 5% hydroxypropyl ether were added. The mixture was stirred at 200 rpm for 16 hours to obtain a viscous substance. The resulting viscous substance was washed with ethanol, granulated, dried at 50°C for 8 hours, and then pulverized into a 200-mesh dry powder.

[0048] The molecular formula of the obtained product is:

[0049]

[0050] Where: n = 21000

[0051] The product obtained in Example 3 was subjected to a high-temperature, high-pressure filtration loss test, and the results are shown in Table 4. After grafting 2-acrylamide-2-methylpropanesulfonic acid, the high-temperature, high-pressure filtration loss was reduced to 89 ml.

[0052] Table 4. High-temperature and high-pressure filtration loss in Example 3

[0053] Filtration reducer Working fluid composition High temperature and high pressure filtration loss, ml Product of Example 3 Saltwater drilling fluid 89

[0054] Example 4: Grafting vinylpyrrolidone (NVP)

[0055] Vinylpyrrolidone is a five-membered ring monomer containing one nitrogen atom. Grafting cyclic groups can increase the strength of the molecular chain. The specific process is as follows:

[0056] 200 ml of distilled water was stirred at 200 rpm. 20 g of acrylic acid, 40 g of acrylamide, 40 g of vinylpyrrolidone, 20 g of sodium bicarbonate, 2 g of urea, 5 ml of 5% potassium persulfate solution, 5 ml of 5% sodium bisulfite solution, and 10 ml of 5% hydroxypropyl ether were added. The mixture was stirred at 200 rpm for 16 hours to obtain a viscous substance. The resulting viscous substance was washed with ethanol, granulated, dried at 50°C for 8 hours, and then pulverized into a 200-mesh dry powder.

[0057] The molecular formula of the obtained product is:

[0058]

[0059] Where: n = 26000

[0060] The product obtained in Example 4 was subjected to a high-temperature and high-pressure filtration loss test, and the results are shown in Table 5.

[0061] The experimental results show that after grafting with vinylpyrrolidone (NVP), the high-temperature and high-pressure filtration loss decreased significantly, from 89 ml in Example 3 to 75 ml.

[0062] Table 5. High-temperature and high-pressure filtration loss in Example 4

[0063] Filtration reducer Working fluid composition High temperature and high pressure filtration loss, ml Product of Example 4 Saltwater drilling fluid 75

[0064] Example 5: Grafted hydroxybenzoic acid

[0065] Hydroxybenzoic acid is a benzene ring with a carboxyl group attached to it, which is linked to the molecular chain via a C-C bond. The stable structure of the benzene ring can improve the strength of the molecular chain backbone.

[0066] Add 200ml of distilled water, stirring at 200rpm, along with 20g of acrylic acid, 40g of acrylamide, 40g of hydroxybenzoic acid, 20g of sodium bicarbonate, 2g of urea, 5ml of 5% potassium persulfate solution, 5ml of 5% sodium bisulfite solution, and 10ml of 5% hydroxypropyl ether. Stir at 200rpm for 16 hours to obtain a viscous substance. After washing with ethanol, granulate the substance, dry it at 50℃ for 8 hours, and then pulverize it into a 200-mesh dry powder.

[0067] The molecular formula of the obtained product is:

[0068]

[0069] Where: n = 23000

[0070] The product obtained in Example 5 was subjected to a high-temperature and high-pressure filtration loss test, and the results are shown in Table 6.

[0071] The experimental results show that after grafting hydroxybenzoic acid, the high-temperature and high-pressure filtration loss decreased from 75 ml to 70 ml compared to Example 4.

[0072] Table 6. High-temperature and high-pressure filtration loss in Example 5

[0073] Filtration reducer Working fluid composition High temperature and high pressure filtration loss, ml Product of Example 5 Saltwater drilling fluid 70

[0074] Example 6: Grafting methylbenzenesulfonic acid.

[0075] Methylbenzenesulfonic acid is a benzene ring with a sulfonic acid group. The benzene ring is grafted onto the molecular chain by forming a C-C bond with the main chain through the methyl group, thereby increasing the strength of the molecular chain.

[0076] Add 200ml of distilled water, stirring at 200rpm, along with 20g of acrylic acid, 40g of acrylamide, 40g of toluenesulfonic acid, 20g of sodium bicarbonate, 2g of urea, 5ml of 5% potassium persulfate solution, 5ml of 5% sodium bisulfite solution, and 10ml of 5% hydroxypropyl ether. Stir at 200rpm for 16 hours to obtain a viscous substance. After washing with ethanol, granulate the substance, dry it at 50℃ for 8 hours, and then pulverize it into a 200-mesh dry powder.

[0077] The molecular formula of the obtained product is:

[0078]

[0079] Where: n = 28000

[0080] The product obtained in Example 6 was subjected to a high-temperature and high-pressure filtration loss test, and the results are shown in Table 7.

[0081] The experimental results show that after grafting with methylbenzenesulfonic acid, the high-temperature and high-pressure filtration loss decreased from 70 ml in Example 5 to 60 ml.

[0082] Table 7. High-temperature and high-pressure filtration loss in Example 6

[0083] Filtration reducer Working fluid composition High temperature and high pressure filtration loss, ml Product of Example 6 Saltwater drilling fluid 60

[0084] Example 7: This experiment involved molecular linking with two monomers: toluenesulfonic acid and AMPS. Toluenesulfonic acid is a structurally reinforcing monomer, and AMPS provides a strong hydration group. The synthesis method is as follows:

[0085] Add 20g acrylic acid, 40g acrylamide, 30g toluenesulfonic acid, 30g 2-acrylamide-2-methylpropanesulfonic acid (AMPS), 20g sodium bicarbonate, 5g urea, 5ml of 5% potassium persulfate solution, 5ml of 5% sodium bisulfite solution, and 10ml of 5% hydroxypropyl ether. Stir at 200rpm for 16 hours to obtain a viscous substance. After washing with ethanol, granulate, dry at 50℃ for 8 hours, and pulverize into a 200-mesh dry powder.

[0086] The molecular formula of the obtained product is:

[0087]

[0088] Where: n = 12000

[0089] The product obtained in Example 7 was subjected to a high-temperature and high-pressure filtration loss test, and the results are shown in Table 8.

[0090] The experimental results show that after grafting methylbenzenesulfonic acid and AMPS simultaneously, the high-temperature and high-pressure filtration loss decreased from 60 ml in Example 6 to 52 ml.

[0091] Table 8. High-temperature and high-pressure filtration loss in Example 7

[0092] Filtration reducer Working fluid composition High temperature and high pressure filtration loss, ml Product of Example 7 Saltwater drilling fluid 52

[0093] Example 8: As can be seen from Example 7, the method of grafting both reinforcing structural monomers and strong hydration group monomers onto the molecular chain can significantly reduce the heat and salt resistance filtration loss. Later, we tried to improve the polymerization efficiency of the material by adding initiators multiple times.

[0094] Based on Example 7, the method of adding the initiator was adjusted:

[0095] Add all at once: Stir at 200 rpm for 16 hours.

[0096] The mixture was added in two stages: the first addition was followed by stirring at 200 rpm for 16 hours; the second addition was followed by stirring for 3 hours. After all materials were added and thoroughly stirred, a viscous substance was obtained. The resulting viscous substance was washed with ethanol, granulated, dried at 50°C for 8 hours, and then pulverized into a 200-mesh dry powder.

[0097] The results of the high-temperature and high-pressure filtration loss experiment (see Table 9) show that, by comparing the three initiator addition methods, adding the initiator twice in equal amounts yielded the best results (filtration loss 40 ml). Therefore, the polymerization adopted the method of adding the initiator twice in equal amounts.

[0098] Table 9. Effects of three different initiator addition methods

[0099]

[0100] Example 9: To improve the rigidity of polymer molecular chains, an innovative approach was proposed to intercalate the grafted molecular chains with layered clay, adding a layer of rigid silicate particles to the molecular chains, thereby increasing their rigidity. The clay minerals used were mica powder, montmorillonite powder, and vermiculite powder. The experimental steps for intercalating the grafted polymer with clay are as follows.

[0101] Add 100g of clay mineral powder (passed through a 200-mesh sieve) to 900ml of tap water while stirring at 200rpm. After thorough stirring, cure at room temperature for 24 hours. Then add 5g of Na2CO3 and stir thoroughly for 3 hours. After curing for 24 hours, add 60g of polymer powder synthesized according to the initiator addition method in Example 8 while stirring at 200rpm. Heat in a water bath to 75°C and maintain stirring for two hours. After stopping stirring and cooling to room temperature, filter, dry, and pulverize into 200-mesh dry powder.

[0102] The results of Example 9 (see Table 10) show that the filtration loss reduction effect after intercalation with mica powder is the best (28 ml). Therefore, mica was selected as the intercalation clay.

[0103] Table 10. Filtration reduction effect after intercalation

[0104]

[0105] Example 10: To further improve the filtration loss reduction efficiency of the product of Example 10, this invention adds fibrous clay mineral wollastonite powder to mica, montmorillonite, and vermiculite powders. Through the combination of layered and fibrous structures, the structural layers of rigid particles are increased, thereby improving the filtration loss reduction efficiency. The experimental steps are as follows: 900 ml of tap water was stirred at 200 rpm, and 70 g of mica powder (passed through a 200-mesh sieve) and 30 g of wollastonite powder were added. After thorough stirring, the mixture was cured at room temperature for 24 hours. Then, 5 g of Na2CO3 was added, and the mixture was stirred thoroughly for 3 hours. After static curing for 24 hours, 60 g of polymer powder synthesized according to the initiator addition method in Example 8 was added while stirring at 200 rpm. The mixture was heated to 75°C in a water bath and stirred for two hours. After stopping stirring and cooling to room temperature, the mixture was filtered, dried, and pulverized into 200-mesh dry powder. The same steps were used for intercalation of montmorillonite powder and vermiculite powder.

[0106] The experimental results of Example 10 (Table 11) show that the combined intercalation of mica powder and wollastonite powder has a better effect on reducing filtration loss than using mica alone, with the filtration loss reduced to 25 ml. Therefore, the intercalation method combining mica and wollastonite is adopted.

[0107] Table 11. Filtration reduction effect after intercalation of two mineral combinations

[0108]

[0109] This patent innovatively designs and implements a synthesis scheme for a temperature- and salt-resistant filtration loss reducing agent through complex and challenging experiments. Initially, grafting a strongly hydrated monomer did not achieve the desired effect. Through molecular design, a molecule with a stable polygonal structure was chosen as the monomer to strengthen the rigidity of the molecular chain, leading to polymer formation. During polymerization, different initiator addition methods were compared, and adding the initiator twice in equal amounts was determined to be the optimal method, improving polymerization efficiency. To further enhance the rigidity of the molecular chain, intercalation with silicate minerals was performed, ensuring two types of rigid particles on the molecular chain. Mica was selected as the intercalating clay mineral, and fibrous wollastonite was added to improve the structural hierarchy of the clay mineral and enhance sealing efficiency. This combination of two silicate minerals resulted in better temperature- and salt-resistant filtration loss reducing effects.

[0110] Examples 1-3 use dimethylaminoethyl methacrylate, hydroxyethyl methacrylate, and 2-acrylamide-2-methylpropanesulfonic acid to graft the backbone. Examples 4-7 use vinylpyrrolidone, hydroxybenzoic acid, and toluenesulfonic acid, monomers with a stable polygonal ring structure, to graft the backbone (in this application, these monomers with polygonal molecular structures are referred to as "reinforcing monomers"). In terms of implementation results, the filtration loss reducing agent grafted with a stable monomer (such as vinylpyrrolidone, hydroxybenzoic acid, or methylbenzenesulfonic acid) with a polygonal ring structure exhibits better filtration loss reduction effect under high temperature and high salt environment. The preparation method is as follows: 10g-30g acrylic acid, 30-60g acrylamide, 30g-60g reinforcing monomer, 10g-30g sodium bicarbonate, 1g-10g urea, 5ml-10ml of 5%-10% potassium persulfate solution, 5ml-10ml of 5%-10% sodium bisulfite solution, and 10ml-20ml of 5%-10% hydroxypropyl ether are reacted in an aqueous solution.

[0111] Based on Examples 4-7, the inventors made two optimizations.

[0112] First, while grafting the reinforcing monomer, grafting the strong hydration group (AMPS) can effectively reduce the weakening of hydration by high temperature and high salt. Since methylbenzenesulfonic acid has a rigid structure, grafting methylbenzenesulfonic acid and AMPS at the same time achieves good temperature and salt resistance and filtration loss reduction effect.

[0113] Second, adding the initiator in stages, especially when it is added in two equal amounts, will further improve polymerization efficiency and enhance the filtration loss reduction effect. Specific procedures are shown in Example 8.

[0114] The inventors further optimized the experiment by using layered clay for intercalation. The layered clay consisted of mica powder, montmorillonite powder, and vermiculite powder. After experimental verification, the results showed that mica had the best intercalation effect.

[0115] This invention improves the sealing efficiency of mineral particles on micropores by increasing their shape combinations. It employs a strategy combining layered clay and fibrous clay structures. Mica is selected as the layered clay mineral, and wollastonite as the fibrous clay mineral. The ratio of the two minerals is 7:3 by mass. Evaluation results show that using a mixed intercalation of mica and wollastonite can further reduce the high-temperature, high-salt filtration loss of the product, thus forming a complete synthesis method for a polymer-based filtration loss reducer with a dual-rigid particle-reinforced structure (see Example 10).

[0116] Filtration reduction agents are used during drilling to prevent water from seeping into the wellbore, causing wellbore collapse, wellbore deformation, and other drilling accidents. They also protect the rheological properties of the drilling fluid system from drastic changes. Conventional filtration reduction agents often fail severely in high-temperature, high-salt environments, eventually losing their filtration reduction function entirely. The main innovation of this invention is ensuring that the performance of the filtration reduction agent remains unchanged in high-temperature, high-salt downhole environments, exhibiting excellent temperature and salt resistance in filtration reduction.

Claims

1. A high-temperature and salt-resistant polymer filtration loss reducer, characterized in that, The high-temperature and salt-resistant polymer filtration reducer is grafted with monomers having polygonal ring structures, and the initiator is added in stages during the grafting process.

2. The temperature- and salt-resistant polymer filtration loss reducer according to claim 1, characterized in that, The grafted monomer with a polygonal ring structure refers to vinylpyrrolidone, hydroxybenzoic acid, or methylbenzenesulfonic acid.

3. The temperature- and salt-resistant polymer filtration loss reducer according to claim 2, characterized in that, This heat- and salt-resistant polymer filtration reducer is also grafted with 2-acrylamide-2-methylpropanesulfonic acid.

4. The high-temperature and salt-resistant polymer filtration loss reducer according to claim 1, characterized in that, This high-temperature and salt-resistant polymer filtration reducer has a layered clay intercalation structure.

5. A method for preparing the temperature- and salt-resistant polymer filtration loss reducing agent according to any one of claims 1-4, characterized in that, Including but not limited to: 10g-30g acrylic acid, 30-60g acrylamide, 30g-60g vinylpyrrolidone, 10g-30g sodium bicarbonate, and 1g-10g urea are reacted under initiator conditions.

6. The method according to claim 5, characterized in that, The initiator is 5 ml to 10 ml of 5% to 10% potassium persulfate solution, 5 ml to 10 ml of 5% to 10% sodium bisulfite solution, and 10 ml to 20 ml of 5% to 10% hydroxypropyl ether.

7. The method according to claim 6, characterized in that, The initiator is added in two equal portions.

8. The method according to claim 5, characterized in that, Layered clay was used for intercalation.

9. The method according to claim 8, characterized in that, The layered clay is selected from mica powder, montmorillonite powder, and vermiculite powder.

10. The method according to claim 8, characterized in that, Fibrous clay minerals are added to the layered clay.

11. The method of claim 10, characterized in that, The fibrous clay mineral is wollastonite.

12. The application of the temperature- and salt-resistant polymer filtration reducer according to any one of claims 1-4 in oil and gas development.

Images