Preparation method of ultra-high temperature fluid loss additive for cementing

Abstract

The application relates to a preparation method of an ultra-high-temperature fluid loss additive for well cementing, and belongs to the technical field of oilfield chemicals. After surface modification of palygorskite by a silane coupling agent, the surface polymerization sites of the palygorskite are obtained, so as to participate in a polymerization reaction. N,N-dimethyl acrylamide and other non-ionic water-soluble monomers, 2-acrylamide-2-methylpropanesulfonic acid, itaconic acid, sodium styrene sulfonate and other anionic water-soluble monomers, and vinyl pyrrolidone, sodium p-styrene sulfonate and other rigid monomers are used as polymerization raw materials to synthesize polymer grafted palygorskite. The fluid loss additive has excellent temperature resistance and salt resistance, has excellent fluid loss performance in a high-temperature and ultra-high-temperature environment, the fluid loss amount is less than 50 mL at 240 DEG C, has no obvious influence on other basic performances of cement slurry, can effectively improve the suspension stability of the cement slurry at high temperature, and is suitable for being used as a fluid loss additive for cement slurry under harsh conditions.

Description

A method for preparing an ultra-high temperature fluid loss reducing agent for cementing. Technical Field

[0001] This invention relates to a method for preparing an ultra-high temperature fluid loss reducing agent for cementing, belonging to the field of oilfield chemical technology. Background Technology

[0002] Petroleum is an indispensable non-renewable resource in modern society, and its extraction and utilization play a vital role in the development of the national economy. Currently, with the continuous extraction of oil and gas, the focus has gradually shifted from conventional oil and gas to deep reservoirs. However, many problems still need to be solved during the extraction of deep reservoirs. Cementing is an essential and crucial component of oil and gas exploration and development, a key step in drilling engineering, and a critical step in ensuring the lifespan of oil and gas wells, increasing their productivity, and promoting the overall benefits of oil and gas exploration and development. Deep and ultra-deep cementing technologies face challenges such as high temperature, high pressure, complex formations, leakage, salt deposits, and long cementing sections. Compared to conventional well sections, cementing is significantly more difficult, requiring cementing additives to have better performance to cope with these harsh environments.

[0003] Retarder, fluid loss reducer, and dispersant are the three main agents in oil well cementing engineering, playing a crucial role in the overall performance of cement slurry, the safety of the cementing process, and the quality of cementing. Among them, fluid loss reducer can effectively control the amount of cement slurry lost to the formation. However, in deep and ultra-deep well environments, especially above 200°C, conventional fluid loss reducers are prone to hydrolysis and chain breakage, leading to failure and uncontrolled fluid loss. This uncontrolled fluid loss not only causes adverse effects such as oil and gas reservoir contamination, formation damage, and channeling, but also affects cementing quality, potentially leading to cementing accidents and failures. Since conventional linear polymers of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) cannot be used in high-temperature environments, current research mainly focuses on particle grafting and the introduction of heat-resistant monomers to improve the temperature resistance of fluid loss reducers.

[0004] Chinese patent document CN 113651931A discloses a method for preparing an ultra-high temperature modified polymer cementing fluid loss reducer. The preparation method is as follows: graphene oxide is first ultrasonically dispersed, and then reacted with azobisisobutyramidine hydrochloride in an alkaline environment. Then, 2-acrylamido-2-methylpropanesulfonic acid, N,N-dimethylacrylamide and itaconic acid are used as polymer monomers to react with the treated graphene solution to synthesize an ultra-high temperature modified polymer cementing fluid loss reducer. It has the advantages of stable performance, strong temperature resistance (30-240℃), salt saturation resistance, excellent fluid loss reduction performance, strong adaptability, and significant improvement of cement stone mechanical properties. However, due to the high price of graphene oxide and the difficulty in dispersing the modified products, it is difficult to promote its application in oil fields.

[0005] Chinese patent document CN 115404061A discloses a method for preparing a high-temperature and salt-resistant water loss reducing agent composition. The method involves forming an intermediate polymer using an alkaline monomer and a neutral monomer. The alkaline monomer is mainly one or more of p-, ortho-, and meta-olefin sulfonates containing benzene rings. The neutral monomer is a mixture of acrylamide and lauryl methacrylate in any proportion. Ammonium persulfate is used as an initiator. After the reaction is complete, an acidic monomer solution such as acrylic acid is slowly added dropwise to continue the reaction and form a block polymer. The resulting polymer can effectively reduce the water loss of cement slurry without significantly affecting its rheological properties. However, its water loss performance above 120°C has not yet been disclosed.

[0006] While existing technologies, represented by the aforementioned patents, have made breakthroughs in the temperature resistance and salt resistance of polymer-based cementing agents for reducing fluid loss, there are still problems in the application and promotion of ultra-high temperature cementing operations above 200°C. Summary of the Invention

[0007] To address the shortcomings of existing technologies, such as poor temperature and salt resistance and high cost of granular materials, this invention provides a method for preparing an ultra-high temperature water loss reducing agent for cementing. Using palygorskite, which is stable and inexpensive at high temperatures, as a grafting core, and grafting polymers onto its surface, the temperature and salt resistance of the polymer can be effectively improved, the water loss of cement slurry under high and ultra-high temperature environments can be reduced, and the suspension stability of cement slurry can be improved.

[0008]

[0009] This invention utilizes the advantages of palygorskite's stable structure and low cost at high temperatures. It modifies palygorskite with a silane coupling agent to form unsaturated groups on its surface, serving as reaction sites for grafting polymers. Using water-soluble monomers such as itaconic acid, 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrenesulfonate, and N,N-dimethylacrylamide as raw materials, polymer-grafted palygorskite is prepared through aqueous solution polymerization. Testing shows that this product exhibits good dispersibility in solution. When added to cement slurry, it significantly reduces water loss under high and ultra-high temperature environments and improves the suspension stability of cement slurry in high-temperature environments. It has a temperature resistance up to 240℃, a water loss of 38 mL, and is resistant to semi-saturated brine.

[0010]

[0011] The technical solution of the present invention is as follows:

[0012] A method for preparing an ultra-high temperature fluid loss reducing agent for cementing:

[0013] (1) Surface modification treatment of palygorskite

[0014] Palaequa 200-1200 mesh and hydrochloric acid were placed in a three-necked flask equipped with a stirrer and thermometer. Palaequa 1-10% of the total mass was added, and the hydrochloric acid concentration was 1-4 mol / L. The mixture was heated to 50-80℃ and stirred for 1-2 h to activate the hydroxyl groups on the surface of the palaequa 200 mesh. The product was then removed, washed with distilled water until neutral, dried, and pulverized. The activated palaequa 200 mesh was dispersed in toluene, with a mass fraction of 1-5%. A certain amount of silane coupling agent KH570 was added, and the reaction was allowed to proceed for 3-6 h. After the reaction was complete, the product was filtered, washed with anhydrous ethanol, dried at 105℃, and pulverized to obtain modified palaequa 200 mesh. The mass ratio of palaequa 200 mesh to KH570 was 1:(0.5-10).

[0015] (2) Preparation of polymer-grafted palygorskite

[0016] Modified palygorskite, along with nonionic water-soluble monomers, anionic water-soluble monomers, and rigid monomers, were added to a three-necked glass flask equipped with a stirrer, a nitrogen inlet, and a thermometer. The mixture was stirred at high speed until all raw materials were evenly dispersed. The pH was controlled at 5–11, and nitrogen gas was introduced for 30 min. An initiator was then added, and the temperature was controlled at 40–70 °C. After reacting for 2–10 h, the product was dried and pulverized to obtain the desired target product. The monomers accounted for 10–30% of the total mass, and the mass ratio of modified palygorskite, nonionic water-soluble monomers, anionic water-soluble monomers, and rigid monomers was 1:(1–16):(1–10):(0–5). The initiator accounted for 0.1–2% of the total monomer mass.

[0017] According to the present invention, preferably, the nonionic water-soluble monomer is one of acrylamide, N,N-dimethylacrylamide, N-isopropylacrylamide, and N-ethylacrylamide;

[0018] Preferably, the anionic water-soluble monomer is one of itaconic acid, acrylic acid, methacrylic acid, maleic acid, 2-acrylamido-2-methylpropanesulfonic acid, and sodium vinyl sulfonate.

[0019] Preferably, the rigid monomer is vinylpyrrolidone, sodium p-styrene sulfonate, styrene, or N-vinylpyridine;

[0020] Preferably, the initiator is one or more of potassium persulfate, sodium persulfate, ammonium persulfate, azobisisobutyramidine hydrochloride, azobisisobutyronitrile, and azobisisobutyramidoline hydrochloride;

[0021] Preferably, the mesh size of the palygorskite is 300-1000 mesh;

[0022] Preferably, the mass ratio of palygorskite to KH570 is 1:(1~8);

[0023] Preferably, the monomer accounts for 10-25% of the total mass, and the mass ratio of modified palygorskite, nonionic water-soluble monomer, anionic water-soluble monomer and rigid monomer is 1:(1~12):(2~8):(0~4).

[0024] Preferably, the persulfate accounts for 0.5% to 1.5% of the total mass of the monomer;

[0025] Preferably, the pH during polymerization is 5–9, and the temperature is controlled at 50–65°C.

[0026] Preferably, the polymerization reaction time is 3 to 6 hours.

[0027] The superior effects of this invention are as follows:

[0028] 1. This invention relates to polymer-grafted particles. Palaequa calcite exhibits excellent high-temperature stability, effectively maintaining structural stability under high-temperature environments and providing a rigid core for the polymer. By optimizing the monomer types and synthesis methods, the polymer's resistance to high-temperature conditions is enhanced. Combined with the particles, this results in minimal molecular volume change under high temperature or high salt conditions. The introduced carboxyl groups also allow the product to adsorb well onto the surface of cement particles, and the product itself can fill gaps in the filter cake to a certain extent. The combination of these two factors allows for the formation of a thin and tough filter cake during high-temperature and ultra-high-temperature water loss processes, thus achieving excellent water loss reduction effects under high-temperature and ultra-high-temperature environments. Furthermore, due to its inherent temperature-resistant structural design, it also improves the settling stability of cement slurry under high-temperature conditions.

[0029] 2. This invention uses conventional monomers as polymerization raw materials, and the molecular weight of the product is controllable. Compared with graphene and nano-silica modified products, palygorskite is inexpensive and has better hydrophilicity and dispersibility. Its properties are less affected by temperature and alkaline environment.

[0030] 3. The product prepared by this invention has good compatibility with conventional cement slurry systems. Detailed Implementation

[0031] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0032] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0033] In this invention, N,N-dimethylacrylamide can be commercially available, for example, from Jiangsu Bost Chemical Technology Co., Ltd., industrial grade; vinylpyrrolidone can be commercially available, for example, from Shanghai Aladdin Biochemical Technology Co., Ltd., chemically pure; sodium p-styrenesulfonate can be commercially available, for example, from Shanghai Aladdin Biochemical Technology Co., Ltd., chemically pure; itaconic acid can be commercially available, for example, from Sinopharm Chemical Reagent Co., Ltd., chemically pure; palygorskite can be commercially available, for example, from Shijiazhuang Borui Building Materials Co., Ltd.

[0034] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0035] Example 1:

[0036] A method for preparing an ultra-high temperature fluid loss reducing agent for cementing includes the following steps:

[0037] 1000-mesh palygorskite and hydrochloric acid were placed in a three-necked flask equipped with a stirrer and thermometer. The palygorskite accounted for 2% of the total mass, and the hydrochloric acid concentration was 2 mol / L. The mixture was stirred for 0.8 h to activate the hydroxyl groups on the surface of the palygorskite. The product was then removed, washed with distilled water until neutral, dried, and pulverized. One part of the activated palygorskite was added to 94 parts of toluene solution, along with 5 parts of silane coupling agent KH570. After reacting for 4 h, the product was filtered, washed with anhydrous ethanol, dried at 105 °C, and pulverized. Add 1 part modified palygorskite, 6 parts N,N-dimethylacrylamide, 2 parts 2-acrylamido-2-methylpropanesulfonic acid, 2 parts itaconic acid, 2 parts sodium p-styrenesulfonate, and 85 parts deionized water to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. Stir at high speed until all raw materials are evenly dispersed. Control the pH at 6, purge with nitrogen for 30 min, add 1.5 parts ammonium persulfate, and react for 4 h. Dry and pulverize the product to obtain the final product.

[0038] Example 2:

[0039] 1000-mesh palygorskite and hydrochloric acid were placed in a three-necked flask equipped with a stirrer and thermometer. The palygorskite accounted for 2% of the total mass, and the hydrochloric acid concentration was 2 mol / L. The mixture was heated to 80℃ and stirred for 2 h to activate the hydroxyl groups on the surface of the palygorskite. The product was then removed, washed with distilled water until neutral, dried, and pulverized. One part of the activated palygorskite was added to 94 parts of toluene solution, along with 5 parts of silane coupling agent KH570. After reacting for 4 h, the product was filtered, washed with anhydrous ethanol, dried at 105℃, and pulverized. Add 1 part modified palygorskite, 10 parts N,N-dimethylacrylamide, 2 parts itaconic acid, 2 parts 2-acrylamido-2-methylpropanesulfonic acid and 85 parts deionized water to a three-necked glass bottle equipped with a stirrer, a nitrogen purging tube and a thermometer. Stir at high speed until all raw materials are evenly dispersed. Control the pH at 6, purge with nitrogen for 30 min, add 1.5 parts ammonium persulfate, react for 4 h, dry and pulverize the product to obtain the final product.

[0040] Example 3:

[0041] As described in Example 1, except that the hydrochloric acid concentration is 3 mol / L.

[0042] Example 4:

[0043] 1000-mesh palygorskite and hydrochloric acid were placed in a three-necked flask equipped with a stirrer and thermometer. The palygorskite accounted for 2% of the total mass, and the hydrochloric acid concentration was 2 mol / L. The mixture was heated to 80℃ and stirred for 1 h to activate the hydroxyl groups on the surface of the palygorskite. The product was then removed, washed with distilled water until neutral, dried, and pulverized. One part of the activated palygorskite was added to 94 parts of toluene solution, along with 8 parts of silane coupling agent KH570. After reacting for 6 h, the product was filtered, washed with anhydrous ethanol, dried at 105℃, and pulverized. Add 1 part modified palygorskite, 8 parts N,N-dimethylacrylamide, 2 parts itaconic acid, 2 parts 2-acrylamido-2-methylpropanesulfonic acid and 85 parts deionized water to a three-necked glass bottle equipped with a stirrer, a nitrogen purging tube and a thermometer. Stir at high speed until all raw materials are evenly dispersed. Control the pH at 6, purge with nitrogen for 30 min, add 1.7 parts ammonium persulfate, react for 4 h, dry and pulverize the product to obtain the final product.

[0044] Example 5:

[0045] As described in Example 1, except that the nonionic water-soluble monomer is 10 parts acrylamide.

[0046] Example 6:

[0047] As described in Example 1, except that the added monomers are 1 part modified palygorskite, 6 parts N,N-dimethylacrylamide, 4 parts vinylpyrrolidone, 2 parts 2-acrylamido-2-methylpropanesulfonic acid, and the initiator is azobisisobutyrazoline hydrochloride.

[0048] Example 7:

[0049] Papyrrolizite (500 mesh) and hydrochloric acid were placed in a three-necked flask equipped with a stirrer and thermometer. The pyrrolizite accounted for 2% of the total mass, and the hydrochloric acid concentration was 3 mol / L. The mixture was heated to 80°C and stirred for 1 h to activate the hydroxyl groups on the pyrrolizite surface. The product was then removed, washed with distilled water until neutral, dried, and pulverized. One part of the activated pyrrolizite was added to 94 parts of toluene solution, along with 5 parts of silane coupling agent KH570. After reacting for 4 h, the product was filtered, washed with anhydrous ethanol, dried at 105°C, and pulverized. Add 1 part modified palygorskite, 10 parts N,N-dimethylacrylamide, 2 parts acrylic acid, 2 parts 2-acrylamido-2-methylpropanesulfonic acid and 85 parts deionized water to a three-necked glass bottle equipped with a stirrer, a nitrogen purging tube and a thermometer. Stir at high speed until all raw materials are evenly dispersed. Control the pH at 6, purge with nitrogen for 30 min, add 1.3 parts ammonium persulfate, react for 4 h, dry and pulverize the product to obtain the final product.

[0050] Example 8:

[0051] 1000-mesh palygorskite and hydrochloric acid were placed in a three-necked flask equipped with a stirrer and thermometer. The palygorskite accounted for 2% of the total mass, and the hydrochloric acid concentration was 2 mol / L. The mixture was heated to 80°C and stirred for 1 h to activate the hydroxyl groups on the surface of the palygorskite. The product was then removed, washed with distilled water until neutral, dried, and pulverized. One part of the activated palygorskite was added to 94 parts of toluene solution, along with 5 parts of silane coupling agent KH570. After reacting for 4 h, the product was filtered, washed with anhydrous ethanol, dried at 105°C, and pulverized. Add 1 part modified palygorskite, 10 parts N,N-dimethylacrylamide, 2 parts maleic acid, 2 parts sodium p-styrene sulfonate, and 85 parts deionized water to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. Stir at high speed until all raw materials are evenly dispersed. Control the pH at 6, purge with nitrogen for 30 min, add 1.5 parts ammonium persulfate, and react for 4 h. Dry and pulverize the product to obtain the final product.

[0052] Example 9:

[0053] As described in Example 1, except that the anionic water-soluble monomer is 4 parts maleic acid.

[0054] Example 10:

[0055] As described in Example 1, except that the amount of deionized water is 35 parts.

[0056] Example 11:

[0057] As described in Example 1, except that the amount of ammonium persulfate is 0.75 parts.

[0058] Example 12:

[0059] 1000-mesh palygorskite and hydrochloric acid were placed in a three-necked flask equipped with a stirrer and thermometer. The palygorskite accounted for 1.5% of the total mass, and the hydrochloric acid concentration was 2 mol / L. The mixture was heated to 80℃ and stirred for 1 h to activate the hydroxyl groups on the surface of the palygorskite. The product was then removed, washed with distilled water until neutral, dried, and pulverized. One part of the activated palygorskite was added to 89 parts of toluene solution, along with 10 parts of silane coupling agent KH570. After reacting for 4 h, the product was filtered, washed with anhydrous ethanol, dried at 105℃, and pulverized. Add 1 part modified palygorskite, 10 parts N,N-dimethylacrylamide, 2 parts itaconic acid, 2 parts sodium p-styrene sulfonate, and 85 parts deionized water to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. Stir at high speed until all raw materials are evenly dispersed. Control the pH at 8, purge with nitrogen for 30 minutes, add 1.5 parts ammonium persulfate, and react for 6 hours. Dry and pulverize the product to obtain the final product.

[0060] Comparative Example 1:

[0061] This comparative example provides a cementing slurry fluid loss reducing agent, which is prepared through the following specific steps:

[0062] Add 10 parts of N,N-dimethylacrylamide, 2 parts of itaconic acid, 2 parts of 2-acrylamido-2-methylpropanesulfonic acid and 86 parts of deionized water to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube and a thermometer. Stir at high speed until all raw materials are evenly dispersed. Control the pH at 6, purge with nitrogen for 30 min, add 1.5 parts of ammonium persulfate, react for 4 h, dry and pulverize the product to obtain the final product.

[0063] Comparative Example 2:

[0064] This comparative example provides a cementing slurry fluid loss reducing agent, which is prepared through the following specific steps:

[0065] Add 10 parts of N,N-dimethylacrylamide, 2 parts of itaconic acid, 2 parts of sodium p-styrenesulfonate, and 86 parts of deionized water to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. Stir at high speed until all raw materials are evenly dispersed. Control the pH at 6, purge with nitrogen for 30 minutes, add 1.5 parts of ammonium persulfate, and react for 6 hours. Dry and pulverize the product to obtain the final product.

[0066] Comparative Example 3:

[0067] This comparative example provides a cementing slurry fluid loss reducing agent, which is prepared through the following specific steps:

[0068] Add 10 parts of N,N-dimethylacrylamide, 4 parts of itaconic acid, 2 parts of sodium p-styrenesulfonate, and 84 parts of deionized water to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. Stir at high speed until all raw materials are evenly dispersed. Control the pH at 6, purge with nitrogen for 30 minutes, add 1.5 parts of ammonium persulfate, and react for 6 hours. Dry and pulverize the product to obtain the final product.

[0069] Comparative Example 4:

[0070] This comparative example provides a cementing slurry fluid loss reducing agent, which is prepared through the following specific steps:

[0071] Add 10 parts of N,N-dimethylacrylamide, 2 parts of maleic acid, 2 parts of 2-acrylamido-2-methylpropanesulfonic acid, and 86 parts of deionized water to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. Stir at high speed until all raw materials are evenly dispersed. Control the pH at 6, purge with nitrogen for 30 min, add 1.5 parts of ammonium persulfate, and react for 6 h. Dry and pulverize the product to obtain the final product.

[0072] Comparative Example 5:

[0073] This comparative example provides a cementing slurry fluid loss reducing agent, which is prepared through the following specific steps:

[0074] Add 10 parts N,N-dimethylacrylamide, 4 parts acrylic acid, 2 parts 2-acrylamido-2-methylpropanesulfonic acid and 84 parts deionized water to a three-necked glass bottle equipped with a stirrer, a nitrogen purging tube and a thermometer. Stir at high speed until all raw materials are evenly dispersed. Control the pH at 5, purge with nitrogen for 30 min, add 1 part ammonium persulfate, and react for 6 h. Dry and pulverize the product to obtain the final product. Attached Figure Description

[0075] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings:

[0076] Figure 1 is a thickening curve of cement slurry in Test Example 1 of the present invention, which incorporates the water loss reducing agent provided in Example 1 (addition amount is 1% of the dry weight of cement ash), at 240℃ × 120 MPa.

[0077] Figure 2 shows the effect of Example 1 (addition amount of 1% of the dry weight of cement ash), Comparative Example 1 (addition amount of 1% of the dry weight of cement ash), and no water loss reducing agent added on the settling stability of cement slurry at 240℃ in Experiment 4 of the present invention.

[0078] Performance Evaluation

[0079] Experimental Example 1:

[0080] For Example 1 of the provided cementing ultra-high temperature fluid loss reducing agent (addition amount is 1% of the dry weight of cement ash), its thickening time at 240℃ × 120Mpa was tested. The test was conducted in accordance with the national standard GB / T19139-2012 "Test Methods for Cement in Oil Wells". The thickening curve obtained is shown in Figure 1.

[0081] As shown in Figure 1, after adding Example 1, the cement slurry thickening curve remained stable overall, without obvious "bulging" or rapid decrease in consistency. This indicates that Example 1 provided by the present invention has good temperature resistance, good compatibility with the retarder, and minimal impact on the cement slurry thickening process. Furthermore, the cement slurry can still maintain a temperature of around 20 Bc even under ultra-high temperature conditions, indirectly reflecting its good settling stability. Therefore, the present invention, by grafting polymer onto palygorskite, can effectively improve the polymer's temperature resistance and exhibit good compatibility.

[0082] Experimental Example 2:

[0083] For Examples 1-12 and Comparative Examples 1-5, performance parameters such as initial consistency and API water loss of cement slurry were tested according to the relevant provisions of the petroleum and natural gas industry standard SY / T5504.2-2013 "Evaluation Methods for Oil Well Cement Admixtures Part 2: Water Loss Reducing Agents" and the national standard GB / T19139-2012 "Test Methods for Oil Well Cement". The results are shown in Table 1.

[0084] The cement paste formula is: 500 g Jiahua G-grade cement + 50% 200 mesh silica sand + 4% retarder + X% water loss reducer + water-cement ratio 0.57.

[0085] The retarder was prepared in the laboratory and is a carboxylic acid retarder that can withstand temperatures up to 260℃.

[0086] Table 1. Water loss reduction performance of different water loss reducing agents under different conditions

[0087] Note: NaCl concentration is the mass ratio in water.

[0088] As shown in Table 1, the water loss reducing agents prepared in Examples 1-12 of this invention all exhibit good water loss reducing performance at 240℃, and the initial consistency of the cement slurry after addition is low, all less than 30 BC. While the water loss in Example 1 increases slightly with increasing temperature, it remains generally good. Furthermore, with increasing dosage, a good water loss reducing effect is achieved at a dosage of 1.2%. Comparison of different examples also reveals that the polymer monomer has a certain influence on the product's performance, but the overall API water loss is less than 50 mL. Compared to the comparative examples, it is evident that polymer grafting with palygorskite effectively improves the polymer's temperature resistance, maintaining low water loss under ultra-high temperature environments. Simultaneously, it effectively reduces the requirement for polymer molecular weight in terms of water loss, minimizing the product's impact on cement slurry fluidity. Moreover, it still exhibits good water loss reducing performance under semi-saturated brine conditions.

[0089] Experimental Example 3:

[0090] For Examples 1-12 and Comparative Examples 1-5, the compressive strength test, thickening time test, and other test standards in the national standard GB / T19139-2012 "Test Methods for Oil Well Cement" were used to investigate their effects on the performance and compatibility of the cement slurry. The results are shown in Table 2. The compressive strength of the cement slurry system without the addition of the water loss reducer was 48.7 MPa, and the thickening time was 420 min.

[0091] The cement paste formula is: 500 g Jiahua G-grade cement + 50% 200 mesh silica sand + 4% retarder + X% water loss reducer + water-cement ratio 0.57.

[0092] The retarder was prepared in the laboratory and is a carboxylic acid retarder that can withstand temperatures up to 260℃.

[0093] Table 2. Effects of different water loss reducing agents on cement compressive strength and thickening time.

[0094] As shown in Table 2, the water loss reducing agents prepared in Examples 1-12 of this invention have no significant effect on the compressive strength and thickening time of cement slurry. Furthermore, palygorskite can participate in the strength development of cement paste, increasing its mechanical strength to a certain extent. Compared with the comparative examples, polymer grafting onto palygorskite effectively reduces the adverse effects of the water loss reducing agent on other properties of the cement slurry, ensuring the performance requirements of the cement slurry under ultra-high temperature conditions.

[0095] Experimental Example 4:

[0096] For the provided ultra-high temperature fluid loss reducing agent for cementing, Example 1 (addition amount of 1% of the dry weight of cement ash) and Comparative Example 1 (addition amount of 1% of the dry weight of cement ash), cement slurry stability tests were conducted according to the national standard GB / T19139-2012 "Test Methods for Oil Well Cement" at a test temperature of 240℃. Figure 2 shows a comparison of the settling stability of Example 1 and Comparative Example 1 with the cement sample without the fluid loss reducing agent.

[0097] As shown in Figure 2, after treatment at 240℃, the sample without added dehydration reducer exhibited a significant density difference between the free liquid and the cement stone. In contrast, in Example 1, compared to Comparative Example 1, the free liquid volume decreased from 11.3 mL to 1.5 mL, and the density difference between the upper and lower cement stone sections significantly decreased to 0.042 g / cm³. 3 It is evident that the polymer-grafted palygorskite provided by this invention can effectively improve the settling stability of cement slurry under ultra-high temperature conditions. Compared with the comparative example, after introducing palygorskite, due to the stability and rigidity of the particles themselves, the overall temperature resistance of the polymer can be significantly improved, the polymer network structure in the cement slurry can be maintained, the viscosity of the cement slurry can be maintained, and the settling stability of the cement slurry under ultra-high temperature conditions can be improved.

[0098] Although the embodiments disclosed in this application are as described above, the content described is merely for the purpose of understanding this application and is not intended to limit this application. Any person skilled in the art to which this application pertains may make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in this application; however, the scope of patent protection of this application shall still be determined by the scope defined in the appended claims.

Claims

1. A method for preparing an ultra-high temperature fluid loss reducing agent for cementing, comprising the following steps: (1) Pallas's pallasite surface modification treatment: a certain mesh size of pallasite and hydrochloric acid are loaded into a three-necked flask equipped with a stirrer and a thermometer, wherein the pallasite accounts for 1-10% of the total mass, and the hydrochloric acid concentration is 1-4 mol / L. After heating to 50-80℃, the mixture is stirred for 1-2 h to activate the hydroxyl groups on the surface of the pallasite. The product is then removed, washed with distilled water until neutral, dried, and pulverized. The activated pallasite is dispersed in toluene, wherein the mass fraction of pallasite is 1-5%. A certain amount of silane coupling agent KH570 is added, and the mass ratio of pallasite to KH570 is 1:(1-8). The reaction is carried out for 3-6 hours. After h, once the reaction is complete, filter the product, wash it with anhydrous ethanol, dry it at 105℃ and then pulverize it as modified palygorskite; (2) Preparation of polymer-grafted palygorskite: Add modified palygorskite, nonionic water-soluble monomer, anionic water-soluble monomer, and rigid monomer to a three-necked glass bottle equipped with a stirrer, nitrogen tube and thermometer. The monomer accounts for 10-25% of the total mass. The mass ratio of modified palygorskite, nonionic water-soluble monomer, anionic water-soluble monomer and rigid monomer is 1:(6-12):(2-4):(0-4). Stir at high speed until all raw materials are evenly dispersed, adjust the pH and introduce nitrogen gas for 30 minutes. After adding persulfate and maintaining a certain temperature, the reaction proceeds for a period of time. The product is then dried and pulverized to obtain the target product. The nonionic water-soluble monomer is one of acrylamide, N,N-dimethylacrylamide, N-isopropylacrylamide, and N-ethylacrylamide. The anionic water-soluble monomer is one of itaconic acid, acrylic acid, methacrylic acid, maleic acid, 2-acrylamido-2-methylpropanesulfonic acid, and sodium vinyl sulfonate. The rigid monomer is one of vinylpyrrolidone, sodium p-styrene sulfonate, and N-vinylpyridine. The persulfate is one of potassium persulfate, sodium persulfate, and ammonium persulfate.

2. The preparation method of the ultra-high temperature fluid loss reducing agent for cementing according to claim 1, characterized in that, In step (1), the mesh size of the palygorskite is 300 to 1000 mesh.

3. The preparation method of the ultra-high temperature fluid loss reducing agent for cementing according to claim 1, characterized in that, In step (2), persulfate accounts for 0.5 to 1.5% of the total mass of the monomer.

4. The preparation method of the ultra-high temperature fluid loss reducing agent for cementing according to claim 1, characterized in that, In step (2), the pH is 5-9, the temperature is controlled at 50-65℃, and the polymerization reaction time is 3-6 h.

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