High-temperature-resistant and salt-resistant suspending agent for isolation fluid and preparation method thereof

Abstract

The present application relates to a kind of high-temperature-resistant salt-resistant suspending agent for isolation fluid and its preparation method, the high-temperature-resistant salt-resistant suspending agent prepared by the method, it is especially suitable for high-temperature-resistant salt-resistant isolation fluid system;The suspending agent, by adding crosslinking agent, makes polymer form the micro-crosslinking polymer with space net structure, can not only guarantee the rheological property at low temperature and the falling ash time, but also can improve the suspending performance of isolation fluid at high temperature;By intercalation modification to inorganic mineral, its surface is rich in carboxyl, on the one hand, improve its dispersing property, on the other hand, further improve the suspending stability of isolation fluid under high temperature and salt condition;After the combination of the two, the advantages of the two are further exerted;The suspending agent prepared by the present application has good salt resistance, fast falling ash, good rheological property at low temperature, good stability at high temperature and other characteristics, and good comprehensive performance, can effectively guarantee the safety of cementing construction, improve cementing quality.

Description

Technical Field

[0001] This invention relates to the field of cement slurry and drilling fluid isolation technology in drilling cementing, and in particular to a high-temperature resistant and salt-resistant suspending agent for isolation fluid and its preparation method. Background Technology

[0002] Currently, domestic oil and gas exploration and development is advancing towards ultra-deep formations reaching depths of 10,000 meters. Deep and ultra-deep oil and gas formations are becoming important replacement areas for increasing my country's oil and gas reserves and production. Cementing faces challenges such as ultra-high temperatures (>200℃), ultra-high pressures (>150MPa), and high densities (up to 2.60g / cm³). 3 Extreme formation conditions such as high salt content (>10%) pose a significant challenge to wellbore working fluids.

[0003] Separating fluid is a working fluid used during cementing to separate cement slurry from drilling fluid. It serves two purposes: firstly, flushing away mud cake and improving interfacial bonding; and secondly, separating cement slurry and drilling fluid to prevent contamination. Suspension stability is one of the most important properties of separating fluid. Poor stability can lead to solid deposition, causing anything from annular blockage and pump stalling to more serious accidents like "sausage filling" and "flagpole insertion." Currently, research on suspension stabilizers for separating fluids is limited, with xanthan gum as the main component. Xanthan gum has a temperature resistance not exceeding 150℃ and is generally not salt-resistant. Research on suspending agents for cement slurry is more active, shifting from natural polymers to synthetic polymers, which can withstand temperatures up to 200℃. However, the main materials in separating fluids are often inert weighting materials such as barite and iron ore powder, which, unlike cement particles, cannot participate in hydration and adsorb onto polymers to achieve suspension stability. Therefore, some suspending agents that exhibit high temperature resistance and good suspension properties in cement slurry may fail in separating fluids.

[0004] Currently, there is limited research on suspension stabilizers for release fluids, with xanthan gum being the main component. These stabilizers have a temperature resistance of no more than 150℃ and are generally not salt resistant. Most suspension stabilizers for release fluids also have contact thickening issues, which can easily affect the rheological and thickening properties of cement slurry. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a high-temperature resistant and salt-resistant suspending agent for isolation fluids, comprising the following components by weight: 5-10 parts of high molecular weight polymer; 80-100 parts of modified inorganic minerals;

[0006] The polymer comprises the following components in parts by weight: 2-acrylamide-2-methylpropanesulfonic acid, 100 parts; N,N-diethylacrylamide, 5-10 parts; cyclic monomer, 8-10 parts; crosslinking agent, 0.3-0.5 parts; carboxylic acid monomer, 0.5-1.0 parts; and water, 300-400 parts.

[0007] The modified inorganic minerals include raptosite fibers and basalt fibers that have undergone intercalation modification.

[0008] Furthermore, the crosslinking agent is N,N-methylenebisacrylamide.

[0009] Specifically, by selecting N,N-methylenebisacrylamide, the ash settling time and low-temperature rheological properties of the isolation liquid can be guaranteed, as well as the suspension stability at high temperatures.

[0010] Furthermore, the polymer forms a micro-crosslinked structure, with a molecular weight controlled between 1 million and 1.5 million and a molecular weight distribution of 1.5 to 2.0. Specifically, this ensures both the ash settling time and low-temperature rheological properties of the isolation liquid, as well as its suspension stability at high temperatures.

[0011] Specifically, the attapulgite fiber and basalt fiber need to undergo intercalation modification to enrich their surface with carboxyl groups, thereby improving their dispersion and adsorption properties. The rich carboxyl group content means that the fiber itself has a strong negative charge, and the repulsion between charges is conducive to the dispersion of fibers. At the same time, the good hydrophilicity of carboxyl groups is more conducive to the rapid and uniform dispersion of the modified fiber in water. In addition, the charged carboxyl groups can be effectively adsorbed on the positively charged barite and iron ore powder to improve the suspension stability of the weighting material, thereby improving the suspension performance of the suspending agent.

[0012] Further: the cyclic monomer is at least one of N-vinylpyrrolidone and 4-vinylpyridine.

[0013] Furthermore, the carboxylic acid monomer is at least one of itaconic acid and acrylic acid.

[0014] This invention provides a high-temperature resistant and salt-resistant suspending agent for isolation fluids, which has the following beneficial technical effects: This suspending agent is particularly suitable for high-temperature and salt-resistant isolation fluid systems; by adding a crosslinking agent, the polymer forms a micro-crosslinked polymer with a spatial network structure, which can not only ensure the ash release time and rheological properties at low temperatures, but also improve the suspension performance of the isolation fluid at high temperatures; by intercalating and modifying inorganic minerals to make them rich in carboxyl groups, their dispersion performance is improved on the one hand, and the suspension stability of the isolation fluid under high-temperature and salt-containing conditions is further improved on the other hand; by combining the two, the advantages of both are further utilized; The suspending agent prepared by this invention has the characteristics of good salt resistance, fast ash release, good rheological properties at low temperatures, and good stability at high temperatures, with good comprehensive performance, which can effectively ensure the safety of cementing operations and improve cementing quality.

[0015] Another aspect of the present invention provides a method for preparing a high-temperature resistant and salt-resistant suspending agent for a separating fluid, comprising:

[0016] Polymer preparation involves sequentially adding water, 2-acrylamide-2-methylpropanesulfonic acid, N,N-diethylacrylamide, cyclic monomers, crosslinking agents, and carboxylic acid monomers into a reactor to obtain a reaction solution. The solution is stirred and the pH value is adjusted. After adding an initiator and reacting, the solution is dried and pulverized to obtain polymer powder.

[0017] Inorganic mineral modification preparation involves soaking the inorganic minerals in acid to remove impurities and washing them until neutral, then ultrasonically pulverizing and dispersing them, adjusting the pH value to a preset value, adding an initiator to initiate polymerization, and grinding the inorganic mineral components.

[0018] The suspending agent is prepared by mixing the prepared polymer and the inorganic mineral modified powder in a preset ratio to obtain the suspending agent.

[0019] Further, the preparation of the polymer includes:

[0020] According to the weight proportions of each component, water, 2-acrylamide-2-methylpropanesulfonic acid, N,N-diethylacrylamide, cyclic monomer, crosslinking agent and carboxylic acid monomer were added to the reactor in sequence to obtain the reaction solution;

[0021] Stir at 200 rpm until all components are dissolved, adjust the pH of the reaction solution to 6-7, and raise the temperature of the reaction solution to 50-60°C.

[0022] An initiator was added to the reaction solution, and the reaction was carried out for 2-3 hours. The mixture was then cooled to room temperature to obtain colorless and pale yellow viscous liquids. After microwave drying and pulverization, polymer powder materials were obtained.

[0023] Furthermore, the preparation of the inorganic minerals includes:

[0024] Soak attapulgite fibers or basalt fibers in a 10% dilute hydrochloric acid solution to remove impurities such as carbonates, and then rinse them repeatedly with deionized water until neutral to obtain pure attapulgite fibers or basalt fibers.

[0025] Pure raptor fiber or basalt fiber is added to deionized water and dispersed evenly using an ultrasonic cell disruptor.

[0026] Liquid acrylic acid was adjusted to pH 6 with a 28% sodium hydroxide solution and then added to a fiber dispersion. The mixture was heated to 60°C, and a superinitiator was added to initiate polymerization. The polymer particles were washed with hot ethanol solution, dried at room temperature, and ground into powder.

[0027] Further: the initiator is at least one selected from ammonium persulfate, potassium persulfate, azobisisobutyramidine hydrochloride and azobisisobutyramidine hydrochloride.

[0028] This invention provides a method for preparing a high-temperature resistant and salt-tolerant suspension for isolation fluids, which has the following beneficial technical effects: The preparation method is simple, the material ratios are reasonable, and the suspension prepared by this method is suitable for high-temperature salt-tolerant isolation fluid systems; the suspension, by adding a crosslinking agent, forms a micro-crosslinked polymer with a spatial network structure, which not only ensures the ash-setting time and rheological properties at low temperatures, but also improves the suspension performance of the isolation fluid at high temperatures; by intercalating and modifying inorganic minerals to make them rich in carboxyl groups, their dispersion performance is improved, and the suspension stability of the isolation fluid under high-temperature and salt-containing conditions is further enhanced. Combining these two aspects further leverages their advantages. The suspension prepared by this invention has excellent comprehensive performance characteristics such as rapid ash-setting, good rheological properties at low temperatures, and good stability at high temperatures, which can effectively ensure the safety of cementing operations and improve cementing quality. Attached Figure Description

[0029] The above and other objects, features, and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings. The drawings are for illustrative purposes only and are not intended to limit the scope of the invention.

[0030] Figure 1 This is a curing curve of the isolation solution prepared using the suspending agent prepared in Example 1 of the present invention at 240°C. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to the accompanying drawings. However, it should be understood that this disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0032] This invention discloses a high-temperature resistant and salt-resistant suspending agent for isolation fluid, comprising the following components in parts by weight: 5-10 parts of high molecular polymer; 80-100 parts of modified inorganic minerals;

[0033] The polymer comprises the following components in parts by weight: 2-acrylamide-2-methylpropanesulfonic acid, 100 parts; N,N-diethylacrylamide, 5-10 parts; cyclic monomer, 8-10 parts; crosslinking agent, 0.3-0.5 parts; carboxylic acid monomer, 0.5-1.0 parts; and water, 300-400 parts.

[0034] The inorganic minerals include intercalated modified raphe fibers and basalt fibers.

[0035] In this embodiment, the attapulgite fiber and basalt fiber are modified by intercalation to enrich their surface with carboxyl groups, which can improve their dispersion and adsorption properties. The rich carboxyl group content means that the fiber itself has a strong negative charge. The repulsion between charges is conducive to the dispersion of the fibers. At the same time, the good hydrophilicity of the carboxyl group is more conducive to the rapid and uniform dispersion of the modified fiber in water. In addition, the charged carboxyl group can be effectively adsorbed on the positively charged barite and iron ore powder to improve the suspension stability of the weighting material, thereby improving the overall stability of the suspending agent.

[0036] In this embodiment, the crosslinking agent is N,N-methylenebisacrylamide. Specifically, N,N-methylenebisacrylamide can form a micro-crosslinked polymer with a three-dimensional network structure, which can support inert weighting materials and improve suspension stability under high temperature and high salt conditions.

[0037] In this embodiment, the polymer is formed into a micro-crosslinked structure, with its molecular weight controlled between 1 million and 1.5 million, and a molecular weight distribution of 1.5 to 2.0. This ensures both the settling time and low-temperature rheological properties of the isolation liquid, and also guarantees its suspension stability at high temperatures.

[0038] It should be noted that the suspending agent provided in this embodiment of the invention is particularly suitable for salt-resistant isolation fluid systems. The suspension stability of isolation fluids differs from that of cement slurry. In cement slurry systems, most of the cement components and admixtures can effectively participate in hydration, forming an effective cementitious structure, thus ensuring its stability at high temperatures. However, isolation fluids, apart from some functional additives, mainly consist of inert weighting materials such as barite and iron ore powder. Therefore, ensuring the suspension stability of the isolation fluid, especially under ultra-high temperature and salt conditions, is more difficult. If the suspension stability of the isolation fluid is poor, solid phase deposition can occur, leading to anything from minor annular blockage and pump stalling to more serious accidents such as "sausage filling" and "flagpole planting."

[0039] The suspending agent provided in this invention mainly consists of a synthetic polymer and intercalated modified inorganic minerals. The synthetic polymer has a suitable molecular weight and molecular weight distribution, which facilitates rapid dissolution in water and uniform dispersion. Simultaneously, a cross-linking agent is introduced to form a certain spatial network structure, which can support the inert weighting material and provide suspension stability. Therefore, this suspending stabilizer, when added to the isolation liquid, exhibits the characteristics of not thickening at low temperatures and maintaining suspension stability at high temperatures. The introduction of cyclic monomers improves the rigidity of the polymer molecular chains, thereby enhancing the polymer's temperature resistance. The introduction of carboxylic acid monomers further enhances the adsorption performance of the suspending agent, enabling it to adsorb onto the surface of cement particles, supporting the cement particles and further ensuring its suspension stability.

[0040] In this embodiment, the cyclic monomer is at least one of N-vinylpyrrolidone and 4-vinylpyridine. Specifically, N-vinylpyrrolidone and 4-vinylpyridine contain rigid groups, which can improve the rigidity of the polymer molecular chain and enhance its structural stability at high temperatures.

[0041] In this embodiment, the carboxylic acid monomer is at least one of itaconic acid and acrylic acid. Specifically, itaconic acid and acrylic acid have strong adsorption properties and can be adsorbed around cement particles to support them and further ensure their stability. However, excessive addition will prolong the thickening time of the cement slurry and delay the strength development of the cement slurry at low temperatures.

[0042] In this embodiment of the invention, the crosslinking agent can be present in weight parts of 0.3, 0.4, 0.5, etc., and the carboxylic acid monomer can be present in weight parts of 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, etc.

[0043] It should be noted that when the weight percentage of the crosslinking agent exceeds 0.5%, the isolation liquid prepared by the suspending agent provided in the embodiments of the present invention has high viscosity and poor rheological properties, and the thickened linear structure is prone to problems such as "bulging" and "core-encasing". Conversely, when the weight percentage of the crosslinking agent is less than 0.3%, the amount of suspending agent needs to be increased, and the suspension stability of the system is relatively poor. Therefore, in the embodiments of the present invention, the weight percentage of the crosslinking agent does not exceed 0.5%.

[0044] It should be noted that when the weight percentage of carboxylic acid monomers exceeds 1.5%, the thickening time of the cement slurry prepared by the suspending agent provided in the embodiments of the present invention will be prolonged, and the strength development at low temperatures will be slow. Therefore, in the embodiments of the present invention, the weight percentage of carboxylic acid monomers does not exceed 1.0%.

[0045] The high-temperature resistant and salt-resistant suspending agent for the isolation fluid described in the above embodiments is particularly suitable for high-temperature and salt-resistant isolation fluid systems. By adding a crosslinking agent, the polymer forms a micro-crosslinked polymer with a spatial network structure, which can not only ensure the ash release time and rheological properties at low temperatures, but also improve the suspension performance of the isolation fluid at high temperatures. By intercalating and modifying the inorganic minerals to make them rich in carboxyl groups, their dispersion performance is improved on the one hand, and the suspension stability of the isolation fluid under high-temperature and salt-containing conditions is further improved on the other hand. Combining the two further leverages their advantages. The suspending agent prepared by this invention has the characteristics of good salt resistance, fast ash release, good rheological properties at low temperatures, and good stability at high temperatures. It has good comprehensive performance and can effectively ensure the safety of cementing operations and improve cementing quality.

[0046] The embodiments of the present invention also disclose a method for preparing a high-temperature resistant and salt-resistant suspending agent for isolation fluid, comprising the following operations:

[0047] Polymer preparation involves sequentially adding water, 2-acrylamide-2-methylpropanesulfonic acid, N,N-diethylacrylamide, cyclic monomers, crosslinking agents, and carboxylic acid monomers into a reactor to obtain a reaction solution. The solution is stirred and the pH value is adjusted. After adding an initiator and reacting, the solution is dried and pulverized to obtain polymer powder.

[0048] Inorganic mineral modification preparation involves soaking the inorganic minerals in acid to remove impurities and washing them until neutral, then ultrasonically pulverizing and dispersing them, adjusting the pH value to a preset value, adding an initiator to initiate polymerization, and grinding the inorganic mineral components.

[0049] The suspending agent is prepared by mixing the prepared polymer and the inorganic mineral modified powder in a preset ratio to obtain the suspending agent.

[0050] In this embodiment, the method for preparing the polymer described above includes:

[0051] According to the weight proportions of each component, water, 2-acrylamide-2-methylpropanesulfonic acid, N,N-diethylacrylamide, cyclic monomer, crosslinking agent and carboxylic acid monomer were added to the reactor in sequence to obtain the reaction solution;

[0052] Stir at 200 rpm until all components are dissolved, adjust the pH of the reaction solution to 6-7, and raise the temperature of the reaction solution to 50-60°C.

[0053] An initiator was added to the reaction solution, and the reaction was carried out for 2-3 hours. The mixture was then cooled to room temperature to obtain colorless and pale yellow viscous liquids. After microwave drying and pulverization, polymer powder materials were obtained.

[0054] In this embodiment, the method for preparing the aforementioned inorganic minerals includes:

[0055] Soak attapulgite fibers or basalt fibers in a 10% dilute hydrochloric acid solution to remove impurities such as carbonates, and then rinse them repeatedly with deionized water until neutral to obtain pure attapulgite fibers or basalt fibers.

[0056] Pure raptor fiber or basalt fiber is added to deionized water and dispersed evenly using an ultrasonic cell disruptor.

[0057] Liquid acrylic acid was adjusted to pH 6 with a 28% sodium hydroxide solution and then added to a fiber dispersion. The mixture was heated to 60°C, and an initiator was added to initiate polymerization. The initiator was at least one of ammonium persulfate, potassium persulfate, azobisisobutyramidine hydrochloride, and azobisisobutyramidine imidazoline hydrochloride. The polymer particles were then washed with hot ethanol solution, dried at room temperature, and ground into powder.

[0058] Based on the suspending agent formulation and preparation method disclosed in the above embodiments, the advantages of a high-temperature resistant and salt-resistant suspending agent for isolation liquid disclosed in this invention will be further illustrated below with specific embodiments. The purpose is to better understand the content of this invention and reflect its essential characteristics. Therefore, the examples given should not be regarded as limitations on the scope of protection of this invention.

[0059] Example 1

[0060] According to the weight proportions of each component, 300 parts by weight of water, 100 parts by weight of 2-acrylamide-2-methylpropanesulfonic acid, 5 parts by weight of N,N-diethylacrylamide, 0.3 parts by weight of N,N-methylenebisacrylamide, 8 parts by weight of N-vinylpyrrolidone, and 0.5 parts by weight of itaconic acid were added to the reactor in sequence to obtain a reaction solution. The reaction solution was stirred at a speed of 200 rpm, the pH of the reaction solution was adjusted to 6, and the temperature of the reaction solution was raised to 60°C. After all components were dissolved, ammonium persulfate initiator was added to the reaction solution, the reaction was carried out for 2 hours, cooled to room temperature, and then microwave-dried and pulverized to obtain polymer powder.

[0061] To remove impurities such as carbonates, patazoite or basalt fibers are soaked in a 10% dilute hydrochloric acid solution. They are then repeatedly rinsed with deionized water until neutral to obtain pure patazoite or basalt fibers. The pure patazoite or basalt fibers are added to deionized water and dispersed evenly using an ultrasonic cell disruptor. Liquid acrylic acid is adjusted to pH 6 with a 28% sodium hydroxide solution and added to the fiber dispersion. The mixture is heated to 60°C, and potassium persulfate solution is added to initiate polymerization. The polymer particles are washed with hot ethanol solution, dried at room temperature, and ground into powder.

[0062] A suspending agent was obtained by mixing 5 parts of polymer powder with 100 parts of intercalated modified mineral fiber.

[0063] Example 2

[0064] According to the weight proportions of each component, 350 parts by weight of water, 100 parts by weight of 2-acrylamide-2-methylpropanesulfonic acid, 8 parts by weight of N,N-diethylacrylamide, 0.4 parts by weight of N,N-methylenebisacrylamide, 9 parts by weight of 4-vinylpyridine, and 1 part by weight of acrylic acid were added sequentially to the reactor to obtain a reaction solution. The reaction solution was stirred at a speed of 200 rpm, the pH of the reaction solution was adjusted to 7, and the temperature of the reaction solution was raised to 60°C. After all components were dissolved, ammonium persulfate, the initiator, was added to the reaction solution, and the reaction was carried out for 2 hours. After cooling to room temperature, the polymer powder was obtained by microwave drying and pulverization.

[0065] To remove impurities such as carbonates, patazoite or basalt fibers are soaked in a 10% dilute hydrochloric acid solution. They are then repeatedly rinsed with deionized water until neutral to obtain pure patazoite or basalt fibers. The pure patazoite or basalt fibers are added to deionized water and dispersed evenly using an ultrasonic cell disruptor. Liquid acrylic acid is adjusted to pH 6 with a 28% sodium hydroxide solution and added to the fiber dispersion. The mixture is heated to 60°C, and potassium persulfate solution is added to initiate polymerization. The polymer particles are washed with hot ethanol solution, dried at room temperature, and ground into powder.

[0066] Eight parts of polymer powder were mixed with 90 parts of intercalated modified mineral fiber to obtain a suspending agent.

[0067] Example 3

[0068] According to the weight proportions of each component, 400 parts by weight of water, 100 parts by weight of 2-acrylamide-2-methylpropanesulfonic acid, 10 parts by weight of N,N-diethylacrylamide, 0.5 parts by weight of N,N-methylenebisacrylamide, 5 parts by weight of vinylpyrrolidone, 5 parts by weight of 4-vinylpyridine, 0.5 parts by weight of acrylic acid, and 0.5 parts by weight of itaconic acid were added to the reactor in sequence to obtain a reaction solution. The reaction solution was stirred at a speed of 200 rpm, the pH of the reaction solution was adjusted to 7, and the temperature of the reaction solution was raised to 60°C. After all components were dissolved, ammonium persulfate initiator was added to the reaction solution, the reaction was carried out for 2 hours, cooled to room temperature, and then microwave-dried and pulverized to obtain polymer powder.

[0069] To remove impurities such as carbonates, patazoite or basalt fibers are soaked in a 10% dilute hydrochloric acid solution. They are then repeatedly rinsed with deionized water until neutral to obtain pure patazoite or basalt fibers. The pure patazoite or basalt fibers are added to deionized water and dispersed evenly using an ultrasonic cell disruptor. Liquid acrylic acid is adjusted to pH 6 with a 28% sodium hydroxide solution and added to the fiber dispersion. The mixture is heated to 60°C, and potassium persulfate solution is added to initiate polymerization. The polymer particles are washed with hot ethanol solution, dried at room temperature, and ground into powder.

[0070] A suspending agent was obtained by mixing 10 parts of polymer powder with 80 parts of intercalated modified mineral fiber.

[0071] Comparative Example 1

[0072] According to the weight proportions of each component, 300 parts by weight of water, 100 parts by weight of 2-acrylamide-2-methylpropanesulfonic acid, 5 parts by weight of N,N-diethylacrylamide, 8 parts by weight of N-vinylpyrrolidone, and 0.5 parts by weight of itaconic acid were added to the reactor in sequence to obtain a reaction solution. The reaction solution was stirred at a speed of 200 rpm, the pH of the reaction solution was adjusted to 6, and the temperature of the reaction solution was raised to 60°C. After all components were dissolved, ammonium persulfate initiator was added to the reaction solution, the reaction was carried out for 2 hours, cooled to room temperature, and then microwave-dried and pulverized to obtain polymer powder.

[0073] A suspending agent was obtained by mixing 5 parts of polymer powder with 100 parts of unmodified mineral fiber.

[0074] Comparative Example 2

[0075] According to the weight proportions of each component, 300 parts by weight of water, 100 parts by weight of 2-acrylamide-2-methylpropanesulfonic acid, 5 parts by weight of N,N-diethylacrylamide, 0.3 parts by weight of N,N-methylenebisacrylamide, 8 parts by weight of N-vinylpyrrolidone, and 0.5 parts by weight of itaconic acid were added to the reactor in sequence to obtain a reaction solution. The reaction solution was stirred at a speed of 200 rpm, the pH of the reaction solution was adjusted to 6, and the temperature of the reaction solution was raised to 60°C. After all components were dissolved, ammonium persulfate initiator was added to the reaction solution, the reaction was carried out for 2 hours, cooled to room temperature, and then microwave-dried and pulverized to obtain polymer powder.

[0076] A suspending agent was obtained by mixing 5 parts of polymer powder with 100 parts of unmodified mineral fiber.

[0077] For Examples 1-3 and Comparative Examples 1-2, one set each of low, conventional, and high-density isolation fluids with concentrations of 1.50, 1.90, and 2.40 g / cm³ were designed, as detailed in Table 1. The water used was tap water from Tanggu, and the suspending agent was the product of this patent. The water loss reducing agent was BCF-230L, the flushing agent was BCS-010L, the drag reducing agent was BCD-210L, the retarder was BCR-500L, the defoamer was G603, and the weighting agents barite, micro-manganese, and industrial salt were all purchased from Tianjin Zhongyou Boxing Engineering Technology Co., Ltd.

[0078] Table 1. Separating Fluid Formulation

[0079]

[0080]

[0081] Density is 1.50 g / cm³ 3 The performance of the isolation fluid relative to the suspending agents of Examples 1-3 and Comparative Examples 1-2 is detailed in Table 2.

[0082] Table 2 contains the 1.50 g / cm³ values ​​of the suspensions from the three examples and two comparative examples mentioned above. 3 performance of isolation fluid

[0083]

[0084] The density is 1.90 g / cm³. 3 The performance of the isolation fluid relative to the suspending agents of Examples 1-3 and Comparative Examples 1-2 is detailed in Table 3.

[0085] Table 3 contains the 1.90 g / cm³ values ​​of the suspensions from the three examples and two comparative examples mentioned above. 3 performance of isolation fluid

[0086]

[0087] The density is 2.40 g / cm³. 3 The performance of the isolation fluid relative to the suspending agents of Examples 1-3 and Comparative Examples 1-2 is detailed in Table 4.

[0088] Table 4 contains the 2.40 g / cm³ values ​​of the suspensions from the three examples and two comparative examples mentioned above. 3 performance of isolation fluid

[0089]

[0090]

[0091] As can be seen from Tables 2-4: the suspensions in the three examples and two comparative examples were at 1.50 g / cm³. 3 1.90g / cm 3 and 2.40 g / cm 3 The three isolation liquids exhibited essentially the same performance. When the polymer in the suspending agent did not contain crosslinking monomers and the mineral materials were unmodified, such as in Comparative Example 1, the isolation liquid prepared from it showed slow ash settling at 240℃ for more than 68 seconds; its rheological properties were poor, with a K value greater than 0.45 Pa·s. n The above indicates poor settling stability, with a density difference greater than 0.30 g / cm³. 3 The above-mentioned free fluid concentrations exceeding 0.8% do not meet the requirements for cementing operations. When crosslinking monomers are added to the polymer in the suspending agent and the mineral materials are not modified, as in Comparative Example 2, the free fluid concentration is significantly improved, becoming zero; settling stability is also somewhat improved, but still does not meet the cementing requirements; rheological properties deteriorate, showing a certain thickening trend, and overall still does not meet the cementing requirements. Meanwhile, compared to Comparative Examples 1 and 2, the three isolation fluids prepared in Examples 1, 2, and 3 have a faster ash settling time, which can be controlled within 40 seconds; they also have good rheological properties, with the K value controlled at 0.15 Pa·s. nWithin a certain range; it exhibits good settling stability at high temperatures, with the density difference between the upper and lower sections controllable to within 0.04, and zero free fluid; it also demonstrates good compressive strength and excellent overall performance. It meets the stringent requirements of ultra-high temperature cementing operations at 240℃. Figure 1 The curing experiment in Example 1 was conducted at 240°C. As can be seen from the figure, the consistency of the isolation liquid hardly changed as the temperature increased, indicating that the sedimentation stability of the isolation liquid was good under high-temperature curing conditions.

[0092] In summary, the high-temperature resistant and salt-resistant suspending agent for isolation fluid and its preparation method disclosed in this invention have the following beneficial technical effects: This suspending agent is particularly suitable for high-temperature salt-resistant isolation fluid systems; by adding a crosslinking agent, the polymer forms a micro-crosslinked polymer with a spatial network structure, which can not only ensure the ash release time and rheological properties at low temperatures, but also improve the suspension performance of the isolation fluid at high temperatures; by intercalating and modifying the inorganic minerals to make them rich in carboxyl groups, on the one hand, their dispersion performance is improved, and on the other hand, the suspension stability of the isolation fluid under high-temperature and salt-containing conditions is further improved; by combining the two, the advantages of both are further utilized; the suspending agent prepared by this invention has the characteristics of good salt resistance, fast ash release, good rheological properties at low temperatures, and good stability at high temperatures, with good comprehensive performance, which can effectively ensure the safety of cementing operations and improve cementing quality.

[0093] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0094] Finally, it should be noted that the above embodiments are merely examples for clearly illustrating the present invention and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A high-temperature resistant and salt-resistant suspending agent for isolation fluid, characterized in that, It includes the following components in parts by weight: high molecular weight polymer, 5-10 parts; modified inorganic minerals, 80-100 parts; The polymer comprises the following components in parts by weight: 2-acrylamide-2-methylpropanesulfonic acid, 100 parts; N,N-diethylacrylamide, 5-10 parts; cyclic monomer, 8-10 parts; crosslinking agent, 0.3-0.5 parts; carboxylic acid monomer, 0.5-1.0 parts; and water, 300-400 parts. The modified inorganic minerals include raptosite fibers and basalt fibers that have undergone intercalation modification.

2. The high-temperature resistant and salt-resistant suspending agent for the isolation fluid according to claim 1, characterized in that: The crosslinking agent is N,N-methylenebisacrylamide.

3. The high-temperature resistant and salt-resistant suspending agent for the isolation fluid according to claim 2, characterized in that: The polymer forms a micro-crosslinked structure, with a molecular weight controlled between 1 million and 1.5 million and a molecular weight distribution of 1.5 to 2.

0.

4. The high-temperature resistant and salt-resistant suspending agent for the isolation fluid according to claim 1, characterized in that: The cyclic monomer is at least one of N-vinylpyrrolidone and 4-vinylpyridine.

5. The high-temperature resistant and salt-resistant suspending agent for the isolation fluid according to claim 1, characterized in that: The carboxylic acid monomer is at least one of itaconic acid and acrylic acid.

6. A method for preparing a high-temperature resistant and salt-resistant suspending agent for a separating fluid, characterized in that, include: Polymer preparation involves sequentially adding water, 2-acrylamide-2-methylpropanesulfonic acid, N,N-diethylacrylamide, cyclic monomers, crosslinking agents, and carboxylic acid monomers into a reactor to obtain a reaction solution. The solution is stirred and the pH value is adjusted. After adding an initiator and reacting, the solution is dried and pulverized to obtain polymer powder. The modified inorganic mineral preparation involves soaking the inorganic mineral in acid to remove impurities and washing it until neutral, then ultrasonically pulverizing and dispersing it, adjusting the pH value to a preset value, adding an initiator to initiate polymerization, and grinding the inorganic mineral components. The suspending agent is prepared by mixing the prepared polymer and the inorganic mineral modified powder in a preset ratio to obtain the suspending agent.

7. The method for preparing the high-temperature resistant and salt-resistant suspending agent for the isolation fluid according to claim 6, characterized in that, The polymer preparation includes: According to the weight proportions of each component, water, 2-acrylamide-2-methylpropanesulfonic acid, N,N-diethylacrylamide, cyclic monomer, crosslinking agent and carboxylic acid monomer were added to the reactor in sequence to obtain the reaction solution; Stir at 200 rpm until all components are dissolved, adjust the pH of the reaction solution to 6-7, and raise the temperature of the reaction solution to 50-60°C. An initiator was added to the reaction solution, and the reaction was carried out for 2-3 hours. The mixture was then cooled to room temperature to obtain colorless and pale yellow viscous liquids. After microwave drying and pulverization, polymer powder materials were obtained.

8. The method for preparing the high-temperature resistant and salt-resistant suspending agent for the isolation fluid according to claim 6, characterized in that, The preparation of the modified inorganic minerals includes: Soak attapulgite fibers or basalt fibers in a 10% dilute hydrochloric acid solution to remove impurities such as carbonates, and then rinse them repeatedly with deionized water until neutral to obtain pure attapulgite fibers or basalt fibers. Pure raptor fiber or basalt fiber is added to deionized water and dispersed evenly using an ultrasonic cell disruptor. Liquid acrylic acid was adjusted to pH 6 with a 28% sodium hydroxide solution and then added to a fiber dispersion. The mixture was heated to 60°C, and an initiator was added to initiate polymerization. The polymer particles were washed with hot ethanol solution, dried at room temperature, and then ground into powder.

9. The method for preparing the high-temperature resistant and salt-resistant suspending agent for the isolation fluid according to claim 7, characterized in that: The initiator is at least one selected from ammonium persulfate, potassium persulfate, azobisisobutyramidine hydrochloride, and azobisisobutyramidine hydrochloride.

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