Salt-resistant water-dispersible material for oil well cement and method for producing the same

Abstract

The application discloses a salt-resistant water-non-dispersible material for oil well cement and a preparation method thereof. The salt-resistant water-non-dispersible material for oil well cement comprises the following components in the form of weight parts: 100 parts of N,N-dimethyl acrylamide, 3-6 parts of acrylic acid, 10-20 parts of 2-acrylamide-2-methylpropanesulfonic acid, 5-15 parts of a cyclic monomer, 0.1-0.4 parts of a branching agent, 5-15 parts of a cationic monomer, 0.3-3 parts of a crosslinking agent and 400-500 parts of water. The salt-resistant water-non-dispersible material prepared by the application has good salt resistance, can significantly improve the anti-dispersion performance of the cement slurry when used in a salt water and sea water cement slurry system with a NaCl content of 18 wt% or less, and has excellent rheological performance.

Description

Technical Field

[0001] This invention relates to the field of cementing engineering in oil and gas drilling operations, and more particularly to a salt-resistant, water-resistant, non-dispersible material for oil well cement and its preparation method. Background Technology

[0002] Currently, many oilfields both domestically and internationally that have entered the late stages of development commonly have high-pressure brine layers (or brines). During cementing in high-water-cut formations, traditional cement slurry is easily diluted and washed away by formation water during the setting process, causing cement erosion in the water-bearing section, reducing the quality of interfacial bonding, and compromising the integrity of the cement sheath seal.

[0003] In recent years, considerable research has been conducted on problems such as water intrusion and water channeling that are prone to occur during cementing of high water-cut oil and gas wells. However, existing anti-water intrusion cement slurries do not take into account the situation of seawater or brine slurry preparation, and cannot be used in cementing operations of water-cut and high water-cut oil and gas wells in brine layers (brine layers) as well as in offshore cementing operations. This seriously restricts the normal production of oil and gas wells and affects the exploitation efficiency of oil and gas fields. Summary of the Invention

[0004] This invention provides a salt-resistant, water-resistant, non-dispersible material for oil well cement and its preparation method, which can solve the water intrusion problem in cementing operations with high salt and high water content.

[0005] This invention provides a salt-resistant, water-resistant, non-dispersible material for oil well cement, comprising the following components in parts by weight: 100 parts by weight of N,N-dimethylacrylamide, 3-6 parts by weight of acrylic acid, 10-20 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 5-15 parts by weight of a cyclic monomer, 0.1-0.4 parts by weight of a branching agent, 5-15 parts by weight of a cationic monomer, 0.3-3 parts by weight of a crosslinking agent, and 400-500 parts by weight of water.

[0006] Furthermore, the cyclic monomer includes at least one of N-vinylpyrrolidone, N-vinylvalerolamide, and N-vinylcaprolactam.

[0007] Furthermore, the branching agents include pentaerythritol and / or dipentaerythritol.

[0008] Furthermore, the cationic monomer includes at least one of acryloyloxyethyltrimethylammonium chloride, dimethyldiallylammonium chloride, and dimethyldiallylammonium bromide.

[0009] Furthermore, the crosslinking agent includes at least one of 3-allyloxy-2-hydroxypropanesulfonic acid, N,N-methylenediacrylamide, hydroxyethyl acrylate, and hydroxyethyl methacrylate.

[0010] This invention also provides a method for preparing the above-mentioned salt-resistant, water-resistant non-dispersible material for oil well cement, comprising the following steps: N,N-dimethylacrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, a cyclic monomer, a branching agent, and water are added sequentially to a reaction vessel according to the weight proportions of each component to obtain a reaction solution. The air in the reaction vessel is replaced with an inert gas, and the mixture is stirred at 100 rpm. After all components are completely dissolved, the pH value of the reaction solution is adjusted to 7-9, and the temperature of the reaction solution is raised to 35-55°C. An initiator is added dropwise to the reaction solution, and after reacting for 0.5-1 hour, a mixed solution of a cationic monomer and a crosslinking agent is added dropwise. The reaction is continued for 3-4 hours, and the temperature of the reaction solution is cooled to room temperature to obtain the salt-resistant, water-resistant non-dispersible material for oil well cement.

[0011] Furthermore, the initiators include cerium ammonium sulfate and / or cerium ammonium nitrate.

[0012] Furthermore, the weight ratio of initiator to branching agent is 3:1 to 4:1.

[0013] Furthermore, the inert gases include nitrogen and / or argon.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] The salt-resistant, water-resistant non-dispersible material prepared in this invention is a hyperbranched cationic polymer with a spherical structure. The cations neutralize the negative charge on the surface of cement particles, reducing electrostatic repulsion between particles, inducing particle aggregation, and improving the cohesion of the cement slurry system, thus resisting the intrusion of external water. The salt-resistant, water-resistant non-dispersible material also exhibits a "bonding-bridging" effect with cement particles, adsorbing a single polymer onto the surface of multiple cement particles, maintaining the cohesion of the cement slurry system within a suitable range. This resolves the contradiction between cement slurry flocculation and good fluidity, allowing the cement slurry to maintain good bulk (slurry) integrity even under the scouring of external water and high-mineralized water, achieving the effect of non-dispersion and non-segregation, demonstrating significant water-resistant non-dispersible properties. The addition of N,N-dimethylacrylamide forms the skeletal structure of the salt-resistant, water-resistant non-dispersible material, increasing the polymer molecular weight and facilitating the charge neutralization and "bonding-bridging" effects between a single salt-resistant, water-resistant non-dispersible material and multiple cement particles. The addition of acrylic acid and carboxyl groups on the cement particles... 2+Electrostatic attraction enhances the bonding force between the salt-resistant, water-resistant non-dispersible material and cement particles. Adding 2-acrylamido-2-methylpropanesulfonic acid introduces sulfonic acid groups, improving the salt resistance of the material to some extent. Adding cyclic monomers increases the rigidity of the polymer molecular chain, improving the temperature resistance of the material. Adding branching agents increases the branched structure of the material, which on the one hand facilitates the polymerization of spherical hyperbranched polymers, improving the polymer's salt resistance; on the other hand, it reduces the polymer's viscosity, improving the anti-dispersion properties of the water-resistant cement slurry while maintaining its excellent rheological properties. By adding cationic monomers, on the one hand, the positive charge of the salt-resistant water-dispersible material is increased, neutralizing the negative charge on the surface of cement particles, reducing electrostatic repulsion between particles, inducing particle aggregation, and improving the cohesion of the cement slurry system to resist the intrusion of external water. On the other hand, through the mutual attraction of positive and negative charges, the salt-resistant water-dispersible material is adsorbed onto the surface of cement particles. Combined with the structural characteristics of spherical hyperbranched polymers, each polymer chain segment is adsorbed onto the surface of multiple cement particles, enhancing the cohesion of the cement slurry system. By adding crosslinking agents, multiple molecular chains are bonded and crosslinked to form a three-dimensional network structure. The three-dimensional network structure in aqueous solution is beneficial to enhancing the cohesion of the cement slurry and improving its ability to resist the intrusion of external water. The three-dimensional network structure also increases the connection between the chains of the salt-resistant water-dispersible material and can maintain the stability of this connection under certain mineralization conditions, enhancing the salt resistance of the polymer. By optimizing the free radical polymerization conditions, the molecular weight of the salt-resistant water-dispersible material is controlled within a suitable range. This ensures that the molecular weight is not too small to coat multiple cement particles and thus lacks anti-dispersibility, nor that the molecular weight is too large, which would increase the viscosity of the system and cause the water-dispersible cement slurry to be too thick. The salt-resistant, water-resistant, non-dispersible material prepared by this invention has good salt resistance. When used in brine and seawater cement slurry systems with NaCl content below 18% wt%, it can still significantly improve the anti-dispersion performance of the cement slurry. At the same time, it also has excellent rheological properties, meeting the needs of cementing operations in brine (brine) layers of water-bearing and high-water-cut oil and gas wells, as well as the preparation of cement slurries with high-mineralization water such as brine and seawater during offshore cementing. It avoids the erosion of cement slurry by formation water, ensures the smooth progress of cementing construction, and improves the cementing quality of water-bearing and high-water-cut oil and gas wells, especially the cementing quality of brine (brine) layer sections. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 The graph shows the relationship between the root mean square radius and molar mass of the samples in Example 1 and Comparative Example 4 of this invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] During cementing in high water-cut formations, traditional cement slurries are easily diluted by formation water during the setting process, causing cement erosion in the water-bearing zone, reducing the interfacial bonding quality, and compromising the integrity of the cement sheath seal. Existing water-resistant cement slurries do not consider the use of seawater or brine in their preparation, making them unsuitable for cementing operations in water-bearing and high water-cut oil and gas wells in brine formations, as well as for offshore cementing operations. This severely restricts normal oil and gas well production and affects the efficiency of oil and gas field extraction. Therefore, embodiments of this invention provide a salt-resistant, water-resistant non-dispersible material for oil well cement, used to prepare salt-resistant, water-resistant non-dispersible cement slurry. The salt-resistant, water-resistant, non-dispersible material comprises the following components in parts by weight: 100 parts by weight of N,N-dimethylacrylamide, 3-6 parts by weight of acrylic acid, 10-20 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 5-15 parts by weight of cyclic monomers, 0.1-0.4 parts by weight of branching agent, 5-15 parts by weight of cationic monomers, 0.3-3 parts by weight of crosslinking agent, and 400-500 parts by weight of water.

[0020] In particular, by adding N,N-dimethylacrylamide, a skeleton structure of salt-resistant water-dispersible material is formed, which increases the molecular weight of the polymer and facilitates the occurrence of charge neutralization and "bonding-bridging" effects between individual salt-resistant water-dispersible materials and multiple cement particles.

[0021] Acrylic acid can be used in amounts of 3, 5, or 6 parts by weight. Acrylic acid provides an anchoring group for salt-resistant, water-resistant, non-dispersible materials; the carboxyl groups bind with the CaO on the cement particles. 2+ Electrostatic attraction and adsorption help to enhance the bonding force between salt-resistant, water-resistant non-dispersible materials and cement particles, thereby enhancing the non-dispersible effect when exposed to water.

[0022] The amount of 2-acrylamide-2-methylpropanesulfonic acid can be 10, 15, or 20 parts by weight. By adding 2-acrylamide-2-methylpropanesulfonic acid to introduce sulfonic acid groups, the salt resistance of the salt-resistant, water-resistant, non-dispersible material can be improved to some extent.

[0023] The amount of cyclic monomer can be 5, 10, or 15 parts by weight. The cyclic monomer includes at least one of N-vinylpyrrolidone, N-vinylvalerolamide, and N-vinylcaprolactam. The cyclic monomer can be N-vinylpyrrolidone, N-vinylvalerolamide, or a mixture of N-vinylvalerolamide and N-vinylcaprolactam. N-vinylpyrrolidone, N-vinylvalerolamide, and N-vinylcaprolactam all possess heterocyclic structures, increasing the rigidity of the polymer molecular chain and improving the salt resistance and temperature resistance of the water-resistant non-dispersible material.

[0024] The amount of branching agent can be 0.1, 0.2, or 0.4 parts by weight. The branching agent includes pentaerythritol and / or dipentaerythritol. The branching agent can be pentaerythritol, dipentaerythritol, or a mixture of pentaerythritol and dipentaerythritol. Pentaerythritol and dipentaerythritol increase the branched structure of salt-resistant, water-resistant, non-dispersible materials. On the one hand, this facilitates the polymerization of spherical hyperbranched polymers, improving the polymer's salt resistance; on the other hand, it reduces the polymer's viscosity, improving the anti-dispersion properties of water-resistant cement slurry while ensuring excellent rheological properties.

[0025] The amount of cationic monomer used can be 5, 10, or 15 parts by weight. The cationic monomer includes at least one of acryloyloxyethyltrimethylammonium chloride, dimethyl diallyl ammonium chloride, and dimethyl diallyl ammonium bromide. The cationic monomer can be acryloyloxyethyltrimethylammonium chloride, dimethyl diallyl ammonium chloride, or a mixture of dimethyl diallyl ammonium chloride and dimethyl diallyl ammonium bromide, etc. Acryloyloxyethyltrimethylammonium chloride, dimethyl diallyl ammonium chloride, and dimethyl diallyl ammonium bromide, on the one hand, increase the positive charge of the salt-resistant water-resistant non-dispersible material, neutralize the negative charge on the surface of cement particles, reduce the electrostatic repulsion between particles, induce particle aggregation, improve the cohesion of the cement paste system, and resist the intrusion of external water; on the other hand, through the mutual attraction of positive and negative charges, the salt-resistant water-resistant non-dispersible material is adsorbed onto the surface of cement particles. Combined with the structural characteristics of spherical hyperbranched polymers, each polymer segment is adsorbed onto the surface of multiple cement particles, enhancing the cohesion of the cement paste system.

[0026] The amount of crosslinking agent can be 0.3, 1, or 3 parts by weight. The crosslinking agent includes at least one of 3-allyloxy-2-hydroxypropanesulfonic acid, N,N-methylenediacrylamide, hydroxyethyl acrylate, and hydroxyethyl methacrylate. The crosslinking agent can be 3-allyloxy-2-hydroxypropanesulfonic acid, N,N-methylenediacrylamide, or a mixture of hydroxyethyl acrylate and hydroxyethyl methacrylate. 3-allyloxy-2-hydroxypropanesulfonic acid, N,N-methylenediacrylamide, hydroxyethyl acrylate, and hydroxyethyl methacrylate crosslink multiple molecular segments to form a three-dimensional network structure. This three-dimensional network structure in aqueous solution enhances the cohesion of the cement slurry and improves its resistance to external water intrusion. Furthermore, the three-dimensional network structure increases the connection between segments of salt-resistant, water-dispersible materials and maintains the stability of this connection under certain salinity conditions, thus enhancing the polymer's salt resistance.

[0027] The amount of water used can be 400, 450, or 500 parts by weight.

[0028] In summary, the salt-resistant water-resistant non-dispersible material is a hyperbranched cationic polymer with a spherical structure. The cations neutralize the negative charge on the surface of cement particles, reducing electrostatic repulsion between particles, inducing particle aggregation, and increasing the cohesion of the cement paste system, thus resisting the intrusion of external water. The salt-resistant water-resistant non-dispersible material also exhibits a "bonding-bridging" effect with cement particles, adsorbing individual polymers onto the surface of multiple cement particles, maintaining the cohesion of the cement paste system within a suitable range. This resolves the contradiction between cement paste flocculation and good fluidity, allowing the cement paste to maintain good bulk (paste) integrity even under the scouring of external water and high-mineralized water, achieving a non-dispersible and non-segregating effect, demonstrating significant water-resistant non-dispersible properties. The addition of N,N-dimethylacrylamide forms the framework structure of the salt-resistant water-resistant non-dispersible material, increasing the polymer molecular weight and facilitating charge neutralization and "bonding-bridging" effects between individual salt-resistant water-resistant non-dispersible materials and multiple cement particles. The addition of acrylic acid and carboxyl groups interacts with the Ca on the cement particles... 2+Electrostatic attraction enhances the bonding force between the salt-resistant, water-resistant non-dispersible material and cement particles. Adding 2-acrylamido-2-methylpropanesulfonic acid introduces sulfonic acid groups, improving the salt resistance of the material to some extent. Adding cyclic monomers increases the rigidity of the polymer molecular chain, improving the temperature resistance of the material. Adding branching agents increases the branched structure of the material, which on the one hand facilitates the polymerization of spherical hyperbranched polymers, improving the polymer's salt resistance; on the other hand, it reduces the polymer's viscosity, improving the anti-dispersion properties of the water-resistant cement slurry while maintaining its excellent rheological properties. By adding cationic monomers, on the one hand, the positive charge of the salt-resistant water-dispersible material is increased, neutralizing the negative charge on the surface of cement particles, reducing electrostatic repulsion between particles, inducing particle aggregation, and improving the cohesion of the cement slurry system to resist the intrusion of external water. On the other hand, through the mutual attraction of positive and negative charges, the salt-resistant water-dispersible material is adsorbed onto the surface of cement particles. Combined with the structural characteristics of spherical hyperbranched polymers, each polymer chain segment is adsorbed onto the surface of multiple cement particles, enhancing the cohesion of the cement slurry system. By adding crosslinking agents, multiple molecular chains are bonded and crosslinked to form a three-dimensional network structure. The three-dimensional network structure in aqueous solution is beneficial to enhancing the cohesion of the cement slurry and improving its ability to resist the intrusion of external water. The three-dimensional network structure also increases the connection between the chains of the salt-resistant water-dispersible material and can maintain the stability of this connection under certain mineralization conditions, enhancing the salt resistance of the polymer. By optimizing the free radical polymerization conditions, the molecular weight of the salt-resistant water-dispersible material is controlled within a suitable range. This ensures that the molecular weight is not too small to coat multiple cement particles and thus lacks anti-dispersibility, nor that the molecular weight is too large, which would increase the viscosity of the system and cause the water-dispersible cement slurry to be too thick.

[0029] The salt-resistant, water-resistant, non-dispersible material prepared in this invention exhibits excellent salt resistance. When used in brine and seawater cement slurry systems with NaCl content below 18% wt%, it significantly improves the anti-dispersion performance of the cement slurry. Simultaneously, it possesses excellent rheological properties, meeting the needs of cementing operations in brine (saltwater) layers of water-bearing and high-water-cut oil and gas wells, as well as in offshore cementing operations using brine, seawater, and other high-mineralized water to prepare cement slurries. This avoids formation water erosion of the cement slurry, ensures smooth cementing operations, and improves the cementing quality of water-bearing and high-water-cut oil and gas wells, especially in brine (saltwater) layer sections.

[0030] An embodiment of the present invention also provides a method for preparing the above-mentioned salt-resistant, water-resistant, non-dispersible material for oil well cement, comprising the following steps:

[0031] Step 1: According to the weight proportions of each component, add N,N-dimethylacrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, cyclic monomer, branching agent and water to the reaction vessel in sequence to obtain the reaction solution.

[0032] In the above steps, the weight parts of each component are as follows: 100 parts by weight of N,N-dimethylacrylamide, 3-6 parts by weight of acrylic acid, 10-20 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 5-15 parts by weight of the cyclic monomer, 0.1-0.4 parts by weight of the branching agent, and 400-500 parts by weight of water. The corresponding weight parts of each component are added sequentially to the reaction vessel.

[0033] The reaction vessel can be a four-necked flask equipped with a thermometer, stirrer, and gas delivery tube.

[0034] Step 2: Replace the air in the reaction vessel with inert gas, stir at 100 rpm, and after all components are completely dissolved, adjust the pH value of the hydrogen ion concentration index of the reaction solution to 7-9, and raise the temperature of the reaction solution to 35-55℃.

[0035] In the above steps, the inert gas includes nitrogen and / or argon. The inert gas can be nitrogen, argon, or a mixture of nitrogen and argon.

[0036] The pH value of the reaction solution can be adjusted using NaOH solution. The concentration of the NaOH solution can be prepared and changed as needed; in this embodiment of the invention, no specific limitation is made. For example, the concentration of the NaOH solution can be 0.05 mol / L, 0.1 mol / L, 0.15 mol / L, etc. The pH value can be adjusted to 7, 8, 9, etc. The temperature of the reaction solution can be increased to 35, 45, 55°C, etc.

[0037] Step 3: Add an initiator to the reaction solution. After reacting for 0.5 to 1 hour, add a mixed solution of cationic monomer and crosslinking agent. After reacting for 3 to 4 hours, cool the reaction solution to room temperature to obtain a salt-resistant material that does not disperse in water.

[0038] In the above steps, the initiator includes ceric ammonium sulfate and / or ceric ammonium nitrate. The initiator can be ceric ammonium sulfate, ceric ammonium nitrate, or a mixture of both. The weight ratio of initiator to branching agent is 3:1 to 4:1, and can be 3:1, 3.5:1, 4:1, etc. A water-soluble initiator is selected based on the polymerization process principle for free radical polymerization. By optimizing the free radical polymerization conditions, the molecular weight of the salt-resistant, water-resistant, non-dispersible material is controlled within a suitable range. This ensures that the molecular weight is not too small to coat multiple cement particles, resulting in no anti-dispersibility, nor too large, leading to excessively high viscosity in the cement slurry. The reaction time can be 0.5, 0.8, or 1 hour after adding the initiator. The reaction time can be 3, 3.5, or 4 hours after adding a mixed solution of cationic monomer and crosslinking agent.

[0039] The salt-resistant, water-resistant, non-dispersible material of the present invention is a colorless or pale yellow transparent liquid with a slight viscosity.

[0040] The preparation method of the above-mentioned salt-resistant, water-resistant, non-dispersible material is simple and the process is controllable. It is suitable for preparing cement slurry in brine and seawater, and provides a new material for brine layers (brine layers) in water-bearing and high-water-content oil and gas wells as well as for offshore cementing operations.

[0041] The salt-resistant, water-resistant, non-dispersible material provided in this invention is suitable for preparing cement slurries using high-mineralized water such as brine and seawater. When used in brine and seawater cement slurry systems with a NaCl content of less than 18% wt%, it significantly improves the water-resistant, non-dispersible properties of the cement slurry while ensuring excellent rheological properties. It has a good anti-water intrusion effect, avoids the erosion of cement slurry by formation water, ensures the smooth progress of cementing operations, and improves the cementing quality of water-bearing and high-water-cut oil and gas wells, especially the cementing quality of brine (saltwater) layers.

[0042] The following detailed description is provided with reference to specific embodiments:

[0043] Example 1

[0044] According to the weight proportions of each component, 100 parts by weight of N,N-dimethylacrylamide, 3 parts by weight of acrylic acid, 10 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 5 parts by weight of N-vinylpyrrolidone, 0.1 parts by weight of pentaerythritol, and 400 parts by weight of water were added sequentially to the reaction vessel to obtain a reaction solution. Nitrogen gas was purged into the reaction vessel to replace the air, and the mixture was stirred at 100 rpm until all components were completely dissolved. The pH value of the reaction solution was adjusted to 7, and the temperature of the reaction solution was raised to 35°C. 0.3 parts by weight of cerium ammonium sulfate was added dropwise to the reaction solution. After reacting for 0.5 hours, a mixed solution of 5 parts by weight of dimethyldiallylammonium chloride and 0.3 parts by weight of 3-allyloxy-2-hydroxypropanesulfonic acid was added dropwise. The reaction was continued for 3 hours, and the temperature of the reaction solution was cooled to room temperature to obtain sample 1 of a salt-resistant, water-insoluble material.

[0045] Example 2

[0046] According to the weight proportions of each component, 100 parts by weight of N,N-dimethylacrylamide, 6 parts by weight of acrylic acid, 20 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 15 parts by weight of N-vinylcaprolactam, 0.4 parts by weight of dipentaerythritol, and 500 parts by weight of water were added sequentially to the reaction vessel to obtain a reaction solution. Argon gas was used to replace the air in the reaction vessel, and the mixture was stirred at a speed of 100 rpm. After all components were completely dissolved, the pH value of the reaction solution was adjusted to 9, and the temperature of the reaction solution was raised to 55°C. 1.2 parts by weight of cerium ammonium nitrate were added dropwise to the reaction solution. After reacting for 1 hour, a mixed solution of 15 parts by weight of acryloyloxyethyltrimethylammonium chloride and 3 parts by weight of N,N-methylenediacrylamide was added dropwise. After reacting for 4 hours, the temperature of the reaction solution was cooled to room temperature to obtain sample 2 of salt-resistant, water-insoluble material.

[0047] Example 3

[0048] According to the weight proportions of each component, 100 parts by weight of N,N-dimethylacrylamide, 4.5 parts by weight of acrylic acid, 15 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 10 parts by weight of N-vinylpyrrolidone, 0.2 parts by weight of pentaerythritol, and 450 parts by weight of water were added sequentially to the reaction vessel to obtain a reaction solution. Nitrogen gas was purged to replace the air in the reaction vessel, and the mixture was stirred at a speed of 100 rpm. After all components were completely dissolved, the pH value of the reaction solution was adjusted to 8, and the temperature of the reaction solution was raised to 45°C. 0.8 parts by weight of cerium ammonium sulfate was added dropwise to the reaction solution. After reacting for 0.7 hours, a mixed solution of 10 parts by weight of dimethyldiallylammonium chloride and 1.7 parts by weight of 3-allyloxy-2-hydroxypropanesulfonic acid was added dropwise. After reacting for 3.5 hours, the temperature of the reaction solution was cooled to room temperature to obtain sample 3 of a salt-resistant, water-insoluble material.

[0049] Comparative Example 1

[0050] 240 ml of water, 15 g of acrylamide, 12 g of 2-acrylamido-2-methylpropanesulfonic acid, 2.2 g of vinyltrimethoxysilane, 5 g of sodium vinylsulfonate, 80 g of N,N-dimethylacrylamide, 15 g of acryloyloxyethyltrimethylammonium chloride, 20 g of dimethyldiallylammonium chloride, 17 g of N-vinylpyrrolidone, and 1 g of disodium ethylenediaminetetraacetate were added sequentially to the reaction vessel. The mixture was stirred at 25°C-35°C until completely dissolved. After dissolution, the reaction vessel was placed in a constant temperature water bath, and the water bath temperature was raised to 70°C. When the solution temperature in the reaction vessel reached 40°C, 1 g of ammonium persulfate solution was added to the above mixture and stirred evenly. Then, 1 g of azobisisobutyramidine hydrochloride solution was added, and the reaction was carried out for 4 hours to obtain control sample 1.

[0051] Comparative Example 2

[0052] According to the weight proportions of each component, 100 parts by weight of N,N-dimethylacrylamide, 10 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 5 parts by weight of N-vinylpyrrolidone, 0.1 parts by weight of pentaerythritol, and 400 parts by weight of water were added sequentially to the reaction vessel to obtain a reaction solution. Nitrogen gas was used to purge the air from the reaction vessel, and the mixture was stirred at 100 rpm. After all components were completely dissolved, the pH value of the reaction solution was adjusted to 7, and the temperature of the reaction solution was raised to 35°C. 0.3 parts by weight of cerium ammonium sulfate was added dropwise to the reaction solution. After reacting for 0.5 hours, a mixed solution of 5 parts by weight of dimethyldiallylammonium chloride and 0.3 parts by weight of 3-allyloxy-2-hydroxypropanesulfonic acid was added dropwise. The reaction was continued for 3 hours, and the temperature of the reaction solution was cooled to room temperature to obtain control sample 2.

[0053] Comparative Example 3

[0054] According to the weight proportions of each component, 100 parts by weight of N,N-dimethylacrylamide, 3 parts by weight of acrylic acid, 10 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 0.1 parts by weight of pentaerythritol, and 400 parts by weight of water were added sequentially to the reaction vessel to obtain a reaction solution. Nitrogen gas was used to purge the air from the reaction vessel, and the mixture was stirred at 100 rpm. After all components were completely dissolved, the pH value of the reaction solution was adjusted to 7, and the temperature of the reaction solution was raised to 35°C. 0.3 parts by weight of cerium ammonium sulfate was added dropwise to the reaction solution. After reacting for 0.5 hours, a mixed solution of 5 parts by weight of dimethyldiallylammonium chloride and 0.3 parts by weight of 3-allyloxy-2-hydroxypropanesulfonic acid was added dropwise. The reaction was continued for 3 hours, and the temperature of the reaction solution was cooled to room temperature to obtain control sample 3.

[0055] Comparative Example 4

[0056] According to the weight proportions of each component, 100 parts by weight of N,N-dimethylacrylamide, 3 parts by weight of acrylic acid, 10 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 5 parts by weight of N-vinylpyrrolidone, and 400 parts by weight of water were added sequentially to the reaction vessel to obtain a reaction solution. Nitrogen gas was purged into the reaction vessel to replace the air, and the mixture was stirred at 100 rpm. After all components were completely dissolved, the pH value of the reaction solution was adjusted to 7, and the temperature of the reaction solution was raised to 35°C. 0.3 parts by weight of cerium ammonium sulfate was added dropwise to the reaction solution. After reacting for 0.5 hours, a mixed solution of 5 parts by weight of dimethyldiallylammonium chloride and 0.3 parts by weight of 3-allyloxy-2-hydroxypropanesulfonic acid was added dropwise. The reaction was continued for 3 hours, and the temperature of the reaction solution was cooled to room temperature to obtain control sample 4.

[0057] Comparative Example 5

[0058] According to the weight proportions of each component, 100 parts by weight of N,N-dimethylacrylamide, 3 parts by weight of acrylic acid, 10 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 5 parts by weight of N-vinylpyrrolidone, 0.1 parts by weight of pentaerythritol, and 400 parts by weight of water were added sequentially to the reaction vessel to obtain a reaction solution. Nitrogen gas was purged into the reaction vessel to replace the air, and the mixture was stirred at a speed of 100 rpm. After all components were completely dissolved, the pH value of the reaction solution was adjusted to 7, and the temperature of the reaction solution was raised to 35°C. 0.3 parts by weight of cerium ammonium sulfate was added dropwise to the reaction solution, and after reacting for 0.5 hours, 0.3 parts by weight of 3-allyloxy-2-hydroxypropanesulfonic acid was added dropwise. After reacting for 3 hours, the temperature of the reaction solution was cooled to room temperature to obtain control sample 5.

[0059] Comparative Example 6

[0060] According to the weight proportions of each component, 100 parts by weight of N,N-dimethylacrylamide, 3 parts by weight of acrylic acid, 10 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 5 parts by weight of N-vinylpyrrolidone, 0.1 parts by weight of pentaerythritol, and 400 parts by weight of water were added sequentially to the reaction vessel to obtain a reaction solution. Nitrogen gas was used to purge the air from the reaction vessel, and the mixture was stirred at a speed of 100 rpm. After all components were completely dissolved, the pH value of the reaction solution was adjusted to 7, and the temperature of the reaction solution was raised to 35°C. 0.3 parts by weight of cerium ammonium sulfate was added dropwise to the reaction solution. After reacting for 0.5 hours, 5 parts by weight of dimethyl diallyl ammonium chloride was added dropwise, and the reaction was carried out for 3 hours. The temperature of the reaction solution was then cooled to room temperature to obtain control sample 6.

[0061] Application Example 1

[0062] The samples obtained in each embodiment and comparative example were subjected to performance tests. Cement slurry was prepared according to GB / T 19139-2012 "Test Methods for Cement in Oil Wells". The cement slurry formula was as follows:

[0063] 100g of Jiahua G-grade cement + 3.5g of the above sample + 3g of BXF-200L water loss reducer produced by Tianjin Zhongyou Boxing Engineering Technology Co., Ltd. + 0.5g of CF40L drag reducer produced by Tianjin Zhongyou Boxing Engineering Technology Co., Ltd. + 36.8g of 18%wt% NaCl water + 0.2g of G603 defoamer produced by Tianjin Zhongyou Boxing Engineering Technology Co., Ltd.

[0064] Alternatively, 100g of Jiahua G-grade cement + 3.5g of the above sample + 3g of BXF-200L water loss reducer produced by Tianjin Zhongyou Boxing Engineering Technology Co., Ltd. + 0.5g of CF40L drag reducer produced by Tianjin Zhongyou Boxing Engineering Technology Co., Ltd. + 36.8g of Bohai seawater + 0.2g of G603 defoamer produced by Tianjin Zhongyou Boxing Engineering Technology Co., Ltd.

[0065] The methods for testing the cement loss of the cement slurry prepared in each embodiment and comparative example are as follows:

[0066] First, the prepared cement slurry is stirred for 20 minutes in a thickener at 70±2℃ under normal pressure, and then allowed to stand for 3 minutes. Next, the cement slurry is poured into a beaker containing 300mL of distilled water (beaker size: 500mL), slowly poured in over 2-3 minutes, with a total volume of 350g. After pouring, the beaker is allowed to stand for 1 minute. The top 245mL of solution is then drawn off using a pipette. The drawn-off solution is stirred thoroughly and its density ρ is measured using a digital liquid density meter. The cement loss M = (ρ-1)×245. A smaller cement loss indicates better preservation of the cement slurry's integrity in an external water environment, signifying stronger water resistance.

[0067] The flowability test methods for the cement slurries prepared in each embodiment and comparative example are as follows:

[0068] Place a 400mm × 400mm × 5mm glass plate horizontally and wipe it with a damp cloth to moisten it, but without leaving any water stains. Place a truncated cone mold (a smooth, seamless metal product with an upper diameter of 36mm, a lower diameter of 60mm, and a height of 60mm) in the center of the glass plate and quickly pour the prepared cement into the truncated cone mold until it is full. Vertically lift the truncated cone mold and simultaneously start a stopwatch, allowing the cement slurry to flow on the glass plate for 30 seconds. Use a ruler to measure the maximum diameter of the cement slurry in two mutually perpendicular directions; this is the flowability.

[0069] Table 1 shows the evaluation results of the anti-dispersion performance and fluidity performance of the cement slurry prepared in the examples and comparative examples.

[0070] Table 1. Evaluation results of the anti-dispersion and fluidity properties of the cement slurries prepared in the examples and comparative examples.

[0071]

[0072] The data in Table 1 shows that:

[0073] In Comparative Example 1, the existing technical solution is not resistant to salt / seawater, has poor rheological properties of cement slurry, and cannot be poured out.

[0074] In Comparative Example 2, without the addition of acrylic acid, the polymer sample and the Ca on the cement particles... 2+ The weak electrostatic attraction leads to partial aggregation between polymer molecules, increasing the consistency of the cement slurry, resulting in poor rheological properties and a large amount of cement loss.

[0075] In Comparative Example 3, without the addition of cyclic monomers, the cement slurry was not heat-resistant and its anti-dispersion properties deteriorated after curing.

[0076] In Comparative Example 4, the absence of a branching agent hindered the polymerization of spherical hyperbranched polymers, resulted in poor salt / seawater resistance, poor rheological properties of the cement slurry, and made it impossible to pour out.

[0077] In Comparative Example 5, without the addition of cationic monomers, the polymer sample showed weaker bonding force with cement particles and poorer anti-dispersion performance.

[0078] In Comparative Example 6, without the addition of a crosslinking agent, the polymer sample exhibited a weak three-dimensional network structure and poor anti-dispersion performance.

[0079] The salt-resistant, water-resistant, non-dispersible materials provided in Examples 1-3 of this invention exhibit low cement loss and good anti-dispersion effect, indicating that the addition of each component and the reasonable proportion between them have a significant impact on the anti-dispersion effect of the water-resistant, non-dispersible cement slurry. Figure 1 The molecular conformation diagrams of Sample 1 and Comparative Example 4 show that the slope of the conformation diagram of Sample 1 with respect to molar mass is 0.34 ± 0.00, indicating that Sample 1 is a hyperbranched polymer with a compact structure; the slope of the conformation diagram of Comparative Example 4 with respect to molar mass is 0.54 ± 0.00, indicating that Sample 4 is a linear polymer with a random coil conformation. Hyperbranched polymers can adsorb individual polymers onto the surface of multiple cement particles. Through the "bonding-bridging" effect between the polymer and cement particles, the cohesion of the cement slurry system is maintained within a suitable range, resolving the contradiction between cement slurry flocculation and good fluidity. This allows the cement slurry to maintain good bulk (slurry) integrity even under the scouring of external water and high-mineralized water, achieving the effect of non-dispersion and non-segregation, and exhibiting significant water-resistant non-dispersion properties.

[0080] On the other hand, it can be seen from the results of pouring the cement slurry prepared by the samples of Examples 1-3 and Comparative Examples 1-6 into water that the cement slurry prepared by the salt-resistant, water-resistant, non-dispersible material samples prepared by Examples 1-3 has a large cohesive force and does not diffuse when exposed to external aqueous solutions. The water in the upper layer of the beaker remains clear and transparent, and the cement slurry maintains good slurry integrity. The cement slurry prepared by the samples of Comparative Examples 1, 2, and 4 has poor rheological properties and is difficult to pour out smoothly. The cement slurry prepared by the samples of Comparative Examples 3, 5, and 6 disperses immediately after being poured into the aqueous solution. The cement slurry disperses in the water, and the water in the beaker becomes turbid and opaque.

[0081] Therefore, the salt-resistant, water-resistant, non-dispersible material provided in this embodiment of the invention is suitable for preparing cement slurries with high-mineralization water such as brine and seawater. When used in brine and seawater cement slurry systems with NaCl content below 18% wt%, it significantly improves the water-resistant, non-dispersible properties of the cement slurry while ensuring excellent rheological properties. It has a good anti-water erosion effect, avoids the erosion of cement slurry by formation water, ensures the smooth progress of cementing operations, and improves the cementing quality of water-bearing and high-water-cut oil and gas wells, especially the cementing quality of brine (saltwater) layer sections.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A salt-resistant, water-resistant, non-dispersible material for oil well cement, characterized in that, The components include the following parts by weight: 100 parts by weight of N,N-dimethylacrylamide, 3-6 parts by weight of acrylic acid, 10-20 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 5-15 parts by weight of cyclic monomer, 0.1-0.4 parts by weight of branching agent, 5-15 parts by weight of cationic monomer, 0.3-3 parts by weight of crosslinking agent, and 400-500 parts by weight of water; The cyclic monomer includes at least one of N-vinylpyrrolidone, N-vinylvalerolamide, and N-vinylcaprolactam; The branching agent includes pentaerythritol and / or dipentaerythritol; The cationic monomer includes at least one of acryloyloxyethyltrimethylammonium chloride, dimethyl diallylammonium chloride, and dimethyl diallylammonium bromide; The crosslinking agent includes at least one of 3-allyloxy-2-hydroxypropanesulfonic acid, N,N-methylenediacrylamide, hydroxyethyl acrylate and hydroxyethyl methacrylate; When the cationic monomer is acryloyloxyethyltrimethylammonium chloride, the crosslinking agent is N,N-methylenediacrylamide.

2. A method for preparing a salt-resistant, water-resistant, non-dispersible material for oil well cement as described in claim 1, characterized in that, Includes the following steps: According to the weight proportions of each component, N,N-dimethylacrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, cyclic monomer, branching agent and water are added sequentially to the reaction vessel to obtain the reaction solution; The air in the reaction vessel is replaced with an inert gas, and the mixture is stirred at a speed of 100 rpm. After all components are completely dissolved, the pH value of the hydrogen ion concentration index of the reaction solution is adjusted to 7-9, and the temperature of the reaction solution is raised to 35-55°C. An initiator is added dropwise to the reaction solution. After reacting for 0.5 to 1 hour, a mixed solution of cationic monomer and crosslinking agent is added dropwise. After reacting for 3 to 4 hours, the temperature of the reaction solution is cooled to room temperature to obtain the salt-resistant, water-resistant, non-dispersible material for oil well cement.

3. The preparation method according to claim 2, characterized in that, The initiator includes cerium ammonium sulfate and / or cerium ammonium nitrate.

4. The preparation method according to claim 2, characterized in that, The weight ratio of the initiator to the branching agent is 3:1 to 4:

1.

5. The preparation method according to claim 2, characterized in that, The inert gas includes nitrogen and / or argon.

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