A multifunctional fluid loss additive for oil well cement slurries and a method of making the same

Abstract

The application provides a multifunctional fluid loss additive for oil well cement slurry and a preparation method thereof. The preparation method of the fluid loss additive comprises the following steps: subjecting a reaction mixture containing 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid and acryloyloxyethyl dimethyl benzyl ammonium chloride to a polymerization reaction to obtain the multifunctional fluid loss additive for oil well cement slurry. The multifunctional fluid loss additive for oil well cement slurry provided by the application is prepared by the preparation method. The fluid loss additive provided by the application has excellent high-temperature resistance and salt resistance.

Description

Technical Field

[0001] This invention relates to a multifunctional fluid loss reducing agent for oil well cement slurry and its preparation method, belonging to the field of oilfield cementing technology. Background Technology

[0002] With the emergence of deep and ultra-deep wells, and the mature application of low-temperature, freshwater fluid loss control agents, the development direction of fluid loss control agents will inevitably move towards high-temperature resistance and saturated brine resistance. A superior fluid loss control agent should possess the following five properties: First, excellent fluid loss control capability, requiring only a small amount added to cement slurry to control fluid loss to below 100mL; second, the ability to control the thickening time of cement slurry without affecting the strength development of cement paste; third, strong salt resistance, not increasing fluid loss in brine environments; fourth, good compatibility with other admixtures; and fifth, low cost and no environmental pollution.

[0003] In recent years, polymer-based fluid loss control agents have seen the fastest development among oil well cement slurry admixtures, with new reports constantly appearing in various publications and patent literature. Although many have been practically applied in oilfield cementing with good results, such as common products like LW-1, FC-03, SK-1, TD-X, TD-S, J-2B, T121, T-50A, and W99, these fluid loss control agents can only be used below 160℃ and only have good fluid loss control capabilities in fresh cement slurries.

[0004] Therefore, it is necessary to improve the water loss reducing agent to further enhance its temperature and salt resistance. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a multifunctional fluid loss reducing agent for oil well cement slurry and its preparation method. The fluid loss reducing agent provided by the present invention exhibits excellent high-temperature resistance and salt resistance.

[0006] To achieve the above objectives, the first aspect of the present invention provides a method for preparing a multifunctional fluid loss reducing agent for oil well cement slurry, comprising the following steps:

[0007] The reaction mixture containing 2-acrylamide-2-methylpropanesulfonic acid (AMPS), acrylamide (AM), p-vinylbenzoic acid and acryloyloxyethyl dimethyl benzyl ammonium chloride is subjected to a polymerization reaction to obtain the multifunctional fluid loss reducing agent for oil well cement slurry.

[0008] In the above preparation method, preferably, the weight ratio of 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid and acryloyloxyethyl dimethyl benzyl ammonium chloride is (1-10):(0.1-8):(0.4-8):(0.2-3).

[0009] In some specific embodiments of the present invention, the weight ratio of 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, and acryloyloxyethyl dimethyl benzyl ammonium chloride is (1-2):(7-8):(0.4-0.6):(0.7-0.8). Preferably, the weight ratio of 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, and acryloyloxyethyl dimethyl benzyl ammonium chloride is 1:7:0.5:0.72. Under the above-mentioned ratio conditions of the four monomers, the prepared water loss reducing agent exhibits excellent high-temperature resistance and salt resistance, as well as excellent dispersibility.

[0010] In some specific embodiments of the present invention, the weight ratio of 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, and acryloyloxyethyl dimethyl benzyl ammonium chloride is (4.5-5.5):(6-7):(0.7-0.8):(0.8-1.2). Preferably, the weight ratio of 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, and acryloyloxyethyl dimethyl benzyl ammonium chloride is 5:6.2:0.75:1. Under the above-mentioned ratio conditions of the four monomers, the prepared water loss reducing agent has excellent high temperature resistance, salt resistance, and thickening properties, and is particularly suitable for low-density cement paste systems.

[0011] In some specific embodiments of the present invention, the weight ratio of 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, and acryloyloxyethyl dimethyl benzyl ammonium chloride is (7-8):(1-2):(7-8):(1-3). Preferably, the weight ratio of 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, and acryloyloxyethyl dimethyl benzyl ammonium chloride is (7-8):1.6:7.2:2. Under the above-mentioned ratio conditions of the four monomers, the prepared water loss reducing agent has excellent high temperature resistance and salt resistance, as well as excellent corrosion resistance, and is particularly suitable for use in cement slurry systems where carbon (e.g., carbon dioxide) and sulfur (e.g., hydrogen sulfide) co-corrosion exists.

[0012] In some specific embodiments of the present invention, the weight ratio of 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, and acryloyloxyethyl dimethyl benzyl ammonium chloride is (8-10):(0.1-0.3):(0.6-0.8):(0.2-0.4). Preferably, the weight ratio of 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, and acryloyloxyethyl dimethyl benzyl ammonium chloride is (8-10):0.1:0.7:0.3. Under the above-mentioned ratio conditions of the four monomers, the prepared water loss reducing agent has excellent high temperature resistance and salt resistance, and is particularly suitable for high-density cement slurry systems, such as dispersant-type cement slurry systems with added weighting materials.

[0013] In the above preparation method, preferably, the reaction mixture further includes an initiator, and the amount of the initiator is 0.5-1% based on 100% of the total weight of the reaction mixture. More preferably, the initiator includes a peroxide solution, and the mass concentration of the peroxide solution is 5-20%. More preferably, the peroxide solution includes one or a combination of several of the following: ammonium persulfate solution, potassium persulfate solution, and sodium persulfate solution.

[0014] In the above preparation method, preferably, the reaction mixture further includes water, and based on the total weight of the reaction mixture (100%), the amount of 2-acrylamido-2-methylpropanesulfonic acid is 1-10%, the amount of acrylamide is 0.1-8%, the amount of p-vinylbenzoic acid is 0.4-8%, and the amount of acryloyloxyethyl dimethyl benzyl ammonium chloride is 0.2-3%.

[0015] In some specific embodiments of the present invention, based on the total weight of the reaction mixture (100%), the amount of 2-acrylamido-2-methylpropanesulfonic acid is 1-2%, the amount of acrylamide is 7-8%, the amount of p-vinylbenzoic acid is 0.4-0.6%, and the amount of acryloyloxyethyl dimethyl benzyl ammonium chloride is 0.7-0.8%. Preferably, based on the total weight of the reaction mixture (100%), the amount of 2-acrylamido-2-methylpropanesulfonic acid is 1%, the amount of acrylamide is 7%, the amount of p-vinylbenzoic acid is 0.5%, and the amount of acryloyloxyethyl dimethyl benzyl ammonium chloride is 0.72%.

[0016] In some specific embodiments of the present invention, based on the total weight of the reaction mixture (100%), the amount of 2-acrylamido-2-methylpropanesulfonic acid is 4.5-5.5%, the amount of acrylamide is 6-7%, the amount of p-vinylbenzoic acid is 0.7-0.8%, and the amount of acryloyloxyethyl dimethyl benzyl ammonium chloride is 0.8-1.2%. Preferably, based on the total weight of the reaction mixture (100%), the amount of 2-acrylamido-2-methylpropanesulfonic acid is 5%, the amount of acrylamide is 6.2%, the amount of p-vinylbenzoic acid is 0.75%, and the amount of acryloyloxyethyl dimethyl benzyl ammonium chloride is 1%.

[0017] In some specific embodiments of the present invention, based on the total weight of the reaction mixture (100%), the amount of 2-acrylamido-2-methylpropanesulfonic acid is 7-8%, the amount of acrylamide is 1-2%, the amount of p-vinylbenzoic acid is 7-8%, and the amount of acryloyloxyethyl dimethyl benzyl ammonium chloride is 1-3%. Preferably, based on the total weight of the reaction mixture (100%), the amount of 2-acrylamido-2-methylpropanesulfonic acid is 7-8%, the amount of acrylamide is 1.6%, the amount of p-vinylbenzoic acid is 7.2%, and the amount of acryloyloxyethyl dimethyl benzyl ammonium chloride is 2%.

[0018] In some specific embodiments of the present invention, based on the total weight of the reaction mixture (100%), the amount of 2-acrylamido-2-methylpropanesulfonic acid is 8-10%, the amount of acrylamide is 0.1-0.3%, the amount of p-vinylbenzoic acid is 0.6-0.8%, and the amount of acryloyloxyethyl dimethyl benzyl ammonium chloride is 0.2-0.4%. Preferably, based on the total weight of the reaction mixture (100%), the amount of 2-acrylamido-2-methylpropanesulfonic acid is 8-10%, the amount of acrylamide is 0.1%, the amount of p-vinylbenzoic acid is 0.7%, and the amount of acryloyloxyethyl dimethyl benzyl ammonium chloride is 0.3%.

[0019] According to a specific embodiment of the present invention, preferably, the above-described preparation method includes the following steps:

[0020] (1) Mix 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, acryloyloxyethyl dimethyl benzyl ammonium chloride and water to obtain a mixed solution;

[0021] (2) The mixed solution obtained in step (1) is mixed with an initiator and subjected to a polymerization reaction to obtain the multifunctional water loss reducing agent for oil well cement slurry.

[0022] In the above preparation method, preferably, in step (1), the pH value of the mixed solution is 7.0-10.0, more preferably 8.0-9.0. The pH value of the mixed solution can be adjusted using NaOH solution. The concentration of NaOH solution can be conventionally set by those skilled in the art as needed, and the present invention does not impose any special limitations on it. For example, the concentration of NaOH solution can be 0.05 mol / L, 0.1 mol / L, or 0.2 mol / L, etc. Those skilled in the art should understand that the NaOH solution is also included in the reaction mixture, but its amount is very small and has little effect on the change in the total weight of the reaction mixture.

[0023] In the above preparation method, steps (1) and / or (2) can be carried out under stirring conditions, and the stirring speed can be conventionally adjusted by those skilled in the art.

[0024] In the above preparation method, preferably, the polymerization reaction temperature is 45-65℃ and the polymerization reaction time is 2-4 hours. More preferably, the polymerization reaction temperature is 50-60℃ and the polymerization reaction time is 3 hours.

[0025] A second aspect of the present invention provides a multifunctional fluid loss reducing agent for oil well cement slurry, which is prepared by the above-described method for preparing a multifunctional fluid loss reducing agent for oil well cement slurry.

[0026] This invention employs a free radical aqueous solution polymerization method, using 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, and acryloyloxyethyl dimethylbenzylammonium chloride as monomers. By controlling the weight ratio of the four monomers and the temperature and time of the polymerization reaction, the molecular structure of the water loss reducing agent was designed, improving its rigidity and thus its temperature resistance. Simultaneously, a sulfonic acid group, insensitive to external cation attack, was introduced into the molecular structure of the water loss reducing agent. Furthermore, the hydration ability of the sulfonic acid group is stronger than that of the carboxyl group, and its hydration film exhibits greater stability against external cations, significantly enhancing the salt resistance of the water loss reducing agent. Experimental results show that the API water loss of the water loss reducing agent prepared by this invention meets the requirements at 200℃, indicating excellent high-temperature resistance. The API water loss of the water loss reducing agent prepared by this invention in both semi-saturated and saturated brine is below 100 mL, indicating excellent salt resistance. Furthermore, through extensive research, this invention has designed four monomers in different weight ratios, enabling the prepared water loss reducing agent to not only possess excellent high-temperature and salt resistance properties, but also to have different functions, thus making it suitable for different cement slurry systems such as low-density and high-density slurries.

[0027] The fluid loss control agent provided by this invention is a multifunctional fluid loss control agent, which is not only suitable for dry-mixed or water-mixed field processes, but can also be used in well temperatures of 30-200℃. It is also suitable for cement slurry systems of different densities of 1.15-2.20SG, as well as fresh water, semi-saturated brine and saturated brine systems. It has the characteristics of small dosage and obvious fluid loss control effect; in addition, it also has the function of preventing gas channeling and can be used in various different systems.

[0028] The multifunctional fluid loss reducing agent for oil well cement slurry provided by this invention is not easily chemically or physically degraded and has a weak impact on the rheological properties of cement slurry; it has good compatibility with other admixtures; it is easy to manage and store; the cement slurry system with the fluid loss reducing agent of this invention has good rheological properties and adjustable viscosity; the cement slurry system with the fluid loss reducing agent of this invention has good anti-channeling performance, right-angle thickening function, thickening transition time ≤20min, and static gelation transition time ≤20min. Detailed Implementation

[0029] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0030] In some specific embodiments of the present invention, the present invention provides a method for preparing a multifunctional fluid loss reducing agent for oil well cement slurry, which includes the following steps:

[0031] (1) Mix 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, acryloyloxyethyl dimethyl benzyl ammonium chloride and water to obtain a mixed solution; the pH value of the mixed solution is 7.0-10.0, and the pH value of the mixed solution can be adjusted by NaOH solution;

[0032] (2) The mixed solution obtained in step (1) is mixed with an initiator and polymerized at 45-65°C for 2-4 hours to obtain the multifunctional water loss reducing agent for oil well cement slurry.

[0033] The reaction mixture includes 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, acryloyloxyethyl dimethylbenzylammonium chloride, water, an initiator, and optionally a NaOH solution;

[0034] Based on the total weight of the reaction mixture (100%), the amount of 2-acrylamido-2-methylpropanesulfonic acid is 1-2%, the amount of acrylamide is 7-8%, the amount of p-vinylbenzoic acid is 0.4-0.6%, the amount of acryloyloxyethyl dimethyl benzyl ammonium chloride is 0.7-0.8%, the amount of initiator is 0.5-1%, and the balance is water and a small amount of NaOH solution (optional). Preferably, based on the total weight of the reaction mixture (100%), the amount of 2-acrylamido-2-methylpropanesulfonic acid is 1%, the amount of acrylamide is 7%, the amount of p-vinylbenzoic acid is 0.5%, the amount of acryloyloxyethyl dimethyl benzyl ammonium chloride is 0.72%, the amount of initiator is 0.5-1%, and the balance is water and a small amount of NaOH solution (optional).

[0035] In the above-described specific embodiments of the present invention, under the above-described proportions of the four monomers, the prepared water loss reducing agent has excellent high temperature resistance and salt resistance, as well as excellent dispersibility.

[0036] In other specific embodiments of the present invention, the present invention provides a method for preparing a multifunctional fluid loss reducing agent for oil well cement slurry, comprising the following steps:

[0037] (1) Mix 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, acryloyloxyethyl dimethyl benzyl ammonium chloride and water to obtain a mixed solution; the pH value of the mixed solution is 7.0-10.0, and the pH value of the mixed solution can be adjusted by NaOH solution;

[0038] (2) The mixed solution obtained in step (1) is mixed with an initiator and polymerized at 45-65°C for 2-4 hours to obtain the multifunctional water loss reducing agent for oil well cement slurry.

[0039] The reaction mixture includes 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, acryloyloxyethyl dimethylbenzylammonium chloride, water, an initiator, and optionally a NaOH solution;

[0040] Based on the total weight of the reaction mixture (100%), the amount of 2-acrylamido-2-methylpropanesulfonic acid is 4.5-5.5%, the amount of acrylamide is 6-7%, the amount of p-vinylbenzoic acid is 0.7-0.8%, the amount of acryloyloxyethyl dimethyl benzyl ammonium chloride is 0.8-1.2%, the amount of initiator is 0.5-1%, and the balance is water and a small amount of NaOH solution (optional). Preferably, based on the total weight of the reaction mixture (100%), the amount of 2-acrylamido-2-methylpropanesulfonic acid is 5%, the amount of acrylamide is 6.2%, the amount of p-vinylbenzoic acid is 0.75%, the amount of acryloyloxyethyl dimethyl benzyl ammonium chloride is 1%, the amount of initiator is 0.5-1%, and the balance is water and a small amount of NaOH solution (optional).

[0041] In the above-described specific embodiments of the present invention, under the above-described proportions of the four monomers, the prepared water loss reducing agent has excellent high temperature resistance, salt resistance and thickening properties, and is particularly suitable for low-density cement slurry systems.

[0042] In other specific embodiments of the present invention, the present invention provides a method for preparing a multifunctional fluid loss reducing agent for oil well cement slurry, comprising the following steps:

[0043] (1) Mix 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, acryloyloxyethyl dimethyl benzyl ammonium chloride and water to obtain a mixed solution; the pH value of the mixed solution is 7.0-10.0, and the pH value of the mixed solution can be adjusted by NaOH solution;

[0044] (2) The mixed solution obtained in step (1) is mixed with an initiator and polymerized at 45-65°C for 2-4 hours to obtain the multifunctional water loss reducing agent for oil well cement slurry.

[0045] The reaction mixture includes 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, acryloyloxyethyl dimethylbenzylammonium chloride, water, an initiator, and optionally a NaOH solution;

[0046] Based on the total weight of the reaction mixture (100%), the amount of 2-acrylamido-2-methylpropanesulfonic acid is 7-8%, the amount of acrylamide is 1-2%, the amount of p-vinylbenzoic acid is 7-8%, the amount of acryloyloxyethyl dimethyl benzyl ammonium chloride is 1-3%, the amount of initiator is 0.5-1%, and the balance is water and a small amount of NaOH solution (optional). Preferably, based on the total weight of the reaction mixture (100%), the amount of 2-acrylamido-2-methylpropanesulfonic acid is 7-8%, the amount of acrylamide is 1.6%, the amount of p-vinylbenzoic acid is 7.2%, the amount of acryloyloxyethyl dimethyl benzyl ammonium chloride is 2%, the amount of initiator is 0.5-1%, and the balance is water and a small amount of NaOH solution (optional).

[0047] In the above-described specific embodiments of the present invention, under the above-described proportions of the four monomers, the prepared water loss reducing agent has excellent high temperature resistance and salt resistance, as well as excellent corrosion resistance, and is particularly suitable for cement slurry systems where carbon (e.g., carbon dioxide) and sulfur (e.g., hydrogen sulfide) co-corrosion exists.

[0048] In other specific embodiments of the present invention, the present invention provides a method for preparing a multifunctional fluid loss reducing agent for oil well cement slurry, comprising the following steps:

[0049] (1) Mix 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, acryloyloxyethyl dimethyl benzyl ammonium chloride and water to obtain a mixed solution; the pH value of the mixed solution is 7.0-10.0, and the pH value of the mixed solution can be adjusted by NaOH solution;

[0050] (2) The mixed solution obtained in step (1) is mixed with an initiator and polymerized at 45-65°C for 2-4 hours to obtain the multifunctional water loss reducing agent for oil well cement slurry.

[0051] The reaction mixture includes 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, acryloyloxyethyl dimethylbenzylammonium chloride, water, an initiator, and optionally a NaOH solution;

[0052] Based on the total weight of the reaction mixture (100%), the amount of 2-acrylamido-2-methylpropanesulfonic acid is 8-10%, the amount of acrylamide is 0.1-0.3%, the amount of p-vinylbenzoic acid is 0.6-0.8%, the amount of acryloyloxyethyl dimethyl benzyl ammonium chloride is 0.2-0.4%, the amount of initiator is 0.5-1%, and the balance is water and a small amount of NaOH solution (optional). Preferably, based on the total weight of the reaction mixture (100%), the amount of 2-acrylamido-2-methylpropanesulfonic acid is 8-10%, the amount of acrylamide is 0.1%, the amount of p-vinylbenzoic acid is 0.7%, the amount of acryloyloxyethyl dimethyl benzyl ammonium chloride is 0.3%, the amount of initiator is 0.5-1%, and the balance is water and a small amount of NaOH solution (optional).

[0053] In the above-described specific embodiments of the present invention, under the above-described proportions of the four monomers, the prepared water loss reducing agent has excellent high temperature resistance and salt resistance, and is particularly suitable for high-density cement slurry systems, such as dispersant-type cement slurry systems with added weighting materials.

[0054] In the specific embodiments described above, the concentration of the NaOH solution can be conventionally set by those skilled in the art as needed, and the present invention does not impose any special limitations on it. For example, the concentration of the NaOH solution can be 0.05 mol / L, 0.1 mol / L, or 0.2 mol / L, etc.

[0055] In the above specific embodiments, preferably, the pH value of the mixed solution is 8.0-9.0.

[0056] In the above specific embodiments, preferably, the initiator comprises a peroxide solution, and the mass concentration of the peroxide solution is 5-20%. More preferably, the peroxide solution comprises one or a combination of several of the following: ammonium persulfate solution, potassium persulfate solution, and sodium persulfate solution.

[0057] In the above specific embodiments, preferably, the polymerization reaction temperature is 50-60℃ and the polymerization reaction time is 3h.

[0058] In the specific embodiments described above, steps (1) and / or (2) can be carried out under stirring conditions, and the stirring speed can be conventionally adjusted by those skilled in the art.

[0059] Example 1

[0060] This embodiment provides a multifunctional fluid loss reducing agent for oil well cement slurry, which is prepared through the following steps:

[0061] (1) Under stirring conditions, 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, acryloyloxyethyl dimethyl benzyl ammonium chloride and water were mixed to obtain a mixed solution; the pH of the mixed solution was adjusted to 8.0 using NaOH solution;

[0062] (2) At 50°C and under stirring conditions, the initiator is slowly added dropwise to the mixed solution after pH adjustment obtained in step (1), and the polymerization reaction is continued at 50°C and under stirring conditions for 3 hours to obtain the multifunctional water loss reducing agent for oil well cement slurry.

[0063] The reaction mixture includes 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, acryloyloxyethyl dimethylbenzylammonium chloride, water, initiator, and NaOH solution;

[0064] Based on the total weight of the reaction mixture as 100%, the amount of 2-acrylamido-2-methylpropanesulfonic acid is 1%, the amount of acrylamide is 7%, the amount of p-vinylbenzoic acid is 0.5%, the amount of acryloyloxyethyl dimethyl benzyl ammonium chloride is 0.72%, the amount of initiator is 0.5%, and the balance is water and a small amount of NaOH solution;

[0065] The initiator is a 10% (w / w) ammonium persulfate solution.

[0066] The water loss reducing agent prepared in this embodiment has excellent high temperature resistance and salt resistance, as well as excellent dispersibility.

[0067] Example 2

[0068] This embodiment provides a multifunctional fluid loss reducing agent for oil well cement slurry, which is prepared through the following steps:

[0069] (1) Under stirring conditions, 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, acryloyloxyethyl dimethyl benzyl ammonium chloride and water were mixed to obtain a mixed solution; the pH of the mixed solution was adjusted to 9.0 using NaOH solution;

[0070] (2) At 55°C and under stirring conditions, the initiator is slowly added dropwise to the mixed solution after pH adjustment obtained in step (1), and the polymerization reaction is continued at 55°C and under stirring conditions for 3 hours to obtain the multifunctional water loss reducing agent for oil well cement slurry.

[0071] The reaction mixture includes 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, acryloyloxyethyl dimethylbenzylammonium chloride, water, initiator, and NaOH solution;

[0072] Based on the total weight of the reaction mixture as 100%, the amount of 2-acrylamido-2-methylpropanesulfonic acid is 5%, the amount of acrylamide is 6.2%, the amount of p-vinylbenzoic acid is 0.75%, the amount of acryloyloxyethyl dimethyl benzyl ammonium chloride is 1%, the amount of initiator is 0.7%, and the balance is water and a small amount of NaOH solution;

[0073] The initiator is a 10% (w / w) ammonium persulfate solution.

[0074] The water loss reducing agent prepared in this embodiment has excellent high temperature resistance, salt resistance and thickening properties, and is especially suitable for low-density cement slurry systems.

[0075] Example 3

[0076] This embodiment provides a multifunctional fluid loss reducing agent for oil well cement slurry, which is prepared through the following steps:

[0077] (1) Under stirring conditions, 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, acryloyloxyethyl dimethyl benzyl ammonium chloride and water were mixed to obtain a mixed solution; the pH of the mixed solution was adjusted to 8.0 using NaOH solution;

[0078] (2) At 55°C and under stirring conditions, the initiator is slowly added dropwise to the mixed solution after pH adjustment obtained in step (1), and the polymerization reaction is continued at 55°C and under stirring conditions for 3 hours to obtain the multifunctional water loss reducing agent for oil well cement slurry.

[0079] The reaction mixture includes 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, acryloyloxyethyl dimethylbenzylammonium chloride, water, initiator, and NaOH solution;

[0080] Based on the total weight of the reaction mixture as 100%, the amount of 2-acrylamido-2-methylpropanesulfonic acid is 7.5%, the amount of acrylamide is 1.6%, the amount of p-vinylbenzoic acid is 7.2%, the amount of acryloyloxyethyl dimethyl benzyl ammonium chloride is 2%, the amount of initiator is 1%, and the balance is water and a small amount of NaOH solution;

[0081] The initiator is a 10% (w / w) ammonium persulfate solution.

[0082] The water loss reducing agent prepared in this embodiment has excellent high temperature resistance and salt resistance, as well as excellent corrosion resistance, making it particularly suitable for cement slurry systems where carbon (e.g., carbon dioxide) and sulfur (e.g., hydrogen sulfide) co-corrosion exist.

[0083] Example 4

[0084] This embodiment provides a multifunctional fluid loss reducing agent for oil well cement slurry, which is prepared through the following steps:

[0085] (1) Under stirring conditions, 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, acryloyloxyethyl dimethyl benzyl ammonium chloride and water were mixed to obtain a mixed solution; the pH of the mixed solution was adjusted to 8.0 using NaOH solution;

[0086] (2) Under stirring conditions at 60°C, the initiator is slowly added dropwise to the mixed solution after pH adjustment obtained in step (1), and the polymerization reaction is continued under stirring conditions at 60°C for 3 hours to obtain the multifunctional water loss reducing agent for oil well cement slurry.

[0087] The reaction mixture includes 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, acryloyloxyethyl dimethylbenzylammonium chloride, water, initiator, and NaOH solution;

[0088] Based on the total weight of the reaction mixture as 100%, the amount of 2-acrylamido-2-methylpropanesulfonic acid is 9%, the amount of acrylamide is 0.1%, the amount of p-vinylbenzoic acid is 0.7%, the amount of acryloyloxyethyl dimethyl benzyl ammonium chloride is 0.3%, the amount of initiator is 0.5%, and the balance is water and a small amount of NaOH solution;

[0089] The initiator is a 10% (w / w) ammonium persulfate solution.

[0090] The water loss reducing agent prepared in this embodiment has excellent high temperature resistance and salt resistance, and is especially suitable for high-density cement slurry systems, such as cement slurry systems with dispersants containing weighting materials.

[0091] Comparative Example 1

[0092] This comparative example provides a method for preparing a water loss reducing agent, which is obtained through the following steps:

[0093] (1) Under stirring conditions, 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, acrylic acid, acryloyloxyethyl dimethyl benzyl ammonium chloride and water were mixed to obtain a mixed solution; the pH of the mixed solution was adjusted to 8.0 using NaOH solution;

[0094] (2) At 55°C and under stirring conditions, the initiator is slowly added dropwise to the mixed solution after pH adjustment obtained in step (1), and the polymerization reaction is continued at 55°C and under stirring conditions for 3 hours to obtain the multifunctional water loss reducing agent for oil well cement slurry.

[0095] The reaction mixture includes 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, acrylic acid, acryloyloxyethyl dimethylbenzylammonium chloride, water, initiator, and NaOH solution;

[0096] Based on the total weight of the reaction mixture as 100%, the amount of 2-acrylamide-2-methylpropanesulfonic acid is 1%, the amount of acrylamide is 7%, the amount of acrylic acid is 0.5%, the amount of acryloyloxyethyl dimethyl benzyl ammonium chloride is 0.72%, the amount of initiator is 0.5%, and the balance is water and a small amount of NaOH solution.

[0097] The initiator is a 10% (w / w) ammonium persulfate solution.

[0098] Comparative Example 2

[0099] This comparative example provides a method for preparing a water loss reducing agent, which is obtained through the following steps:

[0100] (1) Under stirring conditions, 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, maleic anhydride, acryloyloxyethyl dimethyl benzyl ammonium chloride and water were mixed to obtain a mixed solution; the pH of the mixed solution was adjusted to 8.0 using NaOH solution;

[0101] (2) At 55°C and under stirring conditions, the initiator is slowly added dropwise to the mixed solution after pH adjustment obtained in step (1), and the polymerization reaction is continued at 55°C and under stirring conditions for 3 hours to obtain the multifunctional water loss reducing agent for oil well cement slurry.

[0102] The reaction mixture includes 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, maleic anhydride, acryloyloxyethyl dimethyl benzyl ammonium chloride, water, initiator, and NaOH solution;

[0103] Based on the total weight of the reaction mixture as 100%, the amount of 2-acrylamide-2-methylpropanesulfonic acid is 5%, the amount of acrylamide is 6.2%, the amount of maleic anhydride is 0.75%, the amount of acryloyloxyethyl dimethyl benzyl ammonium chloride is 1%, the amount of initiator is 0.7%, and the balance is water and a small amount of NaOH solution;

[0104] The initiator is a 10% (w / w) ammonium persulfate solution.

[0105] Comparative Example 3

[0106] This comparative example provides a method for preparing a water loss reducing agent, which is obtained through the following steps:

[0107] (1) Under stirring conditions, 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, acryloyloxyethyl dimethyl benzyl ammonium chloride and water were mixed to obtain a mixed solution; the pH of the mixed solution was adjusted to 8.0 using NaOH solution;

[0108] (2) At 55°C and under stirring conditions, the initiator is slowly added dropwise to the mixed solution after pH adjustment obtained in step (1), and the polymerization reaction is continued at 55°C and under stirring conditions for 3 hours to obtain the multifunctional water loss reducing agent for oil well cement slurry.

[0109] The reaction mixture includes 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, acryloyloxyethyl dimethylbenzylammonium chloride, water, initiator, and NaOH solution;

[0110] Based on the total weight of the reaction mixture as 100%, the amount of 2-acrylamido-2-methylpropanesulfonic acid is 3%, the amount of acrylamide is 2%, the amount of p-vinylbenzoic acid is 3%, the amount of acryloyloxyethyl dimethyl benzyl ammonium chloride is 2%, the amount of initiator is 0.5%, and the balance is water and a small amount of NaOH solution.

[0111] The initiator is a 10% (w / w) ammonium persulfate solution.

[0112] Test case

[0113] The following performance tests were conducted on the water loss reducing agents prepared in Examples 1-4 and Comparative Examples 1-3.

[0114] I. Water Loss Reduction Performance of Water Loss Control Agents

[0115] The water loss reducing agent prepared in Example 1 was tested at 90℃ with an addition amount of 0.5%, 1%, 1.5%, 2%, 2.5%, 5%, and 7% of the cement ash weight. The results are shown in Table 1.

[0116] The cement slurry formula is as follows: 100 parts by weight of Grade G oil well cement + 0.5 to 7 parts by weight of water loss reducer + 42 parts by weight of water; the density of the cement slurry is 1.90 SG.

[0117] Table 1. Water loss reduction performance of the water loss reducing agent in Example 1

[0118] Dosage of water loss reducer (%) API water loss (mL) at 90℃ 0.5 77 1 65 1.5 45 2 32 2.5 20 5 10 7 5

[0119] As can be seen from Table 1, at 90℃, in cement slurry with a density of 1.90SG, when the dosage of the water loss reducing agent is between 0.5% and 7%, the API water loss is below 100mL. Furthermore, when the dosage increases from 0.5% to 7%, the API water loss decreases from 77mL to 5mL.

[0120] The water loss reducing agent prepared in Example 2 was tested at 90℃ with an addition amount of 0.5%, 1%, 1.5%, 2%, 2.5%, 5%, and 7% of the cement ash weight. The results are shown in Table 2.

[0121] The cement slurry formula is as follows: 100 parts by weight of Grade G oil well cement + 0.5 to 7 parts by weight of water loss reducer + 44 parts by weight of water; the density of the cement slurry is 1.85SG.

[0122] Table 2 shows the water loss reduction performance of the water loss reducing agent in Example 2.

[0123] Dosage of water loss reducer (%) API water loss (mL) at 90℃ 0.5 75 1 61 1.5 43 2 30 2.5 22 5 11 7 6

[0124] As can be seen from Table 2, at 90℃, in cement slurry with a density of 1.85SG, when the dosage of the water loss reducing agent is between 0.5% and 7%, the API water loss is below 100mL. Furthermore, when the dosage increases from 0.5% to 7%, the API water loss decreases from 75mL to 6mL.

[0125] The water loss reducing agent prepared in Example 3 was tested at 90℃ with an addition amount of 0.5%, 1%, 1.5%, 2%, 2.5%, 5%, and 7% of the cement ash weight. The results are shown in Table 3.

[0126] The cement slurry formula is as follows: 100 parts by weight of Grade G oil well cement + 0.5 to 7 parts by weight of water loss reducer + 44 parts by weight of water; the density of the cement slurry is 1.85SG.

[0127] Table 3 shows the water loss reduction performance of the water loss reducing agent in Example 3.

[0128]

[0129]

[0130] As can be seen from Table 3, at 90℃, in cement slurry with a density of 1.85SG, when the dosage of the water loss reducing agent is between 0.5% and 7%, the API water loss is below 100mL. Furthermore, when the dosage increases from 0.5% to 7%, the API water loss decreases from 78mL to 6mL.

[0131] The water loss reducing agent prepared in Example 4 was tested at 90℃ with an addition amount of 0.5%, 1%, 1.5%, 2%, 2.5%, 5%, and 7% of the cement ash weight. The results are shown in Table 4.

[0132] The cement slurry formula is as follows: 100 parts by weight of Grade G oil well cement + 0.5 to 7 parts by weight of water loss reducer + 31 parts by weight of water; the density of the cement slurry is 2.02 SG.

[0133] Table 4 shows the water loss reduction performance of the water loss reducing agent in Example 4.

[0134] Dosage of water loss reducer (%) API water loss (mL) at 90℃ 0.5 69 1 56 1.5 40 2 30 2.5 21 5 11 7 5

[0135] As can be seen from Table 4, at 90℃, in cement slurry with a density of 2.02SG, when the dosage of the water loss reducing agent is between 0.5% and 7%, the API water loss is below 100mL. Furthermore, when the dosage increases from 0.5% to 7%, the API water loss decreases from 69mL to 5mL.

[0136] The test results above show that as the amount of water loss reducing agent in the embodiments of the present invention increases, the number of water loss reducing agent molecules per unit volume in the cement slurry system increases, the number of adsorption groups with cement particles increases, and the number of cross-linking points in the network structure of the entire cement slurry system increases. As a result, the cement slurry filter cake has better density and stronger water loss reduction ability.

[0137] II. High-Temperature Resistance of Water Loss Control Agents

[0138] The API water loss of the water-reducing agent prepared in Example 1 was tested after being added to the cement slurry at temperatures ranging from 70 to 200°C. The results are shown in Table 5. The cement slurry formulation was: 100 parts by weight of Grade G oil well cement + 2 parts by weight of water-reducing agent + 42 parts by weight of water; the density of the cement slurry was 1.90 SG.

[0139] Table 5. High-temperature resistance of the water loss reducing agent in Example 1

[0140]

[0141]

[0142] As can be seen from Table 5, when the test temperature is increased from 70℃ to 200℃, the API water loss only increases from 30mL to 40mL. When the temperature is increased to 90℃, 130℃, 160℃ and 200℃, the water loss increases, but the increase is within 10mL. This shows that the water loss reducing agent prepared in Example 1 has excellent high temperature resistance.

[0143] The API water loss of the water loss control agents prepared in Examples 1-4 and Comparative Examples 1-3 was measured after being added to cement slurry at 200°C. The results are shown in Table 6. The cement slurry formulation was: 100 parts by weight of Grade G oil well cement + 2 parts by weight of water loss control agent + 42 parts by weight of water; the density of the cement slurry was 1.90 SG.

[0144] Table 6. API water loss of the water loss control agents in Examples 1-4 and Comparative Examples 1-3 at 200°C.

[0145] serial number Test temperature (°C) API water loss (mL) Example 1 200 40 Example 2 200 42 Example 3 200 36 Example 4 200 45 Comparative Example 1 200 86 Comparative Example 2 200 98 Comparative Example 3 200 79

[0146] As can be seen from Table 6, the high-temperature resistance of the water loss reducing agent provided in the embodiments of the present invention is better than that of the comparative example.

[0147] III. Salt resistance of water loss control agents

[0148] ① Salt tolerance in semi-saturated brine in Example 1

[0149] The salt resistance of the water loss reducing agent prepared in Example 1 in semi-saturated brine after being added to cement slurry was tested, and the results are shown in Table 7.

[0150] The cement slurry formula is as follows: 100 parts by weight of Grade G oil well cement + 3 parts by weight of fluid loss reducer + 42 parts by weight of water + 7.5 parts by weight of NaCl; the density of the cement slurry is 1.90 SG.

[0151] Table 7 Salt tolerance of the water loss reducing agent in Example 1 in semi-saturated brine.

[0152] serial number Test temperature (°C) API water loss (mL) 1 90 36 2 120 42 3 140 46 4 160 50 5 200 57

[0153] As can be seen from Table 7, under conditions of 90-200℃, the API water loss of the water-reducing agent prepared in Example 1 in semi-saturated brine is all below 100mL, indicating that the water-reducing agent prepared in Example 1 has excellent salt resistance.

[0154] ② Salt tolerance in saturated brine in Example 1

[0155] The salt resistance of the water loss reducing agent prepared in Example 1 in saturated brine after being added to cement slurry was tested, and the results are shown in Table 8.

[0156] The cement slurry formula is as follows: 100 parts by weight of Grade G oil well cement + 4 parts by weight of fluid loss reducer + 42 parts by weight of water + 15 parts by weight of NaCl; the density of the cement slurry is 1.90 SG.

[0157] Table 8. Salt tolerance of the water loss reducing agent in Example 1 in saturated brine.

[0158] serial number Test temperature (°C) API water loss (mL) 1 90 50 2 120 56 3 160 62 4 200 69

[0159] As can be seen from Table 8, under the conditions of 90-200℃, the API water loss of the water-reducing agent prepared in Example 1 in saturated brine is less than 100mL, indicating that the water-reducing agent prepared in Example 1 has excellent salt resistance.

[0160] ③ Salt tolerance in saturated brine of other embodiments and comparative examples

[0161] The API water loss of the water loss reducing agents prepared in Examples 1-4 and Comparative Examples 1-3 was tested after being added to cement slurry at 200°C and in saturated brine. The results are shown in Table 9.

[0162] The cement slurry formula is as follows: 100 parts by weight of Grade G oil well cement + 4 parts by weight of fluid loss reducer + 42 parts by weight of water + 15 parts by weight of NaCl; the density of the cement slurry is 1.90 SG.

[0163] Table 9. API water loss of the water loss reducing agents in Examples 1-4 and Comparative Examples 1-3 at 200°C in saturated brine.

[0164] serial number Test temperature (°C) API water loss (mL) Example 1 200 69 Example 2 200 72 Example 3 200 64 Example 4 200 65 Comparative Example 1 200 112 Comparative Example 2 200 128 Comparative Example 3 200 106

[0165] As can be seen from the above experimental data, the water loss reducing agent provided in the above embodiments of the present invention has better high temperature resistance and salt resistance than the water loss reducing agent in the comparative example.

Claims

1. A method for preparing a multifunctional fluid loss reducing agent for oil well cement slurry, comprising the following steps: The reaction mixture containing 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid and acryloyloxyethyl dimethyl benzyl ammonium chloride is subjected to a polymerization reaction to obtain the multifunctional fluid loss reducing agent for oil well cement slurry. The weight ratio of 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid and acryloyloxyethyl dimethylbenzylammonium chloride is (1-2):(7-8):(0.4-0.6):(0.7-0.8). Alternatively, the weight ratio of 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, and acryloyloxyethyl dimethylbenzylammonium chloride is (4.5-5.5):(6-7):(0.7-0.8):(0.8-1.2). Alternatively, the weight ratio of 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid and acryloyloxyethyl dimethyl benzyl ammonium chloride is (7-8):(1-2):(7-8):(1-3); Alternatively, the weight ratio of 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid and acryloyloxyethyl dimethylbenzylammonium chloride is (8-10):(0.1-0.3):(0.6-0.8):(0.2-0.4).

2. The preparation method according to claim 1, wherein, The weight ratio of 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid and acryloyloxyethyl dimethyl benzyl ammonium chloride is 1:7:0.5:0.

72.

3. The preparation method according to claim 1, wherein, The weight ratio of 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid and acryloyloxyethyl dimethyl benzyl ammonium chloride is 5:6.2:0.75:

1.

4. The preparation method according to claim 1, wherein, The weight ratio of 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid and acryloyloxyethyl dimethylbenzylammonium chloride is (7-8):1.6:7.2:

2.

5. The preparation method according to claim 1, wherein, The weight ratio of 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, and acryloyloxyethyl dimethylbenzylammonium chloride is (8-10): 0.1：0.7：0.3。 6. The preparation method according to claim 1, wherein, The reaction mixture further includes an initiator, which is used in an amount of 0.5-1% based on the total weight of the reaction mixture (100%).

7. The preparation method according to claim 6, wherein, The initiator includes a peroxide solution with a mass concentration of 5-20%.

8. The preparation method according to claim 7, wherein, The peroxide solution includes one or a combination of several of the following: ammonium persulfate solution, potassium persulfate solution, and sodium persulfate solution.

9. The preparation method according to claim 1, wherein, The reaction mixture also includes water.

10. The preparation method according to claim 1, wherein, The preparation method includes the following steps: (1) Mix 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, p-vinylbenzoic acid, acryloyloxyethyl dimethyl benzyl ammonium chloride and water to obtain a mixed solution; (2) The mixed solution obtained in step (1) is mixed with an initiator and subjected to a polymerization reaction to obtain the multifunctional water loss reducing agent for oil well cement slurry.

11. The preparation method according to claim 10, wherein, In step (1), the pH value of the mixed solution is 7.0-10.

0.

12. The preparation method according to claim 11, wherein, In step (1), the pH value of the mixed solution is 8.0-9.

0.

13. The preparation method according to claim 1 or 10, wherein, The polymerization reaction is carried out at a temperature of 45-65℃ for 2-4 hours.

14. The preparation method according to claim 13, wherein, The polymerization reaction is carried out at a temperature of 50-60℃ for 3 hours.

15. A multifunctional fluid loss reducing agent for oil well cement slurry, which is prepared by the preparation method of the multifunctional fluid loss reducing agent for oil well cement slurry according to any one of claims 1-14.

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