Gemini polymer composite saline filtrate reducer and preparation method thereof

Abstract

The invention relates to the technical field of petrochemical additives for oil fields, and discloses a gemini polymer composite saline filtrate reducer and a preparation method thereof. The preparation method comprises the following steps: adding water, acrylamide, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid and calcium carbonate into a reactor according to a mass ratio to prepare a mixed solution; adjusting the pH value; adding an initiator to carry out polymerization reaction; and crushing the reaction product to obtain the gemini polymer composite salt water filtrate reducer. The gemini polymer composite salt water filtrate reducer prepared by the invention is high in temperature resistance and composite salt resistance, the rheological property of slurry is improved, the filter loss of the slurry is reduced, the quality of a mud cake is improved, a well wall is effectively stabilized, and particularly, the effect of preventing the well wall from collapsing in a deep well or an ultra-deep well is excellent; natural rigid materials are adopted, and the manufacturing cost is low; the preparation method is simple, convenient and easy to popularize and apply.

Description

Technical Field

[0001] This invention relates to the field of petrochemical additives for oilfields, specifically to a gemini polymer composite brine filtration reducer and its preparation method. Background Technology

[0002] As is well known, petroleum is a non-renewable and high-quality energy source. With the development of the domestic and international petroleum industry and the continuous growth of demand for petroleum, oil and gas field exploration and development are increasingly utilizing and exploiting oil and gas reservoirs in harsh environments, shifting from shallow to deep formations and from shallow to deep sea. This is becoming increasingly difficult, one important manifestation of which is the increase in well depth. According to the internationally accepted classification standards in the drilling industry, wells with a depth of 4570m or more are called deep wells, and wells with a depth of 6100m or more are called ultra-deep wells. In deep or ultra-deep wells, the bottom of the well is exposed to harsh conditions such as high concentrations of formation water containing Na⁺, Ca²⁺, and Mg²⁺, high temperature, and high pressure. Tectonic stress is not released, increasing the hardness and brittleness of the formation and making severe wellbore collapse more likely. However, current filtration reduction agents are relatively effective in preventing wellbore collapse in shallow and medium-deep wells, but their effectiveness is poor in preventing wellbore collapse in deep or ultra-deep wells. Summary of the Invention

[0003] To overcome the shortcomings of existing technologies, this invention provides a gemini polymer composite brine filtration reducer and its preparation method, the technical solution of which is as follows: A method for preparing a gemini polymer composite brine filtration reducer includes the following steps: (1) Preparation of a mixture: Water, acrylamide, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, and calcium carbonate are added to the reactor in a mass ratio of (1-3):(3-8):(2-7):(2-6):(4-8) to prepare a mixture; (2) Adjusting pH value: Add alkaline substances to the mixture prepared in step (1) to control the pH value of the polymerization system to 8.0-9.0; (3) Polymerization reaction: Add an initiator to the polymerization system in step (2) to carry out the polymerization reaction. The initial temperature is controlled at 50-70℃. After the polymerization reaction is completed, the dried gemini polymer is obtained. (4) Crushing: The dried gemini polymer obtained in step (3) is crushed to obtain the gemini polymer composite brine filtration reducer.

[0004] Furthermore, in step (2), the alkaline substance is sodium hydroxide.

[0005] Furthermore, in step (2), the pH value is controlled at 8.5.

[0006] Furthermore, the initiator in step (3) is a mixture of ammonium sulfate and sodium bisulfite.

[0007] Furthermore, the ammonium sulfate accounts for 0.3% of the total mass of acrylamide, acrylic acid, and 2-acrylamide-2-methylpropanesulfonic acid.

[0008] Furthermore, the sodium bisulfite accounts for 0.2% of the total mass of acrylamide, acrylic acid, and 2-acrylamide-2-methylpropanesulfonic acid.

[0009] Furthermore, the initial temperature of step (3) is controlled at 55-65℃. If the temperature is not well controlled, it is easy to cause the temperature to be too high, resulting in the molecular weight of the product being too large or causing explosive polymerization.

[0010] Furthermore, the polymerization reaction time in step (3) is 5 to 10 minutes.

[0011] Furthermore, the polymerization reaction time is 6 to 9 minutes.

[0012] A gemini polymer composite brine filtration reducer is prepared by the method described above.

[0013] The synthesis mechanism and approach of the gemini polymer composite brine filtration loss reducer of this invention are as follows: The product of this invention is a spherical polymer centered on an inorganic linker, possessing a unique three-dimensional molecular structure and strong molecular chain rigidity, exhibiting higher thermal stability compared to linear organic monomer polymers. The flexible polymer segments are linked by -CC-, with a thermal decomposition temperature above 250℃, demonstrating high-temperature stability. The synergistic effect of different types of adsorption groups in the macromolecule makes its adsorption on clay particles more robust, slowing down the high-temperature desorption phenomenon. The introduction of inorganic monomers improves the hydrolytic stability of the adsorbent clusters and suppresses the high-temperature desorption tendency of the adsorption groups, forming a gemini polymer composite brine filtration reducer. The core technology of the completion fluid system developed based on this mechanism involves using organic monomers and the natural rigid material calcium carbonate to concentrate and form micelles on the surface of the wellbore rock. Relying on the interfacial attraction and deformability of polymer micelles or particles, it can seal a large area of ​​pores and throats on the rock surface, forming a dense, impermeable sealing film. This effectively seals formations with varying permeability and micro-fractured shale layers, completely isolating the drilling fluid and its filtrate from the formation. This enables low filtrate loss drilling, preventing fluid loss from the wellbore to the reservoir, improving reservoir inhibition, and protecting oil and gas reservoirs from contamination. It meets the technical requirements of Sinopec's enterprise standard Q / SH CG0073-2023, "Sulfonate Polymer Filtration Reducer for Drilling Fluids (Compound Brine)". This invention selects suitable reactive monomers as linking groups, copolymerizing them with various monomers or raw materials to form block polymers. A reasonable monomer ratio is determined to obtain a series of products with suitable relative molecular mass, functional group ratio, and different configurations. The molecular design combines the polymer's microstructure and macrostructure. A natural rigid material combined with various monomers to form a drilling fluid treatment agent exhibits strong temperature and salt resistance, especially resistance to calcium and magnesium, achieving effects comparable to sulfonate polymers. This invention uses a mixed-liquid polymerization method to synthesize 2-acrylamide-2-methylpropanesulfonic acid copolymers. During synthesis, depending on the required relative molecular mass of the product, the monomer content and polymerization can be adjusted (high relative molecular mass product) or high monomer content and polymerization (relatively high relative molecular mass product). Carbon-chain polymers are selected to improve the polymer's thermal stability; monomers that provide large or rigid side groups, such as 2-acrylamide-2-methylpropanesulfonic acid, are introduced to improve the polymer's thermal stability and salt resistance; monomers that inhibit amide hydrolysis or are hydrolysis-resistant are introduced to improve the polymer's temperature and salt resistance. Meanwhile, as a drilling fluid treatment agent, it should also meet the following requirements: good compatibility with existing treatment agents; relatively abundant raw material sources, low production costs, and product prices acceptable to the market; in addition to the performance of conventional treatment agents, the product should also have a strong ability to inhibit shale expansion and dispersion to meet the needs of stabilizing the drilling wall, preventing collapse, and controlling formation mud making; and be suitable for various types of water-based drilling fluid systems.

[0014] Compared with the prior art, the present invention has the following main advantages: 1. The gemini polymer composite brine filtration reducer of the present invention is a series of products with suitable relative molecular mass and functional group ratio obtained by copolymerizing reactive gemini or raw materials. It has strong resistance to temperature and complex salts, strong anti-collapse ability, and strong lubrication ability. It can effectively improve the rheological properties of drilling mud, reduce the filtration loss of drilling mud, and improve the quality of mud cake. It is an important chemical treatment agent for maintaining the stability of drilling fluid performance, reducing the filtration loss of harmful fluids into the formation, stabilizing the wellbore, ensuring the regularity of well diameter, and protecting oil and gas reservoirs. It plays an important role in safe and efficient drilling and preventing drilling accidents, especially in preventing wellbore collapse in deep or ultra-deep wells.

[0015] 2. The present invention uses natural rigid materials, which can significantly reduce the cost of high-performance drilling fluid treatment agents, giving them a price advantage and achieving the goal of low-cost and high-quality drilling fluid treatment agents.

[0016] 3. The preparation method of this invention is simple and easy to implement, which is conducive to its widespread application. Detailed Implementation

[0017] The present invention will now be described in detail with reference to specific embodiments. Example 1

[0018] Water, acrylamide, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, and calcium carbonate were added to a reactor in a mass ratio of 1:3:2:2:4 to prepare a mixture. Sodium hydroxide was added to the mixture to control the pH of the polymerization system at 8.0. Then, an initiator (a mixture of ammonium sulfate and sodium bisulfite, wherein ammonium sulfate and sodium bisulfite account for 0.3% and 0.2% of the total mass of acrylamide, acrylic acid, and 2-acrylamide-2-methylpropanesulfonic acid, respectively) was added to carry out the polymerization reaction. The initial temperature of the polymerization reaction was 50°C, and the polymerization time was 5 minutes. After the polymerization reaction was completed, a dried gemini polymer was obtained. After pulverization, a gemini polymer composite brine filtration loss reducer was obtained. Example 2

[0019] Water, acrylamide, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, and calcium carbonate were added to a reactor in a mass ratio of 3:8:7:6:8 to prepare a mixture. Sodium hydroxide was added to the mixture to control the pH of the polymerization system at 8.5. Then, an initiator (a mixture of ammonium sulfate and sodium bisulfite, wherein ammonium sulfate and sodium bisulfite account for 0.3% and 0.2% of the total mass of acrylamide, acrylic acid, and 2-acrylamide-2-methylpropanesulfonic acid, respectively) was added to carry out the polymerization reaction. The initial temperature of the polymerization reaction was 55°C, and the polymerization time was 5 minutes. After the polymerization reaction was completed, a dried gemini polymer was obtained. After pulverization, a gemini polymer composite brine filtration loss reducer was obtained. Example 3

[0020] Water, acrylamide, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, and calcium carbonate were added to a reactor in a mass ratio of 2:5:4:4:6 to prepare a mixed solution. Sodium hydroxide was added to the mixed solution to control the pH of the polymerization system at 8.5. Then, an initiator (a mixture of ammonium sulfate and sodium bisulfite, wherein ammonium sulfate and sodium bisulfite account for 0.3% and 0.2% of the total mass of acrylamide, acrylic acid, and 2-acrylamide-2-methylpropanesulfonic acid, respectively) was added to carry out the polymerization reaction. The initial temperature of the polymerization reaction was 50°C, and the polymerization time was 7 minutes. After the polymerization reaction was completed, a dried gemini polymer was obtained. After pulverization, a gemini polymer composite brine filtration loss reducer was obtained. Example 4

[0021] Water, acrylamide, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, and calcium carbonate were added to a reactor in a mass ratio of 1:3:8:7:6 to prepare a mixture. Sodium hydroxide was added to the mixture to control the pH of the polymerization system at 8.0. Then, an initiator (a mixture of ammonium sulfate and sodium bisulfite, wherein ammonium sulfate and sodium bisulfite account for 0.3% and 0.2% of the total mass of acrylamide, acrylic acid, and 2-acrylamide-2-methylpropanesulfonic acid, respectively) was added to carry out the polymerization reaction. The initial temperature of the polymerization reaction was 55°C, and the polymerization time was 6 minutes. After the polymerization reaction was completed, a dried gemini polymer was obtained. After pulverization, a gemini polymer composite brine filtration loss reducer was obtained. Example 5

[0022] Water, acrylamide, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, and calcium carbonate were added to a reactor in a mass ratio of 2:8:2:4:5 to prepare a mixture. Sodium hydroxide was added to the mixture to control the pH of the polymerization system at 8.5. Then, an initiator (a mixture of ammonium sulfate and sodium bisulfite, wherein ammonium sulfate and sodium bisulfite account for 0.3% and 0.2% of the total mass of acrylamide, acrylic acid, and 2-acrylamide-2-methylpropanesulfonic acid, respectively) was added to carry out the polymerization reaction. The initial temperature of the polymerization reaction was 70°C, and the polymerization time was 9 minutes. After the polymerization reaction was completed, a dried gemini polymer was obtained. After pulverization, a gemini polymer composite brine filtration loss reducer was obtained. Example 6

[0023] Water, acrylamide, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, and calcium carbonate were added to a reactor in a mass ratio of 3:8:6:6:4 to prepare a mixture. Sodium hydroxide was added to the mixture to control the pH of the polymerization system at 9.0. Then, an initiator (a mixture of ammonium sulfate and sodium bisulfite, wherein ammonium sulfate and sodium bisulfite account for 0.3% and 0.2% of the total mass of acrylamide, acrylic acid, and 2-acrylamide-2-methylpropanesulfonic acid, respectively) was added to carry out the polymerization reaction. The initial temperature of the polymerization reaction was 65°C, and the polymerization time was 10 minutes. After the polymerization reaction was completed, a dried gemini polymer was obtained. After pulverization, a gemini polymer composite brine filtration loss reducer was obtained. Example 7

[0024] Well 23-12-11 is a new rolling production well developed in the higher part of the No. 5 pile depression in the Zhanhua Depression of the Jiyang Depression. The well is located at 159° azimuth and 207m from the wellhead of Well 23-11-11 in the No. 5 pile oilfield. The designed well depth is 3832.30m, and the drilled formation is the Sha-3 section. The drilling objective is to improve the development well network of the second oil group in the Sha-3 section of the pile 23 fault block. The well section (2130~3832.3m) consists of the Dongying Formation and the upper part of the Shahejie Formation. Drilling fluid treatment focuses on controlling fluid loss and preventing collapse. Add 2 tons of the gemini polymer composite brine filtration reducer prepared in Example 1 to ensure that medium-pressure water loss is less than 5 mL and high-temperature, high-pressure water loss is less than 12 mL. All drilling fluid performance parameters meet design specifications and downhole requirements, improving the inhibition of the drilling fluid system. Simultaneously, proper use of solids control equipment lays a solid foundation for improved drilling speed and stable drilling fluid performance. Fully utilize the gemini polymer composite brine filtration reducer to control water loss, improve mud cake quality, and further stabilize the wellbore. Simultaneously, carefully observe the wellhead return of cuttings, and promptly assess downhole conditions based on changes in the shape of the cuttings returned from the vibrating screen, improving the drilling fluid's suspension and proppant-carrying capacity to ensure drilling safety. In the Dongying and Shahejie Formations, each trip must involve a short trip and run-out to observe the aftereffects and clean the wellbore. Adjust the drilling fluid density promptly according to actual conditions to ensure wellbore stability.

[0025] The filtration loss reducers prepared in Examples 1-6 were tested according to the technical requirements of Table 2 of Sinopec standard Q / SH CG0073-2023 for drilling fluid sulfonate polymer filtration loss reducers (composite brine). The test results are shown in Table 1.

[0026] Table 1. Test results according to the technical requirements of drilling fluid sulfonate polymer filtration reducer (compound brine). ; As can be seen from Table 1, the gemini polymer composite brine filtration reducers prepared in Examples 1 to 6 meet the requirements; Example 7 demonstrated good performance through actual field use.

Claims

1. A method for preparing a gemini polymer composite brine filtration reducer, characterized in that, Includes the following steps: (1) Preparation of a mixture: Water, acrylamide, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, and calcium carbonate are added to the reactor in a mass ratio of (1-3):(3-8):(2-7):(2-6):(4-8) to prepare a mixture; (2) Adjusting pH value: Add alkaline substances to the mixture prepared in step (1) to control the pH value of the polymerization system to 8.0-9.0; (3) Polymerization reaction: Add an initiator to the polymerization system in step (2) to carry out the polymerization reaction. The initial temperature is controlled at 50-70℃. After the polymerization reaction is completed, the dried gemini polymer is obtained. (4) Crushing: The dried gemini polymer obtained in step (3) is crushed to obtain the gemini polymer composite brine filtration reducer.

2. The method for preparing a gemini polymer composite brine filtration reducer according to claim 1, characterized in that, In step (2), the alkaline substance used is sodium hydroxide.

3. The preparation method of the gemini polymer composite brine filtration reducer according to claim 1, characterized in that, In step (2), the pH value is controlled at 8.

5.

4. The method for preparing a gemini polymer composite brine filtration reducer according to claim 1, characterized in that, The initiator in step (3) is a mixture of ammonium sulfate and sodium bisulfite.

5. The method for preparing a gemini polymer composite brine filtration reducer according to claim 4, characterized in that, The ammonium sulfate accounts for 0.3% of the total mass of acrylamide, acrylic acid, and 2-acrylamide-2-methylpropanesulfonic acid.

6. The method for preparing a gemini polymer composite brine filtration reducer according to claim 4, characterized in that, The sodium bisulfite accounts for 0.2% of the total mass of acrylamide, acrylic acid, and 2-acrylamide-2-methylpropanesulfonic acid.

7. The preparation method of the gemini polymer composite brine filtration reducer according to claim 1, characterized in that, The initial temperature of step (3) is controlled at 55-65℃.

8. The method for preparing a gemini polymer composite brine filtration reducer according to claim 1, characterized in that, The polymerization reaction time in step (3) is 5 to 10 minutes.

9. The method for preparing a gemini polymer composite brine filtration reducer according to claim 8, characterized in that, The polymerization reaction time is 6 to 9 minutes.

10. A gemini polymer composite brine filtration reducer, characterized in that, The filtration loss reducer is prepared by the method described in any one of claims 1-9 for preparing a gemini polymer composite brine filtration loss reducer.