A profile control agent for oil exploitation and a preparation method thereof
By copolymerizing and crosslinking epoxy-grafted carboxymethyl cellulose with acrylamide and sodium styrene sulfonate, a multi-crosslinked profile control agent was constructed, which solved the problem of easy hydrolysis of traditional polyacrylamide gel at high temperatures. This resulted in an oil extraction profile control agent with high plugging strength and temperature resistance, improving oil recovery and reducing produced water content.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DONGYING KENUO PETROLEUM TECH CO LTD
- Filing Date
- 2026-05-11
- Publication Date
- 2026-06-05
AI Technical Summary
Traditional polyacrylamide gels are prone to hydrolysis under high-temperature reservoir conditions, which leads to a decrease in gel strength, affects plugging performance, and makes it difficult to effectively improve oil recovery and reduce produced water content.
By copolymerizing and crosslinking carboxymethyl cellulose with grafted epoxy groups with acrylamide and sodium styrene sulfonate, the cellulose skeleton is permanently anchored in the polymer network in the form of covalent bonds through the ring-opening reaction of epoxy groups, thus constructing a multi-crosslinked profile modifier that enhances temperature resistance and sealing strength.
It forms a stable three-dimensional network structure at high temperatures, which improves the plugging strength and temperature resistance of the profile control agent, effectively blocks high-permeability channels, and improves the sweep efficiency and oil displacement efficiency.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of petroleum extraction technology, specifically relating to a profile control agent for petroleum extraction and its preparation method. Background Technology
[0002] In oil extraction, the heterogeneity of the reservoir formation is one of the key factors restricting the improvement of oil recovery. Due to the presence of natural fractures and the formation of high-permeability channels caused by long-term water injection, injected water often flows along the high-permeability layers with low resistance, making it difficult to effectively reach the medium and low-permeability layers. This not only reduces the oil recovery rate but also leads to a significant increase in the produced water content. To solve this problem, profile control technology has emerged. Its core objective is to block high-permeability channels by injecting chemical agents, forcing subsequent injected fluids to redirect to the medium and low-permeability layers, thereby improving the sweep efficiency and oil displacement efficiency.
[0003] As a core material in deep profile control technology, the performance of profile control agents directly affects the profile control effect. Currently, polymer gel-based profile control agents are the most widely used type, with polyacrylamide gel systems dominating. These agents use acrylamide as a monomer and form a three-dimensional network structure through free radical polymerization. However, traditional polyacrylamide gels have significant performance defects under high-temperature reservoir conditions. The amide groups are prone to hydrolysis (CN111087988A, CN120005121A), leading to a decrease in gel strength or even disintegration, severely affecting plugging performance. Summary of the Invention
[0004] To address the problems existing in the prior art, this invention provides a profile control agent for oil exploration and its preparation method. By using epoxy-grafted carboxymethyl cellulose as an active backbone, it is copolymerized and crosslinked with acrylamide and sodium styrene sulfonate. The ring-opening reaction of the epoxy groups permanently anchors the cellulose backbone in the polymer network in the form of covalent bonds, thereby constructing a multi-crosslinked profile control agent with both high plugging strength and excellent temperature resistance.
[0005] The first aspect of this invention provides a profile control agent for petroleum development, comprising, by mass percentage: 5-8% acrylamide, 8-10% sodium styrene sulfonate, 1-2% grafted epoxy group carboxymethyl cellulose, 0.03-0.06% sodium formate, 0.05-0.15% crosslinking agent, 0.03-0.05% ammonium persulfate, with the balance being water.
[0006] Furthermore, the preparation method of grafted epoxy group carboxymethyl cellulose includes the following steps: Carboxymethyl cellulose was added to a sodium hydroxide solution and stirred thoroughly to induce swelling and activation. Then, tetrabutylammonium bromide was added and stirred to disperse the solution. Epichlorohydrin was then slowly added dropwise, and the mixture was heated to 60-70°C under nitrogen protection for 3-6 hours. After the reaction was completed, the pH was adjusted to neutral with dilute hydrochloric acid, the reaction solution was slowly poured into anhydrous ethanol to precipitate, filtered and washed with ethanol, and dried to obtain epoxy-grafted carboxymethyl cellulose.
[0007] Furthermore, the mass concentration of the sodium hydroxide solution is 10% to 15%.
[0008] Furthermore, the mass ratio of carboxymethyl cellulose to sodium hydroxide solution is 1:15~18.
[0009] Furthermore, the mass of tetrabutylammonium bromide is 3% to 5% of the mass of carboxymethyl cellulose.
[0010] Furthermore, the mass ratio of epichlorohydrin to carboxymethyl cellulose is 2~3:1.
[0011] Furthermore, the concentration of dilute hydrochloric acid is 0.5~1 mol / L.
[0012] Furthermore, the drying temperature is 60~80℃.
[0013] Furthermore, the crosslinking agent is N,N-methylenebisacrylamide.
[0014] A second aspect of the present invention provides a method for preparing the above-mentioned profile control agent for oil exploration, comprising the following steps: Acrylamide, sodium styrene sulfonate, grafted epoxy group carboxymethyl cellulose, sodium formate, crosslinking agent, and 60-70% water are mixed and then sealed with nitrogen gas for 5-10 minutes to form liquid A. Ammonium persulfate is dispersed in the remaining water to form liquid B. Liquid A and liquid B are then injected into the oil reservoir formation and thoroughly mixed to form a profile control agent for oil extraction.
[0015] Furthermore, the temperature of the oil reservoir strata is 60~120℃.
[0016] Under the action of the initiator, the components can slowly polymerize and crosslink in the temperature environment of the formation, forming a stable profile control material in situ. Sodium formate, as a free radical retarder, can slow down the polymerization and crosslinking reaction rate to a certain extent, preventing rapid gelation in the high-temperature near-wellbore zone and ensuring that the profile control material can be stabilized and gelled after deep migration.
[0017] The beneficial effects achieved by one or more technical solutions of the present invention are as follows: This invention utilizes epoxy-grafted carboxymethyl cellulose as a backbone, constructing a multi-layered cross-linked network with acrylamide and sodium styrene sulfonate, rather than a simple physical mixture. The principle involves pre-loading epoxy groups onto the carboxymethyl cellulose backbone with epichlorohydrin, and then, under the action of ammonium persulfate initiator, permanently anchoring the cellulose backbone covalently within the polyacrylamide-sodium styrene sulfonate three-dimensional network. Simultaneously, the sulfonate groups of sodium styrene sulfonate provide strong anionicity, maintaining stability over a wide temperature range to enhance temperature resistance, while the rigid benzene ring structure further enhances structural stability and inhibits high-temperature hydrolysis.
[0018] The epoxy groups play three main roles: First, one end of the epoxy group firmly connects to the carboxymethyl cellulose backbone, while the other end forms stable ether bonds with acrylamide and other compounds through ring-opening reactions, transforming cellulose from a physically encapsulated filler into the core backbone of the network. Second, the secondary crosslinking points introduced by the epoxy groups increase the overall crosslinking density, forming a denser and more robust three-dimensional structure, thereby significantly improving the material's strength and resistance to formation water erosion. Third, the amphiphilic hydroxyl ether segments generated after epoxy ring-opening effectively improve the interfacial affinity between the hydrophilic cellulose backbone and the hydrophobic styrene segments, preventing phase separation and ensuring material uniformity and stability. It is the synergistic effect of these three roles that gives this profile control agent both excellent plugging strength and temperature resistance. Detailed Implementation
[0019] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples.
[0020] Example 1
[0021] This embodiment provides a profile control agent for oil extraction, comprising, by mass percentage: 6% acrylamide, 8% sodium styrene sulfonate, 1% grafted epoxy group carboxymethyl cellulose, 0.05% sodium formate, 0.1% N,N-methylenebisacrylamide, 0.04% ammonium persulfate, with the balance being water; The preparation method is as follows: S1: Add carboxymethyl cellulose to a 15% sodium hydroxide solution with a mass ratio of 1:15. Stir thoroughly to allow swelling and activation. Then add tetrabutylammonium bromide, with a mass ratio of 4% of the carboxymethyl cellulose. Continue stirring to disperse. Then slowly add epichlorohydrin, with a mass ratio of 2:1 of epichlorohydrin to carboxymethyl cellulose. Under nitrogen protection, heat to 60°C and react for 4 hours. After the reaction was completed, the pH was adjusted to neutral with 1 mol / L dilute hydrochloric acid. The reaction solution was slowly poured into anhydrous ethanol to precipitate the precipitate. The precipitate was filtered, washed with ethanol, and dried at 70°C to obtain epoxy-grafted carboxymethyl cellulose. S2: Acrylamide, sodium styrene sulfonate, grafted epoxy group carboxymethyl cellulose, N,N-methylenebisacrylamide, sodium formate, and 70% water are mixed and deoxygenated with nitrogen for 10 minutes before sealing to form liquid A. Ammonium persulfate is dispersed in the remaining water to form liquid B. Then, liquid A and liquid B are injected into the oil reservoir formation and thoroughly mixed to form a profile control agent for oil extraction in the formation.
[0022] Example 2
[0023] This embodiment provides a profile control agent for oil extraction, comprising, by mass percentage: 8% acrylamide, 10% sodium styrene sulfonate, 2% grafted epoxy group carboxymethyl cellulose, 0.04% sodium formate, 0.15% N,N-methylenebisacrylamide, 0.05% ammonium persulfate, with the balance being water; The preparation method is as follows: S1: Add carboxymethyl cellulose to a 15% sodium hydroxide solution with a mass ratio of 1:18. Stir thoroughly to allow swelling and activation. Then add tetrabutylammonium bromide, with a mass ratio of 5% of the carboxymethyl cellulose. Continue stirring to disperse. Then slowly add epichlorohydrin, with a mass ratio of 3:1 of epichlorohydrin to carboxymethyl cellulose. Under nitrogen protection, heat to 60°C and react for 6 hours. After the reaction was completed, the pH was adjusted to neutral with 1 mol / L dilute hydrochloric acid. The reaction solution was slowly poured into anhydrous ethanol to precipitate the precipitate. The precipitate was filtered, washed with ethanol, and dried at 80°C to obtain epoxy-grafted carboxymethyl cellulose. S2: Acrylamide, sodium styrene sulfonate, grafted epoxy group carboxymethyl cellulose, N,N-methylenebisacrylamide, sodium formate, and 70% water are mixed and deoxygenated with nitrogen for 5 minutes before sealing to form liquid A. Ammonium persulfate is dispersed in the remaining water to form liquid B. Then, liquid A and liquid B are injected into the oil reservoir formation and thoroughly mixed to form a profile control agent for oil extraction in the formation.
[0024] Example 3
[0025] This embodiment provides a profile control agent for petroleum development, comprising, by mass percentage: 5% acrylamide, 8% sodium styrene sulfonate, 1% grafted epoxy group carboxymethyl cellulose, 0.03% sodium formate, 0.05% N,N-methylenebisacrylamide, 0.03% ammonium persulfate, with the balance being water; The preparation method is as follows: S1: Add carboxymethyl cellulose to a 10% sodium hydroxide solution with a mass ratio of 1:15. Stir thoroughly to allow swelling and activation. Then add tetrabutylammonium bromide, with a mass ratio of 3% of the carboxymethyl cellulose. Continue stirring to disperse. Then slowly add epichlorohydrin, with a mass ratio of 2:1 of epichlorohydrin to carboxymethyl cellulose. Under nitrogen protection, heat to 70°C and react for 5 hours. After the reaction was completed, the pH was adjusted to neutral with 0.5 mol / L dilute hydrochloric acid. The reaction solution was slowly poured into anhydrous ethanol to precipitate the precipitate. The precipitate was filtered, washed with ethanol, and dried at 80°C to obtain epoxy-grafted carboxymethyl cellulose. S2: Acrylamide, sodium styrene sulfonate, grafted epoxy group carboxymethyl cellulose, N,N-methylenebisacrylamide, sodium formate, and 60% water are mixed and deoxygenated with nitrogen for 10 minutes before sealing to form liquid A. Ammonium persulfate is dispersed in the remaining water to form liquid B. Then, liquid A and liquid B are injected into the oil reservoir formation and thoroughly mixed to form a profile control agent for oil extraction in the formation.
[0026] Example 4
[0027] This embodiment provides a profile control agent for petroleum development, comprising, by mass percentage: 6% acrylamide, 10% sodium styrene sulfonate, 2% grafted epoxy group carboxymethyl cellulose, 0.06% sodium formate, 0.1% N,N-methylenebisacrylamide, 0.03% ammonium persulfate, with the balance being water; The preparation method is as follows: S1: Add carboxymethyl cellulose to a 15% sodium hydroxide solution with a mass ratio of 1:15. Stir thoroughly to allow swelling and activation. Then add tetrabutylammonium bromide, with a mass ratio of 3% of the carboxymethyl cellulose. Continue stirring to disperse. Then slowly add epichlorohydrin, with a mass ratio of 3:1 of epichlorohydrin to carboxymethyl cellulose. Heat to 70°C under nitrogen protection and react for 4 hours. After the reaction was completed, the pH was adjusted to neutral with 1 mol / L dilute hydrochloric acid. The reaction solution was slowly poured into anhydrous ethanol to precipitate the precipitate. The precipitate was filtered, washed with ethanol, and dried at 80°C to obtain epoxy-grafted carboxymethyl cellulose. S2: Acrylamide, sodium styrene sulfonate, grafted epoxy group carboxymethyl cellulose, N,N-methylenebisacrylamide, sodium formate, and 70% water are mixed and deoxygenated with nitrogen for 10 minutes before sealing to form liquid A. Ammonium persulfate is dispersed in the remaining water to form liquid B. Then, liquid A and liquid B are injected into the oil reservoir formation and thoroughly mixed to form a profile control agent for oil extraction in the formation.
[0028] Comparative Example 1 This comparative example provides a profile control agent for oil extraction, comprising, by mass percentage: 6% acrylamide, 8% sodium styrene sulfonate, 1% carboxymethyl cellulose, 0.05% sodium formate, 0.1% N,N-methylenebisacrylamide, 0.04% ammonium persulfate, with the balance being water; The preparation method is as follows: Acrylamide, sodium styrene sulfonate, carboxymethyl cellulose, N,N-methylenebisacrylamide, sodium formate, and 70% water are mixed and deoxygenated by purging with nitrogen for 10 minutes before sealing to form solution A. Ammonium persulfate is dispersed in the remaining water to form solution B. Solution A and solution B are then injected into the oil reservoir formation for thorough mixing, forming a profile control agent for oil extraction in the formation.
[0029] Comparative Example 2 This embodiment provides a profile control agent for oil extraction, comprising, by mass percentage: 6% acrylamide, 8% styrene, 1% carboxymethyl cellulose, 0.05% sodium formate, 0.1% N,N-methylenebisacrylamide, 0.04% ammonium persulfate, with the balance being water; The preparation method is as follows: Acrylamide, styrene, carboxymethyl cellulose, N,N-methylenebisacrylamide, sodium formate, and 70% water are mixed and deoxygenated by purging with nitrogen for 10 minutes before sealing to form solution A. Ammonium persulfate is dispersed in the remaining water to form solution B. Solution A and solution B are then injected into the oil reservoir formation for thorough mixing, forming a profile control agent for oil extraction in the formation.
[0030] Performance testing: According to the SY / T 5590-2025 standard, the plugging performance of the profile control agents prepared in Examples 1-4 and Comparative Examples 1 and 2 was tested. Core simulation experiments were conducted to simulate a reservoir formation temperature of 100℃, and the permeability before and after plugging was tested. The experimental results are shown in Table 1. Table 1
[0031] After the profile control agents of Example 1, Comparative Examples 1 and 2 were gelled and cured in the core, the viscosity changes during the isothermal aging process at 100°C were measured. The results are shown in Table 2 (Example 1), Table 3 (Comparative Example 1), and Table 4 (Comparative Example 2).
[0032] Table 2
[0033] Table 3
[0034] Table 4
[0035] Tables 2, 3, and 4 show that the 100℃ environment has little effect on the profile control agent material after gelation in Example 1. No significant dehydration occurred after 120 days of prolonged storage, indicating that the internal network structure of the material is relatively stable. The profile control agent prepared in this invention exhibits excellent temperature resistance. In contrast, the profile control agents in Comparative Examples 1 and 2 showed a significant decrease in blocking rate at high temperatures and exhibited obvious shrinkage and dehydration, indicating that the structure of the profile control agent is unstable under high-temperature conditions, and dehydration and deformation occur over time, resulting in a loss of elasticity.
Claims
1. A profile control agent for oil extraction, characterized in that: By mass percentage, the components include: 5-8% acrylamide, 8-10% sodium styrene sulfonate, 1-2% grafted epoxy group carboxymethyl cellulose, 0.03-0.06% sodium formate, 0.05-0.15% crosslinking agent, 0.03-0.05% ammonium persulfate, and the balance being water.
2. The profile control agent used in oil extraction as described in claim 1, characterized in that: The preparation method of grafted epoxy group carboxymethyl cellulose includes the following steps: Carboxymethyl cellulose was added to a sodium hydroxide solution and stirred thoroughly to induce swelling and activation. Then, tetrabutylammonium bromide was added and stirred to disperse the solution. Epichlorohydrin was then slowly added dropwise and the temperature was raised to 60-70°C for 3-6 hours. After the reaction was completed, the pH was adjusted to neutral with dilute hydrochloric acid, the reaction solution was slowly poured into anhydrous ethanol to precipitate, filtered and washed with ethanol, and dried to obtain epoxy-grafted carboxymethyl cellulose.
3. The profile control agent for oil extraction as described in claim 2, characterized in that: The mass concentration of the sodium hydroxide solution is 10%~15%.
4. The profile control agent used in oil extraction as described in claim 2, characterized in that: The mass ratio of carboxymethyl cellulose to sodium hydroxide solution is 1:15~18.
5. The profile control agent for oil extraction as described in claim 2, characterized in that: The mass of tetrabutylammonium bromide is 3% to 5% of the mass of carboxymethyl cellulose.
6. The profile control agent for oil extraction as described in claim 2, characterized in that: The mass ratio of epichlorohydrin to carboxymethyl cellulose is 2~3:
1.
7. The profile control agent for oil extraction as described in claim 2, characterized in that: The concentration of dilute hydrochloric acid is 0.5~1 mol / L.
8. The profile control agent for oil extraction as described in claim 2, characterized in that: The drying temperature is 60~80℃.
9. The profile control agent for oil extraction as described in claim 1, characterized in that: The crosslinking agent is N,N-methylenebisacrylamide.
10. The method for preparing the profile control agent for petroleum development according to any one of claims 1 to 9, characterized in that: Includes the following steps: Acrylamide, sodium styrene sulfonate, grafted epoxy group carboxymethyl cellulose, sodium formate, crosslinking agent, and 60-70% water are mixed and deoxygenated with nitrogen for 5-10 minutes before being sealed to form solution A. Ammonium persulfate is dispersed in the remaining water to form solution B. Solution A and solution B are then injected into the formation and thoroughly mixed to form a profile control agent for oil extraction.