A corncob modified pre-crosslinked gel particle for profile control and its preparation method
By introducing modified corn cob and nano-bentonite into gel particles, corn cob modified pre-crosslinked gel particles with stable water absorption rate and high strength were prepared, which solved the problems of unstable gelation and deterioration of strength in the existing technology, and improved the deep-penetration regulation effect and increased the recovery rate of low-permeability areas of oilfields.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SOUTHWEST PETROLEUM UNIV
- Filing Date
- 2025-08-21
- Publication Date
- 2026-06-09
AI Technical Summary
Existing deep profile control technologies, such as weak gels and pre-crosslinked gels, suffer from problems in oilfield applications, including unstable gelation, poor colloidal properties, rapid water absorption and swelling rate, small profile control radius, and decreased strength, making it difficult to effectively improve the recovery rate of low-permeability oilfields.
Corn cob modified pre-crosslinked gel particles were prepared by introducing modified corn cob and nano-bentonite into the gel and using acrylamide for polymerization reaction, resulting in gel particles with stable water absorption rate and high strength.
It slows down the water absorption rate of gel particles, improves the strength and water retention of gel particles, enhances the regulation and driving effect, can effectively penetrate deep into the oilfield and play a long-term role, and improves the recovery rate of low-permeability areas of the oilfield.
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Figure CN121086138B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of oilfield chemical technology, specifically to a corn cob modified pre-crosslinked gel particle for pressure regulation and its preparation method. Background Technology
[0002] Most of my country's oilfields have entered the middle and late stages of exploitation, and have entered a high water-cut stage. The heterogeneity of the reservoirs is gradually increasing, forming water flow dominance channels, resulting in ineffective circulation of injected water. Moreover, more than 60% of crude oil remains in the low-permeability areas of the reservoir. Improving the crude oil recovery rate in the low-permeability areas of the oilfield is the only way to improve the overall recovery rate.
[0003] Deep profile control technology is a commonly used technique in tertiary oil recovery. It primarily focuses on deep profile modification, combining the effects of "adjusting the water absorption profile" with "regulating the drive" to simultaneously improve sweep efficiency and oil displacement efficiency. Currently, commonly used deep profile control technologies mainly include weak gel deep profile control, colloidal dispersed gel deep profile control, pre-crosslinked gel particle deep profile control fluid flow diversion technology, oil-bearing sludge composite profile control technology, and microbial profile control.
[0004] The primary function of weak gels is to seal high-permeability layers. Displacement is only a part of the weak gel's role during its movement through these layers, aiming to minimize the entry of displacement agents into unwashed low-permeability areas and reduce damage to the oil reservoir. However, the effectiveness of this technology often varies significantly across different well groups, and unstable gelation prevents the achievement of ideal economic benefits. Furthermore, this technology can damage the reservoir to varying degrees, increasing the complexity of oil-water distribution.
[0005] Colloidal dispersions form dispersed gel clusters through intramolecular and partial intermolecular crosslinking between polymers and crosslinking agents. They exhibit good temperature and salt resistance, are safe and environmentally friendly, and have a lower viscosity than polymer solutions of the same concentration. They are primarily suitable for reservoirs with mild heterogeneity and a coefficient of variation below 0.8, but not for fractured or large-pore oilfields. Furthermore, colloidal dispersions have a narrow gelation range, and the gelation reaction is significantly affected by factors such as reservoir temperature, salinity, pH, polymer concentration, and crosslinking agent concentration, resulting in relatively poor colloidal properties.
[0006] Pre-crosslinked gel particles are dry gels obtained by reacting and processing polymeric monomers, crosslinking agents, and proppants. They effectively avoid the instability of weak gels and the poor colloidal properties of colloidal dispersions. While these plugging agents are widely used and have achieved good results, some problems still exist in field applications: the water absorption and swelling rate is too fast, resulting in a small profile control radius, making deep profile control difficult; the mechanical strength deteriorates after water absorption and swelling, accompanied by degradation, preventing long-term effectiveness. Summary of the Invention
[0007] In view of this, the present invention proposes a corn cob modified pre-crosslinked gel particle for regulated driving and its preparation method, which prepares a gel particle with stable water absorption rate and high strength.
[0008] This invention discloses a method for preparing corn cob-modified pre-crosslinked gel particles for modulated displacement, comprising the following steps:
[0009] By weight, 18-25 parts of acrylamide, 5-10 parts of modified corn cob, and 5-10 parts of nano-bentonite are added to a crosslinking agent and an initiator, and the polymerization reaction is carried out at 30℃-85℃ for 4-8 hours. After the reaction is completed, the product is dried, pulverized, and granulated to obtain the final product.
[0010] One embodiment of the present invention comprises a method for preparing the modified corn cob, including the following steps:
[0011] Step S1: Take 10g~15g of corn cob that has passed through a 100-mesh sieve and add it to 200mL~300mL of NaOH solution with a concentration of 18%~23%, and alkalize it at 110°C~120°C for 4h~6h. Filter and collect the filter residue, and dry it at 60°C~80°C to obtain alkalized corn cob.
[0012] Step S2: Add 5g~10g of alkalized corn cob to 100mL~200mL of toluene and keep it at 40℃~50℃ for 5h~6h. Slowly add 2g~4g of maleic anhydride dissolved in 40mL~60mL of acetone. After the addition is complete, react at 80℃~90℃ for 2h~3h. After the reaction is complete, filter, collect the product, wash it 3~4 times, and dry it under vacuum at 60℃~70℃ to obtain the product.
[0013] One embodiment of the present invention is that the nano-bentonite particles can pass through a 1250-mesh sieve.
[0014] In one embodiment of the present invention, the amount of crosslinking agent added is 0.05 to 0.2 parts by weight.
[0015] Furthermore, the crosslinking agent is one of N,N-methylenebisacrylamide and methyl-reactive phenolic resin.
[0016] In one embodiment of the present invention, the amount of the initiator added is 0.005 to 0.02 parts by weight.
[0017] Furthermore, the initiator is one of a redox initiator, a water-soluble azo initiator, or a persulfate.
[0018] And the corn cob modified pre-crosslinked gel particles prepared using the above steps.
[0019] The technical advantages of this invention are as follows:
[0020] This invention uses acrylamide as the base monomer for gelation and adds modified corn cob for chemical reaction. The modified corn cob introduced into the gel can fully utilize the water absorption and porous properties of corn cob, allowing nano-bentonite and acrylamide to enter the corn cob and react simultaneously. This slows down the water absorption rate of the corn cob-modified pre-crosslinked gel particles, significantly improves the strength and water retention performance of the gel particles, and enables the modified corn cob disclosed in this invention to effectively improve the regulation and driving effect. Attached Figure Description
[0021] Figure 1 The figures show the expansion performance test results of various embodiments and comparative examples in this invention. Detailed Implementation
[0022] The present invention will be further described in detail below with reference to the embodiments. However, the implementation of the present invention is not limited thereto. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.
[0023] Example 1:
[0024] Preparation of modified corn cobs:
[0025] Step S1: Take 10g of corn cob that has passed through a 100-mesh sieve and add it to 200mL of 20% NaOH solution. Alkalize it at 120℃ for 4h. Filter and collect the filter residue. Dry it at 60℃ to obtain alkalized corn cob.
[0026] Step S2: Add 5g of alkalized corn cob to 100mL of toluene and keep it at 40℃ for 5h. Slowly add 2g of maleic anhydride dissolved in 40mL of acetone. After the addition is complete, react at 80℃ for 2h. After the reaction is complete, filter, collect the product, wash it 3 times, and dry it under vacuum at 60℃ to obtain the final product.
[0027] Preparation of modified corn cob pre-crosslinked gel particles:
[0028] 20g acrylamide, 5g modified corn cob, 5g sodium bentonite, and 0.1g N,N-methylenebisacrylamide were dissolved in 70g water and stirred for 30 minutes. Nitrogen gas was then introduced into the system for deoxygenation for 30 minutes. Then, 0.01g ammonium persulfate was added, and nitrogen gas was continued for another 30 minutes. The temperature was then raised to 80°C, and the reaction was carried out for 4 hours. Heating was then stopped to obtain a gel colloid. The colloid was dried at 80°C, pulverized, and granulated to obtain corn cob-modified pre-crosslinked gel particles with a median particle size of 28.6μm.
[0029] Example 2:
[0030] Preparation of modified corn cobs:
[0031] Step S1: Take 10g of corn cob that has passed through a 100-mesh sieve and add it to 200mL of 20% NaOH solution. Alkalize it at 120℃ for 4h. Filter and collect the filter residue. Dry it at 60℃ to obtain alkalized corn cob.
[0032] Step S2: Add 5g of alkalized corn cob to 100mL of toluene and keep it at 40℃ for 5h. Slowly add 2g of maleic anhydride dissolved in 40mL of acetone. After the addition is complete, react at 80℃ for 2h. After the reaction is complete, filter, collect the product, wash it 3 times, and dry it under vacuum at 60℃ to obtain the final product.
[0033] Preparation of modified corn cob pre-crosslinked gel particles:
[0034] 20g acrylamide, 10g modified corn cob, 5g sodium bentonite, and 0.1g N,N-methylenebisacrylamide were dissolved in 65g water and stirred for 30 minutes. Nitrogen gas was then introduced into the system for deoxygenation for 30 minutes. Then, 0.01g ammonium persulfate was added, and nitrogen gas was continued for another 30 minutes. The temperature was then raised to 80°C, and the reaction was carried out for 4 hours. Heating was then stopped to obtain a gel colloid. The colloid was dried at 80°C, pulverized, and granulated to obtain corn cob-modified pre-crosslinked gel particles with a median particle size of 28.6μm.
[0035] Example 3:
[0036] Preparation of modified corn cobs:
[0037] Step S1: Take 10g of corn cob that has passed through a 100-mesh sieve and add it to 200mL of 20% NaOH solution. Alkalize it at 120℃ for 4h. Filter and collect the filter residue. Dry it at 60℃ to obtain alkalized corn cob.
[0038] Step S2: Add 5g of alkalized corn cob to 100mL of toluene and keep it at 40℃ for 5h. Slowly add 2g of maleic anhydride dissolved in 40mL of acetone. After the addition is complete, react at 80℃ for 2h. After the reaction is complete, filter, collect the product, wash it 3 times, and dry it under vacuum at 60℃ to obtain the final product.
[0039] Preparation of modified corn cob pre-crosslinked gel particles:
[0040] 20g acrylamide, 5g modified corn cob, 10g sodium bentonite, and 0.1g N,N-methylenebisacrylamide were dissolved in 65g water and stirred for 30 minutes. Nitrogen gas was then introduced into the system for deoxygenation for 30 minutes. Then, 0.01g ammonium persulfate was added, and nitrogen gas was continued for another 30 minutes. The temperature was then raised to 80°C, and the reaction was carried out for 4 hours. Heating was then stopped to obtain a gel colloid. The colloid was dried at 80°C, pulverized, and granulated to obtain corn cob-modified pre-crosslinked gel particles with a median particle size of 28.6μm.
[0041] Comparative Example 1:
[0042] The implementation method and raw material usage of Comparative Example 1 are basically the same as those of Example 1. The difference is that corn cobs were not added to the raw materials of Comparative Example 1, but all other contents are the same.
[0043] Performance Evaluation
[0044] 1. Expansion performance test
[0045] The median particle size of the corn cob-modified pre-crosslinked gel particles prepared in the examples and comparative examples was measured using a laser particle size analyzer. The corresponding weight expansion factor was calculated based on the weight of the gel particles to determine their slow-swelling property. Figure 1 It can be seen that, under conditions of 100℃ and a mineralization of 200,000, the gel particles in each embodiment swell slowly in the first 30 days, and the swelling rate slows down after 30 days; while the gel particles in the comparative example rapidly reach the maximum swelling ratio within 20 days, and then dehydrate. Therefore, it can be concluded that the corn cob modified gel particles have a slower swelling rate, which is beneficial for ground dispensing and deep migration.
[0046] 2. Strength performance test
[0047] The strength of the gel particles was significantly improved due to the introduction of corn cob and sodium bentonite. The strength of the gel particles prepared in each example and comparative example was evaluated using the directional pressure method. The water salinity was 200,000, and the temperature was 100℃. As shown in Table 1, the introduction of corn cob effectively improved the strength of the gel particles, and the directional pressure continued to increase after 60 days of aging. In contrast, the strength of the gel particles without corn cob significantly decreased after 60 days of aging.
[0048] Table 1. Results of the redirection pressure of gel particles (unit: kPa)
[0049]
[0050] 3. Drive performance test
[0051] The above-described embodiments and comparative examples were selected for sand-filled tube flooding experiments to study the modulated flooding performance of corn cob-modified pre-crosslinked gel particles. The permeability of the sand-filled tubes used in the experiments was approximately 3D, the experimental temperature was 100℃, and the salinity of the water used was 200,000. The experimental steps are as follows:
[0052] (1) Prepare sand-filled tubes (diameter 2.5cm, length 10cm) with similar permeability, and then saturate the sand-filled tubes with water under vacuum conditions;
[0053] (2) Inject crude oil (viscosity of 3.2 mPa·s at 100℃) into the core at a rate of 0.1 mL / min until the outlet end is free of water;
[0054] (3) Inject experimental water into the core at a rate of 0.5 ml / min until the water content of the produced fluid is 98%;
[0055] (4) Inject 0.6 PV of gel particle suspension (concentration 0.5%) into the sand-filled pipe at the same speed.
[0056] (5) Repeat the water drive at the same rate until the water content of the produced liquid is 98%.
[0057] The experimental results are shown in Table 2:
[0058] Table 2. Test Results of Adjustment Drive Performance
[0059]
[0060] The results from the examples and comparative examples show that after introducing corn cob into the gel particles, the gel particles have stronger strength and elastic deformation ability, and can penetrate deep into the sand-filled pipe for regulation and driving, thus improving the recovery rate. This proves that the corn cob modified pre-crosslinked gel particles of the present invention can achieve good results when used for regulation and driving.
[0061] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be defined by the scope of the claims.
Claims
1. A method for preparing corn cob-modified pre-crosslinked gel particles for modulated displacement, characterized in that, Includes the following steps: By weight, 18-25 parts of acrylamide, 5-10 parts of modified corn cob, and 5-10 parts of nano-bentonite are added to a crosslinking agent and an initiator and polymerized at 30℃-85℃ for 4-8 hours. After the polymerization is completed, the product is dried, pulverized, and granulated to obtain the product. The method for preparing modified corn cobs includes the following steps: Step S1: Take 10g~15g of corn cob that has passed through a 100-mesh sieve and add it to 200mL~300mL of NaOH solution with a concentration of 18%~23%, and alkalize it at 110°C~120°C for 4h~6h. Filter and collect the filter residue, and dry it at 60°C~80°C to obtain alkalized corn cob. Step S2: Add 5g~10g of alkalized corn cob to 100mL~200mL of toluene and keep it at 40℃~50℃ for 5h~6h. Slowly add 2g~4g of maleic anhydride dissolved in 40mL~60mL of acetone. After the addition is complete, react at 80℃~90℃ for 2h~3h. After the reaction is complete, filter, collect the product, wash it 3~4 times, and dry it under vacuum at 60℃~70℃ to obtain the product.
2. The method for preparing corn cob-modified pre-crosslinked gel particles for modulated displacement according to claim 1, characterized in that: The nano-bentonite particles can pass through a 1250-mesh sieve.
3. The method for preparing corn cob-modified pre-crosslinked gel particles for modulated displacement according to claim 1, characterized in that: The amount of crosslinking agent added is 0.05~0.2 parts by weight.
4. The method for preparing corn cob-modified pre-crosslinked gel particles for modulated displacement according to claim 3, characterized in that: The crosslinking agent is one of N,N-methylenebisacrylamide and methyl-reactive phenolic resin.
5. The method for preparing corn cob-modified pre-crosslinked gel particles for modulated displacement according to claim 1, characterized in that: The amount of the initiator added is 0.005 to 0.02 parts by weight.
6. The method for preparing corn cob-modified pre-crosslinked gel particles for modulated displacement according to claim 5, characterized in that: The initiator is one of a redox initiator, a water-soluble azo initiator, or a persulfate.
7. A corn cob-modified pre-crosslinked gel particle for modulated displacement, characterized in that, Prepared using the method described in any one of claims 1 to 6.