A gel particle for water plugging in unconsolidated sandstone gas reservoirs and a method for preparing the same
By cross-linking and polymerizing branched salt-tolerant monomers with fibrous sepiolite, the prepared gel particles exhibit high strength and excellent plugging performance in high-salinity reservoirs, solving the problem of gel particles being brittle and easily broken in high-salinity reservoirs, and achieving efficient plugging of water channeling channels.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- PETROCHINA CO LTD
- Filing Date
- 2022-08-29
- Publication Date
- 2026-05-29
AI Technical Summary
Existing gel particles have a brittle and easily broken network structure after absorbing water, resulting in poor long-term stability and making it difficult to effectively block water channeling in high-salinity oil reservoirs.
Gel particles for water shut-off in loose sandstone gas reservoirs were prepared by crosslinking and polymerization of branched salt-resistant monomer 2-acrylamido-2-tetradecyl ethanesulfonic acid with fibrous sepiolite and hydrophilic fibers. Ammonium persulfate and sodium pyrosulfate were used as initiators to control the crosslinking polymerization conditions and improve the tensile properties and salt resistance of the gel particles.
The prepared gel particles exhibit increased strength, significantly enhanced tensile properties, and improved plugging performance under high mineralization conditions, achieving a plugging rate of 93-98%, which is significantly superior to conventional gel particles.
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Figure CN117659314B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the technical field of preparation process technology for water shut-off gel particles, and more specifically to the technical field of water shut-off gel particles for loose sandstone gas reservoirs and their preparation method. Background Technology
[0002] In the mid-to-late stages of gas reservoir development, the uneven water intrusion caused by reservoir heterogeneity and differences in gas / water two-phase flow leads to low production levels in single wells and an increasing number of low-yield and inefficient wells year by year. The successful large-scale application of theoretical technologies such as water-controlled gas production and drainage gas production has effectively promoted the efficient development of heterogeneous water-bearing gas reservoirs in Qinghai. However, under certain water intrusion conditions, the total drainage volume of the gas reservoir is difficult to balance the water intrusion volume, and bubble drainage is limited. Water shut-off can limit the water supply and become an effective technical supplement.
[0003] Currently, gel particles used for water blocking are mainly composed of acrylamide monomer (AM), combined with crosslinking agents (N,N-methylenebisacrylamide), initiators (persulfate, azo, etc.), and fillers such as bentonite to form high-strength gel particles, which is a technical means to block such water channeling.
[0004] Gel toughness is affected by many factors such as the type of crosslinking agent, degree of crosslinking, and polymerization time. Researchers have done a lot of work on crosslinking degree, polymerization time, toughening agent, etc. using various processes such as blending polymerization, nanoparticle surface modification copolymerization, and in-situ (intercalation) polymerization. However, the resulting gel particles are still easily affected by high mineralization after absorbing water and swelling. Their network structure after absorbing water has problems such as high brittleness, easy breakage, and poor long-term stability. Summary of the Invention
[0005] The purpose of this invention is to solve the problems of high brittleness, easy breakage, and poor long-term stability of the existing gel particles after absorbing water. In order to solve the above technical problems, this invention provides a gel particle for water shut-off in loose sandstone gas reservoirs and its preparation method.
[0006] To achieve the above objectives, the present invention specifically adopts the following technical solution:
[0007] A gel particle for plugging water in loose sandstone gas reservoirs, comprising the following components in 100 parts by total weight: 12-18 parts of acrylamide monomer, 1-3 parts of 2-acrylamido-2-tetradecylethanesulfonic acid, 1-3 parts of sepiolite, 0.5-2 parts of hydrophilic fiber, 0.12-0.18 parts of N-hydroxymethylacrylamide, 0.015-0.06 parts of initiator, with the balance being water.
[0008] Furthermore, based on a total weight of 100 parts, it includes the following components: 15 parts of acrylamide monomer, 2 parts of 2-acrylamido-2-tetradecylethanesulfonic acid, 2 parts of sepiolite, 1 part of hydrophilic fiber, 0.15 parts of N-hydroxymethylacrylamide, 0.03 parts of initiator, and 79.82 parts of water.
[0009] The 2-acrylamido-2-tetradecylethanesulfonic acid used in this invention is a branched salt-resistant monomer that can inhibit the hydrolysis of amide groups at high temperatures and is also insensitive to the attack of external divalent cations. It undergoes a cross-linking polymerization reaction with sepiolite with a fibrous structure and hydrophilic fibers with excellent mechanical tensile properties, thereby improving the tensile properties and salt resistance of the prepared gel particles. This solves the technical problem that conventional gel particles have poor elasticity and are brittle after absorbing water in high-salinity oil reservoirs.
[0010] Furthermore, the initiator is a mixture of ammonium persulfate and sodium pyrosulfate.
[0011] Furthermore, the ratio of ammonium persulfate to sodium pyrosulfate is 2:1.
[0012] To achieve the above objectives, the present invention also proposes a method for preparing gel particles for water shut-off in loose sandstone gas reservoirs, comprising the following steps:
[0013] Step 1: Measure acrylamide monomer, 2-acrylamido-2-tetradecylethanesulfonic acid, sepiolite, hydrophilic fiber, and N-hydroxymethylacrylamide according to the specified proportions, and dissolve them in water at room temperature. Stir and mix thoroughly to obtain a mixed solution.
[0014] Step 2: Nitrogen gas is introduced into the mixed solution obtained in Step 1, and then an initiator is added under constant temperature conditions. Nitrogen gas is then introduced again, and a gel is obtained after cross-linking polymerization.
[0015] Step 3: Granulate the gel obtained in Step 2 to obtain high-strength gel particles for water shut-off in gas reservoirs.
[0016] Furthermore, in step two, nitrogen gas is introduced into the mixed solution for 10 minutes before the initiator is added, and for 5 minutes after the initiator is added.
[0017] Furthermore, in step two, the temperature is controlled at 15–20°C when the initiator is added.
[0018] The beneficial effects of this invention are as follows:
[0019] (1) The 2-acrylamido-2-tetradecylethanesulfonic acid used in this invention is a branched salt-resistant monomer that can inhibit the hydrolysis of amide groups at high temperatures and is not sensitive to the attack of external divalent cations. It can crosslink and polymerize with sepiolite with fibrous structure and hydrophilic fibers with excellent mechanical tensile properties, thereby improving the tensile properties and salt resistance of the prepared gel particles. This solves the technical problem that conventional gel particles have poor elasticity and are brittle after absorbing water in high-salinity oil reservoirs.
[0020] (2) The gel particles prepared in this invention are at a density of 10 × 10⁻⁶. 4 mg / L compound saline (9.5×10 mg / L) 4 mg / L NaCl + 0.5×10 4 After absorbing water in mg / L CaCl2, the strength of the high-strength gel particles used for water shut-off in the gas reservoir reaches 4560 Pa, which is 8 times that of conventional cross-linked polymer gel particles.
[0021] (3) The preparation process of gel particles in this invention is simple and the preparation conditions are easy to control. Attached Figure Description
[0022] Figure 1 This is a comparison diagram of the tensile properties of the gel particles prepared in Example 1 of this invention and conventional gel particles after swelling.
[0023] Figure 2 This is a comparison diagram of the tensile properties of the gel particles prepared in Example 2 of this invention and conventional gel particles after swelling.
[0024] Figure 3 This is a comparison diagram of the tensile properties of the gel particles prepared in Example 3 of this invention and conventional gel particles after swelling. Detailed Implementation
[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.
[0026] Example 1
[0027] This embodiment provides a gel particle for water shut-off in loose sandstone gas reservoirs, comprising the following components in a total weight of 100 parts: 12 parts acrylamide monomer, 1 part 2-acrylamido-2-tetradecyl ethanesulfonic acid, 1 part sepiolite, 0.5 parts hydrophilic fiber, 0.12 parts N-hydroxymethylacrylamide, 0.01 parts ammonium persulfate, 0.005 parts sodium metabisulfite, and 85.365 parts water.
[0028] The method for preparing gel particles includes the following steps:
[0029] Step 1: Measure acrylamide monomer, 2-acrylamido-2-tetradecylethanesulfonic acid, sepiolite, hydrophilic fiber, and N-hydroxymethylacrylamide according to the specified proportions, and dissolve them in water at room temperature. Stir and mix thoroughly to obtain a mixed solution.
[0030] Step 2: Purge nitrogen gas into the mixed solution obtained in Step 1 for 10 minutes, then add ammonium persulfate and sodium metabisulfite at a constant temperature of 15°C, and continue purging nitrogen gas for 5 minutes. After cross-linking polymerization, a gel is obtained.
[0031] Step 3: Granulate the gel obtained in Step 2 to obtain high-strength gel particles for water shut-off in gas reservoirs.
[0032] Testing and Inspection
[0033] (1) Temperature and salt resistance test.
[0034] Using 10×10 4 mg / L compound saline (9.5×10 mg / L) 4 mg / L NaCl + 0.5×10 4 High-strength gel particles (prepared using the method in Example 1) for water shut-off in high-mineralized loose sandstone gas reservoirs (mg / LCaCL2) and conventional cross-linked polymer gel particles were prepared separately. The mixture was continuously stirred at 400 r / min for 10 min with an electric stirrer, poured into a 60 mL stainless steel aging tank, and placed in a drying oven at 110℃ for 7 days. After cooling to room temperature, the aging tank was removed. The elastic modulus of the high-strength gel particles prepared in Example 1 was 3024 Pa, which was 3.1 times that of the conventional cross-linked polymer gel particles.
[0035] Compared with conventional cross-linked polymer gel particles, the branched salt-resistant monomers of the high-strength gel particles for gas reservoir water shut-off prepared in Example 1 can suppress amide hydrolysis at high temperatures and are insensitive to external divalent cation attacks, resulting in significantly improved thermal stability under high temperature and high salt conditions.
[0036] (2) Tensile property testing.
[0037] The high-strength gel particles prepared in Example 1 and conventional cross-linked polymer gel particles were subjected to a temperature of 70°C and a striation of 10 × 10⁻⁶. 4 The tensile properties were tested after the product absorbed water from the mg / L composite saline solution. The test results are shown in Table 1-1 below. Please also refer to... Figure 1 .
[0038] Table 1-1
[0039]
[0040]
[0041] According to the above test results, the high-strength gel particles for gas reservoir water shut-off prepared in Example 1 of this application have a strength of 3263 Pa, which is 4.7 times that of conventional cross-linked polymer gel particles. Compared with conventional cross-linked polymer gel particles, the fibrous sepiolite and hydrophilic fibers in the high-strength gel particles for gas reservoir water shut-off act like steel reinforcement in concrete, overcoming the hardness and brittleness of conventional high-strength gel particles. Their tensile (elastic deformation) properties are significantly improved, solving the technical problem of poor elasticity and brittleness of conventional high-strength gel particles after water absorption and swelling in high-salinity oil reservoirs.
[0042] (3) Blocking performance test.
[0043] Utilize 10×10 4 0.3% of the high-strength gel particles and conventional high-strength gel particles prepared in Example 1 for water shut-off in high-mineralized loose sandstone gas reservoirs were prepared using mg / L composite saline. 40-60 mesh quartz sand was used to fill sand-filling tubes with a diameter of 2.5 cm and a length of 50 cm. 0.2 PV of the high-strength gel particles and conventional high-strength gel particles prepared in Example 1 were injected into the sand-filling tubes at a flow rate of 1 mL / min. Both ends of the core tubes were sealed and placed in a 70℃ constant temperature drying oven for 72 hours. Then, simulated saline was injected at the same flow rate for displacement to investigate the plugging ability of the displacer. The results are shown in Tables 1-2.
[0044] Table 1-2
[0045]
[0046] According to the above test results, the high-strength gel particles for water shut-off in gas reservoirs prepared in Example 1 of this application have a plugging rate of over 93%. Compared with conventional high-strength gel particles, the high-strength gel particles for water shut-off in gas reservoirs prepared in Example 1 of this application have a plugging rate that is 9.65% higher, and their plugging performance is significantly improved.
[0047] Example 2
[0048] This embodiment provides a gel particle for water shut-off in loose sandstone gas reservoirs, comprising the following components in a total weight of 100 parts: 15 parts acrylamide monomer, 2 parts 2-acrylamido-2-tetradecyl ethanesulfonic acid, 2 parts sepiolite, 1 part hydrophilic fiber, 0.15 parts N-hydroxymethylacrylamide, 0.02 parts ammonium persulfate, 0.01 parts sodium metabisulfite, and 79.82 parts water.
[0049] The method for preparing gel particles includes the following steps:
[0050] Step 1: Measure acrylamide monomer, 2-acrylamido-2-tetradecylethanesulfonic acid, sepiolite, hydrophilic fiber, and N-hydroxymethylacrylamide according to the specified proportions, and dissolve them in water at room temperature. Stir and mix thoroughly to obtain a mixed solution.
[0051] Step 2: Purge nitrogen gas into the mixed solution obtained in Step 1 for 10 minutes, then add ammonium persulfate and sodium metabisulfite at a constant temperature of 18°C, and continue purging nitrogen gas for 5 minutes. After cross-linking polymerization, a gel is obtained.
[0052] Step 3: Granulate the gel obtained in Step 2 to obtain high-strength gel particles for water shut-off in gas reservoirs.
[0053] Testing and Inspection
[0054] (1) Temperature and salt resistance test.
[0055] Using 10×10 4 mg / L compound saline (9.5×10 mg / L) 4 mg / L NaCl + 0.5×10 4 High-strength gel particles (prepared using the method in Example 2) for water shut-off in high-mineralized loose sandstone gas reservoirs (mg / LCaCL2) and conventional cross-linked polymer gel particles were prepared separately. The mixture was continuously stirred at 400 r / min for 10 min with an electric stirrer, poured into a 60 mL stainless steel aging tank, and placed in a drying oven at 110℃ for 7 days. After cooling to room temperature, the aging tank was removed. The elastic modulus of the high-strength gel particles prepared in Example 2 was 3685 Pa, which was 4.5 times that of the conventional cross-linked polymer gel particles.
[0056] Compared with conventional cross-linked polymer gel particles, the branched salt-resistant monomers of the high-strength gel particles for gas reservoir water shut-off prepared in Example 2 can suppress amide hydrolysis at high temperatures and are insensitive to external divalent cation attacks, resulting in significantly improved thermal stability under high temperature and high salt conditions.
[0057] (2) Tensile property testing.
[0058] The high-strength gel particles prepared in Example 2 and conventional cross-linked polymer gel particles were subjected to a temperature of 70°C and a striation of 10×10⁻⁶. 4 The tensile properties were tested after the product absorbed water from the mg / L composite saline solution. The test results are shown in Table 2-1 below. Please also refer to... Figure 2 .
[0059] Table 2-1
[0060]
[0061] According to the above test results, the high-strength gel particles for gas reservoir water shut-off prepared in Example 2 of this application have a strength of 4315 Pa, which is 7.2 times that of conventional cross-linked polymer gel particles. Compared with conventional cross-linked polymer gel particles, the fibrous sepiolite and hydrophilic fibers in the high-strength gel particles for gas reservoir water shut-off act like steel bars in concrete, overcoming the hardness and brittleness of conventional high-strength gel particles. Their tensile (elastic deformation) properties are significantly improved, solving the technical problem of poor elasticity and brittleness of conventional high-strength gel particles after water absorption and swelling in high-salinity oil reservoirs.
[0062] (3) Blocking performance test.
[0063] Utilize 10×10 4 0.3% of the high-strength gel particles and conventional high-strength gel particles prepared in Example 2 for water shut-off in high-mineralized loose sandstone gas reservoirs were prepared using mg / L composite saline. 40-60 mesh quartz sand was used to fill sand-filling tubes with a diameter of 2.5 cm and a length of 50 cm. 0.2 PV of the high-strength gel particles and conventional high-strength gel particles prepared in Example 2 were injected into the sand-filling tubes at a flow rate of 1 mL / min. Both ends of the core tube were sealed and placed in a 70℃ constant temperature drying oven for 72 hours. Then, simulated saline was injected at the same flow rate for displacement to investigate the plugging ability of the displacer. The results are shown in Table 2-2.
[0064] Table 2-2
[0065]
[0066] According to the above test results, the high-strength gel particles for water shut-off in gas reservoirs prepared in Example 2 of this application have a plugging rate of over 96%. Compared with conventional high-strength gel particles, the high-strength gel particles for water shut-off in gas reservoirs prepared in Example 2 of this application have a plugging rate that is 11.4% higher, and their plugging performance is significantly improved.
[0067] Example 3
[0068] This embodiment provides a gel particle for water shut-off in loose sandstone gas reservoirs, comprising the following components in a total weight of 100 parts: 18 parts acrylamide monomer, 3 parts 2-acrylamido-2-tetradecyl ethanesulfonic acid, 3 parts sepiolite, 2 parts hydrophilic fiber, 0.18 parts N-hydroxymethylacrylamide, 0.04 parts ammonium persulfate, 0.02 parts sodium metabisulfite, and 73.76 parts water.
[0069] The method for preparing gel particles includes the following steps:
[0070] Step 1: Measure acrylamide monomer, 2-acrylamido-2-tetradecylethanesulfonic acid, sepiolite, hydrophilic fiber, and N-hydroxymethylacrylamide according to the specified proportions, and dissolve them in water at room temperature. Stir and mix thoroughly to obtain a mixed solution.
[0071] Step 2: Purge nitrogen gas into the mixed solution obtained in Step 1 for 10 minutes, then add ammonium persulfate and sodium metabisulfite at a constant temperature of 20°C, and continue purging nitrogen gas for 5 minutes. After cross-linking polymerization, a gel is obtained.
[0072] Step 3: Granulate the gel obtained in Step 2 to obtain high-strength gel particles for water shut-off in gas reservoirs.
[0073] (1) Temperature and salt resistance test.
[0074] Using 10×10 4 mg / L compound saline (9.5×10 mg / L) 4 mg / L NaCl + 0.5×10 4 High-strength gel particles (prepared using the method in Example 3) for water shut-off in high-mineralized loose sandstone gas reservoirs (mg / LCaCL2) and conventional cross-linked polymer gel particles were prepared separately. The mixture was continuously stirred at 400 r / min for 10 min with an electric stirrer, poured into a 60 mL stainless steel aging tank, and placed in a drying oven at 110℃ for 7 days. After aging, the tank was removed and cooled to room temperature. The elastic modulus of the high-strength gel particles prepared in Example 3 was 3685 Pa, which was 4.5 times that of the conventional cross-linked polymer gel particles.
[0075] Compared with conventional cross-linked polymer gel particles, the branched salt-resistant monomers of the high-strength gel particles for gas reservoir water shut-off prepared in Example 3 can suppress amide hydrolysis at high temperatures and are insensitive to external divalent cation attacks, resulting in significantly improved thermal stability under high temperature and high salt conditions.
[0076] (2) Tensile property testing.
[0077] The high-strength gel particles prepared in Example 3 and conventional cross-linked polymer gel particles were subjected to a temperature of 70°C and a striation of 10×10⁻⁶. 4 The tensile properties were tested after the product absorbed water from the mg / L composite saline solution. The test results are shown in Table 3-1 below. Please also refer to... Figure 3 .
[0078] Table 3-1
[0079]
[0080] According to the above test results, the high-strength gel particles for gas reservoir water shut-off prepared in Example 3 of this application have a strength of 4560 Pa, which is 8 times that of conventional cross-linked polymer gel particles. Compared with conventional cross-linked polymer gel particles, the fibrous sepiolite and hydrophilic fibers in the high-strength gel particles for gas reservoir water shut-off act like steel bars in concrete, overcoming the hardness and brittleness of conventional high-strength gel particles. Their tensile (elastic deformation) properties are significantly improved, solving the technical problem of poor elasticity and brittleness of conventional high-strength gel particles after water absorption and swelling in high-salinity oil reservoirs.
[0081] (3) Blocking performance test.
[0082] Utilize 10×10 4 0.3% of the high-strength gel particles and conventional high-strength gel particles prepared in Example 3 for water shut-off in high-mineralized loose sandstone gas reservoirs were prepared using mg / L composite saline. 40-60 mesh quartz sand was used to fill sand-filling tubes with a diameter of 2.5 cm and a length of 50 cm. 0.2 PV of the high-strength gel particles prepared in Example 3 and conventional high-strength gel particles were injected into the sand-filling tubes at a flow rate of 1 mL / min. Both ends of the core tube were sealed and placed in a 70℃ constant temperature drying oven for 72 hours. Then, simulated saline was injected at the same flow rate for displacement to investigate the plugging ability of the displacer. The results are shown in Table 3-2.
[0083] Table 3-2
[0084]
[0085] According to the above test results, the high-strength gel particles for water shut-off in gas reservoirs prepared in Example 3 of this application have a plugging rate of over 98%. Compared with conventional high-strength gel particles, the high-strength gel particles for water shut-off in gas reservoirs prepared in Example 3 of this application have a 15.6% higher plugging rate, and their plugging performance is significantly improved.
Claims
1. A type of gel particle for water shut-off in loose sandstone gas reservoirs, characterized in that, Based on a total weight of 100 parts, the product comprises the following components: 12 to 18 parts of acrylamide monomer, 1 to 3 parts of 2-acrylamido-2-tetradecylethanesulfonic acid, 1 to 3 parts of sepiolite, 0.5 to 2 parts of hydrophilic fiber, 0.12 to 0.18 parts of N-hydroxymethylacrylamide, 0.015 to 0.06 parts of initiator, and the balance being water.
2. The gel particles for water shut-off in loose sandstone gas reservoirs according to claim 1, characterized in that, Based on a total weight of 100 parts, the product comprises the following components: 15 parts acrylamide monomer, 2 parts 2-acrylamido-2-tetradecylethanesulfonic acid, 2 parts sepiolite, 1 part hydrophilic fiber, 0.15 parts N-hydroxymethylacrylamide, 0.03 parts initiator, and 79.82 parts water.
3. A gel particle for water shut-off in a loose sandstone gas reservoir according to claim 1 or 2, characterized in that, The initiator is a mixture of ammonium persulfate and sodium pyrosulfate.
4. The gel particles for water shut-off in loose sandstone gas reservoirs according to claim 3, characterized in that, The ratio of ammonium persulfate to sodium pyrosulfate is 2:
1.
5. A method for preparing gel particles for water shut-off in loose sandstone gas reservoirs according to any one of claims 1 to 2, characterized in that, Includes the following steps: Step 1: Measure acrylamide monomer, 2-acrylamido-2-tetradecylethanesulfonic acid, sepiolite, hydrophilic fiber, and N-hydroxymethylacrylamide according to the specified proportions, and dissolve them in water at room temperature. Stir and mix thoroughly to obtain a mixed solution. Step 2: Nitrogen gas is introduced into the mixed solution obtained in Step 1, and then an initiator is added under constant temperature conditions. Nitrogen gas is then introduced again, and a gel is obtained after cross-linking polymerization. Step 3: Granulate the gel obtained in Step 2 to obtain high-strength gel particles for water shut-off in gas reservoirs.
6. The method for preparing gel particles for water shut-off in loose sandstone gas reservoirs according to claim 5, characterized in that, In step two, nitrogen gas is introduced into the mixed solution for 10 minutes before the initiator is added, and for 5 minutes after the initiator is added.
7. The method for preparing gel particles for water shut-off in loose sandstone gas reservoirs according to claim 5, characterized in that, In step two, the temperature is controlled at 15–20°C when the initiator is added.