Gel microsphere profile control agent with salt response characteristics, preparation method and application thereof
By preparing a salt-responsive gel microsphere modulator, the particle size and strength of the gel microspheres in brine were controlled through physical cross-linking and ionic bonding. This solved the problem of the imbalance between the migration and plugging capabilities of traditional gel microspheres in heterogeneous oilfields, and achieved a highly efficient plugging effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA UNIV OF GEOSCIENCES (WUHAN)
- Filing Date
- 2023-04-20
- Publication Date
- 2026-06-26
AI Technical Summary
Existing gel microspheres have difficulty balancing migration and plugging capabilities in heterogeneous, high-water-cut oilfields, and are easily affected by shear forces, resulting in poor construction results.
Gel microspheres with salt-responsive properties were prepared using microfluidic technology. Through physical cross-linking and ionic bonding, the microspheres increased in size and strength in salt water and under shear stress, enabling independent regulation of transport and blocking functions.
It enables full-process sealing of high-permeability layers, improves the water injection development effect of heterogeneous reservoirs, and reduces the difficulty of migration and sealing operations.
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Figure CN116410399B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of oilfield development technology, specifically to a gel microsphere modulator with salt response and shear self-healing properties, its preparation method, and its application. Background Technology
[0002] Heterogeneity is prevalent in my country's oil reservoirs. During water injection development, injected water preferentially flows along highly permeable layers, forming dominant water flow channels. This allows the reservoir to rapidly enter a high water-cut phase, while a large amount of remaining oil cannot be displaced by water. To address this problem, using profile control and water shut-off technology to efficiently seal high-permeability layers is the most reliable production enhancement measure. Among traditional water shut-off systems, gel microspheres, combining transport and sealing functions, theoretically can achieve "full-process sealing" of high-permeability layers, and are therefore widely studied and tested.
[0003] However, due to limitations in previously used materials, existing gel microspheres have performance parameters that are difficult to match with the pore size of high-permeability layers. When the strength or particle size of the gel microspheres is too low, their sealing effect is poor, and subsequent water flow is unlikely to activate fluids in adjacent low-permeability layers. When the strength or particle size of the gel microspheres is too high, the sealing effect is better, and subsequent water flow can activate fluids in adjacent low-permeability layers, but the gel microspheres are difficult to migrate further into the formation, resulting in a small sealing range and limited ability to expand the swept volume. In addition, during the migration and sealing process in high-permeability layers, gel microspheres are constantly subjected to shearing action from the porous medium. Continuous shearing leads to material damage, causing the gel microspheres to break and lose their sealing ability. In summary, due to the difficulty in balancing the migration and sealing capabilities of existing gel microspheres in reservoirs, coupled with the impact of shear breakage, the effectiveness of gel microsphere profile control and water shut-off operations in heterogeneous high-water-cut reservoirs still needs improvement. Therefore, overcoming the performance limitations of traditional gel microspheres is crucial for the efficient development of heterogeneous high-water-cut oilfields. Thus, a novel gel microsphere preparation method is urgently needed to meet the demands of efficient development in heterogeneous high-water-cut oilfields. Summary of the Invention
[0004] The purpose of this invention is to provide a salt-responsive gel microsphere modulator, its preparation method, and its application, to solve the problem that traditional gel microspheres are difficult to balance in terms of migration and plugging capabilities in heterogeneous high water-cut oilfields, and are easily affected by shearing.
[0005] To solve the above-mentioned technical problems, the first solution provided by the present invention is as follows: A method for preparing a gel microsphere modulator with salt-responsive properties includes the following steps: S1, mixing anionic monomer, cationic monomer, acrylamide, persulfate, sodium dodecyl sulfate, and deionized water evenly, adjusting the pH value to neutral, to obtain a first mixture; S2, adding oil-soluble octadecyl methyl β-acryloyloxypropionate to the first mixture, stirring until transparent and homogeneous, to obtain a second mixture; S3, dispersing the second mixture into several microdroplets using microfluidic technology, and generating a polymerization reaction through thermal initiation, solidifying to form several microspheres, thereby obtaining a gel microsphere modulator with salt-responsive properties; In step S1, the anionic monomer is β-acryloyloxypropionate, and the cationic monomer is acryloyloxyethyltrimethylammonium chloride.
[0006] Preferably, the raw material composition in step S1, by mass percentage, is as follows: 1%–4% β-acryloyloxypropionic acid, 1%–4% acryloyloxyethyltrimethylammonium chloride, 1%–4% acrylamide, 0.02%–0.04% persulfate, 5%–10% sodium dodecyl sulfate, and the remainder is deionized water.
[0007] Preferably, in step S2, the mass percentage of octadecyl methyl β-acryloyloxypropionate in the second mixture is 1% to 4%.
[0008] Preferably, in step S2, the stirring rate is 2000 r / min to 6000 r / min, and the stirring time is 30 min to 60 min.
[0009] Preferably, in step S3, a coaxial flow microfluidic device is used to form a single microdroplet at the tip in a dripping mode, dispersing the second mixture into several microdroplets; the microdroplet generation rate is 3000-4000 per minute, the polymerization reaction temperature is 45℃-60℃, and the polymerization reaction time is 5h-6h.
[0010] Preferably, in step S3, the cured microspheres have a particle size of 50–1000 μm and a strength of 5–30 Pa.
[0011] To solve the above-mentioned technical problems, the second solution provided by the present invention is: a gel microsphere modulator with salt-responsive properties, which is prepared by the preparation method of the gel microsphere modulator with salt-responsive properties in the aforementioned first solution. It is prepared by polymerizing anionic monomers (β-acryloyloxypropionic acid, as shown in Formula I) and cationic monomers (acryloyloxyethyltrimethylammonium chloride, as shown in Formula II) with similar chemical structures, as well as octadecyl methyl β-acryloyloxypropionic acid (SMA), acrylamide (AM), and sodium dodecyl sulfate (SDS) in a certain proportion using ammonium persulfate as an initiator, and then processing them into microscale spherical particles using a microfluidic device.
[0012]
[0013] In this invention, the formation of gel microspheres does not involve chemical covalent cross-linking. Instead, a three-dimensional network structure is formed through physical cross-linking such as hydrophobic interactions and hydrogen bonds. Due to the electrostatic adsorption of symmetrical counterions, the gel microspheres exhibit small particle size and low strength in a deionized water environment. Under formation brine conditions in oil reservoirs, the particle size and strength of the gel microspheres increase due to antistatic interactions and the formation of ionic bonds. Because of the reversibility of physical cross-linking, the gel microspheres in this invention exhibit shear self-healing characteristics. Within a certain shear range, the viscoelasticity of the gel does not increase significantly with increasing shear rate but remains within a relatively stable range, exhibiting rheological properties significantly different from conventional gel microsphere-based revelocity modifiers. Based on reversible physical cross-linking, a shear self-healing function is generated to resist the continuous shearing action of porous media. After injecting a small segment of responsive gel microspheres into a heterogeneous, high-water-cut reservoir, the salinity of the injected water is controlled to achieve the following: the responsive gel microspheres shrink and weaken before migrating, expand and strengthen before blocking, and resist the continuous shearing action of the porous rock media, ultimately achieving full-process blocking of water channeling in high-permeability layers. In other words, the particle size and strength of the gel microspheres can be controlled by adjusting the salinity of the injected water, realizing the migration, expansion, blocking, shrinkage, and re-migration of the gel microspheres in high-permeability layers. The expansion and strengthening effects exhibited by the aforementioned gel microspheres mainly originate from the electrostatic shielding of ions against zwitterionic polyelectrolytes with symmetrical structures and the formation of ionic bonds. For details, please refer to [reference needed]. Figure 1 The diagram shown illustrates the reaction principle.
[0014] To address the aforementioned technical problems, the third solution provided by this invention is as follows: The application of the salt-responsive gel microsphere modulator described in the second solution involves two application scenarios: under formation water conditions, the salt-responsive gel microspheres have large particle size and high strength; under clear water conditions, the particle size and strength of the salt-responsive gel microspheres decrease. The application method proposed in this invention can dynamically adjust the particle size and strength of the gel microspheres in real time according to the water channeling dynamics of the reservoir. This separates the traditional transport and blocking capabilities of gel microspheres into two independent functions, independent of each other. Therefore, it eliminates the need to simultaneously balance the transport and blocking capabilities of the gel microspheres, significantly reducing the operational difficulty of transporting and blocking the gel microspheres. Specifically, the two functions of blocking and transport correspond to the following two application methods:
[0015] (1) A gel microsphere modulator with salt response characteristics is mixed with water to prepare a gel microsphere solution. The gel microsphere solution is injected into the high permeability layer of the heterogeneous core. After the gel microspheres in the gel microsphere solution are soaked until they expand to a stable state, secondary brine is injected into the heterogeneous core and the injection pressure is increased to complete the sealing of the high permeability layer.
[0016] (2) A gel microsphere modulator with salt response characteristics is mixed with water to prepare a gel microsphere solution. The gel microsphere solution and water are injected sequentially into the high permeability layer of the heterogeneous core. After the gel microspheres in the gel microsphere solution shrink to a stable state, supplementary brine is injected into the heterogeneous core and the injection pressure is reduced to complete the forward migration of the gel microspheres in the high permeability layer.
[0017] In both methods mentioned above, the permeability of the high-permeability layer is >100×10⁻⁶. -3 μm 2 The volume of the injected gel microsphere solution is 0.1 to 0.3 times the pore volume of the high-permeability layer, and the concentration of gel microspheres in the gel microsphere solution is 1000 mg / L to 5000 mg / L.
[0018] Preferably, in method (1), the formation brine in the heterogeneous core gradually infiltrates the gel microspheres in the gel microsphere solution and causes them to gradually expand; after expanding to a stable state, the particle size of the gel microspheres is 180-3500 μm and the strength is 20-80 Pa; the salinity of the formation brine is >30000 mg / L and the soaking time is >60 min; the injection pressure of the secondary brine is increased by more than twice the injection pressure of the gel microsphere solution.
[0019] Preferably, in method (2), the volume of water injected is 1 to 2 times the volume of the gel microsphere solution, the water soaking time is >180 min, and the reduction in the injection pressure of the supplemented saline is more than 1.6 times the injection pressure of the gel microsphere solution.
[0020] The beneficial effects of this invention are as follows: Unlike existing technologies, this invention provides a salt-responsive gel microsphere modulator, its preparation method, and its application. It utilizes the strong anti-polyelectrolyte phenomenon of zwitterionic polymers in brine, the association between hydrophobic groups, and the ionic bonding between anions and cations to generate gel microspheres with salt-responsive and shear-self-healing properties. On one hand, these gel microspheres exhibit strong stimuli-responsiveness to ionic strength, allowing control of their particle size and strength by adjusting the salinity of the injected water. On the other hand, based on the reversibility of physical cross-linking, these gel microspheres possess self-healing properties, enabling continuous migration in high-permeability layers without damage. Based on these two characteristics, the performance parameters of the gel microspheres in high-permeability layers can be controlled in real time, achieving full-process sealing of high-permeability layers and significantly improving the water injection development effect of heterogeneous reservoirs. Attached Figure Description
[0021] Figure 1 This is a schematic diagram of the reaction principle of the gel microsphere modulator with salt-responsive properties in this invention;
[0022] Figure 2 This is a comparison diagram of the particle size and strength of the sample in Example 1 of the present invention before and after soaking in salt water;
[0023] Figure 3 These are the infrared spectra of the sample in Example 1 of this invention before and after soaking in salt water;
[0024] Figure 4 This is a comparison diagram of the viscoelasticity of the sample in Example 1 of this invention and commercially available polyacrylamide gel;
[0025] Figure 5 This is a pressure gradient distribution diagram of the gel microsphere solution in Example 2 of the present invention during the dynamic plugging process of a high-permeability core. Detailed Implementation
[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0027] Example 1
[0028] The preparation steps of the salt-responsive gel microsphere modulator in this embodiment are as follows:
[0029] Step 1: Add 2g of β-acryloyloxypropionic acid, 3g of acryloyloxyethyltrimethylammonium chloride, 2g of acrylamide, 0.02g of ammonium persulfate, and 7g of sodium dodecyl sulfate to 100mL of deionized water. Stir slowly at a stirring rate of 30r / min until homogeneous. Then adjust the pH value to neutral using NaOH solution to form the first mixture.
[0030] Step 2: Add 3.5g of octadecyl methyl β-acryloyloxypropionate to the first mixture obtained in Step 1, and stir at 5000r / min for 30min to emulsify the octadecyl methyl β-acryloyloxypropionate in the first mixture until the solution becomes transparent and homogeneous, thus obtaining the second mixture.
[0031] Step 3: Using a syringe pump, inject the second mixture obtained in Step 2 into a coaxial flow microfluidic device, adjusting the flow rate to 0.015 mL / min to generate 3500 dispersed microdroplets per minute. Raise the collected microdroplets to 60°C, and initiate a polymerization reaction through thermal initiation (polymerization process as follows). Figure 1 As shown in the figure, gel microspheres are formed after a polymerization reaction time of 6 hours.
[0032] Test 1
[0033] The gel microsphere sample prepared in Example 1 was designated as the initial state sample, which was not soaked in saline solution. Meanwhile, a control group was set up, in which the initial state sample was soaked in 50,000 mg / L saline solution for 60 min (in the experiment, the gel microsphere sample was in a stable state after 60 min), and was designated as the saline solution sample. The saline solution was prepared by 40,000 mg / L NaCl, 10,000 mg / L KCl and deionized water.
[0034] The particle size of the initial samples before and after brine soaking and the brine samples were measured using a particle size analyzer, and the strength of the initial samples before and after brine soaking and the brine samples were measured using a rheometer, respectively. The results are as follows: Figure 2 As shown. From Figure 2 The results show that the initial sample had a particle size of 360 μm and a strength of 15 Pa; after swelling and strengthening in salt water, the particle size was 620 μm and the strength was 40 Pa. This indicates that the ion-pair structure in the gel microspheres is highly sensitive to salt and exhibits the characteristics of increased particle size and enhanced strength under the influence of salt water.
[0035] Test 2
[0036] Infrared spectra of the initial state samples and the saline samples before and after saline immersion were measured using an infrared spectrometer. The results are as follows: Figure 3 As shown. From Figure 3 It can be seen that the significant differences between the two before and after salt water soaking are mainly manifested in the following three places, namely at 3400cm.-1 1720cm -1 and 620cm -1 Location; of which, 3400cm -1 and 1720cm -1 The peak at 620 cm⁻¹ is the vibrational absorption peak of the carboxyl group. -1 The peak at this point represents the bending vibration absorption peak of the methylene group. The brine sample shows an increase in peak value compared to the initial sample, indicating an enhanced interaction force. The mechanism is that, on the one hand, the coordination of metal ions with carboxyl groups can form ionic bonds, thereby increasing the crosslinking strength; on the other hand, the cations in the brine further promote the hydrophobic association of the alkyl chains.
[0037] Test 3
[0038] The viscoelasticity of the gel microspheres prepared in Example 1 was compared with that of conventional polyacrylamide gel to examine their shear self-healing properties. The viscoelasticity test results are as follows: Figure 4 As shown. The polyacrylamide gel used is a commercially available product from Shandong Shida Oilfield Service Co., Ltd., and its composition is 0.6% polyacrylamide, 0.6% phenolic resin crosslinking agent, and brine (the brine is composed of 40000 mg / L NaCl, 10000 mg / L KCl and deionized water). The reaction temperature is 60℃. According to existing technology, this polyacrylamide gel has a three-dimensional network structure composed of covalent bonds.
[0039] from Figure 4 As can be seen, in the shear oscillation region with a frequency of 10-100Hz, the elastic modulus and viscous modulus of conventional polyacrylamide gels increase significantly with increasing shear rate. However, the elastic modulus and viscous modulus of the gel microsphere sample in Example 1 increase slowly with increasing shear rate, remaining almost within a relatively stable range. This is because the hydrophobic gel microsphere sample prepared in this invention has physical crosslinking, which is completely different from the covalent crosslinking of commercially available gel products. The hydrophobic gel microsphere sample prepared in this invention can decompose and release shear stress under shear, thereby protecting the gel skeleton. Due to the difference in crosslinking mechanism, commercially available gel products cannot achieve this effect, resulting in a significant difference in viscoelasticity between the two.
[0040] Example 2
[0041] Step 1: Prepare a 0.2% gel microsphere solution by mixing the gel microsphere sample prepared in Example 1 with deionized water.
[0042] Step 2: A man-made square core, 100cm long, 4.5cm wide, and 4.5cm high, was selected as the high-permeability core. The core had a porosity of 18.3% and a pore volume of 370.6cm³. 3The permeability of the core water was 3000×10⁻⁶. -3 μm 2 .
[0043] Step 3: Load the high-permeability core into a specially designed core holder. The core holder has three pressure measurement points located at the core inlet end, 33 cm from the inlet end, and 66 cm from the inlet end. Then, connect the displacement experimental apparatus according to standard GB / T 28912-2012 "Method for Determination of Relative Permeability of Two-Phase Fluids in Rocks"; this experimental apparatus includes three 500 cm³ volumes. 3 The intermediate containers respectively store a 0.2% concentration gel microsphere solution, deionized water, and saline solution with a mineralization of 50,000 mg / L.
[0044] Step 4, inject 125cm into the rock core. 3 The salt-responsive gel microsphere solution was then shut down for 200 minutes.
[0045] Step 5: Inject brine into the core until the pressure stabilizes, record the injection pressure, and then transfer the injection to a depth of 187 cm. 3 Use deionized water and shut down the injection equipment for 60 minutes.
[0046] Step 6, inject 125cm into the rock core. 3 The brine was removed, and the injection equipment was shut down for 5 hours.
[0047] Step 7: Repeat step 5, except that the injection is transferred to 187cm. 3 After deionizing the water, 94cm of water still needs to be injected. 3 Using saline solution as a displacement plug, deionized water was displaced into the region containing the gel microspheres, and step 6 was repeated. Subsequently, step 5 was repeated again, except that 187 cm⁻¹ of saline solution was transferred to the microspheres. 3 After deionizing the water, 219cm of water still needs to be injected. 3 Using brine as a displacement slug, deionized water is displaced into the area containing the gel microspheres, and step 6 is repeated. This process is repeated three times to achieve dynamic sealing of the entire high-permeability core.
[0048] During the three rounds of salt-response dynamic plugging, the pressure gradient in different regions of the core was as follows: Figure 5 As shown. From Figure 5It is evident that by regulating the salt response characteristics, the pressure enhancement effect can gradually extend throughout the entire core sample. The injection pressure after sealing is 6 times higher than the injection pressure before injecting the gel microspheres; while when shrinkage weakens, the injection pressure is 4 times lower than the previous sealing pressure, ensuring the smooth forward migration of the gel microspheres within the core. This demonstrates that the salt-responsive gel microsphere modulator provided by this invention can independently achieve both the migration and sealing functions of the gel microspheres during application, effectively solving the operational disadvantage of traditional gel microspheres that require simultaneously balancing the migration and sealing capabilities.
[0049] Unlike existing technologies, this invention provides a salt-responsive gel microsphere flood control agent, its preparation method, and its application. It utilizes the strong anti-polyelectrolyte phenomenon of zwitterionic polymers in brine, the association between hydrophobic groups, and the ionic bonding between anions and cations to generate gel microspheres with salt-responsive and shear-self-healing properties. On one hand, these gel microspheres exhibit strong stimuli-responsiveness to ionic strength, allowing control of their particle size and strength by adjusting the salinity of the injected water. On the other hand, based on the reversibility of physical cross-linking, these gel microspheres possess self-healing properties, enabling continuous migration in high-permeability layers without damage. These two characteristics allow for real-time control of the performance parameters of the gel microspheres in high-permeability layers, achieving complete sealing of high-permeability layers and significantly improving the water injection development effect in heterogeneous reservoirs.
[0050] It should be noted that all the above embodiments belong to the same inventive concept, and the descriptions of each embodiment have different focuses. Where the description in a particular embodiment is not detailed, please refer to the description in other embodiments.
[0051] The embodiments described above are merely illustrative of implementation methods of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.
Claims
1. A method for preparing a gel microsphere modulator with salt-responsive properties, characterized in that, Includes the following steps: S1, mix anionic monomer, cationic monomer, acrylamide, persulfate, sodium dodecyl sulfate, and deionized water evenly, adjust the pH value to neutral, and obtain the first mixture; S2, add oil-soluble octadecyl methyl β-acryloyloxypropionate to the first mixture, and stir until transparent and homogeneous to obtain the second mixture; S3, using microfluidic technology, the second mixture is dispersed into several microdroplets, and a polymerization reaction is generated by thermal initiation, solidifying to form several microspheres, thus obtaining a gel microsphere modulator with salt-responsive properties; In step S1, the anionic monomer is β-acryloyloxypropionic acid, and the cationic monomer is acryloyloxyethyltrimethylammonium chloride.
2. The method for preparing the salt-responsive gel microsphere modulator according to claim 1, characterized in that, The raw material composition in step S1, by mass percentage, is as follows: 1%–4% β-acryloyloxypropionic acid, 1%–4% acryloyloxyethyltrimethylammonium chloride, 1%–4% acrylamide, 0.02%–0.04% persulfate, 5%–10% sodium dodecyl sulfate, and the remainder is deionized water.
3. The method for preparing the salt-responsive gel microsphere modulator according to claim 1, characterized in that, In step S2, the octadecyl methyl β-acryloyloxypropionate has a mass percentage of 1% to 4% in the second mixture.
4. The method for preparing the salt-responsive gel microsphere modulator according to claim 1, characterized in that, In step S2, the stirring rate is 2000 r / min to 6000 r / min, and the stirring time is 30 min to 60 min.
5. The method for preparing the salt-responsive gel microsphere modulator according to claim 1, characterized in that, In step S3, a coaxial flow microfluidic device is used to form a single microdroplet at the tip in a droplet mode, thereby dispersing the second mixture into several microdroplets. The microdroplet generation rate is 3000-4000 per minute, the polymerization temperature is 45℃-60℃, and the polymerization time is 5-6 hours.
6. The method for preparing the salt-responsive gel microsphere modulator according to claim 5, characterized in that, In step S3, the solidified microspheres have a particle size of 50–1000 μm and a strength of 5–30 Pa.
7. A gel microsphere modulator with salt-responsive properties, characterized in that, The salt-responsive gel microsphere modulator is prepared by the method described in any one of claims 1 to 6.
8. The application of the salt-responsive gel microsphere modulator as described in claim 7 in oilfield development, characterized in that, The application employs one of the following two methods: (1) The gel microsphere modulator with salt response characteristics is mixed with water to prepare a gel microsphere solution. The gel microsphere solution is injected into the high permeability layer of the heterogeneous core. After the gel microspheres in the gel microsphere solution are soaked until they expand to a stable state, secondary brine is injected into the heterogeneous core and the injection pressure is increased to complete the sealing of the high permeability layer. (2) The gel microsphere modulator with salt response characteristics is mixed with water to prepare a gel microsphere solution. The gel microsphere solution and water are injected sequentially into the high permeability layer of the heterogeneous core. After the gel microspheres in the gel microsphere solution shrink to a stable state, salt water is injected into the heterogeneous core and the injection pressure is reduced to complete the forward migration of the gel microspheres in the high permeability layer. In both methods, the permeability of the high-permeability layer is >100×10⁻⁶. -3 μm 2 The volume of the injected gel microsphere solution is 0.1 to 0.3 times the pore volume of the high-permeability layer, and the concentration of the gel microspheres in the gel microsphere solution is 1000 mg / L to 5000 mg / L.
9. The application according to claim 8, characterized in that, In method (1), the formation brine in the heterogeneous core gradually infiltrates the gel microspheres in the gel microsphere solution and causes them to gradually swell. After swelling to a stable state, the particle size of the gel microspheres is 180–3500 μm and the strength is 20–80 Pa. The salinity of the formation brine is >30000 mg / L, and the soaking time is >60 min; The injection pressure of the secondary saline solution is increased by more than twice the injection pressure of the gel microsphere solution.
10. The application according to claim 8, characterized in that, In method (2), the volume of water injected is 1 to 2 times the volume of the gel microsphere solution, and the water soaking time is >180 min; The reduction in the injection pressure of the supplemental saline solution is more than 1.6 times the injection pressure of the gel microsphere solution.