Composition for salt-responsive self-aggregating gel particles, and salt-responsive self-aggregating gel particles, preparation method therefor and use thereof

Abstract

The present invention relates to the technical field of improving recovery in oil fields. Disclosed are a composition for salt-responsive self-aggregating gel particles, and salt-responsive self-aggregating gel particles, a preparation method therefor and a use thereof. The composition comprises, on the basis of the total weight of the composition, 15-25 wt% of acrylamide, 5-10 wt% of an anionic monomer, 5-10 wt% of a cationic monomer, 0.05-0.2 wt% of an initiator, 0.05-0.2 wt% of a cross-linking agent, and 0.05-0.1 wt% of an accelerator. The initiator is a composite initiator containing initiator A and initiator B, the initiator A is at least one of ammonium persulfate and potassium persulfate, and the initiator B is azobisisobutyrimidazoline hydrochloride. The salt-responsive self-aggregating gel particles provided by the present invention have good temperature and salt resistance, high elastic modulus, and good anti-polyelectrolyte salt-responsive self-aggregating properties.

Description

Compositions for salt-responsive self-aggregating gel particles, salt-responsive self-aggregating gel particles, preparation methods thereof, and applications.

[0001] Cross-references to related applications

[0002] This application claims the benefit of Chinese Patent Application No. 202510381711.6, filed on March 28, 2025, the contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to the field of enhanced oil recovery technology, specifically to a composition for salt-responsive self-aggregating gel particles, salt-responsive self-aggregating gel particles, their preparation method, and applications. Background Technology

[0004] Self-healing / self-aggregating gels are viscoelastic materials that achieve self-healing / self-aggregation through physical (hydrophobic interactions, hydrogen bonds, ionic bonds, etc.) and chemical (imine bonds, disulfide bonds, hydrazone bonds, etc.) interactions. For deep profile control and plugging in oilfields, intelligent responsive self-healing gels can effectively solve problems such as poor injectability, short profile control distance, and weak plugging strength of traditional gels.

[0005] In deep oilfield profile control and plugging applications, polymer gel particles are generally injected into the formation along with the injection fluid. The injection fluid interacts with the formation rocks and fluids, causing changes in the environment of the gel particles (such as temperature, pH, and salinity). Under the stimulus-response environment, the gel particles undergo self-healing, thereby achieving profile control and plugging.

[0006] However, the reservoir environment is usually extremely complex, making it difficult to accurately control changes in the self-healing intelligent response environment of polymer gels, which greatly reduces the self-healing performance of gels. Therefore, developing intelligent response gels with excellent environmental adaptability can help improve the efficiency of water injection development and promote the development of deep profile control technology in heterogeneous reservoirs.

[0007] Gel systems with tunable self-aggregation / self-healing mechanical properties play a crucial role in deep reservoir plugging. To enhance the deep plugging effect of particulate plugging agents, gel particles are prepared using particle coating and environmental stimulus-responsive principles. The coating technology involves applying a stimulus-responsive protective coating to the surface of the gel particles. Under a triggering mechanism, the coating breaks down, releasing the gel particles and enabling them to self-crosslink / self-heal. The stimulus-responsive principle posits that the gel particles only trigger their crosslinking / self-healing under stimulus-responsive conditions.

[0008] For example, CN210085365U discloses a pre-crosslinked polyacrylamide particle for deep-seated flooding. This pre-crosslinked polyacrylamide particle consists of a polyacrylamide-coated zirconium chloride particle core layer 1, a first polymer layer 2, and a second polymer layer 3. During formation migration, the second polymer layer transforms into a viscous polyacrylamide solution, which plays a certain role in fluid flow diversion. The first polymer layer continues to hydrolyze and reacts with the crosslinking agent particles in the core layer to form a three-dimensional gel, achieving deep sealing. The decomposition of the polymer layer of this particle is controlled by reservoir heterogeneity and formation temperature, making it difficult to effectively control the particle decomposition in the target layer and crosslinking at formation temperature. In addition, the coating technology is usually complex and costly.

[0009] Research on the application of stimulus-responsive gels in oilfields mainly includes pH-responsive gels based on imine bonds, temperature-responsive gels based on hydrophobic interactions, salt-responsive gels based on ionic bonds, and smart responsive gels based on dual or multiple healing mechanisms. For example, CN118324986A discloses a CO2-responsive salt-resistant polymer gel particle and its application. This gel is obtained by reacting acrylamide, a temperature- and salt-resistant monomer, and a CO2-responsive monomer with an initiator and a crosslinking agent. This gel is suitable for oil reservoirs where the pH value changes, such as reservoirs injected with CO2. In addition, CN115418206A also discloses a temperature-responsive micro / nano gel particle sealing material and its preparation and application. This gel particle is a dispersed spherical particle at room temperature (25℃), and expands and aggregates to form a stable layered structure above 100℃. Controlling the reservoir temperature field is key to the deep migration of this hydrogel, but the reservoir, as a large temperature field, makes effective temperature field control difficult.

[0010] The biggest challenge in developing smart responsive hydrogels is the gel's adaptability to stimulus response conditions and the effective control of its response performance. However, many response conditions are not available for deep profile control and plugging in oilfields, limiting their widespread application.

[0011] Therefore, in order to address the challenges of complex reservoir environments and the difficulty in accurately controlling the self-healing intelligent response of polymer gels to environmental changes, it is of great significance to provide a novel type of highly adaptable salt-responsive polymer gel particle. Summary of the Invention

[0012] The purpose of this invention is to provide a novel, highly adaptable, salt-responsive, self-aggregating gel particle that can effectively seal cracks or hyperpermeable channels.

[0013] Specifically, this invention addresses the challenge of complex reservoir environments and the difficulty in accurately controlling the changes in the self-healing intelligent response environment of polymer gels. It provides a salt-responsive self-aggregating gel particle that exhibits good salt response performance under different reservoir environments and excellent expansion performance at salinity levels below 10,000 mg / L, effectively sealing fractures, high permeability, and crossflow channels.

[0014] To achieve the above objectives, a first aspect of the present invention provides a composition for salt-responsive self-aggregating gel particles, wherein, based on the total weight of the composition, the composition contains 15 wt%-25 wt% acrylamide, 5 wt%-10 wt% anionic monomer, 5 wt%-10 wt% cationic monomer, 0.05 wt%-0.2 wt% initiator, 0.05 wt%-0.2 wt% crosslinking agent, and 0.05 wt%-0.1 wt% accelerator;

[0015] The anionic monomer is at least one of sodium p-styrene sulfonate and sodium 2-acrylamide-2-methylpropanesulfonate;

[0016] The cationic monomer is at least one of methacrylamidopropyltrimethylammonium chloride and acryloyloxyethyltrimethylammonium chloride;

[0017] The initiator is a composite initiator containing initiator A and initiator B. Initiator A is at least one of ammonium persulfate and potassium persulfate. Initiator B is azobisisobutyrazoline hydrochloride. The weight ratio of initiator A to initiator B is 1-3:1.

[0018] A second aspect of the present invention provides a method for preparing salt-responsive self-aggregating gel particles, the method comprising the following steps: (The method utilizes the components of the salt-responsive self-aggregating gel particle composition described in the first aspect above.)

[0019] S1. Under a protective gas atmosphere and at a temperature T1, the initiator, crosslinking agent, and accelerator are stirred and mixed with a mixed solution containing acrylamide, anionic monomer, and cationic monomer to obtain a first solution; the temperature T1 is 5-25℃.

[0020] S2. The first solution is subjected to a contact reaction at a temperature T2 to obtain a polymer gel; the temperature T2 is 30-50℃.

[0021] S3. The polymer gel is sequentially washed, dried and granulated to obtain salt-responsive self-aggregating gel particles.

[0022] A third aspect of the present invention provides salt-responsive self-aggregating gel particles prepared by the method described in the second aspect above.

[0023] The fourth aspect of this invention provides the application of the salt-responsive self-aggregating gel particles described in the third aspect above in the deep profile control and plugging of heterogeneous oil reservoirs.

[0024] Through the above technical solution, the present invention has at least the following beneficial technical effects:

[0025] (1) The salt-responsive self-aggregating gel particles provided by the present invention, in salt water with a salinity higher than 20000 mg / L, the interaction between ions in the high-salt solution and the anions and cations on the surface of the polymer gel particles shields the anion and cation interaction on the particle surface, so that the particles have good dispersibility and low swelling in high salt. When the salinity is lower than 10000 mg / L, the zwitterionic groups on the surface of the polymer gel particles associate due to electrostatic interaction, and the particles attract and aggregate with the particle surface, which has good self-healing properties and high swelling, and can effectively seal cracks or high-permeability channels.

[0026] (2) The salt-responsive self-aggregating gel particles provided by the present invention can control the placement of the gel particles to block the flow by adjusting the mineralization of the solution carrying the gel particles. As the transport distance increases, the mineralization decreases, and the gel particles aggregate and heal, thereby achieving fixed-point blocking of the flow channel.

[0027] Secondly, the self-aggregation of the gel particles is reversible; when encountering water with a salinity higher than 20,000 mg / L again, the gel particles disperse and migrate again. Therefore, this salt-responsive self-aggregating gel particle has good applicability under different reservoir conditions.

[0028] (3) The salt-responsive self-aggregating gel particles provided by the present invention have a wider range of applications. They can be applied to profile control and plugging of heterogeneous reservoirs, especially reservoirs that have undergone long-term water injection development and whose mineralization has changed in high-permeability or fracture channel flow.

[0029] Meanwhile, the raw materials required for preparing the salt-responsive self-aggregating gel particles of the present invention have advantages such as wide availability, low cost, and environmental friendliness. Attached Figure Description

[0030] Figure 1 is a schematic diagram showing the dispersion and aggregation changes of salt-responsive self-aggregating gel particles prepared in Example 1 in water with different mineralization. Detailed Implementation

[0031] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0032] As previously described, the first aspect of the present invention provides a composition for salt-responsive self-aggregating gel particles, wherein, based on the total weight of the composition, the composition contains 15 wt%-25 wt% acrylamide, 5 wt%-10 wt% anionic monomer, 5 wt%-10 wt% cationic monomer, 0.05 wt%-0.2 wt% initiator, 0.05 wt%-0.2 wt% crosslinking agent, and 0.05 wt%-0.1 wt% accelerator;

[0033] The anionic monomer is at least one of sodium p-styrene sulfonate and sodium 2-acrylamide-2-methylpropanesulfonate;

[0034] The cationic monomer is at least one of methacrylamidopropyltrimethylammonium chloride and acryloyloxyethyltrimethylammonium chloride;

[0035] The initiator is a composite initiator containing initiator A and initiator B. Initiator A is at least one of ammonium persulfate and potassium persulfate. Initiator B is azobisisobutyrazoline hydrochloride. The weight ratio of initiator A to initiator B is 1-3:1.

[0036] According to a preferred embodiment, the composition contains, based on its total weight, 16 wt%-20 wt% acrylamide, 6 wt%-8 wt% anionic monomer, 6 wt%-8 wt% cationic monomer, 0.05 wt%-0.1 wt% initiator, 0.05 wt%-0.1 wt% crosslinking agent, and 0.05 wt%-0.08 wt% accelerator.

[0037] According to a preferred embodiment, the weight ratio of initiator A to initiator B is 1-1.5:1.

[0038] According to a more preferred embodiment, the initiator A is potassium persulfate.

[0039] According to a particularly preferred embodiment, initiator A is potassium persulfate, and initiator B is azobisisobutyrazoline hydrochloride, wherein the weight ratio of potassium persulfate to azobisisobutyrazoline hydrochloride is 1-1.5:1. The inventors of this invention have discovered that, under this preferred embodiment, the salt-responsive self-aggregating gel particles provided by this invention possess temperature and salt resistance, high elastic modulus, and superior salt-responsive adaptability.

[0040] According to a preferred embodiment, the crosslinking agent is selected from at least one of hydroxypropyl acrylate, methacrylic acid, and N,N'-methylenebisacrylamide. In particular, when the crosslinking agent is N,N'-methylenebisacrylamide, the salt-responsive self-aggregating gel particles prepared by the present invention have better self-aggregating and blocking properties when the mineralization is below 10000 mg / L.

[0041] According to a preferred embodiment, the accelerator is one of tetramethylethylenediamine, dimethylethylenediamine, and N-tetramethylethylenediamine.

[0042] According to a particularly preferred embodiment, the accelerator is tetramethylethylenediamine.

[0043] According to a preferred embodiment, the composition further contains the balance of water.

[0044] According to a particularly preferred embodiment, the composition contains, based on its total weight, 16 wt%-20 wt% acrylamide, 6 wt%-8 wt% anionic monomer, 6 wt%-8 wt% cationic monomer, 0.05 wt%-0.1 wt% initiator, 0.05 wt%-0.1 wt% crosslinking agent, 0.05 wt%-0.08 wt% accelerator, and the balance being water.

[0045] As previously described, a second aspect of the present invention provides a method for preparing salt-responsive self-aggregating gel particles, the method comprising the following steps: (The method utilizes the components of the salt-responsive self-aggregating gel particle composition described in the first aspect above.)

[0046] S1. Under a protective atmosphere and at a temperature T1, the initiator, crosslinking agent, and accelerator are stirred and mixed with a mixed solution containing acrylamide, anionic monomer, and cationic monomer to obtain a first solution; the temperature T1 is 5-25℃.

[0047] S2. The first solution is subjected to a contact reaction at a temperature T2 to obtain a polymer gel; the temperature T2 is 30-50℃.

[0048] S3. The polymer gel is sequentially washed, dried and granulated to obtain salt-responsive self-aggregating gel particles.

[0049] According to a preferred embodiment, the method for preparing salt-responsive self-aggregating gel particles includes the following steps in step S1:

[0050] S11. Acrylamide, anionic monomer and cationic monomer are added to water in sequence and stirred until homogeneous to obtain mixed solution I;

[0051] S12. Nitrogen gas is passed through the mixed solution I to purge the air from the solution, resulting in mixed solution II;

[0052] S13. The initiator, crosslinking agent and accelerator are added to the mixed solution II in sequence, and the mixture is stirred to obtain the first solution.

[0053] Preferably, in step S1, the stirring and mixing reaction takes 3-4 hours.

[0054] In this invention, the starting point for timing the stirring and mixing reaction is the time point at which the accelerator is added and the mixing begins.

[0055] Preferably, in step S1, the stirring speed of the stirring and mixing reaction is 200 rpm to 500 rpm.

[0056] More preferably, in step S1, the stirring speed of the stirring and mixing reaction is 250 rpm to 300 rpm.

[0057] Preferably, in step S1, the mass ratio of the acrylamide, the anionic monomer, and the cationic monomer is 2:1:1 to 3:1:1. The inventors of this invention have discovered that, under this specific preferred embodiment, the salt-responsive self-aggregating gel particles provided by this invention exhibit good self-healing properties, high expansion, and superior sealing performance in environments with a mineralization level below 10000 mg / L.

[0058] More preferably, in step S2, the contact reaction time is 8h-10h.

[0059] In this invention, the timing start point of the contact reaction is the time point when the first solution reaches temperature T2.

[0060] Preferably, in step S2, the contact reaction is carried out at a stirring speed of 100 rpm to 200 rpm.

[0061] More preferably, in step S2, the contact reaction is carried out at a stirring speed of 100 rpm to 150 rpm.

[0062] According to a preferred embodiment, in step S3, the washing specifically includes: first cutting the polymer gel into small pieces, and then rinsing it with anhydrous ethanol. There are no particular requirements regarding the number of washes or the rinsing time in this invention; those skilled in the art can determine the number of washes and the rinsing time according to the actual situation.

[0063] According to a more preferred embodiment, in step S3, the drying conditions include: a temperature of 45°C-65°C and a time of 48h-60h.

[0064] According to a particularly preferred embodiment, in step S3, the conditions of the granulation process are controlled such that the particle size of the salt-responsive self-aggregating gel particles is not greater than 150 μm.

[0065] In this invention, the granulation process further includes sieving through a 100-120 mesh Chinese standard sieve to collect the undersize material; it should be noted that the Chinese standard sieve refers to a sieve that conforms to the Chinese sieve industry standard.

[0066] As previously stated, a third aspect of the present invention provides salt-responsive self-aggregating gel particles prepared by the method described in the second aspect above.

[0067] According to a preferred embodiment, the salt-responsive self-aggregating gel particles have at least one of the following characteristics:

[0068] a: The elastic modulus of the salt-responsive self-aggregating gel particles is 95.8 Pa - 105.9 Pa;

[0069] b: In water with a mineralization of 1000 mg / L, the salt-responsive self-aggregating gel particles swell by 7.4-8.6 times;

[0070] c: In water with a salinity of 1000 mg / L, the salt-responsive self-aggregating gel particles achieved a plugging rate of 95.6%-99.1% in the fractures.

[0071] In this invention, the strength of the salt-responsive self-aggregating gel particles is measured by the elastic modulus, which is obtained by rheometer testing, specifically using the flat plate testing system of the rheometer, wherein the test conditions are as follows: frequency of 1Hz-10Hz, amplitude of 0.1%-100%.

[0072] In this invention, the salt response performance of the salt-responsive self-aggregating gel particles is measured by the expansion factor, which is obtained by testing the particle size of the gel particles at different times using a laser particle size analyzer.

[0073] In this invention, the sealing performance of the salt-responsive self-aggregating gel particles is tested using a fracture core displacement experiment. The test conditions are: core length of 8cm-12cm, diameter of 2cm-3cm, and fracture width of 0.4mm-0.6mm.

[0074] As previously stated, the fourth aspect of the present invention provides the application of the salt-responsive self-aggregating gel particles described in the third aspect above in deep profile control and plugging of heterogeneous reservoirs.

[0075] The present invention will be described in detail below through examples, but the scope of protection of the present invention is not limited to the following description. In the following examples, unless otherwise specified, all raw materials and reagents used are common commercially available products, and all are of analytical grade.

[0076] Example 1

[0077] This embodiment is used to prepare a salt-responsive self-aggregating gel particle, including the following steps:

[0078] (1) Add 16g of acrylamide, 8g of sodium 2-acrylamido-2-methylpropanesulfonate and 8g of methacrylamide propyltrimethylammonium chloride to 67.75g of deionized water, mix and stir evenly to obtain mixed solution I;

[0079] (2) Nitrogen gas was passed through mixed solution I to purge air. At a stirring speed of 300 rpm and a temperature of 25°C, 0.1 g of initiator, 0.1 g of N,N'-methylenebisacrylamide, and 0.05 g of tetramethylethylenediamine were added sequentially to obtain the first solution. The initiator was composed of 0.05 g of potassium persulfate and 0.05 g of azobisisobutyrazoline hydrochloride.

[0080] (3) Nitrogen gas was continuously introduced into the first solution above, and the reaction was carried out at a stirring speed of 100 rpm for 4 h. Then the stirring was stopped, the temperature was raised to 40 °C, and the reaction was carried out at this temperature for 10 h to obtain polymer gel.

[0081] (4) The polymer gel obtained above is cut into pieces, rinsed in anhydrous ethanol, dried at 50°C for 60 h, then crushed and granulated, and the sieved material is sieved through a 100-mesh Chinese standard sieve to obtain salt-responsive self-aggregating gel particles with a particle size not greater than 150 μm.

[0082] Unless otherwise specified, Examples 2-3 were carried out using methods similar to those in Example 1, except that some formulations or process parameters were different, as shown in Table 1. Specifically:

[0083] Example 2

[0084] (1) Add 20g of acrylamide, 8g of sodium p-styrene sulfonate and 8g of acryloyloxyethyltrimethylammonium chloride to 63.76g of deionized water, mix and stir evenly to obtain mixed solution I;

[0085] (2) Nitrogen gas was passed through mixed solution I to purge air and remove air. At a stirring speed of 300 rpm and a temperature of 20°C, 0.06 g of initiator, 0.1 g of N,N'-methylenebisacrylamide, and 0.08 g of dimethyl ethylenediamine were added sequentially to obtain the first solution. The initiator was composed of 0.033 g of potassium persulfate and 0.027 g of azobisisobutyrazoline hydrochloride.

[0086] (3) Nitrogen gas was continuously introduced into the first solution above, and the reaction was carried out at a stirring speed of 100 rpm for 3.5 h. Then the stirring was stopped, the temperature was raised to 50 °C, and the reaction was carried out at this temperature for 8 h to obtain polymer gel.

[0087] (4) The polymer gel obtained above is cut into pieces, rinsed in anhydrous ethanol, dried at 50°C for 60 h, then crushed and granulated, and the sieved material is sieved through a 100-mesh Chinese standard sieve to obtain salt-responsive self-aggregating gel particles with a particle size not greater than 150 μm.

[0088] Example 3

[0089] (1) Add 18g of acrylamide, 6g of sodium 2-acrylamido-2-methylpropanesulfonate and 6g of methacrylamide propyltrimethylammonium chloride to 69.79g of deionized water, mix and stir evenly to obtain mixed solution I;

[0090] (2) Nitrogen gas was passed through mixed solution I to purge air. Under the stirring speed of 300 rpm and the temperature of 15℃, 0.1 g of initiator, 0.06 g of N,N'-methylenebisacrylamide, and 0.05 g of N-tetramethylethylenediamine were added in sequence to obtain the first solution. The initiator was composed of 0.06 g of potassium persulfate and 0.04 g of azobisisobutyrazoline hydrochloride.

[0091] (3) Nitrogen gas was continuously introduced into the first solution and the reaction was carried out at a stirring speed of 100 rpm for 3 h. Then the stirring was stopped, the temperature was raised to 45°C, and the reaction was carried out at this temperature for 9 h to obtain polymer gel.

[0092] (4) The polymer gel obtained above is cut into pieces, rinsed in anhydrous ethanol, dried at 50°C for 60 h, then crushed and granulated, and the sieved material is sieved through a 100-mesh Chinese standard sieve to obtain salt-responsive self-aggregating gel particles with a particle size not greater than 150 μm.

[0093] Table 1

[0094] Example 4

[0095] The method was similar to that in Example 1, except that the initiators were replaced with ammonium persulfate and azobisisobutyrazoline hydrochloride, and the weight ratio of the initiators was adjusted to ammonium persulfate: azobisisobutyrazoline hydrochloride = 2:1, keeping the total amount of initiators in this example the same as the total amount of initiators in Example 1.

[0096] Example 5

[0097] The method was similar to that in Example 1, except that the amount of acrylamide was adjusted to 15g and the amount of water was adjusted to 68.75g. In this example, the mass ratio of acrylamide, anionic monomer and cationic monomer was 1.875:1:1.

[0098] Example 6

[0099] The process was carried out using a method similar to that in Example 1, except that the contact reaction temperature T1 was adjusted to 30°C and the contact reaction temperature T2 was adjusted to 60°C.

[0100] Comparative Example 1

[0101] The procedure was carried out using a method similar to that of Example 1, except that 0.1 g of potassium persulfate, a single initiator, was used instead of the composite initiator in Example 1.

[0102] Comparative Example 2

[0103] The method was similar to that in Example 1, except that no accelerator was added during the stirring and mixing reaction, and the amount of water was adjusted to 67.8g.

[0104] Comparative Example 3

[0105] The procedure was carried out using a method similar to that in Example 1, except that the amount of acrylamide was adjusted to 8g and the amount of water was adjusted to 75.75g.

[0106] Comparative Example 4

[0107] The procedure was carried out using a method similar to that in Example 1, except that the amount of anionic monomer was adjusted to 4g, the amount of cationic monomer was adjusted to 4g, and the amount of water was adjusted to 75.75g.

[0108] Comparative Example 5

[0109] The procedure was carried out using a method similar to that of Example 1, except that the total amount of initiator was adjusted to 0.3 g and the amount of water was adjusted to 67.55 g, while maintaining the same type and weight ratio of initiator as in Example 1.

[0110] Comparative Example 6

[0111] The method was similar to that in Example 1, except that the weight ratio of the initiator was adjusted to potassium persulfate: azobisisobutyrazoline hydrochloride = 4:1, while keeping the total amount and type of initiator in this comparative example the same as in Example 1.

[0112] Test case

[0113] This test example is used to test the elastic modulus, salt response performance, and blocking performance of the salt-responsive self-aggregating gel particles prepared in Examples 1-6 and Comparative Examples 1-6.

[0114] The instruments and related information used in this test example are as follows:

[0115] Rheometer: Model MCR 92, purchased from Anton Paar.

[0116] Core displacement device: purchased from Haian Petroleum Scientific Research Instruments Co., Ltd.

[0117] (1) Salt-responsive self-aggregating gel particle strength test

[0118] The elastic modulus of the salt-responsive self-aggregating gel particles prepared in Examples 1-6 and Comparative Examples 1-6 was tested using a rheometer with a flat plate testing system. The frequency was 1 Hz and the amplitude ranged from 0.1% to 100%. The test results are shown in Table 2.

[0119] (2) Salt response performance test

[0120] The salt-responsive self-aggregating gel particles prepared in Examples 1-6 and Comparative Examples 1-6 were placed in saline solutions with mineralization of 1000 mg / L, 10000 mg / L, 20000 mg / L and 50000 mg / L, respectively, and the swelling, aggregation morphology and aggregation ability of the salt-responsive self-aggregating gel particles were tested. The test results are shown in Table 2.

[0121] The salt-responsive self-aggregating gel particles obtained in Example 1 were placed in water with mineralization of 1000 mg / L, 3000 mg / L, 6000 mg / L, 10000 mg / L, 20000 mg / L and 40000 mg / L, respectively, and their dispersion and aggregation changes were observed. The results are shown in Figure 1.

[0122] (3) Blocking performance test

[0123] Fracture core displacement experiments were conducted to test the sealing ability of salt-responsive self-aggregating gel particles prepared in Examples 1-6 and Comparative Examples 1-6 in fractures. The cores were 10 cm long, 2.5 cm in diameter, and the fractures were 0.5 mm wide.

[0124] The experimental steps are as follows:

[0125] 1) Core preparation: Cut the core along the axial direction, add 0.5mm shims, wrap it with raw rubber tape and assemble it into the displacement device;

[0126] 2) Saturated water: Saturate the core with brine at a rate of 10 mL / min;

[0127] 3) Gel particle injection: Salt-responsive self-aggregating gel particles were injected into the fracture core using brine with a salinity of 50,000 mg / L, with approximately one fracture volume of salt-responsive self-aggregating gel particles injected.

[0128] 4) Water displacement: Inject saline with a mineralization of 1000 mg / L at a rate of 5 mL / min and record the pressure change.

[0129] The test results are shown in Table 2.

[0130] The sealing performance is represented by the sealing rate R%, which is calculated using the following formula:

[0131] In the formula, K1 is the permeability of the water-driven core before gel particle injection, in mD, and K2 is the permeability of the water-driven core after gel particle injection, in mD; K1 and K2 are calculated using Darcy's law.

[0132] Table 2

[0133] As can be seen from the results in Table 2, the salt-responsive self-aggregating gel particles prepared by the methods of Examples 1-6 of this invention have significantly better gel strength, salt-responsive performance, self-aggregating performance, and blocking performance.

[0134] Specifically, the salt-responsive self-aggregating gel particles provided by this invention have an elastic modulus of 95.8-105.9 Pa; in water with a mineralization of 50,000 mg / L, the expansion ratio of the salt-responsive self-aggregating gel particles is 1.4-1.6 times; in water with a mineralization of 20,000 mg / L, the expansion ratio is 2.2-2.5 times; in water with a mineralization of 10,000 mg / L, the expansion ratio is 4.0-4.3 times; in water with a mineralization of 1,000 mg / L, the expansion ratio is 7.4-8.6 times; in water with a mineralization of 1,000 mg / L, the salt-responsive self-aggregating gel particles exhibit strong self-aggregation properties, and their sealing rate in cracks is 95.6-99.1%.

[0135] Furthermore, Figure 1 is a schematic diagram showing the dispersion and aggregation changes of the salt-responsive self-aggregating gel particles prepared in Example 1 in water with different mineralization levels. By placing the salt-responsive self-aggregating gel particles in water with mineralization levels of 1000 mg / L, 3000 mg / L, 6000 mg / L, 10000 mg / L, 20000 mg / L, and 40000 mg / L, as shown in Figure 1(a), the dispersion of the salt-responsive self-aggregating gel particles improves with increasing water mineralization. In water with mineralization levels above 20000 mg / L, it exhibits good dispersibility and low swelling. Under the condition of 1000 mg / L mineralization, the salt-responsive self-aggregating gel particles show good swelling and aggregation self-healing properties (as shown in Figure 1(b)). Therefore, it can be concluded that the salt-responsive self-aggregating gel particles provided by this invention have good salt-responsive performance.

[0136] Compared with Example 1, Comparative Example 1 used an equal weight of single potassium persulfate initiator for monomer polymerization, and the resulting salt-responsive self-aggregating gel particles had weaker self-aggregating properties and relatively lower blocking performance.

[0137] Compared with Example 1, Comparative Example 2 did not use a promoter, and the prepared salt-responsive self-aggregating gel particles had poor self-healing properties and sealing effect.

[0138] Compared with Example 1, the amount of acrylamide used in Comparative Example 3 was significantly reduced. In this comparative example, the ratio of acrylamide, anionic monomer and cationic monomer was: acrylamide: anionic monomer: cationic monomer = 1:1:1. The prepared salt-responsive self-aggregating gel particles had poor self-aggregation performance and blocking effect.

[0139] Compared with Example 1, the amount of anionic and cationic monomers used in Comparative Example 4 was reduced, and the results showed that the prepared salt-responsive self-aggregating gel particles had poor aggregation performance in lower salt solutions.

[0140] Compared with Example 1, the amount of initiator used in Comparative Example 5 was significantly increased, resulting in reduced extensibility and poor swelling properties of the prepared salt-responsive self-aggregating gel particles.

[0141] Compared with Example 1, the content ratio of potassium persulfate to azobisisobutyrazoline hydrochloride in Comparative Example 6 does not conform to the content range of the present invention, and the prepared salt-responsive self-aggregating gel particles have relatively weak self-aggregation performance and low blocking performance.

[0142] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A composition for salt-responsive self-aggregating gel particles, characterized in that, Based on the total weight of the composition, the composition contains 15wt%-25wt% acrylamide, 5wt%-10wt% anionic monomer, 5wt%-10wt% cationic monomer, 0.05wt%-0.2wt% initiator, 0.05wt%-0.2wt% crosslinking agent, and 0.05wt%-0.1wt% accelerator; The anionic monomer is at least one of sodium p-styrene sulfonate and sodium 2-acrylamide-2-methylpropanesulfonate; The cationic monomer is at least one of methacrylamidopropyltrimethylammonium chloride and acryloyloxyethyltrimethylammonium chloride; The initiator is a composite initiator containing initiator A and initiator B. Initiator A is at least one of ammonium persulfate and potassium persulfate. Initiator B is azobisisobutyrazoline hydrochloride. The weight ratio of initiator A to initiator B is 1-3:

1.

2. The composition for salt-responsive self-aggregating gel particles according to claim 1, characterized in that, The weight ratio of initiator A to initiator B is 1-1.5:

1.

3. The composition for salt-responsive self-aggregating gel particles according to claim 2, characterized in that, The initiator A is potassium persulfate.

4. The composition for salt-responsive self-aggregating gel particles according to any one of claims 1-3, characterized in that, The crosslinking agent is N,N'-methylenebisacrylamide.

5. The salt-responsive self-gelling gel particle composition according to any one of claims 1 to 3, wherein The accelerator is one of tetramethylethylenediamine, dimethylethylenediamine, and N-tetramethylethylenediamine.

6. The salt-responsive self-gelling gel particle composition according to any one of claims 1 to 3, wherein The composition also contains a balance of water.

7. A method for preparing salt-responsive self-aggregating gel particles, characterized in that, This method, using the components of the salt-responsive self-aggregating gel particle composition according to any one of claims 1-6, includes the following steps: S1. Under a protective gas atmosphere and at a temperature T1, the initiator, crosslinking agent, and accelerator are stirred and mixed with a mixed solution containing acrylamide, anionic monomer, and cationic monomer to obtain a first solution; the temperature T1 is 5-25℃. S2. The first solution is subjected to a contact reaction at a temperature T2 to obtain a polymer gel; the temperature T2 is 30-50℃. S3. The polymer gel is sequentially washed, dried and granulated to obtain salt-responsive self-aggregating gel particles.

8. The method according to claim 7, characterized in that, In step S1, the stirring and mixing reaction takes 3-4 hours. And / or, in step S1, the stirring speed of the stirring and mixing reaction is 200 rpm to 500 rpm.

9. The method according to claim 7, characterized in that, In step S1, the mass ratio of the acrylamide, the anionic monomer, and the cationic monomer is 2:1:1 to 3:1:

1.

10. The method according to claim 7, characterized in that, In step S2, the contact reaction time is 8-10 hours. And / or, in step S2, the contact reaction is carried out at a stirring speed of 100 rpm to 200 rpm.

11. The method according to claim 7, characterized in that, In step S3, the drying conditions include: a temperature of 45℃-65℃ and a time of 48h-60h.

12. The method according to claim 7, characterized in that, In step S3, the conditions of the granulation process are controlled so that the particle size of the salt-responsive self-aggregating gel particles is no greater than 150 μm.

13. Salt-responsive self-aggregating gel particles prepared by the method according to any one of claims 7-12.

14. The salt-responsive self-aggregating gel particles according to claim 13, characterized in that, The salt-responsive self-aggregating gel particles have at least one of the following characteristics: a: The elastic modulus of the salt-responsive self-aggregating gel particles is 95.8 Pa - 105.9 Pa; b: In water with a mineralization of 1000 mg / L, the salt-responsive self-aggregating gel particles swell by 7.4-8.6 times; c: In water with a salinity of 1000 mg / L, the salt-responsive self-aggregating gel particles achieved a plugging rate of 95.6%-99.1% in the fractures.

15. The application of the salt-responsive self-aggregating gel particles according to claim 13 or 14 in deep profile control and plugging of heterogeneous oil reservoirs.

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