A salt-induced selective water plugging agent, its preparation method and application

Abstract

The application provides a salt-induced selective water plugging agent, a preparation method and application thereof, and more particularly relates to a salt-induced selective water plugging agent for high-salinity reservoir water plugging. The salt-induced selective water plugging agent comprises the following components: modified composite swelling particles, a curing agent, a reinforcing agent and water. The preparation raw material of the modified composite swelling particles comprises the following components: a silane coupling agent, a solubilizing agent, a surfactant, a sodium-based montmorillonite, N-vinyl pyrrolidone, an oil-soluble resin powder, a curable resin powder, acrylamide, a crosslinking agent and an aqueous solution. The modified composite swelling particles have high structural strength and excellent temperature resistance and salt resistance through design, and can significantly swell in a solution with a specific salt concentration, so that the particles can effectively seal a water channel under high-salinity conditions with high strength.

Description

Technical Field

[0001] This invention belongs to the field of oilfield chemical technology, specifically relating to a salt-induced selective water shut-off agent, its preparation method and application, and more specifically to a salt-induced selective water shut-off agent for water shut-off in high-salinity oil reservoirs. Background Technology

[0002] During oilfield development, as crude oil is continuously extracted, it is necessary to replenish the reservoir's energy. Water injection is an effective means of replenishing the bottom layer's energy in oilfield development. Currently, more than 80% of onshore oil and gas fields in my country are developed using water injection. However, the formations are complex and unevenly distributed, with significant differences in reservoir properties. Therefore, in oil and gas fields developed using water injection, as the amount of water injected into the formation gradually increases during the mid-to-late stages of development, the injection profile becomes particularly uneven. In some blocks, the water injected into the formation quickly returns to the surface through high-permeability layers. This repeated scouring of high-permeability layers exacerbates the permeability of injected water and intensifies the uneven distribution of the formation. Ultimately, this leads to increasingly severe water production in oil wells during water injection development, with most oil and gas fields even experiencing water flooding. This results in a significant reduction in oil well productivity, and rising water cuts in oil wells are a serious problem prevalent in most oilfields in China. Therefore, reservoir water shut-off technology is needed to improve the heterogeneity between and within reservoir layers, expand the water injection sweep volume, change the mobility ratio between the displacing fluid and the displaced fluid, and improve reservoir recovery.

[0003] Based on their blocking effect, water-blocking agents can be divided into selective and non-selective water-blocking agents. Selective water-blocking agents react only with water and not with oil, thus causing blockage only in the water layer with minimal impact on the oil layer. Polyacrylamide is the most widely used selective water-blocking agent, and acrylamide or its copolymers are widely used as water-blocking agents in major oilfields both domestically and internationally. Selective water-blocking does not require isolation between the oil and water layers, making the process relatively simple. Selective water-blocking agents can be classified into water-based, oil-based, and alcohol-based agents according to the dispersion medium, and into particulate, precipitated, emulsion, foam, and polymer types according to the water-blocking material. Particulate water-blocking agents have high sealing strength and long sealing time, but their injectability is poor, making them only suitable for near-wellbore areas. Precipitated water-blocking agents have high requirements for the reservoir environment and formation water composition. Foam and polymer-based water-blocking agents perform poorly in high-temperature environments; polymers easily lose water in high-temperature and high-salt environments, reducing sealing strength and ultimately leading to sealing failure. Resin-based water-blocking agents have good temperature and pressure resistance and high sealing strength. Salt-induced volume-swelling particles are a special type of plugging agent whose performance and application effectiveness are influenced by salt concentration. These particles are granular substances that swell upon contact with water but maintain a relatively constant volume upon contact with oil. In solutions with specific salt concentrations, the particles can undergo significant volume expansion, resulting in an effective plugging effect. These particles are typically prepared through on-site synthesis, drying, crushing, and sieving, and possess broad adaptability to various oil reservoirs and fluids.

[0004] Bulk-swellable particles have a wide range of applications in oilfields. Sun Lin of Southwest Petroleum University combined solidifiable coated particles with bulk-swellable particles. The former solidifies at high reservoir temperatures within wide fractures to form an immovable mesh-like blockage, allowing the latter to break through the pressure gradient of wide fractures to be significantly higher than that of narrow fractures. This effectively improves the production profile of heterogeneous fractures and eliminates the negative impact of improper particle size and flow splitting on fracture sealing. A resin coating is applied to the surface of the matrix particles, which, after injection into the formation, forms a mesh structure to seal the fractures. Because the coated particles use ceramic particles as the matrix during preparation, they are rigid materials with poor injectability. Experiments show that this combined particle combination can break through a pressure gradient exceeding 79 MPa / m, exhibiting high sealing strength.

[0005] CN118421046A discloses a selective water-blocking salt-induced selective water-blocking agent, its preparation method, and its application. The modified resin bulk-expanding particles of this invention can be cured under high temperature and high pressure to form a three-dimensional network structure, thereby effectively blocking water channeling. After entering the oil phase channel, the particles can be miscible with the oil phase, having little impact on the oil production channel, and can achieve selective blocking of water channeling. However, this system does not have volume expansion properties, resulting in low blocking strength for water channeling.

[0006] Based on this, and summarizing existing research on bulked particles and resin materials, there is an urgent need to develop selective plugging agents that are suitable for the complex environment of high-temperature, high-salinity reservoirs and have high plugging strength. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a salt-induced selective water shut-off agent, its preparation method, and its application, more specifically relating to a salt-induced selective water shut-off agent for water shut-off in high-salinity oil reservoirs. This invention designs modified composite expanded particles, resulting in particles with high structural strength and excellent temperature and salt resistance. In solutions of specific salt concentrations, the particles undergo significant volume expansion, enabling high-strength and effective sealing of water channeling under high-salinity conditions.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a salt-induced selective water shut-off agent, the salt-induced selective water shut-off agent comprising the following components in weight percentage:

[0010]

[0011] The raw materials for preparing the modified composite swellable particles include the following components in weight percentage:

[0012]

[0013]

[0014] This invention designs modified composite expanded particles, combining expanded particle water-blocking technology with resin materials to form multi-component copolymer composite particles. These particles contain curable resin particles and oil-soluble resin particles, which are polymerized together using acrylamide gel to form the modified composite expanded particles. The modified composite expanded particles provided by this invention exhibit high structural strength and excellent temperature and salt resistance. In solutions with specific salt concentrations (180,000 mg / L–220,000 mg / L), the particles undergo significant volume expansion, achieving high-strength and effective sealing of water channeling under high salinity conditions (180,000 mg / L–220,000 mg / L). Furthermore, the salt-induced selective water-blocking agent provided by this invention uses widely available and low-cost raw materials, offering good economic benefits.

[0015] The salt-induced selective water shut-off agent provided by this invention, after being injected into water channels in high-salinity oil and gas reservoirs, solidifies under high-temperature and high-salinity conditions, generating a three-dimensional network structure. Simultaneously, the salt-induced selective water shut-off agent provided by this invention exhibits salinity responsiveness, allowing for the preparation of specific systems tailored to different reservoir salinities. It demonstrates strong adaptability, and in solutions with specific salt concentrations, the particles undergo significant volume expansion, resulting in an effective sealing effect.

[0016] This invention can effectively and strongly seal water channeling in high-temperature, high-salt reservoirs (temperature 120℃-150℃, salt solution concentration 180000mg / L–220000mg / L). After the salt-induced selective water shut-off agent enters the water production channel, it can adhere and solidify to form a high-strength three-dimensional network structure, which has a good sealing effect on the aqueous phase channel. After the salt-induced selective water shut-off agent enters the oil phase channel, it mixes with the crude oil, reducing damage to the oil phase channel and exhibiting excellent selective sealing effect.

[0017] Furthermore, this invention designs the raw materials for preparing modified composite expanded particles, and through the combined action of the components, prepares high-performance modified composite expanded particles, thereby obtaining a high-performance salt-induced selective water-blocking agent. This salt-induced selective water-blocking agent can achieve highly efficient selective sealing of aqueous phase channels.

[0018] This invention relates to the preparation of modified composite expanded particles by controlling the mass percentage of sodium montmorillonite in the raw materials within a specific range, thereby obtaining modified composite expanded particles with excellent performance. If the amount of sodium montmorillonite in the raw materials for preparing modified composite expanded particles is too small, the temperature and salt resistance of the particles will be insufficient; if the content of sodium montmorillonite in the raw materials for preparing modified composite expanded particles is too large, the system cost will increase and the gelation effect will be poor.

[0019] This invention relates to a method for preparing high-performance modified composite swellable particles by controlling the mass percentage of N-vinylpyrrolidone in the raw materials within a specific range. If the amount of N-vinylpyrrolidone in the raw materials is too low, the particles will have low water absorption capacity and poor water absorption and swelling effect; if the content of N-vinylpyrrolidone in the raw materials is too high, the system cost will increase, resulting in poor economic benefits.

[0020] In this invention, the mass percentage of modified composite swellable particles in the salt-induced selective water plugging agent can be 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%, etc.

[0021] The mass percentage of the curing agent in the salt-induced selective water-blocking plugging agent can be 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, or 0.7%, etc.

[0022] The mass percentage of the reinforcing agent in the salt-induced selective water-blocking plugging agent can be 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, or 0.7%, etc.

[0023] In this invention, the mass percentage of silane coupling agent in the raw materials for preparing the modified composite expanded particles can be 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%, etc.

[0024] The mass percentage of solubilizer in the raw materials for preparing the modified composite swellable particles can be 3%, 3.2%, 3.4%, 3.6%, 3.8%, 4%, 4.2%, 4.4%, 4.6%, 4.8%, or 5%, etc.

[0025] The mass percentage of surfactant in the raw materials for preparing the modified composite expanded particles can be 0.3%, 0.32%, 0.34%, 0.36%, 0.38%, 0.4%, 0.42%, 0.44%, 0.46%, 0.48%, or 0.5%, etc.

[0026] The mass percentage of sodium montmorillonite in the raw materials for preparing the modified composite expanded particles can be 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%, etc.

[0027] The mass percentage of N-vinylpyrrolidone in the raw materials for preparing the modified composite expanded particles can be 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%, etc.

[0028] The mass percentage of oil-soluble resin powder in the raw materials for preparing the modified composite expanded particles can be 1%, 1.05%, 1.1%, 1.15%, 1.2%, 1.25%, 1.3%, 1.35%, 1.4%, 1.45%, or 1.5%, etc.

[0029] The mass percentage of curable resin powder in the raw materials for preparing the modified composite expanded particles can be 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, or 1%, etc.

[0030] The mass percentage of acrylamide in the raw materials for preparing the modified composite expanded particles can be 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, or 30%, etc.

[0031] The mass percentage of crosslinking agent in the raw materials for preparing the modified composite expanded particles can be 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, or 0.3%, etc.

[0032] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The purpose and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0033] As a preferred embodiment of the present invention, the silane coupling agent is selected from any one or a combination of at least two of silane coupling agents KH550, KH560, KH570, or KH792.

[0034] Preferably, the solubilizer is selected from any one or a combination of at least two of ethanol, ethylene glycol, or propylene glycol.

[0035] Preferably, the surfactant is selected from any one or a combination of at least two of APG-0810, APG-1214, DAB-35 or ODAB-35.

[0036] As a preferred embodiment of the present invention, the oil-soluble resin powder is selected from C5 resin powder and / or C9 resin powder.

[0037] Preferably, the curable resin powder is selected from any one or a combination of at least two of phenolic resin 7522, terpene phenolic resin DA-21, phenolic resin 2123, epoxy resin E44, or epoxy resin E-20.

[0038] In this invention, the D of the oil-soluble resin powder 90 Particle size of 50-300 mesh (e.g., 50 mesh, 70 mesh, 100 mesh, 120 mesh, 150 mesh, 180 mesh, 200 mesh, 220 mesh, 250 mesh, 280 mesh, or 300 mesh, etc.); D of curable resin powder 90The particle size is 50-300 mesh (e.g., it can be 50 mesh, 70 mesh, 100 mesh, 120 mesh, 150 mesh, 180 mesh, 200 mesh, 220 mesh, 250 mesh, 280 mesh or 300 mesh, etc.).

[0039] As a preferred embodiment of the present invention, the crosslinking agent is selected from any one or a combination of at least two of the following: ammonium persulfate ((NH4)2S2O8), zinc sulfate (ZnSO4), aluminum sulfate (Al2(SO4)3), copper acetate (Cu(CH3COO)2), or ferric chloride (FeCl3).

[0040] Preferably, the aqueous solution is a weakly alkaline solution with a pH of 8.5-9.5, such as 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4 or 9.5.

[0041] It should be noted that there are no special restrictions on the solutes of the weakly alkaline solutions in this invention. Commonly used alkaline compounds in the art are applicable, including but not limited to: NaOH, KOH, Na2CO3, NaHCO3, K2CO3, KHCO3, etc.

[0042] As a preferred embodiment of the present invention, the raw materials for preparing the modified composite expanded particles further include an initiator with a mass percentage of 0.01-0.02%, such as 0.01%, 0.011%, 0.012%, 0.013%, 0.014%, 0.015%, 0.016%, 0.017%, 0.018%, 0.019%, or 0.02%.

[0043] Preferably, the initiator is selected from any one or a combination of at least two of N,N-methyleneacrylamide (MBA) / azobisisobutyronitrile (AIBN), azoV50 (AIBA), potassium persulfate (KPS), or ammonium persulfate (APS).

[0044] Preferably, the raw materials for preparing the modified composite expanded particles also include an oxygen scavenger with a mass percentage of 0.01-0.02%, such as 0.01%, 0.011%, 0.012%, 0.013%, 0.014%, 0.015%, 0.016%, 0.017%, 0.018%, 0.019%, or 0.02%.

[0045] Preferably, the oxygen scavenger is selected from thiourea (CH4N2S) and / or sodium sulfite (Na2SO3).

[0046] As a preferred embodiment of the present invention, the modified composite swellable particles are prepared by the following method, which includes the following steps:

[0047] S1: Mix the aqueous solution, silane coupling agent, surfactant, sodium montmorillonite, and N-vinylpyrrolidone to obtain a mixture;

[0048] S2: Mix the mixture obtained in step S1, the oil-soluble resin powder, and the curable resin powder to obtain a modified resin dispersion emulsion;

[0049] S3: Mix the modified resin dispersion emulsion obtained in step S2, acrylamide, crosslinking agent, initiator and oxygen scavenger, and react to obtain the modified composite swellable particles.

[0050] As a preferred embodiment of the present invention, the mixing method in step S1 includes stirring.

[0051] Preferably, the mixing time in step S1 is 4-8 minutes, for example, it can be 4 minutes, 5 minutes, 6 minutes, 7 minutes or 8 minutes.

[0052] Preferably, the mixing temperature in step S2 is 50-60°C, for example, it can be 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C or 60°C.

[0053] Preferably, the mixing method in step S2 includes stirring and ultrasonic dispersion.

[0054] Preferably, the stirring speed is 1000-1500 rpm, for example, it can be 1000 rpm, 1050 rpm, 1100 rpm, 1150 rpm, 1200 rpm, 1250 rpm, 1300 rpm, 1350 rpm, 1400 rpm, 1450 rpm or 1500 rpm.

[0055] Preferably, the stirring time is 8-15 minutes, for example, it can be 8 minutes, 9 minutes, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes or 15 minutes.

[0056] Preferably, the ultrasonic dispersion time is 8-15 min, for example, it can be 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min or 15 min, etc.

[0057] Preferably, the mixing method in step S3 includes stirring.

[0058] Preferably, the stirring speed is 800-1000 rpm, for example, it can be 800 rpm, 820 rpm, 840 rpm, 860 rpm, 880 rpm, 900 rpm, 920 rpm, 940 rpm, 960 rpm, 980 rpm or 1000 rpm.

[0059] Preferably, the mixing time in step S3 is 8-15 minutes, for example, it can be 8 minutes, 9 minutes, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes or 15 minutes.

[0060] Preferably, the reaction in step S3 is carried out in a closed container.

[0061] Preferably, the reaction temperature in step S3 is 70-80℃ (e.g., 70℃, 71℃, 72℃, 73℃, 74℃, 75℃, 76℃, 77℃, 78℃, 79℃, or 80℃, etc.), and the time is 30-45min (e.g., 30min, 32min, 34min, 36min, 38min, 40min, 41min, 42min, 43min, 44min, or 45min, etc.).

[0062] Preferably, step S3 further includes a post-processing step after the reaction, and the post-processing method includes drying and pulverizing.

[0063] As a preferred embodiment of the present invention, the modified composite swellable particles are prepared by the following method, which includes the following specific steps:

[0064] Step S1: In an aqueous solution with a pH of 8.5-9.5, add silane coupling agent, solubilizer, surfactant, sodium montmorillonite and N-vinylpyrrolidone (NVP), and stir thoroughly with a magnetic stirrer for 4-8 minutes to ensure that the above reagents are fully mixed to obtain a mixture.

[0065] Step S2: Place the mixture obtained in step S1 into a constant temperature magnetic stirrer, set the temperature to 50-60℃ and the speed to 1000-1500 rpm, add oil-soluble resin powder and curable resin powder, stir for 8-15 min and then place it in an ultrasonic disperser to disperse for 8-15 min to obtain a modified resin dispersion emulsion.

[0066] Step S3: Place the modified resin dispersion emulsion obtained in step S2 on a magnetic stirrer and set the speed to 800-1000 rpm. Add acrylamide, crosslinking agent, initiator and oxygen scavenger to it. After stirring for 8-15 min, place it in a sealed container and react at 70-80℃ for 30-45 min until it is completely gelled. Remove the gel, dry it and pulverize it to obtain modified composite swellable particles.

[0067] As a preferred embodiment of the present invention, the curing agent is selected from any one or a combination of at least two of the following: NL type curing agent, catechol (C6H6O2), ammonium chloride (NH4Cl), p-toluenesulfonic acid (C7H8O3S), T31 curing agent, or TSG-6032 curing agent.

[0068] Preferably, the reinforcing agent is selected from hexamethylenetetramine (HMT), phthalic anhydride (C8H4O3), or pyromellitic dianhydride (C8H4O3). 10 Any one or at least two of H2O6.

[0069] In a second aspect, the present invention provides a method for preparing a salt-induced selective water-blocking agent as described in the first aspect, the preparation method comprising the following steps:

[0070] The modified composite swellable particles, curing agent, reinforcing agent and water are mixed to obtain the salt-induced selective water-blocking plugging agent.

[0071] Preferably, the mixing method includes stirring.

[0072] Preferably, the stirring speed is 1000-1500 rpm, for example, it can be 1000 rpm, 1050 rpm, 1100 rpm, 1150 rpm, 1200 rpm, 1250 rpm, 1300 rpm, 1350 rpm, 1400 rpm, 1450 rpm or 1500 rpm.

[0073] Preferably, the mixing temperature is 20-30℃, for example, it can be 20℃, 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, 29℃ or 30℃, etc.

[0074] Preferably, the mixing time is 12-20 minutes, for example, it can be 12 minutes, 13 minutes, 14 minutes, 15 minutes, 16 minutes, 17 minutes, 18 minutes, 19 minutes or 20 minutes.

[0075] The preparation method of the salt-induced selective water-blocking agent specifically includes the following steps:

[0076] Under conditions of 20-30℃ and 1000-1500rpm, the modified composite swellable particles and water are mixed evenly, and then a curing agent and reinforcing agent are added and mixed. The mixture is stirred at a constant speed and temperature for 12-20 minutes to obtain the salt-induced selective water-blocking agent.

[0077] Thirdly, the present invention provides a salt-induced selective water shut-off agent as described in the first aspect, the salt-induced selective water shut-off agent being used in oilfield development.

[0078] Preferably, the salt-induced selective water shut-off agent is used for water shut-off in high-salinity oil reservoirs or high-salinity gas reservoirs.

[0079] The salt-induced selective water shut-off agent provided by this invention, after being injected into water channels in high-salinity oil and gas reservoirs, solidifies under high-temperature and high-salinity conditions, generating a three-dimensional network structure. Simultaneously, the salt-induced selective water shut-off agent provided by this invention exhibits salinity responsiveness, allowing for the preparation of specific systems tailored to different reservoir salinities. It demonstrates strong adaptability, and in solutions with specific salt concentrations, the particles undergo significant volume expansion, resulting in an effective sealing effect.

[0080] Fourthly, this invention also provides a method for applying a salt-induced selective water shut-off agent. The salt-induced selective water shut-off agent is injected into the reservoir in different ways depending on the specific conditions of the oilfield. For oilfields with production profile testing data, a point injection method is used. After entering the water-bearing channel, the agent absorbs water, expands, and solidifies, achieving water shut-off. For oilfields without production profile testing data, the agent can be directly injected through the tubing channel. Utilizing the selectivity of the salt-induced selective water shut-off agent itself, after entering the water-bearing channel, under high-temperature conditions (120-150℃), the modified composite swellable particles absorb water, expand, and solidify, forming a three-dimensional network structure to seal the water-bearing channel. After the system enters the oil-bearing channel and comes into contact with the oil phase, the modified composite swellable particles can miscible with the crude oil. The resin component in the particles dissolves in the crude oil and does not absorb water or expand, reducing the sealing effect on the oil phase. After the salt-induced selective water shut-off agent enters the gas channel, the particles do not expand because there is no moisture in the channel, resulting in minimal impact on the gas channel. The salt-induced selective water shut-off agent of this invention is applicable to water shut-off operations in both high-salinity oil reservoirs and high-salinity gas reservoirs. It also has selective water shut-off performance, temperature and salt resistance, and can achieve good water shut-off effect.

[0081] Compared with the prior art, the present invention has the following beneficial effects:

[0082] (1) The present invention designs the modified composite expanded particles so that the modified composite expanded particles have high structural strength and excellent temperature and salt resistance. In a solution with a specific salt concentration, the particles can undergo significant volume expansion, which can effectively block water channeling under high mineralization conditions.

[0083] (2) For a permeable core with a permeability of 497 mD, the salt-induced selective water shut-off plugging agent provided by this invention has a permeability of ≤21% for the gas phase channel, ≤41% for the oil phase channel, and a blocking rate of ≥78% for the aqueous phase; for a permeable core with a permeability of 51 mD, the salt-induced selective water shut-off plugging agent provided by this invention has a permeability of ≤28% for the gas phase channel, ≤43% for the oil phase channel, and a blocking rate of ≥84% for the aqueous phase; for a permeable core with a permeability of 5.3 mD, the salt-induced selective water shut-off plugging agent provided by this invention has a permeability of ≤40% for the gas phase channel, ≤50% for the oil phase channel, and a blocking rate of ≥92% for the aqueous phase. Detailed Implementation

[0084] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0085] The sources of some components in the examples and comparative examples are as follows:

[0086] APG-0810: Shandong Yousuo Chemical Technology Co., Ltd.;

[0087] APG-1214: Shandong Yousuo Chemical Technology Co., Ltd.;

[0088] DAB-35: Shandong Yousuo Chemical Technology Co., Ltd.;

[0089] C5 resin powder: Jinan Dahui Chemical Technology Co., Ltd.;

[0090] C9 resin powder: Shandong Yousuo Chemical Technology Co., Ltd.;

[0091] Sodium-based montmorillonite: Shuolong Mineral Products Processing Plant, Lingshou County;

[0092] Phenolic resin 7522: Shenzhen Yoshida Chemical Co., Ltd.;

[0093] Terpene phenolic resin DA-21: Shenzhen Yoshida Chemical Co., Ltd.;

[0094] Phenolic resin 2123: Shenzhen Yoshida Chemical Co., Ltd.;

[0095] Aqueous solution with pH=9: Dissolve NaOH in deionized water to obtain an aqueous solution with pH=9.

[0096] Preparation Examples 1-7, Comparative Preparation Examples 1-8

[0097] Preparation Examples 1-7 and Comparative Preparation Examples 1-8 respectively provide a modified composite expanded granule and its preparation method. The raw materials for preparing the modified composite expanded granule and the mass percentage content of each component are shown in Table 1 and Table 2 below.

[0098] The methods for preparing the modified composite expanded particles provided in Preparation Examples 1-7 and Comparative Preparation Examples 1-8 are as follows:

[0099] Step S1: In an aqueous solution with pH=9, add silane coupling agent, solubilizer, surfactant, sodium montmorillonite and NVP, and stir thoroughly for 5 minutes using a magnetic stirrer to ensure that the above reagents are fully mixed to obtain a mixture;

[0100] Step S2: Place the mixture obtained in step S1 into a constant temperature magnetic stirrer, set the temperature to 55℃ and the speed to 1400 rpm, add oil-soluble resin powder and curable resin powder, stir for 10 min and then place it in an ultrasonic disperser to disperse for 10 min to obtain a modified resin dispersion emulsion.

[0101] Step S3: Place the modified resin dispersion emulsion obtained in step S2 on a magnetic stirrer, set the speed to 900 rpm, add acrylamide, crosslinking agent, initiator and oxygen scavenger, stir for 10 min, then place in a sealed container and react at 75℃ for 36 h until complete gelation. Remove the gel, dry it, and pulverize it to obtain modified composite swellable particles (D). 90 (Particle size: 250 mesh).

[0102] Table 1

[0103]

[0104] Table 2

[0105]

[0106] Evaluation of the water absorption and swelling properties of the modified composite granules provided in the above preparation examples and comparative preparation examples.

[0107] The modified composite swelled particles prepared in the above-mentioned examples and comparative examples were placed in five solutions with different mineralization: deionized water, 10000 mg / L, 15000 mg / L, 20000 mg / L, and 25000 mg / L. They were then heated in a 120°C high-temperature oven for 72 hours. The masses after water absorption and swelling were measured, and the water absorption and swelling rate K was calculated for each solution.

[0108]

[0109] K is the water absorption swelling rate, m0 is the initial mass (g) of the modified composite swellable particles, and m1 is the mass (g) of the modified composite swellable particles after water absorption and swelling.

[0110] The test results are shown in Table 3:

[0111] Table 3

[0112]

[0113] The data above show that the modified composite swellable particles provided in Preparation Example 3 performed best at different mineralization levels, while the comparative preparation example 6, without the addition of NVP monomer, had the worst water absorption and swelling performance. This is because NVP monomer is a hydrophilic monomer, which can introduce hydrophilic groups into the gel, thereby improving the gel's water absorption and swelling capacity. Sodium-based montmorillonite has advantages such as large specific surface area, strong adsorption capacity, slow water absorption rate, and large water absorption rate and swelling ratio. Introducing inorganic particles into this polymer system can combine the rigidity and thermal stability of inorganic materials with their salt resistance, improving the temperature and salt resistance of the water-blocking agent. The five modified resin swellable particles showed the best water absorption and swelling effect in deionized water, and the worst swelling effect in simulated formation water with a mineralization level of 250,000 mg / L. The comparative experimental results show that the swelling degree of the particles increased abnormally at a mineralization level of 200,000 mg / L, exceeding the levels at 150,000 mg / L and 250,000 mg / L. The experimental results show that the modified resin bulk particles in this invention have salt-induced properties. Under specific mineralization conditions, the particles can undergo significant volume expansion, effectively blocking water channeling. Moreover, the blocking effect on water channeling is better as the permeability decreases.

[0114] As can be seen from the above, this invention, through the design of the composition of modified composite swellable particles, has prepared modified composite swellable particles with excellent performance. The water absorption and swelling degree in deionized water is 10.2–15.2%, and the water absorption and swelling degree in deionized water is 1×10⁻⁶. 5 The water absorption swelling degree is 8.6%–12.6% at a concentration of mg / L, and at a mineralization of 1.5 × 10⁻⁶ mg / L. 5 The water absorption swelling degree at mg / L is 7.2–9.8%, and the water absorption swelling degree at a mineralization of 2×10⁻⁶ mg / L is 7.2–9.8%. 5 The water absorption swelling degree is 8.5–10.8% at mg / L, and at a mineralization degree of 2.5 × 10⁻⁶ mg / L. 5 The water absorption swelling degree at mg / L ranges from 4.2% to 7.4%.

[0115] Examples 1-7, Comparative Examples 1-8

[0116] Examples 1-7 and Comparative Examples 1-8 respectively provide a salt-induced selective water-blocking agent and its preparation method. The mass percentage content of modified composite swellable particles, curing agent, reinforcing agent and deionized water in the salt-induced selective water-blocking agent is shown in Table 4 below.

[0117] The preparation method of the above-mentioned salt-induced selective water shut-off agent specifically includes the following steps:

[0118] At 25°C and 1300 rpm, the modified composite swellable particles and water were mixed evenly, and then a curing agent and reinforcing agent were added and mixed. The mixture was stirred at a constant speed and temperature for 15 minutes to obtain the salt-induced selective water-blocking agent.

[0119] Table 4

[0120]

[0121]

[0122] The selective plugging performance of the salt-induced selective water shut-off agents provided in the above embodiments and comparative examples was evaluated using the following specific evaluation methods:

[0123] Three core samples with permeabilities of 497 mD, 51 mD, and 5.3 mD were selected and dried in a 90°C oven. The core samples were then placed in a core holder and subjected to nitrogen flooding, water flooding, and oil displacement experiments in a 120°C constant temperature oven.

[0124] In the gas drive experiment, nitrogen was used to drive the core, and the initial gas phase permeability was calculated. Then, 0.7 PV of the salt-induced selective water shut-off plugging agent from the above-mentioned examples and comparative examples was injected into the core, and gas drive was continued. The gas phase permeability after the injection of the salt-induced selective water shut-off plugging agent was calculated.

[0125] In the water flooding experiment, simulated formation water with a salinity of 200,000 mg / L was used to flood the core. After the pressure stabilized, the initial water phase permeability was calculated. 0.7 PV of the salt-induced selective water plugging agent used in the above-mentioned examples and comparative examples was injected into the core. Water flooding was then continued. After the pressure stabilized, the subsequent water phase permeability of the core was calculated.

[0126] In the oil displacement experiment, crude oil was injected into the core, and the initial oil phase permeability was calculated after the pressure stabilized. Then, 0.7 PV of the salt-induced selective water shut-off agent from the above-mentioned examples and comparative examples was injected into the core. Crude oil was then injected again, and the subsequent oil phase permeability was calculated after the pressure stabilized. The sealing effect of the salt-induced selective water shut-off agent in the oil, gas, and water channels, as well as the sealing strength under different permeability conditions, were investigated. The test results are shown in Tables 5-7.

[0127] Table 5. Measurement results of core flow experiments at 120℃ with a permeability of 497 mD.

[0128]

[0129]

[0130] Table 6. Measurement results of core flow experiments at 120℃ with a permeability of 51 mD.

[0131]

[0132]

[0133] Table 7. Measurement results of core flow experiments at 120℃ with a permeability of 5.3 mD.

[0134]

[0135]

[0136] The above results show that, for cores with permeability of 497 mD, 51 mD, and 5.3 mD, the salt-induced selective water shut-off agent can maintain a water phase plugging efficiency of over 75% while minimizing the impact on the permeability of the gas and oil phase channels. This achieves highly efficient selective plugging of the water phase channels. Furthermore, the comparative examples show that particles without sodium-based bentonite and NVP monomers have a poorer plugging effect on water channel penetration. This indicates that sodium-based bentonite and NVP monomers play an important role in modifying the composite bentonite particles and can significantly improve particle performance.

[0137] Specifically, for a core with a permeability of 497 mD, the salt-induced selective water shut-off agent provided by this invention has a permeability of ≤21% for the gas phase channel, ≤41% for the oil phase channel, and a blocking rate of ≥78% for the aqueous phase; for a core with a permeability of 51 mD, the salt-induced selective water shut-off agent provided by this invention has a permeability of ≤28% for the gas phase channel, ≤43% for the oil phase channel, and a blocking rate of ≥84% for the aqueous phase; and for a core with a permeability of 5.3 mD, the salt-induced selective water shut-off agent provided by this invention has a permeability of ≤40% for the gas phase channel, ≤50% for the oil phase channel, and a blocking rate of ≥92% for the aqueous phase.

[0138] Based on the experimental data above, it can be seen that the salt-induced selective water shut-off agent can effectively seal the aqueous phase channel under high temperature and high salinity conditions of 120℃. Depending on the specific oilfield conditions, it can be injected into the reservoir in different ways. For oilfields with production profile testing data, a targeted injection method is used, achieving water shut-off after entering the water-bearing channel. For oilfields without production profile testing data, it can be directly injected through the tubing channel. Utilizing the selectivity of the salt-induced selective water shut-off agent itself, it solidifies and adheres under high temperature conditions after entering the water-bearing channel, forming a high-strength three-dimensional spatial network structure, thus sealing the water-bearing channel.

[0139] Meanwhile, it has minimal impact on the permeability of both the gas and oil phase channels, achieving the effect of blocking water without blocking gas or oil. Its working principle is as follows: due to the small particle size of the salt-induced selective water-blocking agent, it can enter micropores. After the system enters the oil-bearing channel and comes into contact with the oil phase, the modified composite expanded particles can interact with the crude oil, reducing the blocking effect on the oil phase. After the salt-induced selective water-blocking agent enters the gas channel, under high-temperature conditions, the particles lose water due to liquid evaporation, reducing their volume and minimizing the impact on the gas channel, thus achieving the effect of blocking water without blocking gas. The salt-induced selective water-blocking agents in each embodiment can be applied to both oil and gas reservoirs, exhibiting selective water-blocking performance and salinity responsiveness, achieving good water-blocking effects.

[0140] The applicant declares that the detailed process flow of this invention is illustrated by the above embodiments, but this invention is not limited to the above detailed process flow, that is, it does not mean that this invention must rely on the above detailed process flow to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials for the product of this invention, addition of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of this invention.

Claims

1. A salt-induced selective water-blocking agent, characterized in that, The salt-induced selective water shut-off agent comprises the following components in weight percentage: The raw materials for preparing the modified composite swellable particles include the following components in mass percentage:

2. The salt-induced selective water-blocking agent according to claim 1, characterized in that, The silane coupling agent is selected from any one or a combination of at least two of the following: silane coupling agent KH550, silane coupling agent KH560, silane coupling agent KH570, or silane coupling agent KH792. Preferably, the solubilizer is selected from any one or a combination of at least two of ethanol, ethylene glycol, or propylene glycol; Preferably, the surfactant is selected from any one or a combination of at least two of APG-0810, APG-1214, DAB-35 or ODAB-35.

3. The salt-induced selective water-blocking agent according to claim 1 or 2, characterized in that, The oil-soluble resin powder is selected from C5 resin powder and / or C9 resin powder; Preferably, the curable resin powder is selected from any one or a combination of at least two of phenolic resin 7522, terpene phenolic resin DA-21, phenolic resin 2123, epoxy resin E44, or epoxy resin E-20.

4. The salt-induced selective water-blocking agent according to any one of claims 1-3, characterized in that, The crosslinking agent is selected from any one or a combination of at least two of ammonium persulfate, zinc sulfate, aluminum sulfate, copper acetate, or ferric chloride; Preferably, the aqueous solution is a weakly alkaline solution with a pH of 8.5-9.

5.

5. The salt-induced selective water-blocking agent according to any one of claims 1-4, characterized in that, The raw materials for preparing the modified composite swellable particles also include an initiator with a mass percentage of 0.01-0.02%; Preferably, the initiator is selected from any one or a combination of at least two of N,N-methyleneacrylamide, azobisisobutyronitrile, azoV50, potassium persulfate, or ammonium persulfate; Preferably, the raw materials for preparing the modified composite expanded particles also include an oxygen scavenger with a mass percentage of 0.01-0.02%; Preferably, the oxygen scavenger is selected from thiourea and / or sodium sulfite.

6. The salt-induced selective water-blocking agent according to any one of claims 1-5, characterized in that, The modified composite swellable particles are prepared by the following method, which includes the following steps: S1: Mix the aqueous solution, silane coupling agent, surfactant, sodium montmorillonite, and N-vinylpyrrolidone to obtain a mixture; S2: Mix the mixture obtained in step S1, the oil-soluble resin powder, and the curable resin powder to obtain a modified resin dispersion emulsion; S3: Mix the modified resin dispersion emulsion obtained in step S2, acrylamide, crosslinking agent, initiator and oxygen scavenger, and react to obtain the modified composite swellable particles.

7. The salt-induced selective water-blocking agent according to claim 6, characterized in that, The mixing temperature in step S2 is 50-60℃; Preferably, the mixing method in step S2 includes stirring and ultrasonic dispersion; Preferably, the stirring speed is 1000-1500 rpm and the stirring time is 8-15 min; Preferably, the ultrasonic dispersion time is 8-15 minutes; Preferably, the reaction in step S3 is carried out in a closed container; Preferably, the reaction in step S3 is carried out at a temperature of 70-80°C for 30-45 minutes. Preferably, step S3 further includes a post-processing step after the reaction, and the post-processing method includes drying and pulverizing.

8. The salt-induced selective water-blocking agent according to any one of claims 1-7, characterized in that, The curing agent is selected from any one or a combination of at least two of the following: NL type curing agent, catechol, ammonium chloride, p-toluenesulfonic acid, T31 curing agent or TSG-6032 curing agent; Preferably, the reinforcing agent is selected from any one or a combination of at least two of hexamethylenetetramine, phthalic anhydride, or pyromellitic dianhydride.

9. A method for preparing a salt-induced selective water-blocking agent as described in any one of claims 1-8, characterized in that, The preparation method includes the following steps: The modified composite swellable particles, curing agent, reinforcing agent and water are mixed to obtain the salt-induced selective water-blocking plugging agent.

10. A salt-induced selective water-blocking agent as described in any one of claims 1-8, characterized in that, The salt-induced selective water shut-off agent is used in oilfield development; Preferably, the salt-induced selective water shut-off agent is used for water shut-off in high-salinity oil reservoirs or high-salinity gas reservoirs.

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