Modified nano active material, preparation method thereof, water lock removing agent and application

Abstract

The invention relates to the technical field of low-permeability tight sandstone gas reservoir development, and discloses a modified nano active material, a preparation method thereof, a water lock removing agent and application, the modified nano active material contains a nano material monomer, a hydrophilic group and a hydrophobic group, and the hydrophilic group and the hydrophobic group are grafted on the nano material monomer, the nano-material monomer is oligomeric silsesquioxane with a cage-shaped structure, and the molar ratio of the nano-material monomer to the hydrophilic group to the hydrophobic group is 1: (0.3-0.7): (0.3-0.9); the water blocking removing agent has relatively strong interfacial activity, and can greatly reduce surface tension, improve rock surface wettability, effectively remove water blocking damage of low-permeability tight sandstone gas reservoirs and recover gas well productivity.

Description

Technical Field

[0001] This invention relates to the field of low-permeability tight sandstone gas reservoir development technology, specifically to a modified nano-active material and its preparation method, water-locking agent, and application. Background Technology

[0002] Low-permeability tight sandstone gas reservoirs have poor reservoir properties, low porosity and permeability, and narrow pore throats. Generally, a combination of horizontal wells and volumetric fracturing is required for industrially viable development. Liquid phase trapping damage caused by fracturing operations, drilling, and completion techniques is a key factor restricting the efficient development of low-permeability tight sandstone gas reservoirs. Research data shows that water-locking damage can cause 70-90% of formation damage. Therefore, relieving water-locking damage is crucial for restoring and improving the productivity of low-permeability tight sandstone gas wells and achieving their economically viable development.

[0003] Researchers have conducted extensive studies on the causes and methods of water-lock damage in low-permeability tight sandstone gas reservoirs. Common methods for removing water-lock are mainly divided into physical and chemical methods. Physical methods mainly include increasing the production pressure differential, heating the formation, hydraulic fracturing, and gas injection / huffing, but their effectiveness in removing water-lock is limited, their effective period is short, and their cost is high. Currently, chemical methods are the main approach to removing water-lock. The main mechanism is to inject chemical agents into the formation to reduce the gas-water surface tension and / or improve the wettability of the rock surface, thereby effectively improving the flow capacity of the liquid phase and achieving the function of removing water-lock. For example, CN113429956B (A water-locking agent and its preparation method and application) describes the polymerization of sheet-like nanomaterials with double bond modification, hydrophilic monomers and hydrophobic monomers to obtain nano-active agent materials. The nano-active agent materials, cationic surfactants and solubilizers are then compounded in a certain proportion to form a water-locking agent. This water-locking agent has high interfacial activity and good temperature and salt resistance, effectively reducing the flow resistance on the rock surface. However, due to the poor dispersion stability of the sheet-like nano-active agent materials, it is prone to phenomena such as superposition, aggregation and precipitation. It is necessary to add organic solvents such as methanol and ethanol as dispersants, which results in high economic costs. In actual mine construction, it is easy to contact formation water and change its performance, resulting in poor performance stability and poor adaptability of the water-locking agent. CN102899011A (A low-permeability water-locking agent and its preparation method) synthesizes a water-locking agent using ethylene glycol ether, sodium dodecyl dicarboxylate, ethylene glycol silyl ether, etc. as raw materials. This water-locking agent has strong surface activity, but the production conditions are harsh, the economic cost is high, and in actual field applications, the active agent will be discharged with the formation water, resulting in a short effective period. CN112708407B (Water-locking chemical agent applicable to low-permeability natural gas reservoirs, its preparation method and application) uses a fluorocarbon surfactant and alcohol compound to form a water-locking agent. This water-locking agent has low surface tension and strong wettability improvement ability. It can modify the rock surface from hydrophilic to neutral to weakly hydrophobic, and the rock permeability recovery rate can reach more than 90%. However, the effective period of this water-locking agent is short due to the backflow of formation fluids, and the fluorocarbon recalcitrant components can easily cause secondary damage to the formation. In addition, the water-locking agent has a single composition, which makes it difficult to take into account the geological conditions and construction technology of low-permeability tight sandstone gas reservoirs. The effect of relieving water-locking damage is not ideal, and the application scope is limited.

[0004] Therefore, there is an urgent need in this field for a water-locking agent that has a long effective period, stable performance, and strong universality, so as to remove water locks in low-permeability tight sandstone gas reservoirs and restore gas well productivity. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of short effective period, poor performance stability and lack of universality of existing water-locking agents, and to provide a modified nano-active material, its preparation method, water-locking agent and application.

[0006] To achieve the above objectives, the first aspect of the present invention provides a modified nano-active material, wherein the modified nano-active material contains a nanomaterial monomer and hydrophilic and hydrophobic groups grafted onto the nanomaterial monomer, wherein the nanomaterial monomer is an oligomeric silsesquioxane with a cage-like structure, and wherein the molar ratio of the nanomaterial monomer, the hydrophilic group, and the hydrophobic group is 1:0.3-0.7:0.3-0.9.

[0007] A second aspect of the present invention provides a method for preparing a modified nano-active material, comprising the following steps: mixing a nanomaterial monomer, a hydrophilic monomer, a hydrophobic monomer and a catalyst to react and obtain the modified nano-active material, wherein the nanomaterial monomer is an oligomeric silsesquioxane with a cage-like structure, and the molar ratio of the nanomaterial monomer, the hydrophilic monomer and the hydrophobic monomer is 1:0.3-0.7:0.3-0.9.

[0008] A third aspect of the present invention provides a water-locking agent, wherein the water-locking agent comprises: the modified nano-active material described in the first aspect, a nonionic surfactant, an optional co-solvent, and an optional water.

[0009] The fourth aspect of this invention provides an application of the aforementioned water-lock-removing agent in releasing water locks in low-permeability tight sandstone gas reservoirs.

[0010] Through the above technical solution, the modified nano-active material of the present invention can construct a micro-nano binary structure on the rock surface, modify the micro-appearance of the rock surface, reduce the surface energy of the rock, and promote the rock surface to be modified into a bi-hydrophobic state. When added to the water-locking agent, the water-locking agent has the advantages of long effective period, stable wetting reversal performance, and strong universality. It has a very good effect in low-permeability tight sandstone gas reservoirs. The water-locking agent has strong interfacial activity, can significantly reduce surface tension, improve the wettability of the rock surface, effectively relieve water-locking damage in low-permeability tight sandstone gas reservoirs, and restore gas well productivity. Attached Figure Description

[0011] Figure 1 The particle size distribution of the modified nano-active material prepared in Example 1;

[0012] Figure 2 The particle size distribution of the modified nano-active material prepared in Example 2;

[0013] Figure 3 The particle size distribution of the modified nano-active material prepared in Example 3;

[0014] Figure 4 The particle size distribution of the modified nano-active material prepared in Example 4;

[0015] Figure 5The particle size distribution of the modified nano-active material prepared in Comparative Example 1 is shown.

[0016] Figure 6 The particle size distribution of the modified nano-active material prepared in Comparative Example 2 is shown.

[0017] Figure 7 The particle size distribution of the modified nano-active material prepared in Comparative Example 3 is shown.

[0018] Figure 8 It is a surface tension diagram of deionized water and air;

[0019] Figure 9 This is the surface tension diagram of 0.05 wt% water-locking agent-air in Example 1;

[0020] Figure 10 This is the surface tension diagram of 0.1 wt% water-locking agent-air in Example 1;

[0021] Figure 11 This is the surface tension diagram of 0.2 wt% water-locking agent-air in Example 1;

[0022] Figure 12 This is the surface tension diagram of 0.3wt% water-locking agent-air in Example 1;

[0023] Figure 13 This is the surface tension diagram of 0.5 wt% water-locking agent-air in Example 1;

[0024] Figure 14 It is a contact angle diagram of deionized water, air, and rock core;

[0025] Figure 15 This is a contact angle diagram of 0.05wt% water-locking agent-air-core from Example 1;

[0026] Figure 16 This is a contact angle diagram of 0.1 wt% water-locking agent-air-core from Example 1;

[0027] Figure 17 This is a contact angle diagram of 0.2 wt% water-locking agent-air-core from Example 1;

[0028] Figure 18 This is a contact angle diagram of 0.3wt% water-locking agent-air-core from Example 1;

[0029] Figure 19 This is a contact angle diagram of 0.5 wt% water-locking agent-air-core from Example 1;

[0030] Figure 20 This is a contact angle diagram of 3PV after being flushed with salt water in Example 1;

[0031] Figure 21 This is a contact angle diagram of Example 1 after 5PV of brine flushing;

[0032] Figure 22 This is a contact angle diagram of the brine after rinsing with 10PV in Example 1. Detailed Implementation

[0033] 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.

[0034] The first aspect of the present invention provides a modified nano-active material, wherein the modified nano-active material contains a nanomaterial monomer and hydrophilic and hydrophobic groups grafted onto the nanomaterial monomer, wherein the nanomaterial monomer is an oligomeric silsesquioxane with a cage-like structure, and wherein the molar ratio of the nanomaterial monomer, the hydrophilic group and the hydrophobic group is 1:0.3-0.7:0.3-0.9.

[0035] In this invention, the modified nano-active material can construct a micro-nano binary structure on the rock surface, modifying the microscopic appearance of the rock surface, reducing the surface energy of the rock, and promoting the rock surface to become a bi-hydrophobic state. When added to the water-locking agent, the water-locking agent has the advantages of long effective period, stable wetting reversal performance, and strong universality. It has a very good effect in low-permeability tight sandstone gas reservoirs. The water-locking agent has strong interfacial activity, which can significantly reduce surface tension, improve the wettability of the rock surface, effectively relieve water-locking damage in low-permeability tight sandstone gas reservoirs, and restore gas well productivity.

[0036] In some specific embodiments of the present invention, the nanomaterial monomer is selected from cage-like octahedral semisiloxanes or cage-like hexahedral semisiloxanes. The cage-like octahedral semisiloxane has the molecular formula (RSiO). 3 / 2 ) 10 With a molecular weight of 540 g / mol, the molecular formula of the cage-like hexahedral semisiloxane is (RSiO). 3 / 2 )8, with a molecular weight of 455 g / mol.

[0037] In some specific embodiments of the present invention, the hydrophilic group is derived from at least one of polyoxyethylene ether monomers, preferably from maleic anhydride-modified lauryl polyoxyethylene ether and / or allyl-modified lauryl polyoxyethylene ether. The hydrophilic group selected in the present invention has a better binding effect with the nanomaterial monomer, and the modified nano-active material prepared has excellent performance.

[0038] In some specific embodiments of the present invention, the hydrophobic group is derived from at least one of acrylamidoalkylsiloxanes, preferably from one or more of acrylamidopropyltrimethoxysilane, acrylamidopropyltriethoxysilane, and N-methyl-3-acrylamidopropyltrimethoxysilane. The hydrophobic groups selected in this invention have better binding effects with nanomaterial monomers, resulting in modified nano-active materials with excellent performance.

[0039] In some specific embodiments of the present invention, the molar ratio of the nanomaterial monomer, hydrophilic group, and hydrophobic group is 1:0.4-0.6:0.5-0.7. The performance of the modified nano-active material is further improved within the above-mentioned preferred molar ratio range.

[0040] In some specific embodiments of the present invention, the average particle size of the modified nano-active material is 100-150 nm. The modified nano-active material within this average particle size range has advantages as a water-locking agent, including a long effective period, stable wetting reversal performance, and strong versatility.

[0041] A second aspect of the present invention provides a method for preparing a modified nano-active material, comprising the following steps: mixing a nanomaterial monomer, a hydrophilic monomer, a hydrophobic monomer and a catalyst to react and obtain the modified nano-active material, wherein the nanomaterial monomer is an oligomeric silsesquioxane with a cage-like structure, and the molar ratio of the nanomaterial monomer, the hydrophilic monomer and the hydrophobic monomer is 1:0.3-0.7:0.3-0.9.

[0042] In some specific embodiments of the present invention, the double bonds in the cage-like structure of the nanomaterial monomers and the double bonds in the structures of hydrophilic and hydrophobic monomers react. The cage-like structure of the nanomaterial monomers contains multiple double bonds, and the double bond reaction positions are equal, so the reaction can be carried out at any double bond position.

[0043] In some specific embodiments of the present invention, the nanomaterial monomer is selected from cage-like octahedral semisiloxanes or cage-like hexahedral semisiloxanes, wherein the cage-like octahedral semisiloxane has the following structure:

[0044] In some specific embodiments of the present invention, the hydrophilic monomer is selected from at least one of polyoxyethylene ether monomers, preferably maleic anhydride-modified lauryl polyoxyethylene ether and / or allyl-modified lauryl polyoxyethylene ether. The molecular weight of the hydrophilic monomer is 1000-2000 g / mol. In some specific embodiments of the present invention, the molecular weight of the maleic anhydride-modified lauryl polyoxyethylene ether is 1297 g / mol, and the molecular weight of the allyl-modified lauryl polyoxyethylene ether is 1198 g / mol.

[0045] In some specific embodiments of the present invention, the hydrophobic monomer is selected from at least one of acrylamidoalkylsiloxanes, preferably one or more of acrylamidopropyltrimethoxysilane, acrylamidopropyltriethoxysilane, and N-methyl-3-acrylamidopropyltrimethoxysilane. The molecular weight of the hydrophobic monomer is 200-300 g / mol. In some specific embodiments of the present invention, the molecular weight of acrylamidopropyltrimethoxysilane is 233 g / mol, the molecular weight of acrylamidopropyltriethoxysilane is 276 g / mol, and the molecular weight of N-methyl-3-acrylamidopropyltrimethoxysilane is 248 g / mol.

[0046] In some specific embodiments of the present invention, the catalyst is selected from one or more of chloroplatinic acid, ferric nitrate, and nickel sulfate.

[0047] In some specific embodiments of the present invention, the molar ratio of the nanomaterial monomer, hydrophilic monomer, and hydrophobic monomer is 1:0.4-0.6:0.5-0.7. The modified nano-active material prepared within the above-mentioned preferred molar ratio range exhibits further improved adsorption performance, and its addition to a water-locking agent results in better interfacial activity, demonstrating excellent performance in low-permeability tight sandstone gas reservoirs.

[0048] In some specific embodiments of the present invention, the amount of catalyst is 0.03-0.1 wt%, preferably 0.04-0.08 wt%, relative to the total amount of nanomaterial monomers, hydrophilic monomers, and hydrophobic monomers. The catalyst is prepared as a solution for the reaction. The catalyst is uniformly added to the reaction system at a rate of 1-10 g / min, relative to 70-80 g of nanomaterial monomers.

[0049] In some specific embodiments of the present invention, the reaction temperature is 60-80°C and the reaction time is 4-8 hours.

[0050] In some specific embodiments of the present invention, after the reaction is completed, the catalyst can be removed first, and then the solvent can be removed to obtain the modified nano-active material. Specifically, 5% NaOH solution is added to the mixture after the reaction is completed, the solid precipitate is separated by centrifugation, and the remaining liquid is rotary evaporated until no ethanol flows out, to obtain the modified nano-active material.

[0051] In this invention, the composition and structure of the modified nano-active material can be determined by NMR, IR, GPC, elemental analysis, or by preparation and feeding.

[0052] A third aspect of the present invention provides a water-locking agent, wherein the water-locking agent comprises: the modified nano-active material described in the first aspect, a nonionic surfactant, an optional co-solvent, and an optional water.

[0053] The present invention discloses a method for preparing a water-locking agent, wherein the modified nano-active material, a nonionic surfactant, a co-solvent, and water are mixed to obtain the water-locking agent.

[0054] In some specific embodiments of the present invention, the preparation method of the water-locking agent includes:

[0055] (1) Mix the modified nano-active material, co-solvent and water evenly to obtain mixture I;

[0056] (2) Mix the mixture I and the nonionic surfactant evenly to obtain the water-locking agent.

[0057] In some specific embodiments of the present invention, in step (2), the stirring speed is 200-500 rpm and the stirring time is 10-30 min.

[0058] In some specific embodiments of the present invention, the nonionic surfactant is selected from one or more of dodecyl diethanolamide, coconut oil fatty acid diethanolamide, lauryl propyl betaine, Tween 80, and Tween 60.

[0059] In some specific embodiments of the present invention, the co-solvent is mainly used to disperse the modified nano-active material, and the co-solvent is selected from one or more of methanol, ethanol and ethylene glycol.

[0060] In some specific embodiments of the present invention, the weight ratio of the modified nano-active material to the nonionic surfactant is 1:0.5-4.

[0061] In some specific embodiments of the present invention, the content of modified nano-active agent is 5-15 parts by weight, the content of nonionic surfactant is 10-20 parts by weight, the content of co-solvent is 2-8 parts by weight, and the content of water is 57-83 parts by weight, relative to 100 parts by weight of the water-locking agent.

[0062] In some specific embodiments of the present invention, the gas-water surface tension of the 0.35-4.5wt% water-locking agent solution is 22-28 mN / m.

[0063] The fourth aspect of this invention provides the application of the aforementioned water-lock-removing agent in removing water locks in low-permeability tight sandstone gas reservoirs.

[0064] In some specific embodiments of the present invention, the concentration of the water-locking agent can be 0.35-4.5wt%, the injection amount can be 0.2-0.5PV, and the aging time can be 12-36h.

[0065] To further optimize the performance of the hydrolytic lock agent and enable it to possess strong interfacial activity, this invention provides a particularly preferred embodiment, which provides a modified nano-active material. This modified nano-active material contains a nanomaterial monomer and hydrophilic and hydrophobic groups grafted onto the nanomaterial monomer. The nanomaterial monomer is selected from cage-type octahedral semisiloxanes or cage-type hexahedral semisiloxanes. The hydrophilic group is derived from maleic anhydride-modified lauryl polyoxyethylene ether and / or allyl-modified lauryl polyoxyethylene ether. The hydrophobic group is derived from one or more of acrylamidopropyltrimethoxysilane, acrylamidopropyltriethoxysilane, and N-methyl-3-acrylamidopropyltrimethoxysilane. The molar ratio of the nanomaterial monomer, hydrophilic group, and hydrophobic group is 1:0.4-0.6:0.5-0.7. The average particle size of the modified nano-active material is 100-150 nm.

[0066] The present invention will be described in detail below through embodiments.

[0067] In this invention, the maleic anhydride-modified lauryl alcohol polyoxyethylene ether was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., model number D725829, and the allyl-modified lauryl alcohol polyoxyethylene ether was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., model number A303301.

[0068] Unless otherwise specified in the following examples and comparative examples, all conditions were performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available products.

[0069] Preparation Example 1

[0070] (1) Weigh out 70g of the nanomaterial monomer cage-type octahedral semisiloxane, 73g of the hydrophilic monomer maleic anhydride modified lauryl alcohol polyoxyethylene ether, and 16g of the hydrophobic monomer acrylamidopropyltrimethoxysilane (the molar ratio of nanomaterial monomer: hydrophilic monomer: hydrophobic monomer is 1:0.43:0.53), pour them into a three-necked flask, add 53g of anhydrous ethanol, stir until dissolved, and purge with nitrogen for 30min to remove oxygen;

[0071] (2) Prepare 10g of ferric nitrate nonahydrate catalyst solution with a mass concentration of 1.0%, and purge with nitrogen for 30min to remove oxygen;

[0072] (3) Set the stirrer speed to 300 r / min and the heating temperature to 70℃;

[0073] (4) Stir and heat the solution prepared in step (1) to a set temperature of 70°C, and then add the catalyst solution prepared in step (2) at a rate of 2g / min.

[0074] (5) After the catalyst solution is added, the heating temperature is set to 70°C. After the reaction solution reaches 70°C, the reaction is stopped after 5 hours. Add 5% NaOH solution and centrifuge to separate the solid precipitate. The remaining liquid is rotary evaporated until no ethanol flows out, and the modified nano-active material A1 is obtained.

[0075] The particle size distribution test results of the modified nano-active material are as follows: Figure 1 As shown, the average particle size of the modified nano-active material is 115.8 nm.

[0076] Preparation Example 2

[0077] (1) Weigh out 80g of the nanomaterial monomer cage-type hexahedral semisiloxane, 97g of the hydrophilic monomer allyl modified lauryl alcohol polyoxyethylene ether, and 24g of the hydrophobic monomer acrylamidopropyltrimethoxysilane (the molar ratio of nanomaterial monomer: hydrophilic monomer: hydrophobic monomer is 1:0.46:0.59), pour them into a three-necked flask, add 45g of anhydrous ethanol, stir until dissolved, and purge with nitrogen for 30min to remove oxygen;

[0078] (2) Prepare 10g of ferric nitrate nonahydrate catalyst solution with a mass concentration of 1.0%, and purge with nitrogen for 30min to remove oxygen;

[0079] (3) Set the stirrer speed to 300 r / min and the heating temperature to 70℃;

[0080] (4) Stir and heat the solution prepared in step (1) to a set temperature of 70°C, and then add the catalyst prepared in step (2) at a rate of 5g / min.

[0081] (5) After the catalyst solution is added, the heating temperature is set to 70°C. After the reaction solution reaches 70°C, the reaction is stopped after 5 hours. Add 5% NaOH solution and centrifuge to separate the solid precipitate. The remaining liquid is rotary evaporated until no ethanol flows out, and the modified nano-active material A2 is obtained.

[0082] The particle size distribution test results of the modified nano-active material are as follows: Figure 2 As shown, the average particle size of the modified nano-active material is 118.5 nm.

[0083] Preparation Example 3

[0084] The preparation method in this example is the same as that in Preparation Example 1, except that the amount of the hydrophobic monomer acrylamide propyltrimethoxysilane added is 10g (the molar ratio of nanomaterial monomer: hydrophilic monomer: hydrophobic monomer is 1:0.43:0.33), and the other addition amounts and experimental steps are the same as in Preparation Example 1.

[0085] The particle size distribution test results of the modified nano-active material are as follows: Figure 3 As shown, the average particle size of the modified nano-active material is 141.1 nm.

[0086] Preparation Example 4

[0087] The preparation method in this example is the same as that in Preparation Example 1, except that the amount of the hydrophobic monomer dodecyltrimethylammonium bromide added is 34g (the molar ratio of nanomaterial monomer: hydrophilic monomer: hydrophobic monomer is 1:0.43:0.85), and the other addition amounts and experimental steps are the same as in Preparation Example 1.

[0088] The particle size distribution test results of the modified nano-active material are as follows: Figure 4 As shown, the average particle size of the modified nano-active material is 120.2 nm.

[0089] Comparative Preparation Example 1

[0090] The preparation method in this example is the same as that in Preparation Example 1, except that the amount of the hydrophobic monomer acrylamide propyltrimethoxysilane added is 2g (the molar ratio of nanomaterial monomer: hydrophilic monomer: hydrophobic monomer is 1:0.43:0.07), and the other addition amounts and experimental steps are the same as in Preparation Example 1.

[0091] The particle size distribution test results of the modified nano-active material are as follows: Figure 5 As shown, the average particle size of the modified nano-active material is 260.6 nm.

[0092] Comparative Preparation Example 2

[0093] The preparation method in this example is the same as that in Preparation Example 1, except that the amount of maleic anhydride-modified lauryl alcohol polyoxyethylene ether modified with the hydrophilic monomer is 5g (the molar ratio of nanomaterial monomer: hydrophilic monomer: hydrophobic monomer is 1:0.03:0.53), and the other addition amounts and experimental steps are the same as in Preparation Example 1.

[0094] The particle size distribution test results of the modified nano-active material are as follows: Figure 6 As shown, the average particle size of the modified nano-active material is 223.6 nm.

[0095] Comparative preparation example 3

[0096] The preparation method in this example is the same as that in Preparation Example 1, except that the amount of molybdenum disulfide monomer added is 21g (the molar ratio of nanomaterial monomer: hydrophilic monomer: hydrophobic monomer is 1:0.43:0.53), and the other addition amounts and experimental steps are the same as in Preparation Example 1.

[0097] The particle size distribution test results of the modified nano-active material are as follows: Figure 7 As shown, the average particle size of the modified nano-active material is 221.3 nm.

[0098] Test Example 1

[0099] The adsorption performance of nanomaterials on the core surface was determined by detecting the content of modified nanomaterial solution before and after contact with the plunger-made artificial sandstone using ultraviolet spectrophotometry. The test results of the modified nano-active materials in the prepared examples and comparative prepared examples are shown in Table 1.

[0100] Table 1

[0101] serial number Nanomaterial adsorption capacity (mg / g) Preparation Example 1 2.46 Preparation Example 2 2.35 Preparation Example 3 1.64 Preparation Example 4 1.48 Comparative Preparation Example 1 0.86 Comparative Preparation Example 2 0.75 Comparative preparation example 3 0.68

[0102] As can be seen from Table 1, the modified nano-active material of the present invention contains oligomeric silsesquioxane with a cage-like structure, which has a high adsorption capacity on the core surface.

[0103] Example 1

[0104] (1) Add 5g of the modified nano-active material obtained in Preparation Example 1, 5g of the cosolvent ethylene glycol and 80g of water to a beaker and stir at 500rpm for 20min to obtain mixture II;

[0105] (2) Add 15g of nonionic surfactant lauramide propyl betaine to a beaker and stir at 500rpm for 20min to obtain water-locking agent S1.

[0106] Example 2

[0107] (1) Add 15g of the modified nano-active material obtained in Preparation Example 1, 8g of the co-solvent, ethanol and 67g of water to a beaker and stir at 500rpm for 20min to obtain mixture II;

[0108] (2) Add 10g of nonionic surfactant lauramide propyl betaine to a beaker and stir at 500rpm for 20min to obtain water-locking agent S2.

[0109] Example 3

[0110] (1) Add 15g of the modified nano-active material obtained in Preparation Example 2, 8g of the cosolvent, ethanol and 67g of water to a beaker and stir at 500rpm for 20min to obtain mixture II;

[0111] (2) Add 10g of nonionic surfactant lauramide propyl betaine to a beaker and stir at 500rpm for 20min to obtain water-locking agent S3.

[0112] Example 4

[0113] (1) Add 15g of the modified nano-active material obtained in Preparation Example 2, 8g of the cosolvent ethylene glycol and 67g of water to a beaker and stir at 500rpm for 20min to obtain mixture II;

[0114] (2) Add 10g of nonionic surfactant Tween to a beaker and stir at 500rpm for 20min to obtain water-locking agent S4.

[0115] Example 5

[0116] (1) Add 5g of the modified nano-active material obtained in Preparation Example 1, 5g of the cosolvent ethylene glycol and 80g of water to a beaker and stir at 500rpm for 20min to obtain mixture II;

[0117] (2) Add 15g of nonionic surfactant sodium fatty alcohol polyoxyethylene ether carboxylate to a beaker and stir at 500rpm for 20min to obtain water-locking agent S5.

[0118] Example 6

[0119] (1) Add 5g of the modified nano-active material obtained in Preparation Example 3, 5g of the cosolvent ethylene glycol and 80g of water to a beaker and stir at 500rpm for 20min to obtain mixture II;

[0120] (2) Add 15g of nonionic surfactant lauramide propyl betaine to a beaker and stir at 500rpm for 20min to obtain water-locking agent S6.

[0121] Example 7

[0122] (1) Add 5g of the modified nano-active material obtained in Preparation Example 4, 5g of the cosolvent ethylene glycol and 80g of water to a beaker and stir at 500rpm for 20min to obtain mixture II;

[0123] (2) Add 15g of nonionic surfactant lauramide propyl betaine to a beaker and stir at 500rpm for 20min to obtain water-locking agent S7.

[0124] Comparative Example 1

[0125] (1) Add 5g of the modified nano-active material obtained in Comparative Preparation Example 1, 5g of the cosolvent ethylene glycol and 80g of water to a beaker and stir at 500rpm for 20min to obtain mixture II;

[0126] (2) Add 15g of nonionic surfactant lauramide propyl betaine to a beaker and stir at 500rpm for 20min to obtain water-locking agent S8.

[0127] Comparative Example 2

[0128] (1) Add 5g of the modified nano-active material obtained in Comparative Preparation Example 2, 5g of the cosolvent ethylene glycol and 80g of water to a beaker and stir at 500rpm for 20min to obtain mixture II;

[0129] (2) Add 15g of nonionic surfactant lauramide propyl betaine to a beaker and stir at 500rpm for 20min to obtain water-locking agent S9.

[0130] Comparative Example 3

[0131] (1) Add 5g of the modified nano-active material obtained in Comparative Preparation Example 3, 5g of the cosolvent ethylene glycol and 80g of water to a beaker and stir at 500rpm for 20min to obtain mixture II;

[0132] (2) Add 15g of nonionic surfactant lauramide propyl betaine to a beaker and stir at 500rpm for 20min to obtain water-locking agent S10.

[0133] Test Example 2

[0134] (1) Surface tension test

[0135] The water-locking agent in Example 1 was diluted with deionized water to prepare solutions of different concentrations. A small amount of each diluted solution was taken, and the gas-water interfacial tension was measured using a surface tension meter. The gas-water surface tensions of the water-locking agent at different concentrations are shown below. Figures 8-13 As shown, the surface tension of deionized water is 51.13 mN / m. After adding the water-locking agent, the gas-water interfacial tension is significantly reduced. When the concentration of the water-locking agent reaches 0.2 wt%, the gas-water interfacial tension is approximately 24.0 mN / m. Further increasing the concentration of the water-locking agent has little effect on the gas-water interfacial tension.

[0136] The hydrolytic lock-in agents from the examples and comparative examples were diluted with distilled water to prepare 0.2 wt% surfactant solutions, and the interfacial tension of the degassed water was measured as shown in Figure 2.

[0137] Table 2

[0138]

[0139] (2) Salt resistance test

[0140] The water-locking agents in Examples 1-7 were diluted with simulated formation water (20,000 ppm MgCl2) to prepare a solution with a concentration of 0.3 wt%. After stirring evenly, no suspended matter or precipitation was observed in the solution. After standing for 5 hours, the diluted solution remained clear without any suspended matter or precipitation, indicating that the water-locking agent of the present invention has good salt resistance.

[0141] (3) Improved wetting performance test

[0142] Six core slices, each approximately 1 cm thick, were cut from a dense sandstone core using a diamond wire cutter. The slices were then polished and dried in an oven at 80°C for 5 hours. The rock-air-water three-phase contact angle of one core slice was measured. The remaining five core slices were immersed in diluted solutions of the water-locking agent obtained in Example 1 at concentrations of 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, and 0.5 wt%, respectively, for 12 hours. After drying, the rock-air-water three-phase contact angles were measured. The criteria for determining wettability using the contact angle method are shown in Table 3. The contact angles after treatment with different concentrations of the water-locking agent in Example 1 are shown in Table 3. Figure 14-19 As shown.

[0143] Table 3

[0144]

[0145] according to Figure 12-17 It can be seen that the core was initially strongly hydrophilic, and the contact angle showed an increasing trend after treatment with different concentrations of dehydrating agent; when the concentration of dehydrating agent reached 0.3wt%, the wettability of the core changed from strongly hydrophilic to neutral wettability.

[0146] The water-locking agents from the examples and comparative examples were diluted with distilled water to form 0.3 wt% solutions. Core slices of the same specifications as those in Example 1 were soaked for 12 hours, then dried and the contact angles of the rock-air-water three phases were measured as shown in Table 4.

[0147] Table 4

[0148]

[0149] (4) Erosion resistance test

[0150] Three core slices, each approximately 2.5 cm thick, were cut from a dense sandstone core using a diamond wire cutter. The core slices were then polished to a smooth surface and immersed in a 0.3 wt% solution of the dehydrating agent obtained in Example 1 for 12 hours. After immersion, the slices were dried in an oven at 80°C for 10 hours. The core was then displaced at a constant rate using a 2 wt% KCl solution. After injecting brine at 3, 5, and 10 PV, the cores were removed and dried at 80°C for 10 hours. The three-phase contact angles were then measured. The contact angles after different scouring times in Example 1 are shown below. Figures 20-22 As shown, the initial contact angle (80.3°) and the contact angle after rinsing (77.6°) are shown. It can be seen that the changes in wetting contact angle after rinsing with salt water for 3 PV, 5 PV and 10 PV are 1.62%, 2.49% and 3.36% respectively, and the contact angle is basically unchanged, indicating that the water-locking agent has a strong adsorption effect, a long effective period and good rinsing resistance.

[0151] In addition, core slices of the same specifications as those used in Example 1 were soaked in the 0.3wt% dehydrating agent solution used in the examples and comparative examples for 12 hours, and then dried in an oven at 80°C for 10 hours for later use. The core slices were displaced at a constant rate using a 2wt% KCl solution, and after injecting 10 PV of brine, the core slices were removed and dried at 80°C for 10 hours. The three-phase contact angles were then measured, and the test results are shown in Table 5.

[0152] Table 5

[0153]

[0154] (5) Core permeability recovery test

[0155] The experimental steps were as follows: ① Vacuum the core and pressurize it with saturated standard brine (2wt% KCl); ② Place the core with saturated brine into a core holder and set the temperature of the constant temperature chamber to 85℃; ③ After the temperature stabilized, use nitrogen to drive water to the bound water state at a pressure of 0.5MPa and measure the gas phase permeability K1; ④ Inject the water-locking agent obtained in Example 1 into the core outlet direction until the inlet end breaks through; ⑤ Aging for 24 hours; ⑥ Drive the core with gas in the forward direction until the outlet end breaks through and measure the gas phase permeability K2.

[0156] The formula for calculating the core permeability recovery rate is as follows:

[0157] The results of the core permeability recovery experiments in the examples and comparative examples are shown in Table 6.

[0158] Table 6

[0159]

[0160] As can be seen from the results in Table 6, the water-locking agent described in this invention has a good water-locking effect and a high permeability recovery rate.

[0161] 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 modified nano-active material, characterized in that, The modified nano-active material contains a nanomaterial monomer and hydrophilic and hydrophobic groups grafted onto the nanomaterial monomer. The nanomaterial monomer is an oligomeric silsesquioxane with a cage-like structure. The molar ratio of the nanomaterial monomer, hydrophilic group, and hydrophobic group is 1:0.3-0.7:0.3-0.

9.

2. The modified nano-active material according to claim 1, wherein, The nanomaterial monomers are selected from cage-type octahedral semisiloxanes or cage-type hexahedral semisiloxanes.

3. The modified nano-active material according to claim 1 or 2, wherein, The hydrophilic group is derived from at least one of polyoxyethylene ether monomers, preferably from maleic anhydride-modified lauryl polyoxyethylene ether and / or allyl-modified lauryl polyoxyethylene ether; Preferably, the hydrophobic group is derived from at least one of acrylamidoalkylsiloxanes, more preferably from one or more of acrylamidopropyltrimethoxysilane, acrylamidopropyltriethoxysilane, and N-methyl-3-acrylamidopropyltrimethoxysilane.

4. The modified nano-active material according to any one of claims 1-3, wherein, The molar ratio of the nanomaterial monomer, hydrophilic group, and hydrophobic group is 1:0.4-0.6:0.5-0.7; Preferably, the average particle size of the modified nano-active material is 100-150 nm.

5. A method for preparing a modified nano-active material, characterized in that, The process includes the following steps: mixing nanomaterial monomers, hydrophilic monomers, hydrophobic monomers and a catalyst for reaction, wherein the nanomaterial monomers are oligomeric silsesquioxanes with cage-like structures, and the molar ratio of the nanomaterial monomers, hydrophilic monomers and hydrophobic monomers is 1:0.3-0.7:0.3-0.

9.

6. The preparation method according to claim 5, wherein, The nanomaterial monomers are selected from cage-type octahedral semisiloxanes or cage-type hexahedral semisiloxanes; Preferably, the hydrophilic monomer is selected from at least one of polyoxyethylene ether monomers, preferably maleic anhydride-modified lauryl polyoxyethylene ether and / or allyl-modified lauryl polyoxyethylene ether; Preferably, the hydrophobic monomer is selected from at least one of acrylamidoalkylsiloxanes, and more preferably one or more of acrylamidopropyltrimethoxysilane, acrylamidopropyltriethoxysilane, and N-methyl-3-acrylamidopropyltrimethoxysilane. Preferably, the catalyst is selected from one or more of chloroplatinic acid, ferric nitrate, and nickel sulfate.

7. The preparation method according to claim 5 or 6, wherein, The molar ratio of the nanomaterial monomers, hydrophilic monomers, and hydrophobic monomers is 1:0.4-0.6:0.5-0.7; Preferably, the amount of the catalyst is 0.03-0.1 wt%, more preferably 0.04-0.08 wt%, relative to the total amount of nanomaterial monomers, hydrophilic monomers and hydrophobic monomers.

8. The preparation method according to any one of claims 5-7, wherein, The reaction temperature is 60-80℃, and the reaction time is 4-8h.

9. The modified nano-active material prepared by the method according to any one of claims 5-8.

10. A water-locking agent, characterized in that, The water-locking agent comprises: the modified nano-active material according to any one of claims 1-4 and 9, a nonionic surfactant, an optional co-solvent, and an optional water.

11. The water-locking agent according to claim 10, wherein, The nonionic surfactant is selected from one or more of dodecyl diethanolamide, coconut oil fatty acid diethanolamide, laurylaminopropyl betaine, Tween 80, and Tween 60. Preferably, the co-solvent is selected from one or more of methanol, ethanol and ethylene glycol.

12. The water-locking agent according to claim 10 or 11, wherein, The weight ratio of the modified nano-active material to the nonionic surfactant is 1:0.5-4; Alternatively, relative to the 100 parts by weight of the dehydrating agent, the content of the modified nano-active agent is 5-15 parts by weight, the content of the nonionic surfactant is 10-20 parts by weight, the content of the cosolvent is 2-8 parts by weight, and the content of water is 57-83 parts by weight.

13. The application of the water-locking agent according to claims 10-12 in releasing water locks in low-permeability tight sandstone gas reservoirs.

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