A wetting reversal agent, its preparation method and application

Abstract

The application relates to a wetting reversal agent and a preparation method and application thereof, and belongs to the technical field of unconventional oil and gas exploitation. Raw materials of the wetting reversal agent include strong hydrophobic modified nano silicon dioxide and a synergist; the strong hydrophobic modified nano silicon dioxide is obtained by modifying and treating nano silicon dioxide with heptadecafluorodecyltrimethoxysilane; and the synergist includes polydimethylsiloxane, glycerol trioleate and 2-ethylhexanol polyoxyethylene ether. According to the embodiment of the application, the excellent water-repellent performance provided by the strong hydrophobic modified nano silicon dioxide and the surface tension reduction effect brought by the synergist are synergized, a more effective water lock inhibition system is formed, and the system jointly acts on the key link of the water lock problem possibly occurring in the fracturing process of deep tight gas reservoirs, so that the water lock inhibition capacity of the wetting reversal agent is improved in all directions.

Description

Technical Field

[0001] This application relates to the field of unconventional oil and gas extraction technology, and in particular to a wetting reversal agent, its preparation method and application. Background Technology

[0002] Low-permeability gas reservoirs have become a key area for exploration and development. Generally, low-permeability gas reservoirs are characterized by small pore throats, poor permeability, and severe heterogeneity. During fracturing, water-based fracturing fluid enters the gas reservoir channels under the action of capillary force, increasing the water saturation of the near-wellbore reservoir. At the same time, water-sensitive mineral components in the reservoir absorb water or undergo hydration expansion, blocking the gas flow channels, reducing gas permeability, and causing water-lock damage, resulting in the inability to produce gas or drain fluid.

[0003] Typically, the water-locking effect is relieved by reducing surface tension with surfactants. However, surfactants have weak erosion resistance and short effective period, only restoring about 10% of the gas reservoir permeability. The effect of mitigating water-locking damage in gas reservoirs is not significant and cannot meet the actual needs in the field. Furthermore, for the harsh conditions of ultra-deep (>4500m), high temperature (>180℃), and strong hydrophilicity of core surfaces in tight gas reservoirs, surfactants need to simultaneously meet both superhydrophobic and temperature resistance requirements. Summary of the Invention

[0004] This application provides a wetting reversal agent, its preparation method, and its application to solve the following technical problem: how to improve the water-locking inhibition ability of the wetting reversal agent.

[0005] In a first aspect, embodiments of this application provide a wetting reversal agent, the raw materials of which include:

[0006] Strongly hydrophobic modified nano-silica with synergists;

[0007] The strongly hydrophobic modified nano-silica is obtained by modifying nano-silica with heptadecafluorodecyltrimethoxysilane;

[0008] The synergists include polydimethylsiloxane, glyceryl trioleate, and 2-ethylhexanol polyoxyethylene ether.

[0009] Optionally, the mass ratio of the silicon dioxide to the heptadecafluorodecyltrimethoxysilane is 1:(0.2-0.5).

[0010] Optionally, the process parameters for the modification treatment include: a reaction temperature of 50℃~60℃ and a reaction time of 4h~6h.

[0011] Optionally, the mass ratio of the polydimethylsiloxane, the glyceryl trioleate, and the 2-ethylhexanol polyoxyethylene ether is 1:(0.3-0.5):(0.1-0.2).

[0012] Optionally, by weight, the strongly hydrophobic modified nano-silica is 1 to 4 parts and the synergist is 4 to 8 parts.

[0013] Optionally, the raw materials may also include a co-solvent and a solvent.

[0014] Optionally, the co-solvent includes at least one of the following: ethanol and acetone.

[0015] Optionally, the co-solvent is 25 to 40 parts by weight.

[0016] Secondly, embodiments of this application provide a method for preparing the wetting reversal agent according to any one of the first aspects, the method comprising:

[0017] Strongly hydrophobic modified nano-silica, co-solvent, and solvent are ultrasonically mixed to obtain a dispersion.

[0018] The dispersion is mixed with a synergist to obtain a wetting reversal agent.

[0019] Optionally, the temperature of the ultrasonic mixing is 40℃~70℃;

[0020] The flow rate of the synergist is 2 ml / s to 5 ml / s.

[0021] Thirdly, embodiments of this application provide the application of the wetting reversal agent described in any one of the first aspects in the fracturing of deep tight gas wells with a well temperature not exceeding 200°C.

[0022] The technical solutions provided in this application have the following advantages compared with the prior art:

[0023] The wetting reversal agent provided in this application embodiment comprises the following raw materials: strongly hydrophobically modified nano-silica and synergists; the strongly hydrophobically modified nano-silica is obtained by modifying nano-silica with heptadecafluorodecyltrimethoxysilane; the synergists include polydimethylsiloxane, glyceryl trioleate, and 2-ethylhexanol polyoxyethylene ether. The strongly hydrophobically modified nano-silica, as a hydrophobic agent, is obtained by modifying nano-silica with heptadecafluorodecyltrimethoxysilane. Heptadecafluorodecyltrimethoxysilane has the characteristics of fast hydrolysis rate and high efficiency, which allows the modified nano-silica obtained by heptadecafluorodecyltrimethoxysilane modification to have extremely low surface energy and extremely poor wettability, thereby giving the wetting reversal agent excellent hydrophobic properties and improving its ability to inhibit water lock-in; the synergists include polydimethylsiloxane, glyceryl trioleate, and... 2-Ethylhexanol polyoxyethylene ether, along with polydimethylsiloxane, exhibits low surface tension due to its molecular structure. Glyceryl trioleate acts as an emulsifier, effectively reducing the oil-water interfacial tension by emulsifying crude oil. 2-Ethylhexanol polyoxyethylene ether is a nonionic surfactant, and its combination with polydimethylsiloxane further reduces surface tension. Therefore, the synergistic effect of polydimethylsiloxane, glyceryl trioleate, and 2-ethylhexanol polyoxyethylene ether enhances the surface tension reduction of this synergist, further improving its water-locking inhibition ability. Thus, the synergistic effect of strongly hydrophobic modified nano-silica and the synergist improves the water-locking inhibition ability of the wetting reversal agent. Attached Figure Description

[0024] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0025] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic flowchart illustrating a method for preparing a wetting reversal agent provided in an embodiment of this application. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0028] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0029] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. Furthermore, in the description of this application, terms such as "comprising" and "including" mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than one" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple. In the proportional relationships discussed in this article, the parameters described by the proportion should be understood as the first term of the proportion in the order of description, while the proportion figures should be understood as the second term. For example, if the mass ratio of substance A, substance B, and substance C is 1:2:3, then substances A, B, and C should correspond one-to-one with the proportion figures in the proportion in the order of description, i.e., the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0030] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0031] Low-permeability gas reservoirs have become a key area for exploration and development. Generally, low-permeability gas reservoirs are characterized by small pore throats, poor permeability, and severe heterogeneity. During fracturing, water-based fracturing fluid enters the reservoir pores under capillary force, increasing the near-wellbore water saturation. Simultaneously, water-sensitive mineral components in the reservoir absorb water or undergo hydration expansion, blocking gas flow channels and reducing gas permeability, resulting in water-lock damage. This leads to both gas recovery and fluid drainage failure. Typically, surfactants are used to reduce surface tension and alleviate the water-lock effect. However, surfactants have weak erosion resistance and a short effective period, only restoring about 10% of the reservoir permeability, which is insufficient to significantly reduce water-lock damage and fails to meet practical field requirements. Therefore, to alleviate the water-lock effect, it is necessary to reduce surface tension while altering the wettability of the rock to reduce the water-lock effect and improve the flowback rate.

[0032] Due to the different geological conditions of different tight gas reservoirs, the performance requirements of wetting reversal agents also vary. Therefore, in response to the harsh conditions of ultra-deep (>4500m), high temperature (>180℃) and strong hydrophilicity of core surfaces in tight gas reservoirs of Liaohe Oilfield, it is urgent to develop a wetting reversal agent that is resistant to high temperature and can change the reservoir rock from hydrophilic to superhydrophobic.

[0033] In a first aspect, embodiments of this application provide a wetting reversal agent, the raw materials of which include:

[0034] Strongly hydrophobic modified nano-silica SiO2 with synergists;

[0035] The strongly hydrophobic modified nano-silica is obtained by modifying nano-silica with heptadecafluorodecyltrimethoxysilane;

[0036] The synergists include polydimethylsiloxane, glyceryl trioleate, and 2-ethylhexanol polyoxyethylene ether.

[0037] The water-locking effect refers to the phenomenon in oil and gas reservoirs where, when external fluids (usually water-based fluids such as fracturing fluids and drilling fluids) enter the reservoir pores, these fluids form a liquid column at the pore throat due to capillary force, blocking or restricting the flow of oil and gas.

[0038] In the embodiments of this application, heptadecafluorodecyltrimethoxysilane possesses the characteristics of rapid hydrolysis and high efficiency. During the chemical reaction process, it can effectively modify silica, transforming it into modified nano-silica with specific properties. The nano-silica modified by heptadecafluorodecyltrimethoxysilane exhibits extremely low surface energy and extremely poor wettability, which directly endow it with excellent hydrophobic properties. In the application scenario of fracturing deep tight gas reservoirs, this hydrophobic property is of great significance because the occurrence of water-locking phenomenon is often closely related to the interaction between rock surface and water. Strong hydrophobic property can prevent water from accumulating and stagnating in rock pores and other parts, thereby effectively inhibiting the occurrence of water-locking phenomenon and improving the overall water-locking inhibition ability of the wetting reversal agent. This plays a fundamental supporting role in achieving the goals of protecting reservoirs and increasing gas well production.

[0039] Synergists include polydimethylsiloxane, glyceryl trioleate, and 2-ethylhexanol polyoxyethylene ether. The molecular structure of polydimethylsiloxane determines its low surface tension. In wetting reversal agent systems, low surface tension means it can alter the interaction forces between the liquid and the solid surface (such as the surface of rock pores), making the liquid less prone to adhesion and retention, thus helping to reduce water-locking problems. Glyceryl trioleate acts as an emulsifier, especially in the case of crude oil, emulsifying it and promoting better mixing and dispersion of oil and water, thereby effectively reducing the oil-water interfacial tension. Lower oil-water interfacial tension can prevent water-locking caused by complex physicochemical interactions at the oil-water interface. 2-ethylhexanol polyoxyethylene ether, as a nonionic surfactant, has the ability to modify surface properties, and when combined with polydimethylsiloxane, it can produce a synergistic effect, further reducing surface tension. Lower surface tension makes the entire system easier for liquid to flow and drain in micro-environments such as rock pores, reducing water retention and enhancing the effect of inhibiting water-locking. Therefore, the three components—polydimethylsiloxane, glyceryl trioleate, and 2-ethylhexanol polyoxyethylene ether—work synergistically to enable the synergist to reduce surface tension. This reduction in surface tension is crucial in the entire wetting reversal agent system, mitigating potential water-locking factors from multiple angles and at multiple stages, further enhancing the wetting reversal agent's ability to inhibit water-locking, and complementing the effect of the strongly hydrophobic modified nano-silica.

[0040] Therefore, the excellent hydrophobic properties provided by the strongly hydrophobic modified nano-silica, and the surface tension reduction effect brought about by the synergist, work synergistically to form a more effective system for inhibiting water lock. This synergistic effect is not a simple superposition of properties, but rather works from different mechanisms to jointly address the key aspects where water lock problems may occur during the fracturing process of deep tight gas reservoirs. It comprehensively improves the water lock inhibition ability of the wetting reversal agent, laying a solid technical foundation for achieving the goals of reducing reservoir water lock damage, improving fracturing fluid flowback rate, and increasing gas well production. It demonstrates the ingenious design and promising application prospects of this wetting reversal agent in solving the water lock problem in deep tight gas reservoirs.

[0041] In some embodiments, the mass ratio of the silicon dioxide to the heptadecafluorodecyltrimethoxysilane is 1:(0.2-0.5).

[0042] In the embodiments of this application, the mass ratio of silica to heptadecafluorodecyltrimethoxysilane can be 1:(0.2-0.5), which fully realizes the modification of nano-silica by heptadecafluorodecyltrimethoxysilane, thereby improving the hydrophobic properties of the strongly hydrophobic modified nano-silica. For example, the mass ratio of silica to heptadecafluorodecyltrimethoxysilane can be 1:0.2, 1:0.3, 1:0.4, 1:0.5, etc.

[0043] In some embodiments, the process parameters for the modification treatment include: a reaction temperature of 50°C to 60°C and a reaction time of 4 to 6 hours.

[0044] In this embodiment, the strongly hydrophobic modified nano-silica is obtained by modifying nano-silica with heptadecafluorodecyltrimethoxysilane. The modification process parameters include a reaction temperature of 50°C to 60°C and a reaction time of 4 to 6 hours to obtain the desired strongly hydrophobic modified nano-silica with excellent hydrophobic properties. For example, the reaction temperature can be 50°C, 52°C, 54°C, 56°C, 58°C, 60°C, etc.; and the reaction time can be 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, etc.

[0045] An exemplary method for preparing strongly hydrophobic modified nano-silica includes: (1) adding unmodified SiO2 with a particle size of 20-50 nm into ethanol (the mass ratio of SiO2 to ethanol is 1:20-30), mixing and stirring at room temperature for 1-2 hours to obtain a uniformly dispersed system; (2) slowly adding ammonia water to the above dispersion system at room temperature until the pH value of the system reaches 11, and continuing to stir for 1-2 hours; (3) adding heptadecafluorodecyltrimethoxysilane (the mass ratio of SiO2 to heptadecafluorodecyltrimethoxysilane is 1:0.2-0.5) into the system, placing it in a water bath at 50-60℃ and stirring continuously for 4-6 hours to obtain a homogeneous solution; (4) slowly adding ammonium chloride to the solution until the pH value of the system reaches 5, and then filtering to obtain strongly hydrophobic modified nano-SiO2.

[0046] In some embodiments, the mass ratio of the polydimethylsiloxane, the glyceryl trioleate, and the 2-ethylhexanol polyoxyethylene ether is 1:(0.3-0.5):(0.1-0.2).

[0047] In the embodiments of this application, the mass ratio of polydimethylsiloxane, glyceryl trioleate, and 2-ethylhexanol polyoxyethylene ether can be 1:(0.3-0.5):(0.1-0.2) to achieve the best effect of the synergist in reducing surface tension. For example, the mass ratio of polydimethylsiloxane, glyceryl trioleate, and 2-ethylhexanol polyoxyethylene ether can be 1:0.3:0.1, 1:0.4:0.1, 1:0.5:0.1, 1:0.3:0.2, 1:0.5:0.2, 1:0.4:0.2, etc.

[0048] In some embodiments, the strongly hydrophobic modified nano-silica is 1 to 4 parts by weight, and the synergist is 4 to 8 parts by weight.

[0049] In this embodiment, the strongly hydrophobic modified nano-silica can be 1 to 4 parts, which can balance the strong hydrophobicity, dispersibility, and cost of the wetting reversal agent. The synergist can be 4 to 8 parts, which can fully enable the synergist to reduce the surface tension of the wetting reversal agent and further relieve the water-locking effect. For example, the strongly hydrophobic modified nano-silica can be 1 part, 2 parts, 3 parts, 4 parts, etc.; the synergist can be 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, etc.

[0050] In some embodiments, the raw materials also include a co-solvent and a solvent.

[0051] In some embodiments, the cosolvent includes at least one of the following: ethanol and acetone.

[0052] In some embodiments, the co-solvent is 25 to 40 parts by weight.

[0053] In this embodiment, the raw materials also include a co-solvent and a solvent. The co-solvent enables uniform dispersion of the hydrophobic agent and rapid dissolution of the synergist, resulting in a uniform wetting reversal agent. The co-solvent can be one or a combination of ethanol and acetone, and the solvent is generally water. The co-solvent can be 25 to 40 parts to fully achieve the dispersion of the hydrophobic agent and the dissolution of the synergist. For example, the co-solvent can be 25, 28, 30, 33, 35, 38, or 40 parts, etc.

[0054] Secondly, embodiments of this application provide a method for preparing the wetting reversal agent according to any one of the first aspects. Figure 1 A schematic flowchart illustrating a method for preparing a wetting reversal agent provided in this application embodiment; please refer to [link / reference]. Figure 1 The method includes:

[0055] S1. Strongly hydrophobic modified nano-silica, co-solvent, and solvent are ultrasonically mixed to obtain a dispersion.

[0056] S2. The dispersion is mixed with the synergist to obtain a wetting reversal agent.

[0057] In some embodiments, the temperature of the ultrasonic mixing is 40°C to 70°C;

[0058] The flow rate of the synergist is 2 ml / s to 5 ml / s.

[0059] In this embodiment, the ultrasonic mixing temperature can be 40℃ to 70℃ to increase the dispersion rate of the strongly hydrophobic modified nano-silica. The synergist addition flow rate can be 2ml / s to 5ml / s, with slow addition ensuring uniform wetting and reversing agent. For example, the ultrasonic mixing temperature can be 40℃, 43℃, 45℃, 48℃, 50℃, 53℃, 55℃, 58℃, 60℃, 63℃, 65℃, 68℃, 70℃, etc.; the synergist addition flow rate can be 2ml / s, 2.5ml / s, 3ml / s, 3.5ml / s, 4ml / s, 4.5ml / s, 5ml / s, etc.

[0060] The preparation method of this wetting reversal agent is based on the above-mentioned wetting reversal agent. The specific raw materials of the wetting reversal agent can be referred to the above embodiments. Since the preparation method of this wetting reversal agent adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0061] Thirdly, embodiments of this application provide the application of the wetting reversal agent described in any one of the first aspects in the fracturing of deep tight gas wells with a well temperature not exceeding 200°C.

[0062] In this embodiment, a wetting reversal agent is a material that reverses the wettability of a rock surface from strongly hydrophilic to strongly hydrophobic, thereby relieving waterlock. After the wetting reversal agent is injected into the reservoir, it can be adsorbed on the surface of rock pores, thus changing the wettability of the rock pore surface. Originally, the rock pore surface is strongly hydrophilic; due to capillary forces, water is drawn into the gas reservoir channels, causing a waterlock effect. After the pore surface is adsorbed with the wetting reversal agent, it becomes strongly hydrophobic. In this case, the water flow is enhanced, promoting water outflow from the channels, relieving waterlock damage, and increasing gas reservoir production. Simultaneously with the wetting reversal, the wetting reversal agent also reduces surface tension. Because the formation of waterlock is closely related to surface tension, reducing surface tension helps reduce capillary forces, thereby weakening the self-absorption effect of capillaries, mitigating the liquid phase trapping effect, and ultimately helping to relieve waterlock. The raw materials of the wetting reversal agent also have certain high temperature resistance properties. Therefore, this wetting reversal agent can be fully applied to the fracturing of deep tight gas wells with well temperatures not exceeding 200℃.

[0063] The application of this wetting reversal agent is based on the above-mentioned wetting reversal agent. The specific raw materials of the wetting reversal agent can be referred to in the above embodiments. Since the application of this wetting reversal agent adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0064] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0065] Example 1

[0066] Preparation of hydrophobic agent A: (1) Add 10g of unmodified SiO2 with a particle size of 20-50nm to 250g of ethanol and mix and stir at room temperature for 1 hour to obtain a uniformly dispersed system; (2) Slowly add ammonia water to the above dispersion system at room temperature until the pH value of the system reaches 11, and continue stirring for 1 hour; (3) Add 2g of heptadecafluorodecyltrimethoxysilane to the system and place it in a 50℃ water bath and stir continuously for 5 hours to obtain a homogeneous solution; (4) Slowly add ammonium chloride to the solution until the pH value of the system reaches 5, and then filter to obtain hydrophobic agent A.

[0067] Preparation of synergist A: Mix 20g of polydimethylsiloxane, 6g of glyceryl trioleate and 2g of 2-ethylhexanol polyoxyethylene ether and stir for 10min, then let stand for 1h to obtain synergist A.

[0068] The raw materials for wetting reversal agent A are: 5g hydrophobic agent A, 20g synergist A, 125g ethanol and 350g water (1 part hydrophobic agent A, 4 parts synergist A, 25 parts ethanol and 70 parts water).

[0069] Preparation method of wetting reversal agent A: (1) Place a mixture of 5g hydrophobic agent A, 125g ethanol and 350g water in a beaker and place it in a water bath at 50℃ and ultrasonically stir for 2 hours to obtain a uniform dispersion; (2) Slowly add 20g synergist A to the dispersion at a speed of 2ml / s and stir for 4 hours to obtain the wetting reversal agent A.

[0070] Example 2

[0071] Preparation of hydrophobic agent B: (1) Add 10g of unmodified SiO2 with a particle size of 20-50nm to 300g of ethanol and mix and stir at room temperature for 2 hours to obtain a uniformly dispersed system; (2) Slowly add ammonia water to the above dispersion system at room temperature until the pH value of the system reaches 11, and continue stirring for 2 hours; (3) Add 4g of heptadecafluorodecyltrimethoxysilane to the system and place it in a 60℃ water bath and stir continuously for 4 hours to obtain a homogeneous solution; (4) Slowly add ammonium chloride to the solution until the pH value of the system reaches 5, and then filter to obtain hydrophobic agent B.

[0072] Preparation of synergist B: Mix 15g of polydimethylsiloxane, 6g of glyceryl trioleate and 2.25g of 2-ethylhexanol polyoxyethylene ether and stir for 10min, then let stand for 1h to obtain synergist B.

[0073] The raw materials for wetting reversal agent B include: 5g hydrophobic agent B, 15g synergist B, 75g ethanol and 155g water (2 parts hydrophobic agent B, 6 parts synergist A, 30 parts ethanol and 62 parts water).

[0074] Preparation method of wetting reversal agent B: (1) Place a mixture of 5g hydrophobic agent B, 75g ethanol and 155g water in a beaker and place it in a water bath at 50℃ and ultrasonically stir for 2 hours to obtain a uniform dispersion; (2) Slowly add 15g synergist B to the dispersion at a speed of 5ml / s and stir for 5 hours to obtain the wetting reversal agent B.

[0075] Example 3

[0076] Preparation of hydrophobic agent C: (1) Add 10g of unmodified SiO2 with a particle size of 20-50nm to 300g of ethanol and mix and stir at room temperature for 2 hours to obtain a uniformly dispersed system; (2) Slowly add ammonia water to the above dispersion system at room temperature until the pH value of the system reaches 11, and continue stirring for 2 hours; (3) Add 4g of heptadecafluorodecyltrimethoxysilane to the system and place it in a 50℃ water bath and stir continuously for 4 hours to obtain a homogeneous solution; (4) Slowly add ammonium chloride to the solution until the pH value of the system reaches 5, and then filter to obtain hydrophobic agent C.

[0077] Preparation of synergist C: Mix 20g of polydimethylsiloxane, 10g of glyceryl trioleate and 3g of 2-ethylhexanol polyoxyethylene ether and stir for 10min, then let stand for 1h to obtain synergist C.

[0078] The raw materials for wetting reversal agent C include: 5g hydrophobic agent C, 10g synergist C, 50g ethanol and 60g water (4 parts hydrophobic agent C, 8 parts synergist C, 40 parts ethanol and 48 parts water).

[0079] Preparation method of wetting reversal agent C: (1) Place a mixture of 5g hydrophobic agent C, 50g ethanol and 60g water in a beaker and place it in a water bath at 70℃ and ultrasonically stir for 3 hours to obtain a uniform dispersion; (2) Slowly add 10g synergist C to the dispersion at a rate of 3ml / s and stir for 4 hours to obtain the wetting reversal agent C.

[0080] Comparative Example 1

[0081] Based on the content disclosed in Example 1, the difference between Comparative Example 1 and Example 1 is that synergist A in the system is removed, while the rest of the preparation method remains unchanged, to obtain wetting reversal agent D.

[0082] The wetting reversal agents prepared in Examples 1-3 and Comparative Example 1 were aged in an oven at 200°C for 24 hours. Their surface tension, water contact angle and fracturing fluid flowback rate were measured respectively. The results are shown in Table 1 below.

[0083] Table 1. Surface tension, water contact angle, and fracturing fluid flowback rate of wetting reversal agent.

[0084]

[0085] The test results in Table 1 show that the lower the surface tension and the larger the water contact angle, the higher the backflow rate of the degelatinized liquid, i.e., the better the water-locking effect. Meanwhile, after aging the wetting reversal agents prepared in Examples 1-3 in a 200℃ oven for 24 hours, their surface tension and water wetting angle did not change significantly, indicating that the wetting reversal agents in this application can be used in high-temperature gas wells at 200℃.

[0086] One or more technical solutions in the embodiments of this application have at least the following technical effects or advantages:

[0087] (1) When the wetting reversal agent provided in this application is applied to the fracturing of deep tight gas reservoirs, it can suppress the occurrence of water lock phenomenon, reduce water lock damage to the reservoir, increase the flowback rate of fracturing fluid, and increase gas well production while ensuring the needs of on-site construction.

[0088] (2) The wetting reversal agent provided in this application has stronger temperature resistance and can be applied to reservoirs with well temperatures not exceeding 200°C;

[0089] (3) The wetting reversal agent provided in this application is not easily spoiled, has a simple preparation process, a wide range of raw material sources, and is inexpensive, and has broad application prospects.

[0090] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A wetting reversal agent, wherein the raw materials of the wetting reversal agent include: Strongly hydrophobic modified nano-silica with synergists; The strongly hydrophobic modified nano-silica is obtained by modifying nano-silica with heptadecafluorodecyltrimethoxysilane. The synergists include polydimethylsiloxane, glyceryl trioleate, and 2-ethylhexanol polyoxyethylene ether.

2. The wetting reversal agent according to claim 1, characterized in that, The mass ratio of silicon dioxide to heptadecafluorodecyltrimethoxysilane is 1:(0.2-0.5).

3. The wetting reversal agent according to claim 1 or 2, characterized in that, The process parameters for the modification treatment include: a reaction temperature of 50℃~60℃ and a reaction time of 4h~6h.

4. The wetting reversal agent according to claim 1, characterized in that, The mass ratio of the polydimethylsiloxane, the glyceryl trioleate, and the 2-ethylhexanol polyoxyethylene ether is 1:(0.3-0.5):(0.1-0.2).

5. The wetting reversal agent according to claim 1, characterized in that, By weight, the strongly hydrophobic modified nano-silica is 1 to 4 parts, and the synergist is 4 to 8 parts.

6. The wetting reversal agent according to claim 1, characterized in that, The raw materials also include cosolvents and solvents.

7. The wetting reversal agent according to claim 6, characterized in that, The co-solvent includes at least one of the following: ethanol and acetone.

8. The wetting reversal agent according to claim 6 or 7, characterized in that, The co-solvent is 25 to 40 parts by weight.

9. A method for preparing a wetting reversal agent according to any one of claims 1 to 8, the method comprising: Strongly hydrophobic modified nano-silica, co-solvent, and solvent are ultrasonically mixed to obtain a dispersion. The dispersion is mixed with a synergist to obtain a wetting reversal agent; wherein... The temperature of the ultrasonic mixing is 40℃~70℃; The flow rate of the synergist is 2 ml / s to 5 ml / s.

10. The application of the wetting reversal agent according to any one of claims 1 to 8 in the fracturing of deep tight gas wells with a well temperature not exceeding 200°C.

Images