An oil-displacing self-suspending material and a method for preparing the same

Abstract

The application provides an oil displacement self-suspension material and a preparation method thereof, and belongs to the technical field of fracturing materials in the petroleum and natural gas industry. The method uses spherical quartz sand as a "core part", dopamine hydrochloride as a polymerization monomer, and obtains a polydopamine "shell part" with different thicknesses through the concentration of dopamine hydrochloride and the reaction time under weak alkaline oxidation conditions, so as to obtain a "core-shell" structure of quartz sand@polydopamine, as an intermediate. The intermediate is subjected to lipophilic hydrophobic modification, and specifically, the mercapto group of 1H, 1H, 2H, 2H-perfluorodecyl mercaptan is reacted with the amine group of polydopamine to generate a polymer rich in lipophilic hydrophobic properties with a crosslinked structure. By utilizing the characteristics that the polymer has a small density and is lipophilic and hydrophobic, a fracturing support material with oil displacement and self-suspension functions is obtained.

Description

Technical Field

[0001] This invention belongs to the field of fracturing materials technology in the oil and gas industry, specifically relating to an oil displacement self-suspending material and its preparation method. Background Technology

[0002] With the continuous increase in domestic and international demand for oil and gas, the difficulty of oil and gas extraction is constantly increasing, especially in the face of highly dense and low-permeability oil and gas reservoirs. Under the new circumstances of energy structure adjustment, strong oil and gas demand, and rapid technological development, how to increase oil and gas production has become an important research area. Fracturing technology can effectively develop highly dense and low-permeability oil and gas reservoirs, achieving the goal of increasing oil and gas production. Globally, hydraulic fracturing has been the main method of oil and gas development in recent decades. However, hydraulic fracturing, due to the use of high-viscosity fracturing fluids, brings water resource consumption and pollution risks, easily causing reservoir damage such as water lock-in and water sensitivity, and difficulties in fracturing and creating a network of fractures. More importantly, my country's main oil and gas reservoirs are highly dense and low-permeability, and hydraulic fracturing alone cannot meet current extraction requirements and energy demands. Self-suspended materials, due to their low density and water-free self-suspending properties, can avoid the use of high-viscosity fracturing fluids, thus effectively avoiding reservoir damage such as water lock-in and water sensitivity, and difficulties in fracturing and creating a network of fractures. However, relying solely on self-suspended materials is still insufficient to increase oil and gas production.

[0003] Furthermore, existing technologies only include self-suspending materials used in hydraulic fracturing, which are commonly used in clear water fracturing. This involves coating quartz sand with water-swellable polymers to suspend the quartz sand in clear water. However, the swellable polymers are prone to dissolving or suspending in the fracturing fluid, thereby increasing the viscosity of the fracturing fluid and causing reservoir damage. This is not conducive to the widespread and long-term application of hydraulic fracturing, and it cannot achieve oil displacement, making it difficult to meet the current requirements of oil and gas extraction and energy demand. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide an oil displacement self-suspending material and its preparation method. The material and its preparation method of the present invention can not only solve the problems of reservoir damage caused by high viscosity fracturing fluid "water lock-in and water sensitivity" and difficulty in fracturing and creating a network of fractures, but also provide oil displacement function by taking advantage of the oleophilic and hydrophobic properties of polymers, which helps to increase oil and gas production and meet existing extraction requirements and energy demands.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] This invention provides a method for preparing an oil displacement self-suspending material, comprising the following steps:

[0007] S1: Take quartz sand and pretreat it. Place the pretreated quartz sand in a dopamine hydrochloride aqueous solution, add tris(hydroxymethyl)methane-hydrochloric acid aqueous solution, adjust to the set pH value and then stop adding. Then add Cu. 2+ A salt solution was used to carry out a condensation reaction to obtain a core-shell structured intermediate of quartz sand@polydopamine;

[0008] S2: Take the core-shell structure intermediate of quartz sand@polydopamine and 1H,1H,2H,2H-perfluorodecyl mercaptan, place them in petroleum ether, add ammonia water, adjust to the set pH value, carry out the amino group reaction, and then filter to obtain the oil displacement self-suspending material.

[0009] Furthermore, the pH value is set to 8.0–9.0.

[0010] In a further step of the present invention, in step S1, the pretreatment involves ultrasonically treating the quartz sand for 30 to 60 minutes, washing it with water once to twice, washing it with petroleum ether once, and then drying it at 80°C for 12 to 24 hours.

[0011] In a further step of the present invention, in S1, the quartz sand is used as a fracturing material, the quartz sand is spherical in shape, and the specifications of the quartz sand are 20 / 40 mesh, 30 / 50 mesh, 40 / 70 mesh, and 70 / 140 mesh.

[0012] In a further step of the present invention, in step S1, the concentration of the dopamine hydrochloride aqueous solution is 0 to 2.0 g / L.

[0013] Furthermore, in S1, the Cu 2+ The salt solution contains water-soluble Cu. 2+ Salt solution, the Cu 2+ The concentration of the salt solution is 0.001 mol / L, and the Cu... 2+ The salt solution is any one of CuCl2, CuSO4, Cu(NO3)3, or Cu(Ac)2 solution.

[0014] In a further step of the present invention, in step S1, the reaction temperature of the condensation reaction is 20-40°C, and the reaction time of the condensation reaction is 2-6 hours.

[0015] In a further step of the present invention, in step S2, the mass ratio of the core-shell structure intermediate of the quartz sand@polydopamine to 1H,1H,2H,2H-perfluorodecylthiol is (100-1000:1).

[0016] In a further embodiment of the present invention, in step S2, the reaction temperature of the amino group reaction is 55-65°C, and the reaction time of the amino group reaction is 20-30 min.

[0017] An oil displacement self-suspending material prepared according to any one of the methods described above.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] This invention uses spherical quartz sand as the "core" and dopamine hydrochloride as the polymer monomer. Under alkaline and weakly oxidizing conditions, polydopamine "shells" of different thicknesses are obtained by varying the concentration of dopamine hydrochloride and the reaction time, thus obtaining a quartz sand@polydopamine "core-shell" structural intermediate. This quartz sand@polydopamine "core-shell" structural intermediate is obtained by reacting treated quartz sand with dopamine hydrochloride, providing a basis for the next step of imparting oleophilic and hydrophobic properties to the material. Subsequently, the thiol groups of 1H,1H,2H,2H-perfluorodecylthiol react with the amino groups of polydopamine to generate a polymer with a cross-linked structure rich in oleophilic and hydrophobic properties. Taking advantage of the polymer's lower density than fracturing fluid and its oleophilic and hydrophobic properties, a fracturing support material with both oil displacement and self-suspension functions is obtained.

[0020] Furthermore, the dopamine hydrochloride serves as the reactant monomer for the formation of polydopamine. Simultaneously, under alkaline weak oxidation conditions, the dopamine hydrochloride exposes abundant OH- ions, which undergo a condensation reaction with OH- ions on the surface of the treated quartz sand. These alkaline weak oxidation conditions are necessary to increase the reaction rate of dopamine hydrochloride in the formation of polydopamine. The polydopamine reduces the material density and provides abundant amine groups.

[0021] Furthermore, the quartz sand needs to be subjected to ultrasonication, water washing, petroleum ether washing and drying to obtain treated quartz sand, so that the surface of the quartz sand is exposed with abundant hydroxyl groups (OH-), which is conducive to the condensation reaction with the OH- of dopamine hydrochloride. Then, polydopamine can be coated on the surface of the treated quartz sand to form a "core-shell" structure intermediate of quartz sand@polydopamine.

[0022] Furthermore, the 1H,1H,2H,2H-perfluorodecylthiol is used to provide thiol groups, which react with the amino groups of polydopamine to generate a cross-linked polymer rich in oleophilic and hydrophobic properties, thereby imparting oleophilic and hydrophobic properties to the material. The fracturing support material with both oil displacement and self-suspension functions utilizes the fact that the density of the oleophilic and hydrophobic polymer is lower than that of the fracturing fluid and has oleophilic and hydrophobic properties, so that the treated quartz sand has both oil displacement and self-suspension functions.

[0023] The method for preparing an oil displacement self-suspending material described in this invention has the advantages of being simple, easy to implement, and having both suspension and oil displacement functions. It is conducive to promotion in the field of fracturing in the oil and gas industry and has broad application prospects.

[0024] This invention provides an oil displacement self-suspension material. The polymer has a cross-linked structure and oleophilic-hydrophobic properties, with a density lower than that of fracturing fluid. It is a fracturing support material that combines oil displacement and self-suspension functions. It not only solves problems such as reservoir "water lock-in" and "water sensitivity" damage caused by high-viscosity fracturing fluids, as well as difficulties in fracturing and creating a network of fractures, but also provides oil displacement functionality by leveraging the polymer's oleophilic-hydrophobic properties, thus helping to increase oil and gas recovery rates and meet current extraction requirements and energy demands. Attached Figure Description

[0025] Figure 1 This is an oil displacement self-suspending material according to Embodiment 3 of the present invention;

[0026] Figure 2 The image shown is a transmission electron microscope (TEM) image of the sample from Example 1.

[0027] Figure 3 The image shown is a TEM image of the sample from Example 2 of this invention.

[0028] Figure 4 The image shown is a TEM image of the sample from Example 3 of this invention.

[0029] Figure 5 The image shown is a TEM image of the sample from Example 4 of this invention.

[0030] Figure 6 This is a scanning electron microscope (SEM) image of the sample from Example 3 of the present invention. Detailed Implementation

[0031] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0032] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0033] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0034] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0035] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0036] This invention provides an oil displacement self-suspending material and its preparation method.

[0037] The present invention will be 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 invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0038] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0039] This invention provides a method for preparing an oil displacement self-suspension material. Spherical quartz sand is used as the "core," and dopamine hydrochloride is used as the polymer monomer. Under alkaline weak oxidizing conditions, different thicknesses of polydopamine "shells" are obtained by adjusting the concentration of dopamine hydrochloride and the reaction time, thus obtaining a quartz sand@polydopamine "core-shell" structural intermediate. Then, the thiol groups of 1H,1H,2H,2H-perfluorodecylthiol react with the amino groups of polydopamine to generate a cross-linked polymer rich in oleophilic and hydrophobic properties. Taking advantage of the polymer's lower density than fracturing fluid and its oleophilic and hydrophobic characteristics, a fracturing support material with both oil displacement and self-suspension functions is obtained.

[0040] The fracturing propping material prepared according to the method described above utilizes the polymer's lower density than fracturing fluid and its oleophilic and hydrophobic properties, thus possessing both oil displacement and self-suspension functions.

[0041] This invention provides a method for preparing an oil displacement self-suspending material, comprising the following steps:

[0042] (1) Weigh 100g of quartz sand, sonicate it for 30min to 60min, wash it with water once to twice, wash it with petroleum ether once, and dry it at 80℃ for 12h to 24h to obtain the treated quartz sand for later use.

[0043] As an optional option, the quartz sand is fracturing material quartz sand with specifications including 20 / 40 mesh, 30 / 50 mesh, 40 / 70 mesh, and 70 / 140 mesh, as a mechanical compressive support material.

[0044] (2) Place the treated quartz sand from (1) into 1L of dopamine hydrochloride aqueous solution with concentrations of 0, 0.5, 1.0, and 2.0 g / L to create alkaline conditions (add tris(hydroxymethyl)methane-hydrochloric acid aqueous solution, adjust the pH to 8.5 and then stop adding), and create weak oxidizing conditions (add 1L of Cu with a concentration of 0.001 mol / L). 2+ The condensation reaction was carried out by stirring at a reaction temperature of T = 20-40℃. After the condensation reaction was carried out for 2-6 hours, the quartz sand@polydopamine core-shell structure intermediate was obtained by filtration and then set aside for later use.

[0045] As an optional feature, the concentration of dopamine hydrochloride is 0–2.0 g / L; the alkaline weak oxidizing conditions include both alkaline and weak oxidizing conditions, wherein the alkaline conditions are maintained at pH 8.0–9.0 in a trihydroxymethoxymethane-hydrochloric acid aqueous solution; and the weak oxidizing conditions refer to the presence of water-soluble Cu. 2+ Salt solution, water-soluble Cu 2+ The concentration of the salt solution is 0.001 mol / L, including CuCl2, CuSO4, Cu(NO3)3, Cu(Ac)2, etc.

[0046] As an optional solution, the polydopamine is made from Cu 2+ Dopamine hydrochloride of a certain concentration and volume was placed in a salt solution at pH 8.5 and a reaction temperature of T = 25℃ and kept in the solution for 2 to 6 hours. After the reaction was completed, the solution was filtered to obtain the product. Polydopamine was not prepared separately but was used as a coating layer for the treated quartz sand.

[0047] As an optional solution, the "core-shell" structure intermediate of quartz sand@polydopamine refers to weighing a certain amount of treated quartz sand and a certain amount of dopamine hydrochloride aqueous solution, mixing and stirring the two, and maintaining the condensation reaction for 2h to 6h under alkaline weak oxidation conditions, pH 8.0 to 9.0, and reaction temperature 20 to 40℃, and filtering after the reaction is completed.

[0048] (3) Weigh out the core-shell structure intermediate of quartz sand@polydopamine and 1H,1H,2H,2H-perfluorodecyl mercaptan in (2) according to a mass ratio of 100:1. Place them in 1L of petroleum ether, add ammonia water, adjust the pH to 8.0-9.0 and then stop adding. Stir continuously at 55-65℃ for 20-30 minutes to carry out the amino group reaction. After the reaction is completed, filter to obtain the oil displacement self-suspending material.

[0049] As an optional embodiment, the amount of 1H,1H,2H,2H-perfluorodecyl mercaptan is 0.1% to 1% of the mass of the core-shell structure intermediate of quartz sand@polydopamine; that is, the mass ratio of the core-shell structure intermediate of quartz sand@polydopamine to 1H,1H,2H,2H-perfluorodecyl mercaptan is (100 to 1000:1).

[0050] As an optional solution, the fracturing propping material with both oil displacement and self-suspension functions is prepared by mixing 100 parts by mass of a core-shell structure intermediate of quartz sand@polydopamine and 1 part by mass of 1H,1H,2H,2H-perfluorodecyl mercaptan in a certain volume of petroleum ether, adding ammonia water to maintain pH=8.0, and continuously stirring at 60°C for 30 minutes to carry out an amine reaction. After the reaction is completed, the material is filtered to obtain the oil displacement and self-suspension material.

[0051] The working principle is as follows: First, the quartz sand undergoes ultrasonic treatment, water washing, petroleum ether washing, and drying to obtain treated quartz sand. This exposes abundant hydroxyl groups (OH-) on the surface of the quartz sand, which facilitates a condensation reaction with the OH- of dopamine hydrochloride. Polydopamine can then be coated onto the surface of the treated quartz sand, forming a core-shell structure intermediate of quartz sand@polydopamine. Second, the dopamine hydrochloride serves as the monomer for the formation of polydopamine. Simultaneously, under alkaline weak oxidation conditions, the dopamine hydrochloride exposes abundant OH-, which condenses with the OH- on the surface of the treated quartz sand. The alkaline weak oxidation conditions are necessary to increase the reaction rate of dopamine hydrochloride to generate polydopamine. Third, the polydopamine reduces the material density and provides abundant amine groups. The core-shell structure intermediate of quartz sand@polydopamine is obtained by reacting the treated quartz sand and dopamine hydrochloride, providing a basis for the next step of imparting oleophilic and hydrophobic properties to the material. Finally, the 1H,1H,2H,2H-perfluorodecylthiol is used to provide thiol groups, which react with the amino groups of polydopamine to generate a cross-linked polymer rich in oleophilic and hydrophobic properties, thereby imparting oleophilic and hydrophobic properties to the material.

[0052] Example

[0053] This invention provides multiple embodiments to further explain and illustrate the oil displacement self-suspending material, its preparation method, and the beneficial effects thereof.

[0054] Examples 1-8 all use 70 / 140 mesh to illustrate the patterns, and the formulations for other quartz sand specifications are the same as those for 70 / 140 mesh. Examples 1-4 show the effects of changing the dopamine hydrochloride concentration to 0, 0.5, 1.0, and 2.0 g / L while maintaining a reaction time of 5 hours on the parameters and properties of the self-suspended oil displacement material. Example 1, with a dopamine hydrochloride concentration of 0 g / L, refers to the sample obtained without the addition of dopamine hydrochloride and serves as a control sample. Examples 3, 5-8 show the effects of changing the reaction time to 5 hours, 2 hours, 3 hours, 4 hours, and 6 hours while maintaining a dopamine hydrochloride concentration of 1.0 g / L on the parameters and properties of the self-suspended oil displacement material.

[0055] Example 1

[0056] Weigh 100g of quartz sand, sonicate it for 60min, wash it twice with water, wash it once with petroleum ether, and dry it at 80℃ for 24h to obtain the treated quartz sand for later use. Place the treated quartz sand in 1L of 0g / L dopamine hydrochloride aqueous solution, add tris(hydroxymethyl)methane-hydrochloric acid aqueous solution, adjust the pH to 8.5 and then stop adding. Add 1L of 0.001mol / L Cu 2+ A brine solution was stirred at a reaction temperature of T = 25℃ for 5 hours. The intermediate was obtained by filtration and set aside. The intermediate and 1H,1H,2H,2H-perfluorodecylthiol were weighed out at a mass ratio of 100:1 and placed in 1L of petroleum ether. Ammonia was added to adjust the pH to 8.0, and then the addition was stopped. The mixture was stirred continuously at 60℃ for 30 minutes. After the reaction was complete, the sample was obtained by filtration. The parameters and performance results of the obtained sample are shown in Table 1.

[0057] Example 2

[0058] Weigh 100g of quartz sand, sonicate it for 60min, wash it twice with water, wash it once with petroleum ether, and dry it at 80℃ for 24h to obtain the treated quartz sand for later use. Place the treated quartz sand in 1L of 0.5g / L dopamine hydrochloride aqueous solution, add tris(hydroxymethyl)methane-hydrochloric acid aqueous solution, adjust the pH to 8.5 and then stop adding. Add 1L of 0.001mol / L Cu2+. +A brine solution was stirred at a reaction temperature of T = 25℃ for 5 hours. The resulting intermediate, a core-shell structure of quartz sand@polydopamine, was obtained by filtration and set aside. The core-shell structure intermediate of quartz sand@polydopamine and 1H,1H,2H,2H-perfluorodecyl mercaptan were weighed out at a mass ratio of 100:1 and placed in 1L of petroleum ether. Ammonia was added to adjust the pH to 8.0, and then the addition was stopped. The mixture was stirred continuously at 60℃ for 30 minutes. After the reaction was complete, the material was filtered to obtain the oil-displacing self-suspending material. The parameters and performance results of the obtained samples are shown in Table 1.

[0059] Example 3

[0060] Weigh 100g of quartz sand, sonicate it for 60min, wash it twice with water, wash it once with petroleum ether, and dry it at 80℃ for 24h to obtain the treated quartz sand for later use. Place the treated quartz sand in 1L of 1.0g / L dopamine hydrochloride aqueous solution, add tris(hydroxymethyl)methane-hydrochloric acid aqueous solution, adjust the pH to 8.5 and then stop adding. Add 1L of 0.001mol / L Cu2+. + A brine solution was stirred at a reaction temperature of T = 25℃ for 5 hours. The resulting intermediate, a core-shell structure of quartz sand@polydopamine, was obtained by filtration and set aside. The core-shell structure intermediate of quartz sand@polydopamine and 1H,1H,2H,2H-perfluorodecyl mercaptan were weighed out at a mass ratio of 100:1 and placed in 1L of petroleum ether. Ammonia was added to adjust the pH to 8.0, and then the addition was stopped. The mixture was stirred continuously at 60℃ for 30 minutes. After the reaction was complete, the material was filtered to obtain the oil-displacing self-suspending material. The parameters and performance results of the obtained samples are shown in Table 1.

[0061] The difference between this embodiment and Example 2 is that the treated quartz sand was placed in 1L of a 1.0g / L dopamine hydrochloride aqueous solution to complete the preparation process. The parameters and performance results of the obtained samples are shown in Table 1.

[0062] Example 4

[0063] Weigh 100g of quartz sand, sonicate it for 60min, wash it twice with water, wash it once with petroleum ether, and dry it at 80℃ for 24h to obtain the treated quartz sand for later use. Place the treated quartz sand in 1L of 2.0g / L dopamine hydrochloride aqueous solution, add tris(hydroxymethyl)methane-hydrochloric acid aqueous solution, adjust the pH to 8.5 and then stop adding. Add 1L of 0.001mol / L Cu2+. +A brine solution was stirred at a reaction temperature of T = 25℃ for 5 hours. The resulting intermediate, a core-shell structure of quartz sand@polydopamine, was obtained by filtration and set aside. The core-shell structure intermediate of quartz sand@polydopamine and 1H,1H,2H,2H-perfluorodecyl mercaptan were weighed out at a mass ratio of 100:1 and placed in 1L of petroleum ether. Ammonia was added to adjust the pH to 8.0, and then the addition was stopped. The mixture was stirred continuously at 60℃ for 30 minutes. After the reaction was complete, the material was filtered to obtain the oil-displacing self-suspending material. The parameters and performance results of the obtained samples are shown in Table 1.

[0064] The difference between this embodiment and Example 2 is that the treated quartz sand was placed in 1L of a 2.0g / L dopamine hydrochloride aqueous solution to complete the preparation process. The parameters and performance results of the obtained samples are shown in Table 1.

[0065] Table 1. Effects of changing dopamine hydrochloride concentration on the parameters and properties of the self-suspending material for oil displacement.

[0066] Example 1 1.83 sink 20 Example 2 1.09 Slowly sinking 112 Example 3 0.93 30 165 Example 4 0.93 30 165

[0067] Combination Figures 1 to 6 As shown in Table 1, the sample density decreased continuously with the increase of dopamine hydrochloride concentration, until it fell below the density of pure water (1.0 g / cm³). 3 This causes self-suspension; when the dopamine hydrochloride concentration increases from 1.0 g / L to 2.0 g / L, the sample density remains unchanged (0.93 g / cm³). 3The density plateau was observed, which may be because the dopamine hydrochloride concentration, upon reaching a certain level, no longer effectively increases the thickness of the polydopamine. In other words, simply increasing the dopamine hydrochloride concentration to increase the polydopamine thickness fails to further reduce the material's density, indicating that increasing the dopamine hydrochloride concentration will reach an extreme value in reducing the sample's density. The self-suspension time shows that as the dopamine hydrochloride concentration increases, the sample initially sinks, then slowly sinks, and finally becomes self-suspensive. When the dopamine hydrochloride concentration increases to 1.0 g / L, the sample can self-suspense for 30 minutes. Further increasing the concentration to 2.0 g / L results in a self-suspension time that remains unchanged at 30 minutes, indicating a plateau in self-suspension performance, consistent with the density change. Regarding the oil displacement performance of the sample, a larger contact angle generally indicates greater oleophilicity, with a contact angle of 90° as the limit. A contact angle greater than 90° indicates strong oleophilicity and good or excellent oil displacement performance, and vice versa. As the concentration of dopamine hydrochloride increased, the contact angle of the sample changed from 20° (hydrophilic) to 165° (oleophilic), indicating that the oil displacement property of the sample continuously increased until a plateau was reached (where the oleophilicity no longer increased). This result is consistent with the changes in density and self-suspension performance. Considering both the self-suspension and oil displacement properties of the sample, as well as the preparation conditions, the conditions in Example 3 were optimal, i.e., when the dopamine hydrochloride concentration was 1.0 g / L, the resulting oil-displacing self-suspension material had the lowest density, the longest self-suspension time, and the best oil displacement performance.

[0068] Example 5

[0069] Weigh 100g of quartz sand, sonicate it for 60min, wash it twice with water, wash it once with petroleum ether, and dry it at 80℃ for 24h to obtain the treated quartz sand for later use. Place the treated quartz sand in 1L of 1.0g / L dopamine hydrochloride aqueous solution, add tris(hydroxymethyl)methane-hydrochloric acid aqueous solution, adjust the pH to 8.5 and then stop adding. Add 1L of 0.001mol / L Cu 2+ A brine solution was stirred at a reaction temperature of T = 25℃ for 2 hours. After filtration, a core-shell structure intermediate of quartz sand@polydopamine was obtained for later use. The core-shell structure intermediate of quartz sand@polydopamine and 1H,1H,2H,2H-perfluorodecyl mercaptan were weighed out at a mass ratio of 100:1 and placed in 1L of petroleum ether. Ammonia was added to adjust the pH to 8.0, and then the addition was stopped. The mixture was stirred continuously at 60℃ for 30 minutes. After the reaction was complete, the mixture was filtered to obtain the oil-displacing self-suspending material. The parameters and performance results of the obtained samples are shown in Table 2.

[0070] Example 6

[0071] Weigh 100g of quartz sand, sonicate it for 60min, wash it twice with water, wash it once with petroleum ether, and dry it at 80℃ for 24h to obtain the treated quartz sand for later use. Place the treated quartz sand in 1L of 1.0g / L dopamine hydrochloride aqueous solution, add tris(hydroxymethyl)methane-hydrochloric acid aqueous solution, adjust the pH to 8.5 and then stop adding. Add 1L of 0.001mol / L Cu 2+ A brine solution was stirred at a reaction temperature of T = 25℃ for 3 hours. After filtration, a core-shell structure intermediate of quartz sand@polydopamine was obtained for later use. The core-shell structure intermediate of quartz sand@polydopamine and 1H,1H,2H,2H-perfluorodecyl mercaptan were weighed out at a mass ratio of 100:1 and placed in 1L of petroleum ether. Ammonia was added to adjust the pH to 8.0, and then the addition was stopped. The mixture was stirred continuously at 60℃ for 30 minutes. After the reaction was complete, the mixture was filtered to obtain the oil-displacing self-suspending material. The parameters and performance results of the obtained samples are shown in Table 2.

[0072] The difference between this embodiment and Example 5 is that the reaction time for dopamine hydrochloride was 3 hours to complete the preparation process. The parameters and performance results of the obtained samples are shown in Table 2.

[0073] Example 7

[0074] Weigh 100g of quartz sand, sonicate it for 60min, wash it twice with water, wash it once with petroleum ether, and dry it at 80℃ for 24h to obtain the treated quartz sand for later use. Place the treated quartz sand in 1L of 1.0g / L dopamine hydrochloride aqueous solution, add tris(hydroxymethyl)methane-hydrochloric acid aqueous solution, adjust the pH to 8.5 and then stop adding. Add 1L of 0.001mol / L Cu 2+ A brine solution was stirred at a reaction temperature of T = 25℃ for 4 hours. The resulting intermediate, a core-shell structure of quartz sand@polydopamine, was obtained by filtration and set aside. The core-shell structure intermediate of quartz sand@polydopamine and 1H,1H,2H,2H-perfluorodecyl mercaptan were weighed out at a mass ratio of 100:1 and placed in 1L of petroleum ether. Ammonia was added to adjust the pH to 8.0, and then the addition was stopped. The mixture was stirred continuously at 60℃ for 30 minutes. After the reaction was complete, the material was filtered to obtain the oil-displacing self-suspending material. The parameters and performance results of the obtained samples are shown in Table 2.

[0075] The difference between this embodiment and Example 5 is that the reaction time for dopamine hydrochloride was 4 hours to complete the preparation process. The parameters and performance results of the obtained samples are shown in Table 2.

[0076] Example 8

[0077] Weigh 100g of quartz sand, sonicate it for 60min, wash it twice with water, wash it once with petroleum ether, and dry it at 80℃ for 24h to obtain the treated quartz sand for later use. Place the treated quartz sand in 1L of 1.0g / L dopamine hydrochloride aqueous solution, add tris(hydroxymethyl)methane-hydrochloric acid aqueous solution, adjust the pH to 8.5 and then stop adding. Add 1L of 0.001mol / L Cu 2+ A brine solution was stirred at a reaction temperature of T = 25℃ for 6 hours. The resulting intermediate, a core-shell structure of quartz sand@polydopamine, was obtained by filtration and set aside. The core-shell structure intermediate of quartz sand@polydopamine and 1H,1H,2H,2H-perfluorodecyl mercaptan were weighed out at a mass ratio of 100:1 and placed in 1L of petroleum ether. Ammonia was added to adjust the pH to 8.0, and then the addition was stopped. The mixture was stirred continuously at 60℃ for 30 minutes. After the reaction was complete, the material was filtered to obtain the oil-displacing self-suspending material. The parameters and performance results of the obtained samples are shown in Table 2.

[0078] The difference between this embodiment and Example 5 is that the reaction time for dopamine hydrochloride was 6 hours to complete the preparation process. The parameters and performance results of the obtained samples are shown in Table 2.

[0079] Table 2 shows the influence of changing the reaction time on the parameters and properties of the self-suspending material for oil displacement.

[0080]

[0081]

[0082] Combination Figure 4 , Figure 6 As shown in Table 2, the sample density decreased continuously with increasing reaction time, until it fell below the density of pure water (1.0 g / cm³). 3 This causes self-suspension; when the reaction time increases from 5 h to 6 h, the sample density remains unchanged (0.93 g / cm³). 3The density plateau was observed, which may indicate that increasing the reaction time beyond a certain point no longer increases the polydopamine thickness. In other words, simply increasing the reaction time to increase the polydopamine thickness fails to further reduce the material's density, suggesting that increasing the reaction time will reach an extreme value in reducing the sample's density. The self-suspension time shows that as the reaction time increases, the sample progresses from sinking to slow sinking, and then to self-suspension. When the reaction time reaches 4 hours, the sample self-suspension time is 12 minutes; increasing it further to 5 hours results in 30 minutes; however, increasing the reaction time to 6 hours results in a constant self-suspension time (30 minutes), indicating a plateau in self-suspension performance, consistent with the density change. Regarding the oil displacement performance, as the reaction time increases, the contact angle changes from 87° (hydrophilic) to 165° (oleophilic), indicating an increasing oil displacement capacity until a plateau is reached (where oleophilicity no longer increases), consistent with the density and self-suspension performance trends. Taking into account the self-suspension and oil displacement properties of the samples, as well as the preparation conditions, the conditions in Example 3 are optimal, that is, when the reaction time is 5h, the resulting oil displacement self-suspension material has the lowest density, the longest self-suspension time, and the best oil displacement performance.

[0083] Example 9

[0084] Weigh 100g of quartz sand, sonicate it for 30min, wash it once with water, wash it once with petroleum ether, and dry it at 80℃ for 12h to obtain the treated quartz sand for later use; place the treated quartz sand in 1L of 0g / L dopamine hydrochloride aqueous solution, add tris(hydroxymethyl)methane-hydrochloric acid aqueous solution, adjust the pH to 9.0 and then stop adding, then add 1L of 0.001mol / L Cu 2+ A brine solution was stirred at a reaction temperature of T = 20℃ for 4 hours. The intermediate was obtained by filtration and set aside. The intermediate and 1H,1H,2H,2H-perfluorodecylthiol were weighed out at a mass ratio of 1000:1 and placed in 1L of petroleum ether. Ammonia was added to adjust the pH to 9.0, and then the addition was stopped. The mixture was stirred continuously at 55℃ for 20 minutes. After the reaction was complete, the sample was obtained by filtration. The parameters and performance results of the obtained sample are shown in Table 1.

[0085] Example 10

[0086] Weigh 100g of quartz sand, sonicate it for 30min, wash it once with water, wash it once with petroleum ether, and dry it at 80℃ for 20h to obtain treated quartz sand for later use; place the treated quartz sand in 1L of 0g / L dopamine hydrochloride aqueous solution, add tris(hydroxymethyl)methane-hydrochloric acid aqueous solution, adjust the pH to 8.5 and then stop adding, then add 1L of 0.001mol / L Cu 2+A brine solution was stirred at a reaction temperature of T = 40℃ for 5 hours. The intermediate was obtained by filtration and set aside. The intermediate and 1H,1H,2H,2H-perfluorodecylthiol were weighed out at a mass ratio of 1000:1 and placed in 1L of petroleum ether. Ammonia was added to adjust the pH to 8.5, and then the addition was stopped. The mixture was stirred continuously at 65℃ for 30 minutes. After the reaction was complete, the sample was obtained by filtration. The parameters and performance results of the obtained sample are shown in Table 1.

[0087] The comparison of the results of the above embodiments shows that the oil-dispatch self-suspending material provided by the present invention can reduce the material density to 0.93 g / cm³. 3 It is less than the density of pure water (1.0 g / cm³). 3 It can self-suspend in clean water for 30 minutes with a contact angle of 165°, exhibiting obvious oleophilicity. It can be used as a self-suspended oil displacement material. Due to its simple preparation process, clear method, and well-defined formula, it can be widely applied in the field of fracturing materials for the oil and gas industry.

[0088] This invention provides an oil displacement self-suspending material and its preparation method, addressing the current technical bottleneck in the field of self-suspending materials, namely, the difficulty in simultaneously achieving self-suspending and oil displacement functions. This invention uses spherical quartz sand as the "core" and dopamine hydrochloride as the polymer monomer. Under alkaline and weakly oxidizing conditions, different thicknesses of polydopamine "shells" are obtained by varying the concentration of dopamine hydrochloride and the reaction time, thus obtaining a quartz sand@polydopamine "core-shell" structural intermediate. The thiol groups of 1H,1H,2H,2H-perfluorodecylthiol react with the amino groups of polydopamine to generate a cross-linked polymer rich in oleophilic and hydrophobic properties. Utilizing the polymer's lower density than fracturing fluid and its oleophilic and hydrophobic characteristics, a fracturing support material with both oil displacement and self-suspending functions is obtained. The method and product provided by this invention not only solve problems such as reservoir "water lock-in" and "water sensitivity" damage caused by high-viscosity fracturing fluids and difficulties in fracturing network formation, but also provide oil displacement function by leveraging the polymer's oleophilic and hydrophobic properties, helping to increase oil and gas recovery and meet current extraction requirements and energy demands. The method for preparing an oil displacement self-suspending material described in this invention has the advantages of being simple, easy to implement, and having both suspension and oil displacement functions. It is conducive to promotion in the field of fracturing in the oil and gas industry and has broad application prospects.

[0089] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing an oil displacement self-suspending material, characterized in that, Includes the following steps: S1: Take quartz sand and pretreat it. Place the pretreated quartz sand in a dopamine hydrochloride aqueous solution, add tris(hydroxymethyl)methane-hydrochloric acid aqueous solution, adjust to the set pH value and then stop adding. Then add Cu. 2+ A salt solution was used to carry out a condensation reaction to obtain a core-shell structured intermediate of quartz sand@polydopamine; S2: Take the core-shell structure intermediate of quartz sand@polydopamine and 1H, 1H, 2H, 2H-perfluorodecyl mercaptan, place them in petroleum ether, add ammonia water, adjust to the set pH value, carry out the amino group reaction, and then filter to obtain the oil displacement self-suspending material.

2. The method for preparing the oil displacement self-suspending material according to claim 1, characterized in that, The set pH value is 8.0~9.

0.

3. The method for preparing the oil displacement self-suspending material according to claim 1, characterized in that, In step S1, the pretreatment involves ultrasonically treating the quartz sand for 30 to 60 minutes, washing it with water once to twice, washing it with petroleum ether once, and then drying it at 80 ℃ for 12 to 24 hours.

4. The method for preparing the oil displacement self-suspending material according to claim 1, characterized in that, In S1, the quartz sand is used as a fracturing material. The quartz sand is spherical in shape and has a specification of 20 / 40 mesh, 30 / 50 mesh, 40 / 70 mesh, and 70 / 140 mesh.

5. The method for preparing the oil displacement self-suspending material according to claim 1, characterized in that, In step S1, the concentration of the dopamine hydrochloride aqueous solution is 1.0 g / L to 2.0 g / L.

6. The method for preparing the oil displacement self-suspending material according to claim 1, characterized in that, In S1, the Cu 2 + The salt solution contains water-soluble Cu. 2+ Salt solution, the Cu 2+ The concentration of the salt solution is 0.001 mol / L, and the Cu... 2+ The salt solution is any one of CuCl2, CuSO4, Cu(NO3)3, or Cu(Ac)2 solution.

7. The method for preparing the oil displacement self-suspending material according to claim 1, characterized in that, In S1, the reaction temperature of the condensation reaction is 20~40℃, and the reaction time of the condensation reaction is 2~6h.

8. The method for preparing the oil displacement self-suspending material according to claim 1, characterized in that, In S2, the mass ratio of the core-shell structure intermediate of quartz sand@polydopamine to 1H, 1H, 2H, 2H-perfluorodecylthiol is (100~1000:1).

9. The method for preparing the oil displacement self-suspending material according to claim 1, characterized in that, In S2, the reaction temperature of the amino group reaction is 55~65℃, and the reaction time of the amino group reaction is 20~30min.

10. An oil displacement self-suspending material prepared by the preparation method of the oil displacement self-suspending material according to any one of claims 1 to 9.

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