Monodisperse self-suspension fracturing material for supercritical CO2 fracturing and synthesis device and method

Abstract

The invention discloses a monodisperse self-suspension fracturing material for supercritical CO2 fracturing and a synthesis device and method, relates to the technical field of petroleum and natural gas industrial fracturing materials, and utilizes an in-situ synthesis device to synthesize the monodisperse self-suspension fracturing material with a'core + surface particle 'composite structure in situ, and the monodisperse self-suspension fracturing material can be used for supercritical CO2 fracturing. The'core + surface particle 'composite structure is similar to a'planet + satellite' composite structure, the'planet 'is a light high-strength polymer synthesized from styrene, diethylbenzene alkene, an accelerant, an initiator, a solvent and a dispersing agent, the'satellite' is formed by loading quartz sand on the surface of the'planet 'through an adhesive, and the adhesive is obtained by modifying epoxy resin with a silane coupling agent. The'planet 'structure, the'satellite' structure and the'planet and satellite 'composite structure are synthesized in situ by the in-situ synthesis device, additional equipment is not needed, and the method has the advantages that the synthesis process is simple, and the equipment is easy to operate and popularize.

Description

Technical Field

[0001] The present invention relates to the technical field of fracturing materials for the petroleum and natural gas industries, and in particular to a monodisperse self-suspending fracturing material for supercritical CO2 fracturing and a synthesis device and method. Background Art

[0002] With the continuous increase in demand for oil and gas at home and abroad, the difficulty of oil and gas extraction is increasing in the face of high-density and low-permeability oil and gas reservoirs. Under the new situation of energy structure adjustment, strong demand for oil and gas, and rapid technological development, how to increase oil and gas production is an important research field. The use of fracturing technology can effectively develop high-density and low-permeability oil and gas reservoirs and achieve the goal of increasing oil and gas production. Worldwide, hydraulic fracturing has been the main method of oil and gas development in recent decades. However, hydraulic fracturing will bring water resource consumption and pollution risks, easily cause reservoir "water lock, water sensitivity" damage and difficulties in fracturing fracture network formation. More importantly, my country's main oil and gas reservoirs are high-density and low-permeability, and hydraulic fracturing is difficult to meet the existing mining requirements and energy needs. Carbon dioxide (CO2) has better rock crushing ability than water, so CO2 fracturing can produce more complex fracture networks than hydraulic fracturing, thereby improving oil and gas permeability and recovery rate, and is expected to efficiently exploit high-density and low-permeability oil and gas reservoirs. CO2 fracturing can also effectively relieve water resource pressure, is pollution-free, reduce reservoir damage, and seal CO2. However, due to the low density and low viscosity of CO2, the technology has poor sand-carrying capacity, which is a bottleneck restricting its widespread application. Therefore, how to improve the sand-carrying capacity of CO2 is a key scientific issue facing this field.

[0003] CO2 fracturing usually includes Newtonian fluid, power law fluid, and viscoelastic fracturing fluid. To improve the sand carrying capacity of CO2, the fracturing material must be kept in a suspended state, which requires reducing the sedimentation rate of the fracturing material. The goal can be achieved by increasing the fluid viscosity, increasing the fluid density, increasing the diameter of the fracturing material, and reducing the mass of the proppant. Increasing the fluid viscosity and increasing the fluid density improve the CO2 sand carrying capacity by changing the properties of the fracturing fluid; increasing the diameter of the fracturing material and reducing the mass improve the CO2 sand carrying capacity by changing the properties of the fracturing material. However, blindly increasing the viscosity of the CO2 fracturing fluid will cause damage to the reservoir, increase costs, and other problems. By designing a low density (less than 1.20g / cm 3) The self-suspending material can be suspended in the fracturing fluid without increasing the viscosity of the fracturing fluid, and has the advantages of increasing the sand carrying capacity and reducing reservoir damage. At present, no relevant research and patents on self-suspending materials for CO2 fracturing have been found, and self-suspending materials for hydraulic fracturing can be found. This hydraulic fracturing self-suspending material is usually used for clear water fracturing, using a method of coating quartz sand with a water-swelling polymer so that the quartz sand can be suspended in clear water, but the swelling polymer is easily dissolved or suspended in the fracturing fluid, thereby increasing the viscosity of the fracturing fluid, and then causing the problem of reservoir damage, which is not conducive to extensive and long-term hydraulic fracturing applications. Moreover, since the swelling polymer can only swell in clear water and cannot swell in salt water, brine, foam CO2 fracturing fluid and liquid CO2 fracturing fluid, it is impossible to achieve the self-suspension function and cannot be applied in the field of CO2 fracturing. Summary of the invention

[0004] The purpose of the present invention is to provide a monodisperse self-suspending fracturing material and a synthesis device and method for supercritical CO2 fracturing. The monodisperse self-suspending fracturing material with a "core + surface particles" composite structure is synthesized in situ by an in-situ synthesis device. The "core + surface particles" composite structure is analogous to a "planet + satellite" composite structure and can be used for supercritical CO2 fracturing. To achieve the above purpose, the present invention provides the following technical solutions:

[0005] The first object of the present invention is to provide a synthesis device for monodisperse self-suspended fracturing materials for supercritical CO2 fracturing, the synthesis device comprising: a motor, a rotating shaft, a metering injection port, a reactor, a heating jacket, a water bath or an oil bath, a liquid separation tube, a bracket, a stirrer and a vent; wherein,

[0006] The motor is arranged above the rotating shaft, and a first bracket for supporting the motor is arranged between the two. The rotating shaft is arranged above the reactor, and a second bracket for supporting the rotating shaft is arranged between the two. The metering injection port is arranged in the second bracket located above the reactor, and is higher than a part of the second bracket, and the part higher than the second bracket is used to receive the raw material. The agitator is integrated inside the reactor and connected to the rotating shaft. The water bath or oil bath is arranged between the heating jacket and the reactor, and the heating jacket is arranged at the outermost part of the synthesis device. The liquid dispensing tube is arranged at the bottom of the reactor, and passes through the heating jacket to communicate with the external space. The vent is arranged above the first bracket and communicates with the reactor.

[0007] Furthermore, covers or plugs are provided above the metering injection port, the opening of the liquid dispensing tube and the vent hole to keep the reactor in a closed environment.

[0008] Furthermore, the metering injection port is provided with a scale for quantitative injection of raw materials.

[0009] Furthermore, a filter membrane is provided between the liquid separation tube and the bottom of the reactor, so as to allow the liquid phase to pass through but not the solid phase to pass through.

[0010] The second object of the present invention is to provide a method for synthesizing a monodisperse self-suspending fracturing material for supercritical CO2 fracturing, the method comprising the following steps:

[0011] Step S1, adding the reaction raw materials styrene, diethylstyrene, accelerator, initiator, solvent and dispersant into the reactor in prescribed amounts, turning on the heating jacket to raise the temperature to a prescribed temperature, filling the reactor with inert gas through the vent, and after the reaction is completed under stirring conditions, continuing stirring to completely discharge the liquid phase, washing with deionized water, stopping stirring, and completing the core synthesis;

[0012] Step S2, adding the reaction raw materials KH-550 and epoxy resin into the reactor of step S1 according to the prescribed amount, turning on the heating jacket to raise the temperature to the prescribed temperature, filling the reactor with inert gas through the vent, and stopping stirring after the reaction is completed under stirring conditions, completing the in-situ synthesis of the adhesive and coating the surface of the core;

[0013] Step S3, adding the reaction raw material quartz sand into the reactor of step S2 according to the prescribed amount, and after the reaction is completed under stirring conditions, stopping stirring to complete the stage of loading the surface particles on the surface of the core.

[0014] Furthermore, in step S1, the amount of styrene used is 9 L; the amount of diethylstyrene used is 1 L; the promoter is benzoyl peroxide, the amount is 200 g; the initiator is gelatin, the amount is 500 g; the solvent is deionized water, the amount is 75 L, the dispersant is a 1% methylene blue aqueous solution, the amount is 0.1 L; the specified temperature is 80°C; the stirring speed is 1000 r / min; and the reaction time is 4 h.

[0015] Furthermore, in step S2, the amount of KH-550 used is 1 L; the amount of epoxy resin used is 0.1 L; the specified temperature is 60° C.; the stirring speed is 200 r / min; and the reaction time is 3 h.

[0016] Furthermore, in step S3, the amount of quartz sand is 1kg to 4kg; the stirring speed is 1000r / min; and the reaction time is 2h.

[0017] Furthermore, the core has a specification of 40 / 70 mesh and a density of 0.9 g / cm 3 ; The specification of the quartz sand is 100 / 200 mesh.

[0018] The third object of the present invention is to provide a monodisperse self-suspending fracturing material for supercritical CO2 fracturing, wherein the monodisperse self-suspending fracturing material is a composite structure of "core + surface particles"; wherein:

[0019] The core is synthesized from styrene, diethylstyrene, a promoter, an initiator, a solvent and a dispersant;

[0020] The surface particles are loaded on the surface of the core via a binder;

[0021] The adhesive is synthesized by modifying epoxy resin with a silane coupling agent.

[0022] Technical effects and advantages of the present invention:

[0023] Aiming at the technical bottleneck of CO2 fracturing in the current field of CO2 fracturing, that is, the problem of poor sand carrying capacity of CO2 due to the low density and low viscosity of CO2, and the problem of blindly increasing the viscosity of CO2 fracturing fluid, which will cause damage to the reservoir and increase costs, the present invention has designed a monodisperse self-suspending fracturing material, device and method for in-situ synthesis of supercritical CO2 fracturing, specifically, the present invention uses an in-situ synthesis device to in-situ synthesize a monodisperse self-suspending fracturing material with a "planet + satellite" composite structure, which can be used for supercritical CO2 fracturing. The monodisperse self-suspending fracturing material of the "planet + satellite" composite structure of the present invention is composed of a "planet" of a central lightweight high-strength polymer, and quartz sand on the surface of the "planet" as a "satellite". Specifically, the "planet" is synthesized by styrene, diethylstyrene, a promoter, an initiator, and a dispersant, and the "satellite" is loaded on the surface of the "planet" by an adhesive, and the adhesive is obtained by modifying an epoxy resin using a silane coupling agent. The "planet", "satellite", and "planet + satellite" composite structures of the present invention are all synthesized in situ by an in situ synthesis device, without the need for additional equipment. The obtained monodisperse self-suspended fracturing material can be used for supercritical CO2 fracturing, and has the advantages of simple synthesis process, easy equipment operation, and easy promotion. The present invention utilizes the excellent suspension performance of the central lightweight and high-strength polymer to give the "planet + satellite" composite structure the ability to suspend in liquid CO2, which is conducive to promotion in the field of CO2 fracturing and has broad application prospects.

[0024] Other features and advantages of the present invention will be described in the following description, and partly become obvious from the description, or be understood by implementing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 This is a structural diagram of a synthesis device for a monodisperse self-suspended fracturing material for supercritical CO2 fracturing of the present invention;

[0027] Figure 2 This is a flow chart of a method for synthesizing a monodisperse self-suspending fracturing material for supercritical CO2 fracturing of the present invention;

[0028] Figure 3 This is a schematic diagram of the structure of a monodisperse self-suspending fracturing material for supercritical CO2 fracturing of the present invention;

[0029] Figure 4 The surface morphology of the "planet" synthesized in Example 1 of the present invention;

[0030] Figure 5 This is a cross-sectional morphology image of a "planet" synthesized in Example 1 of the present invention;

[0031] Figure 6 This is a surface topography image of the composite structure of "planet + satellite" synthesized in Example 1 of the present invention;

[0032] Figure 7 This is a cross-sectional morphology diagram of the composite structure of a "planet + satellite" synthesized in Example 1 of the present invention;

[0033] Figure 8 This is a schematic diagram of the suspension ability test of the monodisperse self-suspending fracturing material synthesized in Example 1 of the present invention in supercritical CO2;

[0034] In the figure, 1. motor; 2. rotating shaft; 3. metering injection port; 4. reactor; 5. heating jacket; 6. water bath or oil bath; 7. dispensing tube; 81. first bracket; 82. second bracket; 9. agitator; 10. vent. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] In order to solve the deficiencies of the prior art, the present invention discloses a synthesis device for a monodisperse self-suspended fracturing material for supercritical CO2 fracturing. Figure 1 The structure diagram of the synthesis device of a monodisperse self-suspending fracturing material for supercritical CO2 fracturing of the present invention is as follows: Figure 1As shown, the device comprises: a motor 1, a rotating shaft 2, a metering injection port 3, a reactor 4, a heating jacket 5, a water bath or oil bath 6, a liquid dispensing tube 7, a bracket 81-82, a stirrer 9 and a vent 10; wherein,

[0037] The motor 1 is arranged above the rotating shaft 2, and a first bracket 81 for supporting the motor 1 is arranged between the two. The motor 1 provides horizontal rotation power for the rotating shaft 2 and has a speed regulation function;

[0038] The rotating shaft 2 is arranged above the reactor 4, and a second bracket 82 for supporting the rotating shaft 2 is arranged between the two. The rotating shaft 2 provides horizontal rotation power for the reactor 4;

[0039] The metering injection port 3 is arranged in the second bracket 82 located above the reactor 4, and is higher than a portion of the second bracket 82. At the same time, the portion higher than the second bracket 82 is used to receive raw materials, reagents, samples, etc., and is scaled. The knob integrated below the metering injection port 3 can realize quantitative injection;

[0040] The metering injection port 3 has a cover or a plug at the top, which is used to seal the reactor 4 so that the reactor 4 can be in a closed environment;

[0041] The reactor 4 is located below the rotating shaft 2 and is separated by the second bracket 82, providing the necessary reaction space and reaction conditions for the entire synthesis reaction. The raw materials complete the reaction in the reactor 4;

[0042] The heating jacket 5 is arranged at the outermost part of the in-situ synthesis device, close to the water bath or oil bath 6, and is used for temperature control of the reaction process, including programmed temperature rise and constant temperature insulation;

[0043] The water bath or oil bath 6 is disposed between the heating jacket 5 and the reactor 4, and is used to contain a heat transfer medium, including water or silicone oil. The heating jacket 5 is programmed to increase the temperature, and the reactor 4 is made to reach a predetermined temperature by the heat transfer medium, and the temperature is kept constant by program control;

[0044] The liquid separator 7 is arranged at the bottom of the reactor 4 and penetrates the heating jacket 5, communicates with the external space and the atmosphere, and is used to discharge the liquid phase after the stage reaction and the whole reaction of the reactor 4 are completed. The rotating motion of the stirrer 9 is used to provide centrifugal force to the liquid phase, so that the liquid phase can be quickly discharged from the liquid separator 7. The opening of the liquid separator 7 is provided with a cover or a plug, which is used to seal the reactor 4 so that the reactor 4 can be in a closed environment. The liquid separator 7 and the bottom of the reactor 4 are provided with a filter membrane, which can allow the liquid phase to pass through, but not the solid phase.

[0045] The first bracket 81 and the second bracket 82 are both mechanical structural components, used to support and fix the motor 1, the rotating shaft 2, and the reactor 4;

[0046] The stirrer 9 is integrated inside the reactor 4 and below the rotating shaft 2, and provides stirring power for the reaction in the reactor 4. The stirring rate is controlled by the motor 1, so that the raw materials are mixed evenly, which can accelerate the reaction rate. It also has the function of enabling the liquid phase to be quickly discharged from the liquid separation tube 7;

[0047] The vent hole 10 is disposed above the first bracket 81 and is connected to the reactor 4 for introducing an inert gas, including nitrogen, helium, etc., into the reactor 4. The vent hole 10 has a cover or a plug at the top for sealing the reactor 4 so that the reactor 4 can be in a closed environment.

[0048] The present invention also discloses a method for synthesizing a monodisperse self-suspending fracturing material for supercritical CO2 fracturing. Figure 2 The flow chart of the synthesis method of a monodisperse self-suspending fracturing material for supercritical CO2 fracturing of the present invention is as follows: Figure 2 As shown, the method comprises the following steps:

[0049] Step S1, "planet" synthesis: 9L of styrene, 1L of diethylstyrene, 200g of benzoyl peroxide, 500g of gelatin, 75L of deionized water, and 0.1L of a 1% methylene blue aqueous solution are used as reaction raw materials for actual synthesis; keep the lid or plug of the liquid separatory tube 7 closed, add heat transfer medium to the water bath or oil bath 6, turn on the heating jacket 5 for program heating, and after reaching the specified temperature (80°C), keep the temperature constant by program control; open the lid or plug of the metering injection port 3, add the raw materials into the reactor 4 according to the specified amount through the metering injection port 3, close the lid or plug of the metering injection port 3, and keep the reactor 4 in a closed state; pass the vent 10 to the reactor Inert gas is introduced into the reactor 4. After the reactor 4 is completely filled with inert gas, the cover or plug of the vent 10 is closed to keep the reactor 4 in a sealed state of inert gas; the motor 1 is turned on to provide horizontal rotation power for the shaft 2, and the shaft 2 drives the stirrer 9 to stir continuously at a speed of 1000r / min, so that the raw materials are mixed evenly and the reaction rate can be accelerated; after the reaction is completed for 4h, the cover or plug of the liquid separation tube 7 and the cover or plug of the metering injection port 3 are opened, and the stirrer 9 is kept stirring. After the liquid phase is completely discharged, 100L of deionized water is used for washing. After the liquid phase is completely discharged, the cover or plug of the liquid separation tube 7 is closed, and the stirring of the stirrer 9 is stopped to complete the "planetary" synthesis stage;

[0050] Step S2, the adhesive is synthesized in situ and coated on the surface of the "planet": 1L of KH-550 and 0.1L of epoxy resin are used as raw materials to synthesize the adhesive. The actual synthesis can be based on this ratio as raw materials. In step S1, the raw materials are added to the "planet" system, the lid or plug of the liquid dispensing tube 7 is kept closed, the heating jacket 5 is turned on for program heating, and after the specified temperature (60°C) is reached, the constant temperature is controlled by the program; the lid or plug of the metering injection port 3 is opened, and the raw materials are added to the reactor 4 according to the specified amount through the metering injection port 3, and the lid or plug of the metering injection port 3 is closed, and the temperature is kept constant. The reactor 4 is kept in a closed state; an inert gas is introduced into the reactor 4 through the vent 10, and after the reactor 4 is completely filled with the inert gas, the cover or plug of the vent 10 is closed to keep the reactor 4 in a closed state of the inert gas; the motor 1 is turned on to provide horizontal rotation power for the shaft 2, and the shaft 2 drives the stirrer 9 to stir continuously at a speed of 200r / min, so that the raw materials are mixed evenly and the reaction rate can be accelerated; after the reaction is completed for 3h, the heating jacket 5 is turned off to increase the temperature program, and the stirrer 9 is stopped to stir, and the in-situ synthesis of the adhesive and the coating on the surface of the "planet" are completed;

[0051] Step S3, "satellite" is loaded on the surface of the "planet": 1kg to 4kg of quartz sand is used as the "satellite", and the actual synthesis can be used as the "satellite" according to this ratio, and loaded on the surface of the "planet" through the adhesive. In step S2, the "satellite" is added to the adhesive-coated "planet" system, and the lid or plug of the liquid separation tube 7 is kept in a closed state; the lid or plug of the metering injection port 3 is opened, and the "satellite" is added to the reactor 4 according to the specified amount through the metering injection port 3, and the lid or plug of the metering injection port 3 is closed to keep the reactor 4 in a closed state; the lid or plug of the vent 10 is closed to keep the reactor 4 in a closed state; the motor 1 is turned on to provide horizontal rotation power for the rotating shaft 2, and the rotating shaft 2 drives the stirrer 9 to stir continuously at a speed of 1000r / min, so that the raw materials are mixed evenly, which can accelerate the loading rate; after the loading is completed for 2h, the stirrer 9 is stopped to stir, and the "satellite" is loaded on the surface of the "planet" The stage is completed, and the sample is collected to obtain a monodisperse self-suspended fracturing material for supercritical CO2 fracturing.

[0052] It should be noted that the ratio of styrene, diethylstyrene, benzoyl peroxide, gelatin, deionized water, 1% methylene blue aqueous solution, KH-550, epoxy resin, and quartz sand is 9L: 1L: 200g: 500g: 75L: 0.1L: 1L: 0.1L: 1kg to 4kg. The actual production can be converted in proportion according to this ratio; the specification of the "planet" is 40 / 70 mesh and the density is 0.9g / cm 3 ; The specification of the quartz sand is 100 / 200 mesh.

[0053] Based on the above device and method, the present invention also discloses a monodisperse self-suspending fracturing material for supercritical CO2 fracturing. Figure 3 FIG. 1 is a schematic diagram of the structure of a monodisperse self-suspending fracturing material for supercritical CO2 fracturing of the present invention. Figure 3 As shown, the monodisperse self-suspended fracturing material is a "planet + satellite" composite structure, consisting of a "planet" of a lightweight high-strength polymer in the center and quartz sand on the surface of the "planet" as a "satellite", which can be used for supercritical CO2 fracturing; wherein,

[0054] The "planet" is synthesized from styrene, diethylstyrene, a promoter, an initiator and a dispersant.

[0055] The "satellite" is supported on the surface of the "planet" by an adhesive.

[0056] The adhesive is obtained by modifying epoxy resin with a silane coupling agent.

[0057] Example 1

[0058] Embodiment 1 of the present invention discloses a method for synthesizing a monodisperse self-suspending fracturing material for supercritical CO2 fracturing, the method comprising the following steps:

[0059] Step S1, "planet" synthesis: 9L styrene, 1L diethylstyrene, 200g benzoyl peroxide, 500g gelatin, 75L deionized water, and 0.1L 1% methylene blue aqueous solution are used as raw materials; keep the lid of the separatory tube closed, add heat transfer medium to the water bath or oil bath, turn on the heating jacket to program the temperature, and after the temperature is raised to 80°C, keep the temperature constant by program control; open the lid of the raw material metering injection port, add the raw material into the reactor according to the specified amount through the metering injection port, close the lid of the metering injection port, and keep the reactor in a closed state; introduce inert gas into the reactor through the vent hole After the reactor is completely filled with inert gas, close the cover of the vent to keep the reactor in a closed state of inert gas; turn on the motor to provide horizontal rotation power for the shaft, and the shaft drives the agitator to stir continuously at a speed of 1000r / min to mix the raw materials evenly and accelerate the reaction rate; after the reaction is completed for 4h, open the cover of the separatory tube and the cover of the metering injection port, keep the agitator stirring continuously, and after the liquid phase is completely discharged, use 100L deionized water to wash, and after the liquid phase is completely discharged, close the cover or plug of the separatory tube, stop the agitator stirring, and complete the "planetary" synthesis stage. Figure 4 This is a surface topography of a "planet" synthesized in Example 1 of the present invention, such as Figure 4 As shown, the obtained "planets" are all spherical in shape, with smooth outer surfaces and relatively uniform sizes. Figure 5 This is a cross-sectional morphology image of a "planet" synthesized in Example 1 of the present invention, such as Figure 5As shown, the obtained "planets" are all solid structures with uniform organizational morphology, which is conducive to the next step of loading.

[0060] Step S2, in-situ synthesis of adhesive and coating on the surface of the "planet": then use 1L of KH-550 and 0.1L of epoxy resin to synthesize the adhesive, keep the lid of the dispensing tube in a closed state, adjust the program temperature of the heating jacket to 60°C, and after the temperature reaches 60°C, control the constant temperature by program; open the lid or plug of the raw material metering injection port, add the raw material into the reactor according to the specified amount through the metering injection port, close the lid of the metering injection port, and keep the reactor in a closed state; introduce inert gas into the reactor through the vent, and after the reactor is completely filled with inert gas, close the lid of the vent to keep the reactor in a closed state of inert gas; turn on the motor to enable the motor to provide horizontal rotation power for the shaft, and the shaft drives the stirrer to stir continuously at a speed of 200r / min, so that the raw materials are evenly mixed, which can accelerate the reaction rate; after the reaction is completed for 3h, turn off the heating jacket program temperature increase, stop the stirrer stirring, and complete the in-situ synthesis of the adhesive and coating on the surface of the "planet".

[0061] Step S3, "satellite" loaded on the surface of "planet": 1kg quartz sand is used as "satellite", and the lid or plug of the dispensing tube is kept in a closed state; the lid of the metering injection port for raw materials is opened, and the "satellite" is added into the reactor according to the prescribed amount through the metering injection port, and the lid of the metering injection port is closed to keep the reactor in a closed state; the lid of the vent is closed to keep the reactor in a closed state; the motor is turned on to provide horizontal rotation power for the rotating shaft, and the rotating shaft drives the agitator to continuously stir at a speed of 1000r / min, so that the raw materials are mixed evenly, which can accelerate the loading rate; after the loading is completed for 2h, the agitator is stopped to stir, and the "satellite" is loaded on the surface of the "planet" to complete the stage, and the sample is collected to obtain a monodisperse self-suspended fracturing material for supercritical CO2 fracturing. Figure 6 This is a surface morphology image of the composite structure of "planet + satellite" synthesized in Example 1 of the present invention, such as Figure 6 As shown, there are a large number of "satellites" on the surface of the "planet" and the outer surface is rough. Figure 7 This is a cross-sectional morphology diagram of the composite structure of "planet + satellite" synthesized in Example 1 of the present invention, as shown in Figure 7 As shown, the resulting "planet + satellite" composite structure consists of a relatively large "planet" in the center and multiple relatively small "satellites" on its outer surface, indicating that the surface of the "planet" is loaded with a large number of "satellites".

[0062] The monodisperse self-suspending fracturing material synthesized in the above steps was tested for its suspension ability in supercritical CO2. Figure 8 This is a schematic diagram of the test of the suspension ability of the monodisperse self-suspending fracturing material synthesized in Example 1 of the present invention in supercritical CO2. Figure 8As shown in the figure, the test equipment is a supercritical CO2 visualization device, the internal liquid phase is supercritical CO2, the black suspension is a "planet + satellite" composite structure, and the self-suspension performance test of the "planet + satellite" composite structure is completed using a liquid CO2 visualization device. Below the transparent liquid surface is liquid CO2, and the small black particles are the "planet + satellite" composite structure and are suspended in liquid CO2. The results show that the obtained "planet + satellite" composite structure has excellent suspension performance. The performance results of the obtained samples are shown in Table 1.

[0063] Example 2

[0064] The difference between Example 2 of the present invention and Example 1 is that the amount of "satellite" used is 2 kg. The performance results of the obtained samples are shown in Table 1.

[0065] Example 3

[0066] The difference between Example 3 of the present invention and Example 1 is that the amount of "satellite" used is 3 kg. The performance results of the obtained samples are shown in Table 1.

[0067] Example 4

[0068] The difference between Example 4 of the present invention and Example 1 is that the amount of "satellite" used is 4 kg. The performance results of the obtained samples are shown in Table 1.

[0069] Table 1 Self-suspension properties of monodisperse self-suspension fracturing materials for supercritical CO2 fracturing

[0070] Serial number Self-suspension performance Performance Evaluation Example 1 float excellent Example 2 Suspension + Floating Better Example 3 Suspension good Example 4 Suspension + Sedimentation generally

[0071] Examples 1-4 are monodisperse self-suspending fracturing materials for supercritical CO2 fracturing obtained with different amounts of "satellite" (quartz sand): the ratio of styrene, diethylstyrene, benzoyl peroxide, gelatin, deionized water, 1% methylene blue aqueous solution, KH-550, and epoxy resin is 9L:1L:200g:500g:75L:0.1L:1L:0.1L, which remains unchanged; the changed amounts of "satellite" are 1kg, 2kg, 3kg, and 4kg, respectively. The examples illustrate the suspension performance of the monodisperse self-suspending fracturing materials for supercritical CO2 fracturing in supercritical CO2.

[0072] It can be seen from Examples 1-4 and Table 1 that as the amount of "satellites" increases, the self-suspension performance of the monodisperse self-suspension fracturing material for supercritical CO2 fracturing shows a trend of decreasing. This is because the density of the "satellites" is greater than 1g / cm 3 , supercritical CO2 density equals 1g / cm 3As the use of "satellites" continues to increase, the density of monodisperse self-suspending fracturing materials for supercritical CO2 fracturing continues to increase, reducing the self-suspending performance. The appropriate ratio can be selected according to actual needs and working conditions for supercritical CO2 fracturing.

[0073] By comparing the results of the above embodiments, it can be seen that the method and product of in-situ synthesis of monodisperse self-suspending fracturing materials for supercritical CO2 fracturing provided by the present invention can obtain monodisperse self-suspending fracturing materials with a "planet + satellite" composite structure, which can be used for supercritical CO2 fracturing, and can effectively solve the technical bottleneck of CO2 fracturing in the current CO2 fracturing field from the perspective of material design. Since in-situ synthesis does not require additional equipment, the obtained monodisperse self-suspending fracturing material can be used for supercritical CO2 fracturing, and has the advantages of simple synthesis process, easy equipment operation, and easy promotion, and can be promoted and applied in the field of fracturing materials for the oil and gas industry.

[0074] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A synthesis device for monodisperse self-suspending fracturing material for supercritical CO2 fracturing, characterized in that: The synthesis device comprises: a motor (1), a rotating shaft (2), a metering injection port (3), a reactor (4), a heating jacket (5), a water bath or an oil bath (6), a liquid dispensing tube (7), a bracket (81-82), a stirrer (9) and a vent (10); wherein: The motor (1) is arranged above the rotating shaft (2), and a first bracket (81) for supporting the motor (1) is arranged between the two. The rotating shaft (2) is arranged above the reactor (4), and a second bracket (82) for supporting the rotating shaft (2) is arranged between the two. The metering injection port (3) is arranged in the second bracket (82) located above the reactor (4), and is higher than a part of the second bracket (82), and the part higher than the second bracket (82) is used to receive raw materials. The stirrer (9) is integrated into the reactor (4) and connected to the rotating shaft (2). The water bath or oil bath (6) is arranged between the heating jacket (5) and the reactor (4), and the heating jacket (5) is arranged at the outermost part of the synthesis device. The liquid dispensing tube (7) is arranged at the bottom of the reactor (4), and passes through the heating jacket (5) to communicate with the external space. The vent (10) is arranged above the first bracket (81) and communicates with the reactor (4).

2. The synthesis device of a monodisperse self-suspending fracturing material for supercritical CO2 fracturing according to claim 1, characterized in that: A lid or a plug is provided above the metering injection port (3), the opening of the liquid dispensing tube (7) and the vent hole (10) to place the reactor (4) in a closed environment.

3. A synthesis device for a monodisperse self-suspended fracturing material for supercritical CO2 fracturing according to claim 1 or 2, characterized in that: The metering injection port (3) is provided with a scale for quantitative injection of raw materials.

4. The synthesis device of a monodisperse self-suspended fracturing material for supercritical CO2 fracturing according to claim 2, characterized in that: The liquid separation tube (7) and the bottom of the reactor (4) are provided with a filter membrane for allowing the liquid phase to pass through but preventing the solid phase from passing through.

5. A method for synthesizing a monodisperse self-suspending fracturing material for supercritical CO2 fracturing, the method using a synthesis device as described in any one of claims 1 to 4, characterized in that: The method comprises the following steps: Step S1, adding the reaction raw materials of styrene, diethylstyrene, accelerator, initiator, solvent and dispersant into the reactor (4) in a prescribed amount, turning on the heating jacket (5) to raise the temperature to a prescribed temperature, filling the reactor (4) with an inert gas through the vent (10), and after the reaction is completed under stirring conditions, continuing stirring to completely discharge the liquid phase, washing with deionized water, stopping stirring, and completing the core synthesis; Step S2, adding the reaction raw materials KH-550 and epoxy resin into the reactor (4) of step S1 in a specified amount, turning on the heating jacket (5) to raise the temperature to a specified temperature, filling the reactor (4) with inert gas through the vent (10), and stopping stirring after the reaction is completed under stirring conditions, thereby completing the in-situ synthesis of the adhesive and coating the core surface; Step S3, adding the reaction raw material quartz sand into the reactor (4) of step S2 according to the prescribed amount, and after the reaction is completed under stirring conditions, stopping the stirring to complete the loading of the surface particles on the surface of the core.

6. The method for synthesizing a monodisperse self-suspending fracturing material for supercritical CO2 fracturing according to claim 5, characterized in that: In step S1, the amount of styrene used is 9L; the amount of diethylstyrene used is 1L; the promoter is benzoyl peroxide, the amount is 200g; the initiator is gelatin, the amount is 500g; the solvent is deionized water, the amount is 75L, the dispersant is a 1% methylene blue aqueous solution, the amount is 0.1L; the specified temperature is 80°C; the stirring speed is 1000r / min; the reaction time is 4h.

7. The method for synthesizing a monodisperse self-suspending fracturing material for supercritical CO2 fracturing according to claim 5, characterized in that: In step S2, the amount of KH-550 used is 1 L; the amount of epoxy resin used is 0.1 L; the specified temperature is 60° C.; the stirring speed is 200 r / min; and the reaction time is 3 h.

8. The method for synthesizing a monodisperse self-suspending fracturing material for supercritical CO2 fracturing according to claim 5, characterized in that: In step S3, the amount of quartz sand is 1kg to 4kg; the stirring speed is 1000r / min; and the reaction time is 2h.

9. The method for synthesizing a monodisperse self-suspending fracturing material for supercritical CO2 fracturing according to claim 5, characterized in that: The core has a specification of 40 / 70 mesh and a density of 0.9 g / cm 3 ; The specification of the quartz sand is 100 / 200 mesh.

10. A monodisperse self-suspending fracturing material for supercritical CO2 fracturing, synthesized by the method according to any one of claims 5 to 9, characterized in that: The monodisperse self-suspended fracturing material is a composite structure of "core + surface particles"; wherein, The core is synthesized from styrene, diethylstyrene, a promoter, an initiator, a solvent and a dispersant; The surface particles are loaded on the surface of the core via a binder; The adhesive is synthesized by modifying epoxy resin with a silane coupling agent.

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