Fracturing agent for interlayer type shale oil and preparation process of fracturing agent

Abstract

The invention relates to the technical field of preparation of fracturing agents for rock oil, in particular to a fracturing agent for interlayer type shale oil and a preparation process of the fracturing agent for the interlayer type shale oil. The solute and suspended particles of the fracturing agent comprise 20 to 25 parts of poly dimethyl diallyl ammonium chloride, 19 to 22 parts of PNIPAM, 5 to 7 parts of nano silicon dioxide, 11 to 17 parts of a tackifier, 11 to 17 parts of sodium dodecyl benzene sulfonate, 6 to 6.5 parts of chopped carbon fibers, 2 to 4 parts of ammonium persulfate, 2 to 2.5 parts of MB resin, 1 to 1.6 parts of hydroxylamine hydrochloride, 5 to 5.5 parts of rhamnolipid, 3 to 4 parts of xanthan gum and 4 to 6 parts of lauryl sodium sulfate. The anti-swelling agent solution formed by properly stirring the water and the poly dimethyl diallyl ammonium chloride according to a specific proportion can effectively prevent the clay from swelling when encountering water, and ensures that pores of a reservoir are unblocked; nano silicon dioxide is uniformly dispersed in a PNIPAM solution through ultrasound to prepare a regulator solution, self-adaptive regulation can be performed according to reservoir pressure, and the composite microspheres prepared from MB resin and hydroxylamine hydrochloride can achieve a targeting effect, so that the recovery efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of fracturing agents for rock oil, and specifically relates to a fracturing agent for interbedded shale oil and its preparation process. Background Art

[0002] With the gradual reduction of traditional oil resources, the exploitation of shale oil has become one of the key ways to meet energy demands. Shale oil reservoirs are characterized by low porosity, low permeability, and complex geological structures, which make it difficult to exploit shale oil by conventional means. Fracturing technology is the core technology to improve the recovery rate of shale oil. Its basic principle is to inject fracturing agents into the shale oil reservoir under high pressure, causing the reservoir rock to fracture and form a fracture network, thereby increasing the oil flow channels and improving the permeability.

[0003] At present, there are various fracturing agents on the market, but their applications in the exploitation of interbedded shale oil have certain limitations. These limitations include insufficient adaptability to the reservoir. Existing fracturing agents are difficult to adapt to the special properties of interbedded shale oil reservoirs, resulting in poor fracturing effects. Interbedded shale oil reservoirs have unique rock mineral compositions, such as high contents of clay minerals. Clay minerals are prone to swelling when exposed to water, and many existing fracturing agents bring a large amount of water during the injection process, which will cause changes in the physical and chemical properties of the reservoir rock, further blocking the pore throats of the reservoir with low porosity and low permeability, hindering the flow channels of shale oil, and thus reducing the fracturing effect.

[0004] At the same time, the pressure system of interbedded shale oil reservoirs is relatively complex, significantly different from that of conventional shale oil reservoirs. Existing fracturing agents cannot well match this complex pressure system in terms of pressure response. There may be situations such as too fast decomposition of the agent under high pressure or ineffective performance under low pressure, and it is impossible to accurately form an effective fracture network in the reservoir as expected, resulting in ineffective improvement of the recovery rate of shale oil.

[0005] Moreover, when existing fracturing agents are used to treat interbedded shale oil reservoirs, their adaptability to different interlayer structures is poor. Interbedded shale oil reservoirs often have a multi-layer structure, and there are significant variations in physical properties and rock mechanical properties between layers. Existing fracturing agents are difficult to carry out effective fracturing operations for this complex multi-layer structure, thereby affecting the overall exploitation efficiency. Summary of the Invention

[0006] In order to solve the above problems, the present invention provides a fracturing agent for interbedded shale oil and its preparation process.

[0007] The technical solution of the present invention is: A fracturing agent for interlayer shale oil and its preparation process. The solvent is water. By mass ratio, the solute and suspended particles of the fracturing agent include 20 - 25 parts of polydimethyldiallylammonium chloride, 19 - 22 parts of PNIPAM, 5 - 7 parts of nano-silica, 11 - 17 parts of viscosifier, 11 - 17 parts of sodium dodecylbenzenesulfonate, 6 - 6.5 parts of short carbon fiber, 2 - 4 parts of ammonium persulfate, 2 - 2.5 parts of MB resin, 1 - 1.6 parts of hydroxylamine hydrochloride, 5 - 5.5 parts of rhamnolipid, 3 - 4 parts of xanthan gum, and 4 - 6 parts of sodium dodecyl sulfate.

[0008] Note: As a derivative of guar gum, hydroxypropyl guar gum has excellent viscosity-increasing performance. During the fracturing process, it can significantly increase the viscosity of the fracturing agent, helping to carry the proppant smoothly to the fracture site. When the pressure is released, the proppant can effectively support the fracture, while reducing the filtration loss of the agent in the reservoir; Sodium dodecylbenzenesulfonate is a surfactant that can effectively reduce the interfacial tension between different interlayers, enabling the agent to better penetrate into each layer structure; After the fracturing operation is completed, ammonium persulfate decomposes to generate free radicals, triggering the degradation of components such as polymers in the fracturing agent, thereby reducing the viscosity of the fracturing agent and enabling it to flow back from the reservoir smoothly, thus reducing the damage to the reservoir.

[0009] Furthermore, a preparation process for a fracturing agent for interlayer shale oil includes the following steps:

[0010] S1. Add water and polydimethyldiallylammonium chloride with a mass ratio of 5:1 - 3 to the reaction kettle in sequence, continuously stir for 40 - 60 min, and the stirring speed is 350 - 550 r / min to obtain an anti-swelling agent solution;

[0011] S2. Dissolve PNIPAM in an organic solvent to obtain a PNIPAM solution with a mass concentration of 10 - 20%, and add nano-silica under ultrasonic conditions. The ultrasonic power is 150 - 350 W, and the ultrasonic time is 30 - 50 min to uniformly disperse the nano-particles in the polymer solution to obtain a regulator solution;

[0012] S3. The preparation method of the viscosifier is: Add hydroxypropyl guar gum to water at a temperature of 50 - 60 °C. The mass of hydroxypropyl guar gum accounts for 2 - 5% of the total mass of the viscosifier, and stir evenly to obtain the viscosifier;

[0013] S4. Dissolve sodium dodecylbenzenesulfonate in water to obtain a sodium dodecylbenzenesulfonate solution with a mass concentration of 5 - 10%, then add short carbon fibers with a length of 2 - 5 mm. The addition amount of the short carbon fibers is 1 - 5% of the mass of the sodium dodecylbenzenesulfonate solution. At the same time, stir at a stirring speed of 200 - 400 r / min for 45 - 65 min to obtain a structure adapter solution; dissolve ammonium persulfate in water and stir until completely dissolved to obtain an ammonium persulfate solution with a mass concentration of 0.5 - 1.5%; mix rhamnolipid and xanthan gum according to the formula ratio to obtain a synergist solution;

[0014] S5. Add the weighed hydroxylamine hydrochloride to ethanol. The mass ratio of hydroxylamine hydrochloride to ethanol is 1:3. Stir evenly while adding to obtain a hydroxylamine hydrochloride solution; add MB resin and sodium dodecyl sulfate to the hydroxylamine hydrochloride solution according to the formula ratio and stir for 10 - 30 min at a stirring speed of 500 - 1500 r / min to obtain a pre-emulsion; add an initiator to the pre-emulsion and carry out a polymerization reaction at a temperature of 60 - 80 °C for 2 - 6 h to obtain a microsphere suspension; perform centrifugation, washing, drying and screening on the microsphere suspension to obtain composite microspheres;

[0015] S6. Mix the anti-swelling agent solution, regulator solution, viscosifier, structure adapter solution, ammonium persulfate solution, synergist solution and composite microspheres prepared in the steps S1 - S5 above, and stir at a speed of 200 - 300 r / min for 30 - 45 min to ensure that each component is fully mixed evenly to obtain a fracturing agent for interlayer shale oil.

[0016] Note: In the preparation of the anti-swelling agent solution, the anti-swelling agent solution formed by appropriately stirring a specific ratio of water and polydimethyldiallylammonium chloride can effectively prevent clay from swelling in water and ensure the smoothness of reservoir pores; the regulator solution prepared by uniformly dispersing nano-silica in the PNIPAM solution through ultrasound can adaptively adjust according to the reservoir pressure and improve the recovery rate; the viscosifier prepared from hydroxypropyl guar gum helps to carry the proppant to the fracture site and reduce filtration loss; the structure adapter solution prepared from the sodium dodecylbenzenesulfonate solution and short carbon fibers can reduce the interfacial tension and form a bridging effect; the ammonium persulfate solution is used for subsequent gel breaking, and the synergist solution mixed with rhamnolipid and xanthan gum can improve the oil displacement efficiency and the stability of the agent; the composite microspheres prepared from MB resin and hydroxylamine hydrochloride can have a targeted effect; finally, mixing each component can give full play to the synergistic effect, and the obtained fracturing agent meets the requirements of interlayer shale oil exploitation and improves the exploitation effect.

[0017] Further, the organic solvent in S2 is dimethylformamide.

[0018] Description: Dimethylformamide is a high-boiling hydrophilic aprotic solvent that can dissolve a variety of organic and inorganic substances, including components such as PNIPAM and nano-silica, which helps to form a uniform regulator solution.

[0019] Furthermore, the particle size of the nano-silica described in S2 is 15 - 75 nm.

[0020] Description: The smaller particle size enables it to penetrate into the tiny pores of the reservoir. Under different pressure conditions, when interacting with other reagent components synergistically, it can respond more precisely to the reservoir characteristics. It has a large specific surface area and can interact better with PNIPAM.

[0021] Furthermore, the stirring speed in S3 is 400 - 600 r / min, and the stirring time is 60 - 90 min until the hydroxypropyl guar gum is completely dissolved to obtain a viscosifier.

[0022] Description: Appropriate stirring speed and sufficient stirring time can ensure that the hydroxypropyl guar gum is fully and evenly dissolved in water. Sufficient stirring speed helps to overcome the intermolecular forces of the hydroxypropyl guar gum molecules, enabling the molecules to quickly diffuse in the solvent. Controlling the stirring time ensures the thoroughness of the dissolution process. The viscosifier obtained in this way has stable and reliable viscosity-increasing performance. During the fracturing process, it can more effectively increase the viscosity of the fracturing agent, thus better carrying the proppant to reach the fracture site smoothly. And after the pressure is released, the proppant can effectively support the fracture, while reducing the filtration loss of the agent in the reservoir and improving the overall effect of the fracturing operation.

[0023] Furthermore, in S5, the temperature of the hydroxylamine hydrochloride solution is controlled at 25 - 35 °C, the stirring speed is 100 - 200 r / min, and the stirring time is 20 - 40 min.

[0024] Description: Within this temperature range, the dissolution process of hydroxylamine hydrochloride in ethanol is relatively stable. It will neither dissolve too slowly due to too low temperature nor cause side reactions or affect its chemical activity due to too high temperature. Controlling the stirring speed and stirring time can make the hydroxylamine hydrochloride fully and evenly dissolve in ethanol to obtain a hydroxylamine hydrochloride solution with better homogeneity, which helps to mix evenly with the MB resin subsequently, ensuring the preparation quality of the composite microspheres, and enabling the composite microspheres to better play the role of their internal active substances during the shale oil exploitation process.

[0025] Furthermore, in S5, the initiator is azobisisobutyronitrile, and the addition amount of the initiator is 0.1 - 1% of the mass of the pre-emulsion.

[0026] Description: Azobisisobutyronitrile can decompose to generate free radicals at an appropriate temperature, thereby effectively initiating a polymerization reaction; by controlling the addition amount of azobisisobutyronitrile, the rate and degree of the polymerization reaction can be precisely controlled, so as to obtain the desired polymer properties.

[0027] Further, the method for centrifuging, washing, drying and sieving the microsphere suspension described in S5 is as follows: introducing the microsphere suspension into a centrifuge tube and centrifuging at a speed of 3000 - 5000 r / min for 4 - 8 min to precipitate the microspheres at the bottom of the centrifuge tube, then pouring off the supernatant, adding water until the microspheres are resuspended, repeating the centrifugation operation to precipitate the microspheres at the bottom of the centrifuge tube, then pouring off the supernatant, repeating the water addition and centrifugation washing 3 - 7 times, putting the washed microspheres into a vacuum drying oven, setting the temperature at 30 - 50 °C and the vacuum degree at 0.08 - 0.1 MPa, drying until the microspheres reach a constant weight, and sieving to obtain composite microspheres with a particle size of 1 - 80 μm.

[0028] Description: The centrifugation speed of 3000 - 5000 r / min and the centrifugation time of 4 - 8 min can effectively precipitate the microspheres at the bottom of the centrifuge tube, realizing the preliminary separation of the microspheres from the supernatant. This process is efficient and can ensure the relative integrity of the microsphere precipitation; after pouring off the supernatant, adding water to resuspend the microspheres and then centrifuging and washing multiple times can thoroughly remove the impurities on the surface of the microspheres and improve the purity of the microspheres; appropriate temperature and vacuum degree can not only ensure the effective removal of moisture in the microspheres, but also prevent damage to the microspheres due to too high temperature or vacuum degree; finally, sieving to obtain composite microspheres with appropriate particle size can ensure that the particle size of the microspheres meets the requirements, so that in the process of shale oil exploitation, the composite microspheres can better adapt to the pore structure of the reservoir.

[0029] The beneficial effects of the present invention are:

[0030] In the present invention, through the organic cationic polymer poly(dimethyldiallylammonium chloride), it adheres to the surface of clay minerals by electrostatic adsorption to form a protective film, effectively preventing the clay mineral layer from swelling when encountering water, thereby maintaining the smoothness of the pore throats in the reservoir and ensuring the smooth flow of shale oil; the regulator composed of PNIPAM and nano-silica can adaptively adjust according to the complex pressure system of the interlayered shale oil reservoir, maintain the stability of the medicament under high pressure, and avoid too fast decomposition; under low pressure, it can form an effective fracture network in the reservoir to improve the recovery rate of shale oil; the short carbon fiber has high strength and good dispersibility, and can form a bridging effect in each layer structure, contributing to the formation of effective fractures penetrating multiple layer structures and enhancing the adaptability to the multi-layer structure of the interlayered shale oil reservoir.

[0031] The polymer shell of the composite microspheres is composed of MB resin that has an affinity for polycyclic aromatic hydrocarbons in shale oil, which can capture the shale oil components in the reservoir during the injection process and actively flow to the key areas in the reservoir; hydroxylamine hydrochloride that can dissolve some carbonate minerals is used as the internal active substance of the composite microspheres. When the composite microspheres reach the target position, the internal active substance is released to dissolve some rock minerals to expand the pores, further improving the effect of the agent on the complex reservoir structure; rhamnolipid can significantly reduce the interfacial tension between oil and water and improve the oil displacement efficiency; xanthan gum can enhance the stability of the agent, and its unique molecular structure helps to improve the distribution and effect of the agent in the reservoir. Description of the Drawings

[0032] Figure 1 It is a bar chart of the demulsification rate test of the samples of Examples 1-3, 6, 7, 10-13, 20, 21 and Comparative Examples 1-4 of the present invention;

[0033] Figure 2 It is a bar chart of the surface tension test of the samples of Examples 1-3, 6, 7, 10-13, 20, 21 and Comparative Examples 1-4 of the present invention;

[0034] Figure 3 It is a bar chart of the interfacial tension test of the samples of Examples 1-3, 6, 7, 10-13, 20, 21 and Comparative Examples 1-4 of the present invention;

[0035] Figure 4 It is a bar chart of the drag reduction rate test of the samples of Examples 1-3, 6, 7, 10-13, 20, 21 and Comparative Examples 1-4 of the present invention. Detailed Embodiments

[0036] To further illustrate the methods adopted and the effects achieved by the present invention, the technical solutions of the present invention will be clearly and completely described below in combination with experiments.

[0037] Example 1:

[0038] A fracturing agent for interlayer shale oil and its preparation process, the solvent is water. By mass fraction ratio, the solute and suspended particles of the fracturing agent include 22.5 parts of polydimethyldiallylammonium chloride, 20.5 parts of PNIPAM, 6 parts of nano-silica, 14 parts of thickener, 14 parts of sodium dodecylbenzenesulfonate, 6.25 parts of short carbon fiber, 3 parts of ammonium persulfate, 2.25 parts of MB resin, 1.3 parts of hydroxylamine hydrochloride, 5.25 parts of rhamnolipid, 3.5 parts of xanthan gum and 5 parts of sodium dodecyl sulfate;

[0039] The preparation process includes the following steps:

[0040] S1. Add water and poly(dimethyldiallylammonium chloride) with a mass ratio of 5:2 into the reactor in sequence, continuously stir for 50 min at a stirring speed of 450 r / min to obtain an anti-swelling agent solution;

[0041] S2. Dissolve PNIPAM in an organic solvent to obtain a PNIPAM solution with a mass concentration of 15%. Add nano-silica under ultrasonic conditions. The ultrasonic power is 250 W and the ultrasonic time is 40 min to uniformly disperse the nano-particles in the polymer solution to obtain a regulator solution. The organic solvent is dimethylformamide. The particle size of the nano-silica is 50 - 60 nm;

[0042] S3. The preparation method of the viscosifier is as follows: Add hydroxypropyl guar gum into water at a temperature of 55 °C. The mass of hydroxypropyl guar gum accounts for 3.5% of the total mass of the viscosifier. Stir evenly to obtain the viscosifier. The stirring speed is 500 r / min and the stirring time is 75 min until the hydroxypropyl guar gum is completely dissolved to obtain the viscosifier;

[0043] S4. Dissolve sodium dodecylbenzenesulfonate in water to obtain a sodium dodecylbenzenesulfonate solution with a mass concentration of 7.5%. Then add short-cut carbon fibers with a length of 3.2 - 3.6 mm. The addition amount of the short-cut carbon fibers is 2.5% of the mass of the sodium dodecylbenzenesulfonate solution. Stir simultaneously at a stirring speed of 300 r / min for 55 min to obtain a structure adaptor solution. Dissolve ammonium persulfate in water and stir until completely dissolved to obtain an ammonium persulfate solution with a mass concentration of 1%. Mix rhamnolipid and xanthan gum according to the formula ratio to obtain a synergist solution;

[0044] S5. Add the weighed hydroxylamine hydrochloride into ethanol. The mass ratio of hydroxylamine hydrochloride to ethanol is 1:3. Stir evenly while adding to obtain a hydroxylamine hydrochloride solution. The temperature of the hydroxylamine hydrochloride solution is controlled at 30 °C, the stirring speed is 150 r / min, and the stirring time is 30 min;

[0045] Add MB resin and sodium dodecyl sulfate into the hydroxylamine hydrochloride solution according to the formula ratio and stir for 20 min at a stirring speed of 1000 r / min to obtain a pre-emulsion;

[0046] Add an initiator into the pre-emulsion. The initiator is azobisisobutyronitrile. The addition amount of the initiator is 0.5% of the mass of the pre-emulsion. Carry out a polymerization reaction at a temperature of 70 °C for 4 h to obtain a microsphere suspension. Centrifuge, wash, dry and screen the microsphere suspension to obtain composite microspheres;

[0047] The method for centrifuging, washing, drying, and screening the microsphere suspension is as follows: Introduce the microsphere suspension into a centrifuge tube and centrifuge it at a speed of 4000 r / min for 6 min to precipitate the microspheres at the bottom of the centrifuge tube. Then pour out the supernatant, add water until the microspheres are resuspended, repeat the centrifugation operation to precipitate the microspheres at the bottom of the centrifuge tube, then pour out the supernatant, and repeat the water addition and centrifugation washing 5 times. Place the washed microspheres in a vacuum drying oven, set the temperature to 40 °C, and the vacuum degree to 0.09 MPa, and dry until the microspheres reach a constant weight. Screen to obtain microspheres with a particle size in the range of 40-50 μm;

[0048] S6. Mix the anti-swelling agent solution, regulator solution, viscosifier, structure adapter solution, ammonium persulfate solution, synergist solution, and composite microspheres prepared in the above S1-S5 steps, and stir at a speed of 250 r / min for 37.5 min to ensure that all components are fully and evenly mixed to obtain a fracturing agent for interlayer shale oil; After testing, the mass ratio of the water content in the total mass of the fracturing agent prepared in this example is 87.7%.

[0049] Example 2: This example is basically the same as Example 1, except that the solute and suspended particles of the fracturing agent include 20 parts of polydimethyldiallylammonium chloride, 19 parts of PNIPAM, 5 parts of nano-silica, 11 parts of viscosifier, 11 parts of sodium dodecylbenzenesulfonate, 6 parts of short-cut carbon fiber, 2 parts of ammonium persulfate, 2 parts of MB resin, 1 part of hydroxylamine hydrochloride, 5 parts of rhamnolipid, 3 parts of xanthan gum, and 4 parts of sodium dodecyl sulfate; After testing, the mass ratio of the water content in the total mass of the fracturing agent prepared in this example is 88.5%.

[0050] Example 3: This example is basically the same as Example 1, except that the solute and suspended particles of the fracturing agent include 25 parts of polydimethyldiallylammonium chloride, 22 parts of PNIPAM, 7 parts of nano-silica, 17 parts of viscosifier, 17 parts of sodium dodecylbenzenesulfonate, 6.5 parts of short-cut carbon fiber, 4 parts of ammonium persulfate, 2.5 parts of MB resin, 1.6 parts of hydroxylamine hydrochloride, 5.5 parts of rhamnolipid, 4 parts of xanthan gum, and 6 parts of sodium dodecyl sulfate; After testing, the mass ratio of the water content in the total mass of the fracturing agent prepared in this example is 84.1%.

[0051] Example 4: This example is basically the same as Example 1, except that water and polydimethyldiallylammonium chloride with a mass ratio of 5:1 are added to the reaction kettle in sequence and stirred continuously for 40 min at a stirring speed of 350 r / min to obtain an anti-swelling agent solution; After testing, the mass ratio of the water content in the total mass of the fracturing agent prepared in this example is 88.2%.

[0052] Example 5: This example is basically the same as Example 1, except that water and polydimethyldiallylammonium chloride with a mass ratio of 5:3 are successively added to the reaction kettle, and stirred continuously for 60 min at a stirring speed of 550 r / min to obtain an anti-swelling agent solution; after detection, the mass proportion of water content in the total mass of the fracturing agent prepared in this example is 85.9%.

[0053] Example 6: This example is basically the same as Example 1, except that PNIPAM is dissolved in an organic solvent to obtain a PNIPAM solution with a mass concentration of 10%, and nano-silica is added under ultrasonic conditions. The ultrasonic power is 150 W and the ultrasonic time is 30 min to uniformly disperse the nano-particles in the polymer solution to obtain a regulator solution; after detection, the mass proportion of water content in the total mass of the fracturing agent prepared in this example is 89.3%.

[0054] Example 7: This example is basically the same as Example 1, except that PNIPAM is dissolved in an organic solvent to obtain a PNIPAM solution with a mass concentration of 20%, and nano-silica is added under ultrasonic conditions. The ultrasonic power is 350 W and the ultrasonic time is 50 min to uniformly disperse the nano-particles in the polymer solution to obtain a regulator solution; after detection, the mass proportion of water content in the total mass of the fracturing agent prepared in this example is 85.7%.

[0055] Example 8: This example is basically the same as Example 1, except that hydroxypropyl guar gum is added to water at a temperature of 50 °C, and the mass of hydroxypropyl guar gum accounts for 2% of the total mass of the thickener, and stirred evenly to obtain a thickener; after detection, the mass proportion of water content in the total mass of the fracturing agent prepared in this example is 86.1%.

[0056] Example 9: This example is basically the same as Example 1, except that hydroxypropyl guar gum is added to water at a temperature of 60 °C, and the mass of hydroxypropyl guar gum accounts for 5% of the total mass of the thickener, and stirred evenly to obtain a thickener; after detection, the mass proportion of water content in the total mass of the fracturing agent prepared in this example is 88.6%.

[0057] Example 10: This example is basically the same as Example 1, except that sodium dodecylbenzenesulfonate is dissolved in water to obtain a sodium dodecylbenzenesulfonate solution with a mass concentration of 5%, and then short carbon fibers with a length of 2 mm are added. The addition amount of the short carbon fibers is 1% of the mass of the sodium dodecylbenzenesulfonate solution, and stirred simultaneously at a stirring speed of 200 r / min for 45 min to obtain a structure adapter solution; after detection, the mass proportion of water content in the total mass of the fracturing agent prepared in this example is 88.5%.

[0058] Example 11: This example is basically the same as Example 1, except that sodium dodecylbenzenesulfonate is dissolved in water to obtain a sodium dodecylbenzenesulfonate solution with a mass concentration of 10%. Then, short carbon fibers with a length of 5 mm are added, and the addition amount of the short carbon fibers is 5% of the mass of the sodium dodecylbenzenesulfonate solution. At the same time, stirring is carried out at a stirring speed of 400 r / min for 65 min to obtain a structure adapter solution. After testing, the mass percentage of water content in the total mass of the fracturing agent prepared in this example is 87.2%.

[0059] Example 12: This example is basically the same as Example 1, except that MB resin and sodium dodecyl sulfate are added to the hydroxylamine hydrochloride solution according to the formula ratio and stirred for 10 min at a stirring speed of 500 r / min to obtain a pre-emulsion. An initiator is added to the pre-emulsion, and a polymerization reaction is carried out at a temperature of 60 °C for 2 h to obtain a microsphere suspension. After testing, the mass percentage of water content in the total mass of the fracturing agent prepared in this example is 87.7%.

[0060] Example 13: This example is basically the same as Example 1, except that MB resin and sodium dodecyl sulfate are added to the hydroxylamine hydrochloride solution according to the formula ratio and stirred for 30 min at a stirring speed of 1500 r / min to obtain a pre-emulsion. An initiator is added to the pre-emulsion, and a polymerization reaction is carried out at a temperature of 80 °C for 6 h to obtain a microsphere suspension. After testing, the mass percentage of water content in the total mass of the fracturing agent prepared in this example is 86.9%.

[0061] Example 14: This example is basically the same as Example 1, except that the swelling inhibitor solution, regulator solution, thickener, structure adapter solution, ammonium persulfate solution, synergist solution, and composite microspheres prepared in the S1-S5 steps are mixed and stirred at a speed of 200 r / min for 30 min to ensure that all components are fully mixed evenly, obtaining a fracturing agent for interbedded shale oil. After testing, the mass percentage of water content in the total mass of the fracturing agent prepared in this example is 88.5%.

[0062] Example 15: This example is basically the same as Example 1, except that the swelling inhibitor solution, regulator solution, thickener, structure adapter solution, ammonium persulfate solution, synergist solution, and composite microspheres prepared in the S1-S5 steps are mixed and stirred at a speed of 300 r / min for 45 min to ensure that all components are fully mixed evenly, obtaining a fracturing agent for interbedded shale oil. After testing, the mass percentage of water content in the total mass of the fracturing agent prepared in this example is 88.8%.

[0063] Example 16: This example is basically the same as Example 1, except that the particle size of the nano-silica in S2 is 15 - 25 nm; after testing, the mass percentage of water content in the total mass of the fracturing agent prepared in this example is 84.2%.

[0064] Example 17: This example is basically the same as Example 1, except that the particle size of the nano-silica in S2 is 65 - 75 nm; after testing, the mass percentage of water content in the total mass of the fracturing agent prepared in this example is 89.1%.

[0065] Example 18: This example is basically the same as Example 1, except that the addition amount of the initiator is 0.1% of the mass of the pre-emulsion; after testing, the mass percentage of water content in the total mass of the fracturing agent prepared in this example is 87.6%.

[0066] Example 19: This example is basically the same as Example 1, except that the addition amount of the initiator is 1% of the mass of the pre-emulsion; after testing, the mass percentage of water content in the total mass of the fracturing agent prepared in this example is 87.8%.

[0067] Example 20: This example is basically the same as Example 1, except that the method of centrifuging, washing, drying and screening the microsphere suspension in S5 is as follows: The microsphere suspension is introduced into a centrifuge tube and centrifuged at a speed of 3000 r / min for 4 min to precipitate the microspheres at the bottom of the centrifuge tube, then the supernatant is poured off, water is added until the microspheres are resuspended, the centrifugation operation is repeated to precipitate the microspheres at the bottom of the centrifuge tube, then the supernatant is poured off, and the water addition and centrifugation washing are repeated 3 times. The washed microspheres are placed in a vacuum drying oven, the temperature is set at 30 °C, and the vacuum degree is 0.08 MPa, and dried until the microspheres reach a constant weight, and composite microspheres with a particle size of 1 - 10 μm are obtained by screening; after testing, the mass percentage of water content in the total mass of the fracturing agent prepared in this example is 88.4%.

[0068] Example 21: This example is basically the same as Example 1, except that the method of centrifuging, washing, drying and screening the microsphere suspension in S5 is as follows: The microsphere suspension is introduced into a centrifuge tube and centrifuged at a speed of 5000 r / min for 8 min to precipitate the microspheres at the bottom of the centrifuge tube, then the supernatant is poured off, water is added until the microspheres are resuspended, the centrifugation operation is repeated to precipitate the microspheres at the bottom of the centrifuge tube, then the supernatant is poured off, and the water addition and centrifugation washing are repeated 7 times. The washed microspheres are placed in a vacuum drying oven, the temperature is set at 50 °C, and the vacuum degree is 0.1 MPa, and dried until the microspheres reach a constant weight, and composite microspheres with a particle size of 70 - 80 μm are obtained by screening; after testing, the mass percentage of water content in the total mass of the fracturing agent prepared in this example is 88.3%.

[0069] Comparative Example 1: Referring to Example 1, with water as the solvent, by mass fraction, the solute and suspended particles of the fracturing agent include 18 parts of polydimethyldiallylammonium chloride, 15 parts of PNIPAM, 3 parts of nano-silica, 9 parts of thickening agent, 9 parts of sodium dodecylbenzenesulfonate, 5 parts of short carbon fiber, 1 part of ammonium persulfate, 1 part of MB resin, 0.5 part of hydroxylamine hydrochloride, 3 parts of rhamnolipid, 2 parts of xanthan gum, and 2 parts of sodium dodecyl sulfate; after detection, the mass proportion of water content in the total mass of the fracturing agent prepared in this example is 89.6%.

[0070] Comparative Example 2: Referring to Example 1, add MB resin and sodium dodecyl sulfate to the hydroxylamine hydrochloride solution according to the formula ratio and stir for 50 min at a stirring speed of 2500 r / min to obtain a pre-emulsion; add an initiator to the pre-emulsion and carry out a polymerization reaction at a temperature of 90 °C for 10 h to obtain a microsphere suspension; after detection, the mass proportion of water content in the total mass of the fracturing agent prepared in this example is 87.9%.

[0071] Comparative Example 3: Referring to Example 1, the method for centrifuging, washing, drying, and screening the microsphere suspension in S5 is as follows: Pour the microsphere suspension into a centrifuge tube and centrifuge at a speed of 6000 r / min for 15 min to precipitate the microspheres at the bottom of the centrifuge tube, then pour out the supernatant, add water until the microspheres are resuspended, repeat the centrifugation operation, precipitate the microspheres at the bottom of the centrifuge tube, then pour out the supernatant, repeat the water addition and centrifugation washing 9 times, put the washed microspheres into a vacuum drying oven, set the temperature to 60 °C, and the vacuum degree to 0.2 MPa, dry until the microspheres reach a constant weight, and screen to obtain composite microspheres with a particle size of 190 - 210 μm; after detection, the mass proportion of water content in the total mass of the fracturing agent prepared in this example is 88.7%.

[0072] Comparative Example 4: Do not add composite microspheres in S1-2; after detection, the mass proportion of water content in the total mass of the fracturing agent prepared in this example is 89.2%.

[0073] In order to explore the performance of the fracturing agents in some examples and comparative examples, determine the main materials according to the experimental formula and obtain samples for testing, and the results are as Figures 1 to 4 shown. The specific exploration is as follows:

[0074] 1. Explore the influence of the parameters of the raw material ratio on the performance of the fracturing agent:

[0075] As Figures 1 to 4As shown in the figure, by comparing Examples 1 to 3, it can be seen that the demulsification rate of Example 1 is the highest, the surface tension and interfacial tension are the lowest, and the drag reduction rate is the highest. The comprehensive performance of Example 1 is the best. Changing the raw material ratio parameters will have a certain impact on the prepared fracturing fluid samples. The demulsification rate of Example 2 is the lowest, the surface tension is the highest, and the drag reduction rate is the lowest. The interfacial tension of Example 3 is the highest.

[0076] By comparing Examples 1 to 3 with Comparative Example 1, it can be seen that the demulsification, drainage assistance, and drag reduction performances of the samples prepared using process parameters outside the scope of this method have significantly decreased. The demulsification, drainage assistance, and drag reduction performances of Comparative Example 1 are all lower than those of Examples 1 to 3. The comprehensive performance of Comparative Example 1 is far lower than that of Example 1. The comprehensive performance of the fracturing fluid prepared using the process parameter values of Example 1 is the best.

[0077] 2. Explore the influence of the process parameters for preparing the regulator solution on the performance of the fracturing fluid:

[0078] As Figures 1 to 4 shown, by comparing Examples 1, 6, and 7, it can be seen that the performance of Example 1 is the best in all aspects. The demulsification rate of Example 6 is better than that of Example 7. The surface tension and interfacial tension of Example 7 are slightly lower than those of Example 6. The drag reduction rate of Example 7 is slightly higher than that of Example 6, but the difference is not obvious. Changing the process parameters for preparing the regulator solution will have a certain impact on the performance of the fracturing fluid samples. Among them, the closer the process parameter values are to those of Example 1, the better the comprehensive performance of the prepared fracturing fluid.

[0079] 3. Explore the influence of the process parameters for preparing the structure adapter solution on the performance of the fracturing fluid:

[0080] As Figures 1 to 4 shown, by comparing Examples 1, 10, and 11, it can be seen that the comprehensive performance of the fracturing fluid prepared according to the method of Example 1 is the best. The demulsification rate and drag reduction rate of Example 10 are higher than those of Example 11. The surface tension and interfacial tension of Example 10 are slightly lower than those of Example 11. The demulsification, drainage assistance, and drag reduction performances of Example 10 are better than those of Example 11. It can be seen that the process parameters for preparing the structure adapter solution can have a certain impact on the performance of the fracturing fluid.

[0081] 4. Explore the influence of the process parameters for preparing the composite microspheres on the performance of the fracturing fluid:

[0082] As Figures 1 to 4 shown, by comparing Examples 1, 12, and 13, it can be seen that the performance of Example 1 is the best in all aspects and is similar to that of Example 13. The demulsification, drainage assistance, and drag reduction performances of the samples of Example 12 are slightly lower than those of Example 13. Changing the process parameters for preparing the microsphere suspension can have a certain impact on the sample performance, but the difference is not obvious;

[0083] Comparing Example 1, 12, 13 with Comparative Example 2, 3, it can be seen that the demulsification rate, surface tension and interfacial tension of Example 12 are significantly better than those of Comparative Example 2, and the various properties of Comparative Example 2 are significantly better than those of Comparative Example 3. It can be seen that the preparation and addition of composite microspheres have an obvious positive effect on oil recovery efficiency;

[0084] Comparing Example 1, 20, 21, it can be seen that the comprehensive performance of Example 1 is the best. The demulsification, drainage assistance and drag reduction performance of the samples in Example 20 are lower than those in Example 21. Changing the process parameters for preparing composite microspheres can have a certain impact on the sample properties;

[0085] Comparing Example 1, 20, 21 with Comparative Example 4, it can be seen that the various properties of Example 20 are significantly better than those of Comparative Example 4. The change in the process parameter range for preparing composite microspheres has a more obvious impact on the effect of fracturing agents. The comprehensive performance of the fracturing agents prepared with the parameters within the parameter range of this solution is better.

Claims

1. A fracturing agent for interlayer shale oil, characterized in that: The solvent is water. Calculated by mass, the solute and suspended particles of the fracturing agent include 20-25 parts of polydimethyldiallyl ammonium chloride, 19-22 parts of PNIPAM, 5-7 parts of nano-silica, 11-17 parts of viscosity enhancer, 11-17 parts of sodium dodecylbenzene sulfonate, 6-6.5 parts of chopped carbon fibers, 2-4 parts of ammonium persulfate, 2-2.5 parts of MB resin, 1-1.6 parts of hydroxylamine hydrochloride, 5-5.5 parts of rhamnolipid, 3-4 parts of xanthan gum and 4-6 parts of sodium dodecyl sulfate.

2. The preparation process of a fracturing agent for interlayer shale oil according to claim 1, characterized in that: The following steps are involved: S1. Add water and polydimethyldiallylammonium chloride in a mass ratio of 5:1 to 3 into a reaction kettle, and continue stirring for 40 to 60 minutes at a stirring speed of 350 to 550 r / min to obtain an anti-swelling agent solution; S2, dissolving PNIPAM in an organic solvent to obtain a PNIPAM solution with a mass concentration of 10-20%, adding nano-silicon dioxide under ultrasonic conditions, wherein the ultrasonic power is 150-350W and the ultrasonic time is 30-50min, so that the nanoparticles are evenly dispersed in the polymer solution to obtain a regulator solution; S3. The preparation method of the thickener is as follows: adding hydroxypropyl guar gum to water at a temperature of 50 to 60° C., wherein the mass of the hydroxypropyl guar gum accounts for 2 to 5% of the total mass of the thickener, and stirring evenly to obtain the thickener; S4, dissolving sodium dodecylbenzene sulfonate in water to obtain a sodium dodecylbenzene sulfonate solution with a mass concentration of 5-10%, then adding short-cut carbon fibers with a length of 2-5 mm, the amount of short-cut carbon fibers added being 1-5% of the mass of the sodium dodecylbenzene sulfonate solution, stirring at the same time, the stirring speed being 200-400 r / min, the stirring time being 45-65 min, to obtain a structural adapter solution; dissolving ammonium persulfate in water, stirring until completely dissolved, to obtain an ammonium persulfate solution with a mass concentration of 0.5-1.5%; mixing rhamnolipid and xanthan gum according to the formula ratio to obtain a synergist solution; S5. Add the weighed hydroxylamine hydrochloride to ethanol in a mass ratio of hydroxylamine hydrochloride to ethanol of 1:3, and stir evenly while adding to obtain a hydroxylamine hydrochloride solution; add MB resin and sodium dodecyl sulfate to the hydroxylamine hydrochloride solution according to the formula ratio and stir for 10 to 30 minutes at a stirring speed of 500 to 1500 r / min to obtain a pre-emulsion; Adding an initiator to the pre-emulsion, performing a polymerization reaction at a temperature of 60 to 80° C. for 2 to 6 hours to obtain a microsphere suspension; centrifuging, washing, drying and sieving the microsphere suspension to obtain composite microspheres; S6. Mix the anti-swelling agent solution, regulator solution, viscosity enhancer, structural adapter solution, ammonium persulfate solution, synergist solution and composite microspheres prepared in steps S1 to S5, and stir at a speed of 200 to 300 r / min for 30 to 45 minutes to ensure that all components are fully mixed and uniform, so as to obtain a fracturing agent for interlayer shale oil.

3. The preparation process of a fracturing agent for interlayer shale oil according to claim 1, characterized in that: The organic solvent in S2 is dimethylformamide.

4. The preparation process of a fracturing agent for interlayer shale oil according to claim 1, characterized in that: The particle size of the nano silicon dioxide in S2 is 15 to 75 nm.

5. The preparation process of a fracturing agent for interlayer shale oil according to claim 1, characterized in that: The stirring speed in S3 is 400-600 r / min, and the stirring time is 60-90 min, until the hydroxypropyl guar gum is completely dissolved to obtain a viscosity enhancer.

6. The preparation process of a fracturing agent for interlayer shale oil according to claim 1, characterized in that: The temperature of the hydroxylamine hydrochloride solution in S5 is controlled at 25-35°C, the stirring speed is 100-200 r / min, and the stirring time is 20-40 min.

7. The preparation process of a fracturing agent for interlayer shale oil according to claim 1, characterized in that: The initiator in S5 is azobisisobutyronitrile, and the amount of the initiator added is 0.1-1% of the mass of the pre-emulsion.

8. The process for preparing a fracturing agent for interlayer shale oil according to claim 1, characterized in that: The method for centrifuging, washing, drying and sieving the microsphere suspension described in S5 is: introducing the microsphere suspension into a centrifuge tube and centrifuging it at a speed of 3000-5000 r / min for 4-8 minutes to allow the microspheres to settle at the bottom of the centrifuge tube, then pouring out the supernatant, adding water until the microspheres are resuspended, repeating the centrifugation operation to allow the microspheres to settle at the bottom of the centrifuge tube, then pouring out the supernatant, repeating the centrifugation washing with water 3-7 times, placing the washed microspheres in a vacuum drying oven, setting the temperature to 30-50°C and the vacuum degree to 0.08-0.1MPa, drying until the microspheres reach constant weight, and sieving to obtain composite microspheres with a particle size of 1-80μm.

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