Shale oil imbibition agent, its preparation method and slickwater fracturing fluid

Abstract

The present invention relates to the field of shale oil reservoir stimulation, and particularly to a shale oil imbibition agent, a preparation method thereof, and a slickwater fracturing fluid. The shale oil imbibition agent contains: a) an imbibition main agent, b) an amphoteric surfactant, c) a polycyclic aromatic hydrocarbon, and d) an organic solvent; wherein, the imbibition main agent includes a polyoxyalkylene ether; the polyoxyalkylene ether is prepared by using trimethylolpropane diallyl ether as an initiator and reacting with an alkylene oxide. The shale oil imbibition agent of the present invention has the characteristics of fast initial imbibition start-up, low interfacial tension, high imbibition height at 10 min, etc. The shale oil imbibition agent of the present invention has good compatibility with the slickwater system, excellent drainage assistance and imbibition performance after gel breaking, and can effectively improve the recovery rate of shale oil.

Description

Technical Field

[0001] The present invention relates to the field of shale oil reservoir stimulation, and particularly relates to a shale oil imbibition agent, a preparation method thereof, and a slickwater fracturing fluid. Background Art

[0002] The land-based shale oil resources in China are about 150 billion tons, and the recoverable resources are about 3 billion - 6 billion tons. Shale oil has no natural productivity or commercial exploitation value under natural conditions and requires special exploitation technologies such as fracturing. The exploitation of shale oil mainly relies on spontaneous imbibition dominated by capillary force, gravity, etc. The imbibition rate is related to the permeability of the rock, pore structure, wettability, fluid viscosity, fluid saturation, etc.

[0003] At present, under certain reservoir properties and fracturing processes, to improve the recovery rate of shale oil, it is necessary to supplement energy, improve fluid flow, prevent scale formation, improve water injection efficiency, work on hydrodynamics, improve the oil - water migration ability, improve the sweep efficiency and oil washing efficiency, increase the permeability, allow the crude oil to fully enter the main pore channels, improve the productivity of a single well, and achieve the purpose of increasing production and improving the recovery rate.

[0004] Shale oil reservoirs are the main targets for further exploitation in the future. The reason for their exploitable nature is related to the fracture system existing in the reservoirs. The matrix rock blocks play the role of storing oil, while the fractures play the role of guiding oil. For fractured low - permeability oil reservoirs, the main oil displacement mechanism is to promote the water in the fractures to be imbibed into the matrix through imbibition, replacing the crude oil for oil production. Therefore, for shale oil reservoirs, the imbibition additive is the key additive for pressure - drive enhanced production.

[0005] Definition of imbibition. Imbibition occurs in porous media and is an effective method for exploiting the crude oil in matrix rock blocks and low - permeability intervals. Imbibition is also called self - imbibition, that is, spontaneous imbibition, which refers to the process in which water automatically imbibes into the core and displaces the crude oil without pressurization. Broadly speaking, imbibition includes pressurized imbibition and spontaneous imbibition. Pressurized imbibition is so - called water - drive oil production, also called forced imbibition. Usually, the imbibition referred to means self - imbibition and does not include pressurized imbibition. Imbibition is divided into single - side contact imbibition, double - side contact imbibition, and surrounding contact imbibition. Single - side imbibition is when the core contacts the water on one side, and the water is drawn into the core under the traction of capillary pressure and displaces the oil in it. This imbibition is also called capillary pressure imbibition.

[0006] It is generally believed that during the secondary migration of oil and gas, due to the change of pore structure, when the curvature radius of the opposite end of the continuous oil (gas) phase is greater than that of the front end, the capillary force is the resistance to the migration of oil and gas; while when the curvature radius of the opposite end of the continuous oil (gas) phase is less than that of the front end, the capillary force is the driving force for the migration of oil and gas. The capillary force always tends to make the non-wetting phase occupy a larger pore space. Under the combined action of buoyancy, hydrodynamic force and capillary force, oil (gas) moves intermittently, which has been confirmed in physical simulation experiments. In fact, there are three kinds of capillary forces in a capillary. The first and second kinds are parallel to the extension direction of the capillary, and the third kind is perpendicular to the capillary wall and points to the non-wetting phase; the third kind of capillary force mainly plays the role of increasing the frictional resistance between the non-wetting phase and the pore throat wall, and this kind of capillary force is often ignored in media with relatively thick pore throats (such as reservoirs). For oil and gas to migrate, the driving force in its forward direction must exceed the capillary resistance and frictional resistance in that direction. There is a view that in the primary migration process of oil and gas from the source rock to the reservoir, the capillary force is an important driving force. Therefore, under the condition of water wetting, the oil and gas phases will automatically move from small pores and fine throats to larger and coarser pores and throats under the action of capillary force.

[0007] An important determining factor for the development efficiency of oil and gas reservoirs is the oil-water imbibition capacity. Especially for some low-permeability oil reservoirs, the imbibition force determines the productivity of oil and gas wells.

[0008] In addition, from the perspective of green chemistry, the oilfield development has entered the efficiency-driven stage. The efficiency of the allocation of production factors needs to be improved. While replenishing water, more crude oil can be displaced with the same amount of water to obtain good benefits, taking into account the protection of the reservoir, energy conservation and environmental protection. The imbibition enhanced oil recovery technology is designed and developed to address the above issues. First, it can change the wettability of the rock, convert the rock into hydrophilicity, strengthen the imbibition effect, displace the crude oil in the pore channels, and improve the recovery rate. Second, the agent is safe, environmentally friendly, protects the reservoir, and can be reused.

[0009] The imbibition technology displaces the crude oil in the fractures through a high-performance imbibition extractant with a new structure and related auxiliary agents, and this technology is specifically designed and developed for the imbibition problem.

[0010] The imbibition enhanced oil recovery technology developed for the low-permeability characteristics of shale oil reservoirs is used to solve the problems of low efficiency, high cost and insignificant oil production increase in shale oil exploitation. It is a technology that can be widely developed, and the technology prominently reflects the characteristics of protecting the reservoir, reducing pressure and increasing injection, simple operation and obvious benefits, and has very feasible operability. Summary of the Invention

[0011] The object of the present invention is to overcome the problems of low shale oil production efficiency, high cost and insignificant oil production increase in the existing technology, and to provide a shale oil imbibition agent, a preparation method thereof and a slickwater fracturing fluid. The shale oil imbibition agent has the characteristics of fast initial imbibition start, low interfacial tension, high imbibition height at 10 minutes, etc. The shale oil imbibition agent of the present invention has good compatibility with the slickwater system, excellent drainage and imbibition performance after gel breaking, and can effectively improve the recovery rate of shale oil.

[0012] In order to achieve the above object, on the one hand, the present invention provides a shale oil imbibition agent, which contains: a) an imbibition main agent, b) an amphoteric surfactant, c) a polycyclic aromatic hydrocarbon, and d) an organic solvent; wherein, the imbibition main agent includes a polyoxyalkylene ether; the polyoxyalkylene ether is prepared by using trimethylolpropane diallyl ether as an initiator and reacting with an alkylene oxide.

[0013] On the second aspect, the present invention provides a preparation method of the shale oil imbibition agent described in the present invention, which includes: uniformly mixing the imbibition main agent, amphoteric surfactant, polycyclic aromatic hydrocarbon and organic solvent described in the present invention to obtain the shale oil imbibition agent.

[0014] On the third aspect, the present invention provides a slickwater fracturing fluid, which contains the shale oil imbibition agent described in the present invention.

[0015] The shale oil imbibition agent of the present invention has the characteristics of fast initial imbibition start, low interfacial tension, thorough imbibition, etc.

[0016] The shale oil imbibition agent of the present invention can effectively reduce the fracturing cost, improve the fracturing stimulation efficiency, improve the overall water flooding efficiency, and significantly improve the recovery rate of shale oil.

[0017] The flowback fluid of the slickwater fracturing fluid of the present invention can be recycled, and after simple treatment, it can be reused for single well plugging removal and stimulation, and reinjected into the formation for oil displacement. Detailed Embodiments

[0018] In the ranges disclosed herein, the endpoints and any value are not limited to the exact range or value, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0019] The present invention provides a shale oil imbibition agent, which contains: a) an imbibition main agent, b) an amphoteric surfactant, c) a polycyclic aromatic hydrocarbon, and d) an organic solvent; wherein, the imbibition main agent includes a polyoxyalkylene ether; the polyoxyalkylene ether is prepared by using trimethylolpropane diallyl ether as an initiator and reacting with an alkylene oxide.

[0020] According to a particularly preferred embodiment of the present invention, the shale oil imbibition agent contains, based on 100 parts by weight: a) 20-40 parts by weight of the main imbibition agent, b) 10-20 parts by weight of an amphoteric surfactant, c) 3-8 parts by weight of a polycyclic aromatic hydrocarbon, and d) 32-67 parts by weight of an organic solvent.

[0021] According to a preferred embodiment of the present invention, the alkylene oxide is one or more of ethylene oxide, propylene oxide, and butylene oxide.

[0022] In order to further improve the permeability and imbibition efficiency of the imbibition agent in shale oil, the imbibition agent molecule is designed to have a multi-branched structure. According to a preferred embodiment of the present invention, the polyoxyalkylene ether is a polyoxyethylene polyoxypropylene ether.

[0023] According to a preferred embodiment of the present invention, the preparation method of the polyoxyethylene polyoxypropylene ether includes: using trimethylolpropane diallyl ether as an initiator and reacting with ethylene oxide and propylene oxide under the action of an alkali metal hydroxide as a catalyst.

[0024] In the present invention, as long as the object of the present invention can be achieved, the reaction conditions in the preparation method of the polyoxyethylene polyoxypropylene ether can be a conventional selection in the art. According to a preferred embodiment of the present invention, the reaction conditions include: the reaction temperature is 120-130 °C, the reaction pressure is 0.2-0.4 MPa, and the reaction time is 1-4 hours.

[0025] In order to further improve the permeability of the imbibition agent in shale oil, according to a preferred embodiment of the present invention, the weight ratio of the initiator, ethylene oxide, propylene oxide, and catalyst is (1.5-5):(250-400):(120-220):1.

[0026] According to a particularly preferred embodiment of the present invention, the weight ratio of the initiator, ethylene oxide, propylene oxide, and catalyst is (2.5-4):(300-350):(150-200):1.

[0027] In the present invention, as long as the object of the present invention can be achieved, the amphoteric surfactant can be a conventional selection in the art. According to a preferred embodiment of the present invention, the amphoteric surfactant includes alkyl betaine, which is one or more of dodecyl betaine, dodecyl dihydroxyethyl betaine, octadecyl dihydroxyethyl betaine, and hexadecyl betaine. By adopting the foregoing preferred scheme, the surface and interfacial tension of the imbibition agent can be further reasonably adjusted, and the imbibition start-up speed can be increased.

[0028] In order to further improve the startup speed of the imbibition agent, the alkyl betaine is a mixture of dodecyl betaine and cetyl betaine, and the weight ratio of dodecyl betaine to cetyl betaine is (0.5 - 2):1.

[0029] In the present invention, as long as the object of the present invention can be achieved, the polycyclic aromatic hydrocarbon can be a conventional selection in the art. According to a preferred embodiment of the present invention, the polycyclic aromatic hydrocarbon is one or more of fluorene, naphthalene, anthracene, and phenanthrene. By adopting the foregoing preferred scheme, the permeability of the imbibition agent to shale oil at the interface can be improved, and the stripping of heavy components in shale oil can be increased.

[0030] In the present invention, the organic solvent includes benzene-based solvents, preferably one or more of xylene, toluene, and mesitylene.

[0031] According to a preferred embodiment of the present invention, the organic solvent is a mixed solvent composed of xylene and dimethyl sulfoxide. By adopting the foregoing preferred scheme, the good mutual solubility and homogeneity of the components of the imbibition agent can be improved, which is convenient for storage and application.

[0032] In order to further improve the good mutual solubility and homogeneity of the components of the imbibition agent, according to a preferred embodiment of the present invention, the weight ratio of dimethyl sulfoxide to xylene is (1 - 6):1.

[0033] In the present invention, the shale oil imbibition agent having the foregoing characteristics can achieve the object of the present invention, and there is no special requirement for the preparation method of the catalyst. It can be prepared by mixing the main imbibition agent, amphoteric surfactant, polycyclic aromatic hydrocarbon, and organic solvent raw materials, and the mixing conditions only need to make the various raw materials mix evenly.

[0034] The present invention provides a slickwater fracturing fluid, which contains the shale oil imbibition agent of the present invention.

[0035] In the present invention, the slickwater fracturing fluid refers to a fracturing fluid that can effectively reduce the friction of the fracturing fluid, has a certain viscosity, and meets a certain sand-carrying performance. Its specific composition is not limited and can be selected according to needs.

[0036] When using the shale oil imbibition agent of the present invention, the shale oil imbibition agent can be added to the slickwater fracturing fluid system, or the components of the shale oil imbibition agent can be directly added to the slickwater system, and the addition order of each component is not limited.

[0037] According to a preferred embodiment of the present invention, the slickwater fracturing fluid contains 0.05 - 1 wt% of the shale oil imbibition agent of the present invention.

[0038] The imbibition agent for shale oil provided by the present invention can effectively improve the recovery rate of shale oil, and has the characteristics of fast initial imbibition start-up, low interfacial tension, and thorough imbibition. At the same time, the imbibition agent for shale oil of the present invention has good compatibility with the slickwater system, and excellent drainage assistance and imbibition performance after gel breaking.

[0039] The present invention will be further described below through specific examples. The scope of the present invention is not limited to the scope covered by the examples. In the present invention, unless otherwise specified, the reagents used can be obtained through commercial purchase:

[0040] Prepare a slickwater fracturing fluid system: 0.3 wt% emulsion drag reducer (produced by Sinopec Continental Shelf Company, model SFFR), 0.1 wt% high-efficiency drainage aid (produced by Sinopec Continental Shelf Company, model SFCU), 0.3 wt% clay stabilizer (produced by Sinopec Continental Shelf Company, model SFCS), and 99.27 wt% water are mixed, and then 0.03 wt% gel breaker (produced by Sinopec Continental Shelf Company, model SFCP) is added. After gel breaking at 90 °C for 1 hour, it is cooled to room temperature to obtain the slickwater fracturing fluid system after gel breaking.

[0041] The test methods involved in the present invention are as follows:

[0042] 1. Compatibility between the imbibition agent and the slickwater fracturing fluid system

[0043] Prepare a slickwater fracturing fluid product according to the sample and the slickwater fracturing fluid formula. The components are compatible with each other, without stratification, precipitation, turbidity, or color change, which is recorded as good, otherwise it is poor.

[0044] Excess experiment verification: Prepare products according to the formula, and they are compatible with other products in the system. The dosage of all additives in the system is increased by 10 times, and there is no stratification, precipitation, turbidity, or color change.

[0045] 2. Surface and interfacial tension testing

[0046] Testing methods for surface tension and interfacial tension in the water system: Weigh 0.6000 g of the imbibition agent sample with a ten-thousandth balance and transfer it to a 200 mL clean volumetric flask, dilute it to the scale with deionized water to prepare a 0.3 wt% solution, and then use a surface and interfacial tension meter to detect the surface tension of the solution at 25 °C using the "pendant drop method"; measure the interfacial tension value with dehydrated No. 3 aviation kerosene.

[0047] During surface tension testing: The drop is the sample solution, and the external environment is air. The measured value is the "liquid-gas" surface tension value formed by the solution and air.

[0048] During interfacial tension testing: The drop is the sample solution, and the external environment is No. 3 aviation kerosene. The measured value is the "liquid-liquid" interfacial tension value formed by the liquid drop and No. 3 aviation kerosene.

[0049] Testing method for surface tension and interfacial tension under slickwater fracturing fluid system: The method is the same as above. Prepare slickwater fracturing fluid with 0.3 wt% imbibition agent for testing.

[0050] 3. Capillary imbibition test

[0051] Preparation of capillary for imbibition: Capillary specification, standard capillary inner diameter is 0.3 mm. Ultrasonically treat it with chromic acid cleaning solution for 3 hours to remove surface organic substances. Then ultrasonically clean it successively with hydrochloric acid solution (volume ratio 1:10) and hydrofluoric acid solution (concentration 10 wt%) to roughen and activate the capillary surface for 30 min. Then ultrasonically clean it with deionized water to remove residual acid until pH > 6.5, and dry it at 105 °C. Prepare aging oil according to the ratio. The composition of aging oil is crude oil: 3# aviation kerosene: 90# asphalt = 2:5:3 (mass ratio). Immerse the treated capillary completely in the aging oil and age it for 4 weeks at 60 °C. Take out the capillary, clean the asphalt on the outer wall of the capillary with kerosene, and dry it in a sealed environment at 60 °C to obtain an oil-wet capillary for storage and standby.

[0052] Testing method for liquid level height at 10 min under water system: Prepare a 0.3% test solution (mass content of imbibition agent sample in water) with deionized water, keep the temperature of the test solution at 25 °C, pour the test solution into a colorimetric tube, and stand the scale closely against the rear wall at the back. Vertically place the treated capillary in the colorimetric tube, read and record the liquid level height in the tube, and record the liquid level height at 10 min.

[0053] Testing method for liquid level height at 10 min under slickwater fracturing fluid system: The method is the same as above. Prepare slickwater fracturing fluid with 0.3 wt% imbibition agent for testing.

[0054] 4. Testing of flowback rate

[0055] Testing method: Use a 20 - 40 mesh quartz sand-filled tube to simulate the testing of flowback rate. Fill 20 - 40 mesh quartz sand into a sand-filled tube with a length of 25 cm and a diameter of 2.5 cm, vibrate it up and down 200 times to make the permeability basically the same each time. At room temperature, inject the mixed solution of the sample to be tested (the addition amount is 0.3 wt% of the mixed solution) and slickwater fracturing fluid system into the sand-filled tube. The dosage of slickwater fracturing fluid is 0.5 wt% of the quartz sand. Then inject a breaker (produced by Sinopec Continental Shelf Company, model SFCP) into the sand-filled tube, and the dosage of the breaker is 0.03 wt% of the quartz sand. Open the lower valve to let the liquid flow out under the action of gravity, record the outflow liquid volume, and calculate the flowback rate (flowback rate = outflow liquid volume / injected mixed solution volume * 100%); in the blank control group, replace the sample with an equal volume of water.

[0056] Example 1

[0057] Preparation of imbibition main agent: Add ethylene oxide and propylene oxide into tanks 1# and 2# respectively. After metering according to a certain proportion, they enter tank 3#. Add a certain amount of trimethylolpropane diallyl ether and KOH into a dry high-pressure reactor. After installing the high-pressure reactor, displace the air in the reactor with nitrogen for 3 - 5 times and purge the device pipeline. Then heat it. When the temperature in the reactor rises to 75°C, continuously and slowly add the metered mixture of ethylene oxide and propylene oxide, control the pressure at 0.2 MPa and the temperature at 120°C. After the feeding is completed, continue the reaction for 3 hours. Then cool down and purge the residual gas in the pipeline and the reactor with nitrogen to obtain the imbibition main agent.

[0058] Raw material ratio of imbibition main agent: By weight, 0.3 parts by weight of trimethylolpropane diallyl ether, 70 parts by weight of ethylene oxide, 30 parts by weight of propylene oxide, and 0.2 parts by weight of potassium hydroxide.

[0059] Preparation of shale oil imbibition agent: By weight, mix 30 parts by weight of imbibition main agent, 15 parts by weight of dodecyl betaine, 6 parts by weight of naphthalene, 12 parts by weight of xylene, and 37 parts by weight of dimethyl sulfoxide evenly under stirring to obtain the shale oil imbibition agent.

[0060] Test the relevant properties in a water system with a shale oil imbibition agent content of 0.3 wt%, and the results are listed in Table 1. Test the relevant properties in a slickwater fracturing fluid system with a shale oil imbibition agent content of 0.3 wt%, and the results are listed in the table.

[0061] Example 2

[0062] Preparation of imbibition main agent: The same as in Example 1.

[0063] Raw material ratio of imbibition main agent: By weight, 0.4 parts by weight of trimethylolpropane diallyl ether, 65 parts by weight of ethylene oxide, 35 parts by weight of propylene oxide, and 0.2 parts by weight of potassium hydroxide.

[0064] Preparation of shale oil imbibition agent: By weight, mix 20 parts by weight of imbibition main agent, 10 parts by weight of dodecyl betaine, 3 parts by weight of naphthalene, 10 parts by weight of xylene, and 57 parts by weight of dimethyl sulfoxide evenly under stirring to obtain the shale oil imbibition agent.

[0065] Test the relevant properties in a water system with a shale oil imbibition agent content of 0.3 wt%, and the results are listed in Table 1. Test the relevant properties in a slickwater fracturing fluid system with a shale oil imbibition agent content of 0.3 wt%, and the results are listed in Table 2.

[0066] Example 3

[0067] Preparation of imbibition main agent: The same as in Example 1.

[0068] Raw material ratio of imbibition main agent: by weight, 0.6 parts by weight of trimethylolpropane diallyl ether, 60 parts by weight of ethylene oxide, 40 parts by weight of propylene oxide, and 0.2 parts by weight of potassium hydroxide.

[0069] Preparation of shale oil imbibition agent: by weight, mix 40 parts by weight of imbibition main agent, 10 parts by weight of dodecyl betaine, 10 parts by weight of cetyl betaine, 8 parts by weight of naphthalene, 15 parts by weight of xylene, and 17 parts by weight of dimethyl sulfoxide evenly under stirring to obtain the shale oil imbibition agent.

[0070] Test relevant properties in a water system with a shale oil imbibition agent content of 0.3 wt%, and the results are listed in Table 1. Test relevant properties in a slickwater fracturing fluid system with a shale oil imbibition agent content of 0.3 wt%, and the results are listed in Table 2.

[0071] Example 4

[0072] Preparation of imbibition main agent: the same as in Example 1.

[0073] Raw material ratio of imbibition main agent: by weight, 0.5 parts by weight of trimethylolpropane diallyl ether, 67 parts by weight of ethylene oxide, 33 parts by weight of propylene oxide, and 0.2 parts by weight of potassium hydroxide.

[0074] Preparation of shale oil imbibition agent: by weight, mix 40 parts by weight of imbibition main agent, 20 parts by weight of dodecyl betaine, 8 parts by weight of naphthalene, 15 parts by weight of xylene, and 17 parts by weight of dimethyl sulfoxide evenly under stirring to obtain the shale oil imbibition agent.

[0075] Test relevant properties in a water system with a shale oil imbibition agent content of 0.3 wt%, and the results are listed in Table 1. Test relevant properties in a slickwater fracturing fluid system with a shale oil imbibition agent content of 0.3 wt%, and the results are listed in Table 2.

[0076] Example 5

[0077] Preparation of imbibition main agent: the same as in Example 4.

[0078] Raw material ratio of imbibition main agent: the same as in Example 4.

[0079] Preparation of shale oil imbibition agent: by weight, mix 40 parts by weight of imbibition main agent, 20 parts by weight of cetyl betaine, 8 parts by weight of fluorene, 15 parts by weight of toluene, and 17 parts by weight of dimethyl sulfoxide evenly under stirring to obtain the shale oil imbibition agent.

[0080] Test relevant properties in a water system with a shale oil imbibition agent content of 0.3 wt%, and the results are listed in Table 1. Test relevant properties in a slickwater fracturing fluid system with a shale oil imbibition agent content of 0.3 wt%, and the results are listed in Table 2.

[0081] Example 6

[0082] Preparation of the imbibition main agent: The same as Example 4.

[0083] Raw material ratio of the imbibition main agent: The same as Example 4.

[0084] Preparation of the shale oil imbibition agent: By weight, mix 40 parts by weight of the imbibition main agent, 20 parts by weight of dodecyl betaine, 2 parts by weight of naphthalene, 15 parts by weight of xylene, and 17 parts by weight of dimethyl sulfoxide evenly under stirring to obtain the shale oil imbibition agent.

[0085] Test the relevant properties in the water system with a shale oil imbibition agent content of 0.3 wt%, and the results are listed in Table 1. Test the relevant properties in the slickwater fracturing fluid system with a shale oil imbibition agent content of 0.3 wt%, and the results are listed in Table 2.

[0086] Example 7

[0087] Preparation of the imbibition main agent: The same as Example 4.

[0088] Raw material ratio of the imbibition main agent: The same as Example 4.

[0089] Preparation of the shale oil imbibition agent: By weight, mix 40 parts by weight of the imbibition main agent, 20 parts by weight of dodecyl betaine, 8 parts by weight of naphthalene, 15 parts by weight of xylene, and 10 parts by weight of dimethyl sulfoxide evenly under stirring to obtain the shale oil imbibition agent.

[0090] Test the relevant properties in the water system with a shale oil imbibition agent content of 0.3 wt%, and the results are listed in Table 1. Test the relevant properties in the slickwater fracturing fluid system with a shale oil imbibition agent content of 0.3 wt%, and the results are listed in Table 2.

[0091] Example 8

[0092] Preparation of the imbibition main agent: The same as Example 4.

[0093] Raw material ratio of the imbibition main agent: The same as Example 4.

[0094] Preparation of the shale oil imbibition agent: By weight, mix 40 parts by weight of the imbibition main agent, 20 parts by weight of dodecyl betaine, 8 parts by weight of naphthalene, 32 parts by weight of dimethyl sulfoxide evenly under stirring to obtain the shale oil imbibition agent.

[0095] Test the relevant properties in the water system with a shale oil imbibition agent content of 0.3 wt%, and the results are listed in Table 1. Test the relevant properties in the slickwater fracturing fluid system with a shale oil imbibition agent content of 0.3 wt%, and the results are listed in Table 2.

[0096] Comparative Example 1

[0097] Preparation of imbibition main agent: Replace the initiator trimethylolpropane diallyl ether with propylene glycol, and the others are the same as in Example 4 to obtain the imbibition main agent.

[0098] Raw material ratio of imbibition main agent: The same as in Example 4.

[0099] Preparation of shale oil imbibition agent: The same as in Example 4.

[0100] Test relevant properties in a water system with a shale oil imbibition agent content of 0.3 wt%, and the results are listed in Table 1. Test relevant properties in a slickwater fracturing fluid system with a shale oil imbibition agent content of 0.3 wt%, and the results are listed in Table 2.

[0101] Comparative Example 2

[0102] Preparation of imbibition main agent: The same as in Example 4.

[0103] Raw material ratio of imbibition main agent: The same as in Example 4.

[0104] Preparation of shale oil imbibition agent: By weight, mix 40 parts by weight of the imbibition main agent, 8 parts by weight of naphthalene, 15 parts by weight of xylene, and 17 parts by weight of dimethyl sulfoxide evenly under stirring to obtain the shale oil imbibition agent.

[0105] Test relevant properties in a water system with a shale oil imbibition agent content of 0.3 wt%, and the results are listed in Table 1. Test relevant properties in a slickwater fracturing fluid system with a shale oil imbibition agent content of 0.3 wt%, and the results are listed in Table 2.

[0106] Comparative Example 3

[0107] Preparation of imbibition main agent: The same as in Example 4.

[0108] Raw material ratio of imbibition main agent: The same as in Example 4.

[0109] Preparation of shale oil imbibition agent: By weight, mix 40 parts by weight of the imbibition main agent, 20 parts by weight of dodecyl betaine, 15 parts by weight of xylene, and 17 parts by weight of dimethyl sulfoxide evenly under stirring to obtain the shale oil imbibition agent.

[0110] Test relevant properties in a water system with a shale oil imbibition agent content of 0.3 wt%, and the results are listed in Table 1. Test relevant properties in a slickwater fracturing fluid system with a shale oil imbibition agent content of 0.3 wt%, and the results are listed in Table 2.

[0111] Table 1 Test results of shale oil imbibition agent performance

[0112]

[0113]

[0114] As can be seen from Table 2, the imbibition agent of the present invention can effectively reduce the surface and interfacial tensions and increase the imbibition height in 10 minutes. Due to the adsorption of the simulated oil on the capillary wall, pure water is difficult to overcome the adsorption work to drive the oil, that is, no obvious imbibition occurs. After the imbibition agent is added, the imbibition occurs because the imbibition agent has a low interfacial tension. Therefore, the imbibition agent of the present invention has a good imbibition effect.

[0115] Table 2 Test Results of the Properties of the Slickwater Fracturing Fluid

[0116]

[0117] As can be seen from Table 2, the imbibition agent of the present invention is well compatible with the slickwater fracturing fluid system, without stratification, precipitation, turbidity or color change. The slickwater fracturing fluid obtained by mixing the imbibition agent of the present invention with the slickwater fracturing fluid system has relatively low surface and interfacial tensions, relatively high imbibition height and flowback rate, and has a good imbibition effect.

Claims

1. A shale oil imbibition agent, characterized in that, The shale oil imbibition agent contains: a) an imbibition main agent, b) an amphoteric surfactant, c) polycyclic aromatic hydrocarbons, and d) an organic solvent; Among them, the imbibition main agent includes polyoxyalkylene ether, and the polyoxyalkylene ether is polyoxyethylene polyoxypropylene ether; the preparation method of the polyoxyethylene polyoxypropylene ether includes: using trimethylolpropane diallyl ether as an initiator and reacting with ethylene oxide and propylene oxide under the action of an alkali metal hydroxide as a catalyst; The weight ratio of the initiator, ethylene oxide, propylene oxide and the catalyst is (1.5 - 5):(250 - 400):(120 - 220):

1.

2. The shale oil imbibition agent according to claim 1, wherein, Based on 100 parts by weight, the shale oil imbibition agent contains: a) 20 - 40 parts by weight of the imbibition main agent, b) 10 - 20 parts by weight of the amphoteric surfactant, c) 3 - 8 parts by weight of the polycyclic aromatic hydrocarbons, d) 32 - 67 parts by weight of the organic solvent.

3. The shale oil imbibition agent according to claim 1 or 2, wherein, The weight ratio of the initiator, ethylene oxide, propylene oxide and the catalyst is (2.5 - 4): (300-350)：(150-200)：1。 4. The shale oil imbibition agent according to claim 1 or 2, wherein The amphoteric surfactant includes alkyl betaine; the alkyl betaine is one or more of dodecyl betaine, dodecyldihydroxyethyl betaine, octadecyldihydroxyethyl betaine, hexadecyl betaine.

5. The shale oil imbibition agent according to claim 4, wherein, The alkyl betaine is a mixture of dodecyl betaine and hexadecyl betaine, and the weight ratio of dodecyl betaine to hexadecyl betaine is (0.5 - 2):

1.

6. The shale oil imbibition agent according to claim 1 or 2, wherein The polycyclic aromatic hydrocarbons are one or more of fluorene, naphthalene, anthracene and phenanthrene.

7. The shale oil imbibition agent according to claim 1 or 2, wherein, The organic solvent includes benzene solvents.

8. The shale oil imbibition agent according to claim 7, wherein, The organic solvent includes one or more of xylene, toluene, and mesitylene.

9. The shale oil imbibition agent according to claim 7, wherein, The organic solvent is a mixed solvent composed of xylene and dimethyl sulfoxide.

10. The shale oil imbibition agent according to claim 9, wherein, The weight ratio of dimethyl sulfoxide to xylene is (1 - 6):

1.

11. The preparation method of the shale oil imbibition agent according to any one of claims 1-10, characterized in that, The method includes: mixing the imbibition main agent, the amphoteric surfactant, the polycyclic aromatic hydrocarbons and the organic solvent evenly to obtain the shale oil imbibition agent.

12. A slippery water fracturing fluid, characterized in that, The slickwater fracturing fluid contains the shale oil imbibition agent according to any one of claims 1 - 10.

13. The slickwater fracturing fluid according to claim 12, wherein, In the slickwater fracturing fluid, the content of the shale oil imbibition agent is 0.05 - 1 wt%.

Images