Shale oil high-pressure imbibition microfluidic experimental device and method

Abstract

The invention discloses a shale oil high-pressure imbibition micro-fluidic experimental device and method, the shale oil high-pressure imbibition micro-fluidic experimental device comprises a nano-fluidic chip holder, the nano-fluidic chip holder is provided with a matrix type chip model, and the nano-fluidic chip holder is connected with a water bath box; the matrix type chip model is communicated with a pressure tracking pump and a vacuum pump, and the communicating position of the pressure tracking pump and the vacuum pump is communicated with an intermediate container and a power pump in sequence. And a full-period production dynamic process of fracturing fluid injection, well closing and well opening oil extraction under the shale reservoir condition is simulated by utilizing a nanofluidic technology. Meanwhile, a microfluidic experimental method is established by utilizing the experimental device, the flowing process and the distribution state of the oil-water two phases in the whole process of pressing, stuffiness and production are visually monitored and recorded in real time, and the imbibition replacement efficiency is quantitatively calculated by utilizing an image processing method.

Description

Technical Field

[0001] The invention belongs to the technical field of shale oil and gas seepage physical experiments, and specifically relates to a shale oil high-pressure imbibition microfluidic experimental device and method. Background Art

[0002] With the continuous deepening of oil and gas resource exploration and development, unconventional oil and gas resources have gradually received attention. Shale oil and other unconventional oil and gas have shown great potential under the existing economic and technical conditions. Preliminary predictions show that my country's shale oil technically recoverable reserves are about 4.4 billion tons. The complexity of this type of reservoir and its nano-scale pore structure lead to unsatisfactory water injection development results. Therefore, due to the strong capillary force of shale reservoirs, injected water such as fracturing fluid can spontaneously enter the tiny pores to replace the oil phase and thus increase the recovery rate. The imbibition effect has a greater impact on the recovery rate.

[0003] At present, a large number of scholars at home and abroad have carried out in-depth research on the imbibition phenomenon of shale reservoirs, mainly focusing on core-scale imbibition experiments and core and reservoir-scale numerical simulations. The mechanism of shale oil imbibition and its utilization mechanism at the microscopic pore scale are still unclear. Traditional core experiments require the assistance of nuclear magnetic resonance (MRI), electronic computed tomography (CT) and other means to understand the flow phenomenon and seepage law of oil and water phases in porous media. In addition, there are defects such as the inability to visualize the flow state of the fluid inside the core, long experimental cycle, and poor repeatability of experimental results. The results of core-scale and reservoir-scale numerical simulations still need to be verified experimentally. There are also deficiencies in the study of the imbibition process by numerical simulation. The molecular simulation calculation amount of the single nanopore imbibition process is limited, the construction of shale digital cores is difficult, and the numerical simulation of the pore network cannot accurately reflect the flow process of oil and water phases inside the pore throats of porous media.

[0004] In view of the current insufficiency of research on the mechanism of microscopic imbibition, it is necessary to design a shale oil high-pressure imbibition microfluidic experimental device to study the microscopic imbibition law. On this basis, a nanofluidic experimental platform is built to carry out a series of imbibition experiments, so as to have a deeper understanding of the seepage law of oil and water phases in shale porous media. Studying the mechanism of pore-scale imbibition is the key to deeply explain the impact of imbibition and optimize development technology policies. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the prior art and provide a shale oil high-pressure imbibition microfluidic experimental device and method.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A shale oil high-pressure imbibition microfluidic experimental device and method, comprising a nanofluidic chip holder, a matrix chip model is arranged on the nanofluidic chip holder, and the nanofluidic chip holder is connected to a water bath;

[0008] The matrix chip model is connected with a pressure tracking pump and a vacuum pump respectively, and the connection points between the two are connected with an intermediate container and a power pump respectively.

[0009] Preferably, the power pump is used to drive the intermediate container at a constant pressure or a constant speed, and provide a constant pressure or a constant flow rate for the injected fluid in the intermediate container.

[0010] Preferably, the water bath is connected to the thermal fluid circulation interface of the nanofluidic chip holder.

[0011] Preferably, the pressure tracking pump is used to set and adjust a constant outlet pressure during the experiment to simulate the formation pressure during the fracturing fluid injection process.

[0012] Preferably, the vacuum pump is used to evacuate the entire experimental system and the matrix chip model.

[0013] Preferably, the side surfaces of the matrix chip model are respectively provided with a first oil sealing port, a first fracturing fluid injection port and a second oil sealing port.

[0014] Preferably, the pressure tracking pump is connected to the first oil sealing port, and the first fracturing fluid injection port and the second oil sealing port are both connected to a vacuum pump.

[0015] Preferably, the power pump is a double-cylinder constant pressure constant speed pump, and its model is: JMB-01; its volume is 10mL, the flow rate range it can provide is 0.0001-0.2ml / min, and the maximum working pressure is 50MPa.

[0016] Preferably, there are two power pumps, namely power pump No. 1 and power pump No. 2. The power pump No. 1 is connected to the first fracturing fluid injection port and the second oil sealing port through an intermediate container, and the power pump No. 2 is connected to the first oil sealing port through an intermediate container.

[0017] Preferably, two intermediate containers are provided, namely a first intermediate container and a second intermediate container. The first intermediate container is connected to a first power pump, and the second intermediate container is connected to a second power pump.

[0018] Preferably, a first fracturing fluid microchannel, a pore-cavity porous medium and a first shale oil microchannel are provided between the first through hole group of the matrix chip model, the first fracturing fluid injection port is connected to the first fracturing fluid microchannel, the other end of the first fracturing fluid microchannel is connected to the pore-cavity porous medium, and the second oil sealing port is connected to the other end of the pore-cavity porous medium through the first shale oil microchannel, forming a shale oil passage for fracturing fluid infiltration and displacement in the pore-cavity porous medium.

[0019] Preferably, it also includes an optical microscope, a camera and a computer. The camera is arranged on the optical microscope and is used to take pictures to record the backflow process and transmit the image information to the computer.

[0020] Preferably, the first double-cylinder constant pressure and constant speed pump is connected to the first intermediate container through a first pipeline, and the first intermediate container is connected to the first oil sealing port and the fracturing fluid injection port of the nanofluidic chip holder through the second needle valve, the first four-way valve, the three-way valve, the seventh needle valve, and the eighth needle valve in sequence.

[0021] Preferably, the second double-cylinder constant pressure and constant speed pump is connected to the second intermediate container through the second pipeline, and the second intermediate container is connected to the second oil sealing port of the nanofluidic chip holder through the fifth needle valve, the second four-way valve and the sixth needle valve in sequence.

[0022] Preferably, the vacuum pump is connected to the first four-way valve through the ninth needle valve in the fourth pipeline, the pressure tracking pump is connected to the second four-way valve through the fourth needle valve in the third pipeline, and the water bath is connected to the thermal fluid circulation interface of the nanofluidic chip holder.

[0023] Preferably, the first four-way valve and the second four-way valve are also connected to a first vent valve and a second vent valve, respectively.

[0024] In a second aspect, a shale oil high-pressure imbibition microfluidic experimental method comprises the following steps:

[0025] S1: loading simulated fracturing fluid into a first intermediate container and loading simulated shale oil into a second intermediate container;

[0026] S2 establishes a typical petrographic pore structure chip model, installs the matrix chip model into the nanofluidic chip holder, and all valves are initially kept closed;

[0027] S3: Open the third needle valve, the fifth needle valve and the second vent valve, use the second double-cylinder constant pressure and constant speed pump to empty the second intermediate container, and when the oil phase flows out of the second vent valve, close the second double-cylinder constant pressure and constant speed pump, the fifth needle valve and the second vent valve;

[0028] S4 opens the first needle valve, the second needle valve and the first vent valve, uses the first double-cylinder constant pressure and constant speed pump to empty the first intermediate container, and when the first vent valve flows out the water phase, closes the first double-cylinder constant pressure and constant speed pump, the second needle valve and the first vent valve;

[0029] S5: First open the seventh needle valve, the eighth needle valve, and the ninth needle valve, then start the vacuum pump, and after continuously evacuating the entire pipeline and the inside of the matrix chip model for 3 hours, first close the seventh needle valve, the eighth needle valve, and the ninth needle valve, and then turn off the vacuum pump;

[0030] S6 opens the fifth needle valve and the sixth needle valve, and uses the second power pump to inject simulated shale oil into the second oil sealing port of the nanofluidic chip holder at a constant pressure of 1 MPa, and the oil is sealed and matured for more than 24 hours. This process simulates the establishment of initial saturation of the formation;

[0031] S7 After simulating the shale oil saturated matrix chip model, close the No. 2 power pump and the fifth needle valve, open the water bath, heat the chip to a high temperature of 50°C, open the second needle valve and the seventh needle valve, open the No. 1 power pump and inject simulated fracturing fluid into the water injection port of the nanofluidic chip holder at a constant pressure of 1MPa, and low-pressure water is introduced into the fracturing fluid microchannel to ensure that the inside of the fracturing fluid microchannel is filled;

[0032] S8 opens the fourth needle valve and starts the pressure tracking pump. While maintaining a high pressure of 30 MPa on the oil side, the No. 1 power pump increases the pressure to 31 MPa, and injects water at a constant low pressure difference of 1 MPa for 20 minutes to simulate the fracturing fluid injection process. At the same time, take photos with an optical microscope to record the simulated fracturing fluid injection process, including the flow path and distribution of the water phase.

[0033] S9, reduce the pressure of the water injection channel to 30MPa, which is consistent with the pressure of the oil sealing channel, seal the chip under high temperature and high pressure conditions for 2h, and simulate the fracturing fluid to enter the porous medium saturated with simulated shale oil under the action of capillary force and replace the simulated oil. This process simulates the imbibition process of the shale porous medium in the well-clogging stage. At the same time, take pictures with an optical microscope to record the imbibition process, including the oil phase path of water phase imbibition and the distribution of oil and water phases;

[0034] S10, reduce the pressure of the water injection channel to 29MPa to make it lower than the pressure of the oil sealing channel, and flow back for 2h to simulate the fracturing fluid flowback process in the production stage. At the same time, take pictures with an optical microscope to record the flowback process, including the distribution of residual water phase, microscopic cumulative oil production and flowback water volume.

[0035] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0036] In the present invention, the pore structure of the shale core is replicated on the nanofluid chip, which can truly simulate the characteristics of the shale reservoir, and the nanofluidic technology is used to simulate the full-cycle production dynamic process of fracturing fluid injection, well blocking, and well opening for oil production under shale reservoir conditions. At the same time, the microfluidic experimental method is established using the experimental device, and the flow process and distribution state of the oil and water phases in the whole process of pressure-blocking-production are recorded in real time visual monitoring, and the imbibition replacement efficiency is quantitatively calculated using image processing methods. In addition, the invention also has the advantages of fast and accurate measurement, reveals the mechanism of imbibition of shale micro-nano pores, and realizes microscopic pressure-blocking-production dynamic analysis. The present invention provides new technical means and good technical guarantees for truly simulating the high temperature and high pressure environment of underground reservoirs and studying the mechanism of microscopic imbibition through scheme optimization. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic diagram of the structure of a microfluidic experimental device for shale oil high-pressure imbibition according to a specific embodiment of the present invention.

[0038] Figure 2 This is a schematic diagram of the structural design of the matrix chip model for studying the microscopic visualization experiment of high-pressure imbibition in shale oil reservoirs in the present invention.

[0039] Figure 3 This is the oil-water distribution diagram at the end of the matrix chip well blocking in the microscopic visualization experiment of high-pressure imbibition in shale oil reservoirs studied in the present invention.

[0040] Figure numerals: 101, double-cylinder constant pressure and constant speed pump; 102, double-cylinder constant pressure and constant speed pump; 2, first intermediate container; 3, second intermediate container; 4, pressure tracking pump; 5, water bath; 6, nanofluidic chip holder; 7, matrix chip model; 8, optical microscope; 9, camera; 10, computer; 11, vacuum pump; 1201, first pipeline; 1202, second pipeline; 1203, third pipeline; 1204, fourth pipeline; 13, three-way valve; 1401, first four-way valve ; 1402, second four-way valve; 1501, first needle valve; 1502, second needle valve; 1503, third needle valve; 1504, fourth needle valve; 1505, fifth needle valve; 1506, sixth needle valve; 1601, first vent valve; 1602, second vent valve; 701, first oil sealing port; 702, first fracturing fluid injection port; 703, second oil sealing port; 704, first fracturing fluid microchannel; 705, first shale oil microchannel; 706, pore-cavity type porous medium. DETAILED DESCRIPTION

[0041] The following is combined with Figure 1-3 , further illustrating the specific implementation of a shale oil high pressure infiltration microfluidic experimental device and method of the present invention. A shale oil high pressure infiltration microfluidic experimental device and method of the present invention are not limited to the description of the following embodiments.

[0042] Embodiment 1:

[0043] A shale oil high pressure imbibition microfluidic experimental device, such as Figure 1 As shown, it includes a nanofluidic chip holder 6, on which a matrix chip model 7 is provided, and the nanofluidic chip holder 6 is connected to a water bath 5;

[0044] The matrix chip model 7 is connected to the pressure tracking pump 4 and the vacuum pump 11 respectively, and the connection points between the two are connected to the intermediate container and the power pump in sequence.

[0045] Furthermore, the power pump is used to drive the intermediate container at a constant pressure or a constant speed, so as to provide a constant pressure or a constant flow rate for the injected fluid in the intermediate container.

[0046] Furthermore, the water bath 5 is connected to the thermal fluid circulation interface of the nanofluidic chip holder 6 .

[0047] Furthermore, the water bath 5 is used to heat the nanofluidic chip holder 6 and the nanofluidic chip to simulate the actual formation temperature.

[0048] Furthermore, the nanofluidic chip holder 6 can withstand a high pressure of 100 MPa and a high temperature of 200° C. The nanofluidic chip holder is used to clamp the matrix chip model, can effectively fix the matrix chip model, and can simulate the high temperature and high pressure formation conditions of shale reservoirs.

[0049] Furthermore, the pressure tracking pump 4 is used to set and adjust a constant outlet pressure during the experiment to simulate the formation pressure during the fracturing fluid injection process.

[0050] Furthermore, the vacuum pump 11 is used to evacuate the entire experimental system and the matrix chip model.

[0051] Furthermore, the side surfaces of the matrix chip model 7 are respectively provided with a first oil sealing port 701 , a first fracturing fluid injection port 702 and a second oil sealing port 703 .

[0052] Furthermore, the pressure tracking pump 4 is connected to the first oil sealing port 701 , and the first fracturing fluid injection port 702 and the second oil sealing port 703 are both connected to the vacuum pump 11 .

[0053] Furthermore, the power pump is a double-cylinder constant pressure constant speed pump, and its model is: JMB-01; its volume is 10mL, the flow rate range it can provide is 0.0001-0.2ml / min, and the maximum working pressure is 50MPa.

[0054] Furthermore, the power pump is a double-cylinder constant pressure and constant speed pump, which is used to drive the intermediate container at a constant pressure or constant speed, and provide a constant pressure or a constant flow rate for the injected fluid in the intermediate container. The double-cylinder constant pressure and constant speed pump can provide a flow rate range of 0.0001 to 30 ml / min, and a maximum working pressure of 120 MPa.

[0055] Furthermore, two power pumps are provided, namely power pump No. 1 101 and power pump No. 2 102. Power pump No. 1 101 is connected to the first fracturing fluid injection port 702 and the second oil sealing port 703 through an intermediate container, and power pump No. 2 102 is connected to the first oil sealing port 701 through an intermediate container.

[0056] Furthermore, the pressure tracking pump 4 is used to set and adjust a constant outlet pressure during the experiment to simulate the formation pressure during the fracturing fluid injection process.

[0057] Furthermore, two intermediate containers are provided, namely a first intermediate container 2 and a second intermediate container 3 . The first intermediate container 2 is connected to the first power pump 101 , and the second intermediate container 3 is connected to the second power pump 102 .

[0058] Furthermore, two intermediate containers are used to contain the oil and water phases used in the experiment respectively. The intermediate containers have a pressure resistance of 100 MPa and a working temperature of 200° C. The material is preferably but not limited to 316L stainless steel.

[0059] Furthermore, the vacuum pump 11 is used to evacuate the entire experimental system and the matrix chip model.

[0060] Furthermore, the first through hole group of the matrix chip model 7 is provided with a first fracturing fluid microchannel 704, a pore-cavity porous medium 706 and a first shale oil microchannel 705, the first fracturing fluid injection port 702 is connected to the first fracturing fluid microchannel 704, the other end of the first fracturing fluid microchannel 704 is connected to the pore-cavity porous medium 706, and the second oil sealing port 703 is connected to the other end of the pore-cavity porous medium 706 through the first shale oil microchannel 705, forming a shale oil passage for the fracturing fluid to absorb and displace the shale oil in the pore-cavity porous medium. The width of the fracturing fluid microchannel and the shale oil microchannel are both 400 μm and the depth is both 20 μm.

[0061] Furthermore, it also includes an optical microscope 8, a camera 9 and a computer 10. The camera 9 is arranged on the optical microscope 8 to take pictures and record the backflow process, and transmit the image information to the computer 10.

[0062] Furthermore, the optical microscope 8, the camera 9 and the computer 10 together constitute an imaging system. The optical microscope 8 is used to observe the fluid changes in the matrix chip model in real time, and transmit the image in real time through the camera 9 and store it in the computer 10, and use image processing software for visual analysis and quantitative evaluation.

[0063] Further, the nanofluidic chip holder is connected to the water bath through a fluid circulation interface;

[0064] Above the nanofluidic chip holder is an optical microscope, which is connected to a computer via a camera;

[0065] The vacuum pump is connected to the first four-way valve through a fourth pipeline;

[0066] The pressure tracking pump is connected to the second four-way valve through a third pipeline;

[0067] The first pipeline is respectively provided with a first needle valve, a second needle valve, a seventh needle valve, an eighth needle valve, a first four-way valve, a first three-way valve, and a first vent valve;

[0068] The second pipeline is respectively provided with a third needle valve, a fifth needle valve, a sixth needle valve, a second four-way valve, and a second vent valve;

[0069] The third pipeline and the fourth pipeline are respectively provided with a fourth needle valve and a ninth needle valve.

[0070] Furthermore, the first double-cylinder constant pressure and constant speed pump 101 is connected to the first intermediate container 2 through the first pipeline 1201, and the first intermediate container 2 is connected to the first oil sealing port 701 and the fracturing fluid injection port 702 of the nanofluidic chip holder 6 through the second needle valve 1502, the first four-way valve 1401, the three-way valve 13, the seventh needle valve 1507, and the eighth needle valve 1508 in sequence.

[0071] Furthermore, the second double-cylinder constant pressure and constant speed pump 102 is connected to the second intermediate container 3 through the second pipeline 1202, and the second intermediate container is connected to the second oil sealing port 703 of the nanofluidic chip holder 6 through the fifth needle valve 1505, the second four-way valve 1402, and the sixth needle valve 1506 in sequence.

[0072] Furthermore, the vacuum pump 11 is connected to the first four-way valve 1401 through the ninth needle valve 1509 in the fourth pipeline 1204, the pressure tracking pump 4 is connected to the second four-way valve 1402 through the fourth needle valve 1504 in the third pipeline 1203, and the water bath 5 is connected to the thermal fluid circulation interface of the nanofluidic chip holder 6.

[0073] Furthermore, the first four-way valve 1401 and the second four-way valve 1402 are also connected to the first vent valve 1601 and the second vent valve 1602 respectively.

[0074] Example 2

[0075] A shale oil high-pressure imbibition microfluidic experimental method comprises the following steps:

[0076] S1: loading simulated fracturing fluid into a first intermediate container 2 and loading simulated shale oil into a second intermediate container 3;

[0077] S2 establishes a typical petrographic pore structure chip model, installs the matrix chip model 7 into the nanofluidic chip holder 6, and all valves are initially kept closed;

[0078] S3: Open the third needle valve 1503, the fifth needle valve 1505 and the second vent valve 1602, and use the second double-cylinder constant pressure and constant speed pump 102 to empty the second intermediate container 3. When the oil phase flows out of the second vent valve, close the second double-cylinder constant pressure and constant speed pump 102, the fifth needle valve 1505 and the second vent valve 1602;

[0079] S4 opens the first needle valve 1501, the second needle valve 1502 and the first vent valve 1601, and uses the first double-cylinder constant pressure and constant speed pump 101 to empty the first intermediate container 2. When the first vent valve flows out the water phase, close the first double-cylinder constant pressure and constant speed pump 101, the second needle valve 1502 and the first vent valve 1601;

[0080] S5: First open the seventh needle valve 1507, the eighth needle valve 1508, and the ninth needle valve 1509, then start the vacuum pump 11, and after the entire pipeline and the inside of the matrix chip model are continuously evacuated for 3 hours, first close the seventh needle valve 1507, the eighth needle valve 1508, and the ninth needle valve 1509, and then close the vacuum pump 11;

[0081] S6: Open the fifth needle valve 1505 and the sixth needle valve 1506, and use the second power pump 102 to inject simulated shale oil into the second oil sealing port 703 of the nanofluidic chip holder 6 at a constant pressure of 1 MPa, and seal the oil for more than 24 hours. This process simulates the establishment of initial saturation of the formation;

[0082] S7 After simulating the shale oil saturated matrix chip model, close the second power pump 102 and the fifth needle valve 1505, open the water bath 5, heat the chip to a high temperature of 50°C, open the second needle valve 1502 and the seventh needle valve 1507, open the first power pump 101 and inject simulated fracturing fluid into the water injection port 702 of the nanofluidic chip holder 6 at a constant pressure of 1 MPa, and low-pressure water is introduced into the fracturing fluid microchannel 704 to ensure that the inside of the fracturing fluid microchannel is filled;

[0083] S8 opens the fourth needle valve 1504 and starts the pressure tracking pump 4. While maintaining the high pressure of 30MPa on the oil side, the power pump No. 101 increases the pressure to 31MPa, and injects water at a constant low pressure difference of 1MPa for 20 minutes to simulate the fracturing fluid injection process. At the same time, take pictures with an optical microscope to record the simulated fracturing fluid injection process, including the flow path and distribution of the water phase.

[0084] S9, reduce the pressure of the water injection channel to 30MPa, which is consistent with the pressure of the oil sealing channel, seal the chip under high temperature and high pressure conditions for 2h, and simulate the fracturing fluid to enter the porous medium saturated with simulated shale oil under the action of capillary force and replace the simulated oil. This process simulates the imbibition process of the shale porous medium in the well-clogging stage. At the same time, take pictures with an optical microscope to record the imbibition process, including the oil phase path of water phase imbibition and the distribution of oil and water phases;

[0085] S10, reduce the pressure of the water injection channel to 29MPa to make it lower than the pressure of the oil sealing channel, and flow back for 2h to simulate the fracturing fluid flowback process in the production stage. At the same time, take pictures with an optical microscope to record the flowback process, including the distribution of residual water phase, microscopic cumulative oil production and flowback water volume.

[0086] Example 3

[0087] like Figure 1 A shale oil high-pressure imbibition microfluidic experimental device, used for shale oil reservoir microscopic imbibition visualization and evaluation device, a first double-cylinder constant pressure and constant speed pump 101 is connected to the first intermediate container 2 through a first pipeline 1201, the first intermediate container is connected to the first oil sealing port 701 and the fracturing fluid injection port 702 of the nanofluidic chip holder 6 through a second needle valve 1502, a first four-way valve 1401, a three-way valve 13, a seventh needle valve 1507, and an eighth needle valve 1508, a second double-cylinder constant pressure and constant speed pump 102 is connected to the second intermediate container 3 through a second pipeline 1202, and the second intermediate container is connected to the first oil sealing port 701 and the fracturing fluid injection port 702 of the nanofluidic chip holder 6 through a second needle valve 1502, a first four-way valve 1401, a three-way valve 13, a seventh needle valve 1507, and an eighth needle valve 1508 in sequence, 02. The sixth needle valve 1506 is connected to the second oil sealing port 703 of the nanofluidic chip holder 6. Above the nanofluidic chip holder 6 is an optical microscope 8, which is connected to the computer 10 through a camera 9. The vacuum pump 11 is connected to the first four-way valve 1401 through the ninth needle valve 1509 in the fourth pipeline 1204. The pressure tracking pump 4 is connected to the second four-way valve 1402 through the fourth needle valve 1504 in the third pipeline 1203. The water bath 5 is connected to the thermal fluid circulation interface of the nanofluidic chip holder 6. The first four-way valve 1401 and the second four-way valve 1402 are also connected to the first vent valve 1601 and the second vent valve 1602, respectively.

[0088] Example 4

[0089] like Figure 2 , a shale oil high-pressure imbibition microfluidic experimental device, a schematic diagram of the structural design of the matrix chip model, a first oil sealing port 701, a first fracturing fluid inlet 702 and a second oil sealing port 703 are respectively opened in the upper, middle and lower parts of the left side of the chip, and the first oil sealing port 701 is connected to the second oil sealing port 703 through the first fracturing fluid microchannel.

[0090] The first through hole group of the matrix chip model is provided with a first fracturing fluid microchannel 704, a pore-cavity porous medium 706 and a first shale oil microchannel 705, the first fracturing fluid inlet 702 is connected to the first fracturing fluid microchannel 704, the other end of the first fracturing fluid microchannel is connected to the pore-cavity porous medium, and the second oil sealing port 703 is connected to the other end of the pore-cavity porous medium 706 through the first shale oil microchannel 705, thereby forming a shale oil passage for the fracturing fluid to absorb and displace in the pore-cavity porous medium. The first fracturing fluid microchannel and the first shale oil microchannel have a width of 400 μm and a depth of 20 μm, the pore width in the pore-cavity porous medium 706 varies from 3 to 15 μm, the depth is 50 nm, and the depth of the irregular-shaped cave is 50 nm; for the irregular-shaped cave, different numbers of pore throat coordination numbers are provided, ranging from 0 to 4.

[0091] Example 5

[0092] Taking the matrix chip model imbibition process as an example, the experimental method of the present invention is:

[0093] S1, the first intermediate container 2 is filled with simulated fracturing fluid, and the second intermediate container 3 is filled with simulated shale oil;

[0094] S2, installing the matrix chip model 7 into the nanofluidic chip holder 6, and all valves are initially kept closed;

[0095] S3, open the third needle valve 1503, the fifth needle valve 1505 and the second vent valve 1602, use the second double-cylinder constant pressure and constant speed pump 102 to empty the second intermediate container 3, and when the oil phase flows out of the second vent valve, close the second double-cylinder constant pressure and constant speed pump 102, the fifth needle valve 1505 and the second vent valve 1602;

[0096] S4, open the first needle valve 1501, the second needle valve 1502 and the first vent valve 1601, use the first double-cylinder constant pressure and constant speed pump 101 to empty the first intermediate container 2, and when the first vent valve flows out the water phase, close the first double-cylinder constant pressure and constant speed pump 101, the second needle valve 1502 and the first vent valve 1601;

[0097] S5, first open the seventh needle valve 1507, the eighth needle valve 1508, and the ninth needle valve 1509, then start the vacuum pump 11, and after the entire pipeline and the inside of the matrix chip model are continuously evacuated for 3 hours, first close the seventh needle valve, the eighth needle valve, and the ninth needle valve, and then close the vacuum pump 11;

[0098] S6, open the fifth needle valve 1505 and the sixth needle valve 1506, use the second double-cylinder constant pressure constant speed pump 102 to inject simulated shale oil into the second oil sealing port 703 of the nanofluidic chip holder 6, and seal the oil for more than 24 hours. This process simulates the establishment of initial saturation of the formation;

[0099] S7, after simulating the shale oil saturated matrix chip model, close the second double-cylinder constant pressure and constant speed pump 102 and the fifth needle valve 1505, open the water bath 5, heat the chip to a high temperature condition, open the second needle valve 1502 and the seventh needle valve 1507, use the first double-cylinder constant pressure and constant speed pump 101 to inject simulated fracturing fluid into the water injection port 702 of the nanofluidic chip holder 6, and low-pressure water is introduced into the fracturing fluid microchannel 704 to ensure that the inside of the fracturing fluid microchannel is filled;

[0100] S8, open the fourth needle valve 1504 and start the pressure tracking pump 4, and inject water for a specified time at a constant low pressure difference under the condition of maintaining the high pressure on the oil side to simulate the fracturing fluid injection process, and take pictures with an optical microscope to record the simulated fracturing fluid injection process, including the flow path and distribution of the water phase;

[0101] S9, lowering the pressure of the water injection channel to be consistent with the pressure of the oil sealing channel, sealing the chip under high temperature and high pressure conditions for a specified time, simulating the fracturing fluid to enter the porous medium saturated with simulated shale oil under the action of capillary force and replace the simulated oil. This process simulates the imbibition process of the shale porous medium in the well-clogging stage, and taking pictures with an optical microscope to record the imbibition process, including the oil phase path of water phase imbibition and the distribution of oil and water phases;

[0102] S10, reduce the pressure of the water injection channel to make it lower than the pressure of the oil sealing channel, simulate the fracturing fluid backflow process in the production stage, and take pictures with an optical microscope to record the backflow process, including the distribution of residual water phase, microscopic cumulative oil production and backflow water volume.

[0103] As a preferred embodiment of the present invention, the simulated fracturing fluid is deionized water with the same composition as formation water; in S4, the second double-cylinder constant pressure and constant speed pump 102 injects simulated shale oil into the second oil sealing port 703 of the nanofluidic chip holder 6 at a flow rate of 0.1-10 μL / min; in S5, the first double-cylinder constant pressure and constant speed pump 101 injects simulated fracturing fluid into the water injection port of the nanofluidic chip holder 6 at a flow rate of 5-20 μL / min;

[0104] As a preferred embodiment of the present invention, after S8 is completed, the intermediate container is replaced with toluene, methanol and deionized water in turn, and the matrix chip model 7 is flushed with toluene, methanol and deionized water at a flow rate of 1 mL / min-200 mL / min in turn until there is no residue inside the chip; the chip is removed, wiped clean and placed in an oven for drying to remove water and organic residues. The matrix chip model is placed in the oven for more than 12 hours for use in the next experiment.

[0105] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A shale oil high-pressure imbibition microfluidic experimental device, characterized in that: It comprises a nanofluidic chip holder (6), on which a matrix chip model (7) is arranged, and the nanofluidic chip holder (6) is connected to a water bath (5); The matrix chip model (7) is connected to a pressure tracking pump (4) and a vacuum pump (11), respectively, and the connection points between the two are connected to an intermediate container and a power pump in sequence.

2. A shale oil high pressure imbibition microfluidic experimental device as claimed in claim 1, characterized in that: The power pump is used to drive the intermediate container at a constant pressure or a constant speed, and provide a constant pressure or a constant flow rate for the injected fluid in the intermediate container.

3. A shale oil high pressure imbibition microfluidic experimental device as claimed in claim 1, characterized in that: The water bath (5) is connected to the thermal fluid circulation interface of the nanofluidic chip holder (6).

4. A shale oil high pressure imbibition microfluidic experimental device according to claim 1, characterized in that: The pressure tracking pump (4) is used to set and adjust a constant outlet pressure during the experiment to simulate the formation pressure during the fracturing fluid injection process.

5. A shale oil high pressure imbibition microfluidic experimental device as claimed in claim 1, characterized in that: The vacuum pump (11) is used to evacuate the entire experimental system and the matrix chip model.

6. A shale oil high pressure imbibition microfluidic experimental device as claimed in claim 1, characterized in that: The side surface of the matrix chip model (7) is respectively provided with a first oil sealing port (701), a first fracturing fluid injection port (702) and a second oil sealing port (703).

7. A shale oil high pressure imbibition microfluidic experimental device as claimed in claim 6, characterized in that: The pressure tracking pump (4) is connected to the first oil sealing port (701), and the first fracturing fluid injection port (702) and the second oil sealing port (703) are both connected to the vacuum pump (11).

8. A shale oil high pressure imbibition microfluidic experimental device as claimed in claim 1, characterized in that: The power pump is a double-cylinder constant pressure and constant speed pump, and its model is: JMB-01; its volume is 10mL, the flow rate range it can provide is 0.0001-0.2ml / min, and the maximum working pressure is 50MPa.

9. A shale oil high pressure imbibition microfluidic experimental device as claimed in claim 6, characterized in that: The power pumps are provided with two, namely, a first power pump (101) and a second power pump (102). The first power pump (101) is connected to the first fracturing fluid injection port (702) and the second oil sealing port (703) through an intermediate container, and the second power pump (102) is connected to the first oil sealing port (701) through an intermediate container.

10. A shale oil high pressure imbibition microfluidic experimental device according to claim 9, characterized in that: The intermediate containers are provided with two, namely a first intermediate container (2) and a second intermediate container (3). The first intermediate container (2) is connected to a first power pump (101), and the second intermediate container (3) is connected to a second power pump (102).

11. A shale oil high pressure imbibition microfluidic experimental device according to claim 6, characterized in that: A first fracturing fluid microchannel (704), a pore-cavity porous medium (706) and a first shale oil microchannel (705) are provided between the first through hole group of the matrix chip model (7); a first fracturing fluid injection port (702) is connected to the first fracturing fluid microchannel (704); the other end of the first fracturing fluid microchannel (704) is connected to the pore-cavity porous medium (706); and a second oil sealing port (703) is connected to the other end of the pore-cavity porous medium (706) through the first shale oil microchannel (705), thereby forming a shale oil passage for the fracturing fluid to infiltrate and displace in the pore-cavity porous medium.

12. A shale oil high pressure imbibition microfluidic experimental device as claimed in claim 1, characterized in that: It also includes an optical microscope (8), a camera (9) and a computer (10). The camera (9) is arranged on the optical microscope (8) and is used to take pictures and record the flowback process, and transmit image information to the computer (10).

13. A shale oil high pressure imbibition microfluidic experimental device according to claim 10, characterized in that: The first double-cylinder constant pressure and constant speed pump (101) is connected to the first intermediate container (2) via the first pipeline (1201), and the first intermediate container (2) is connected to the first oil sealing port (701) and the fracturing fluid injection port (702) of the nanofluidic chip holder (6) via the second needle valve (1502), the first four-way valve (1401), the three-way valve (13), the seventh needle valve (1507), and the eighth needle valve (1508) in sequence.

14. A shale oil high pressure imbibition microfluidic experimental device according to claim 10, characterized in that: The second double-cylinder constant pressure and constant speed pump (102) is connected to the second intermediate container (3) via the second pipeline (1202), and the second intermediate container is connected to the second oil sealing port (703) of the nanofluidic chip holder (6) via the fifth needle valve (1505), the second four-way valve (1402), and the sixth needle valve (1506) in sequence.

15. The shale oil high pressure imbibition microfluidic experimental device according to claim 10, characterized in that: The vacuum pump (11) is connected to the first four-way valve (1401) via the ninth needle valve (1509) in the fourth pipeline (1204), the pressure tracking pump (4) is connected to the second four-way valve (1402) via the fourth needle valve (1504) in the third pipeline (1203), and the water bath (5) is connected to the thermal fluid circulation interface of the nanofluidic chip holder (6).

16. A shale oil high pressure imbibition microfluidic experimental device according to claim 15, characterized in that: The first four-way valve (1401) and the second four-way valve (1402) are also connected to a first vent valve (1601) and a second vent valve (1602), respectively.

17. A shale oil high pressure imbibition microfluidic experimental method, characterized in that: The following steps are involved: S1: loading simulated fracturing fluid into a first intermediate container (2), and loading simulated shale oil into a second intermediate container (3); S2 establishes a typical petrographic pore structure chip model, installs the matrix chip model (7) into the nanofluidic chip holder (6), and all valves are initially kept closed; S3 opens the third needle valve (1503), the fifth needle valve (1505) and the second vent valve (1602), and uses the second double-cylinder constant pressure and constant speed pump (102) to empty the second intermediate container (3). When the oil phase flows out of the second vent valve, closes the second double-cylinder constant pressure and constant speed pump (102), the fifth needle valve (1505) and the second vent valve (1602); S4: opening the first needle valve (1501), the second needle valve (1502) and the first vent valve (1601), and using the first double-cylinder constant-pressure constant-speed pump (101) to empty the first intermediate container (2); when the first vent valve flows out the water phase, closing the first double-cylinder constant-pressure constant-speed pump (101), the second needle valve (1502) and the first vent valve (1601); S5: First open the seventh needle valve (1507), the eighth needle valve (1508), and the ninth needle valve (1509), and then start the vacuum pump (11). After the entire pipeline and the inside of the matrix chip model are continuously evacuated for 3 hours, the seventh needle valve (1507), the eighth needle valve (1508), and the ninth needle valve (1509) are first closed, and then the vacuum pump (11) is closed; S6: Open the fifth needle valve (1505) and the sixth needle valve (1506), and use the second power pump (102) to inject simulated shale oil into the second oil sealing port (703) of the nanofluidic chip holder (6) at a constant pressure of 1 MPa, and seal the oil for more than 24 hours. This process simulates the establishment of initial saturation of the formation; S7 After simulating the shale oil saturated matrix chip model, close the second power pump (102) and the fifth needle valve (1505), open the water bath (5), heat the chip to a high temperature condition of 50°C, open the second needle valve (1502) and the seventh needle valve (1507), open the first power pump (101) to inject simulated fracturing fluid into the water injection port (702) of the nanofluidic chip holder (6) at a constant pressure of 1 MPa, and low-pressure water is introduced into the fracturing fluid microchannel (704) to ensure that the inside of the fracturing fluid microchannel is filled; S8 opens the fourth needle valve (1504) and starts the pressure tracking pump (4). While maintaining the high pressure of 30 MPa on the oil side, the power pump (101) increases the pressure to 31 MPa, and injects water at a constant low pressure difference of 1 MPa for 20 minutes to simulate the fracturing fluid injection process. At the same time, an optical microscope is used to take pictures to record the simulated fracturing fluid injection process, including the flow path and distribution of the water phase. S9, reduce the pressure of the water injection channel to 30MPa, which is consistent with the pressure of the oil sealing channel, seal the chip under high temperature and high pressure conditions for 2h, and simulate the fracturing fluid to enter the porous medium saturated with simulated shale oil under the action of capillary force and replace the simulated oil. This process simulates the imbibition process of the shale porous medium in the well-clogging stage. At the same time, take pictures with an optical microscope to record the imbibition process, including the oil phase path of water phase imbibition and the distribution of oil and water phases; S10, reduce the pressure of the water injection channel to 29MPa to make it lower than the pressure of the oil sealing channel, and flow back for 2h to simulate the fracturing fluid flowback process in the production stage. At the same time, take pictures with an optical microscope to record the flowback process, including the distribution of residual water phase, microscopic cumulative oil production and flowback water volume.

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