Device for simulating improvement of huff-puff recovery ratio of shale oil by using carbon dioxide-hydrocarbon mixed gas

Abstract

The invention discloses a device for simulating utilization of carbon dioxide-hydrocarbon mixed gas to improve shale oil huff and puff recovery efficiency, which comprises a main branch, and the main branch is provided with a first auxiliary branch, a second auxiliary branch, a third auxiliary branch and a fourth auxiliary branch. The main branch is provided with a first auxiliary branch, a second auxiliary branch, a third auxiliary branch and a fourth auxiliary branch which are all arranged in the constant-temperature box, the first auxiliary branch is used for simulating saturated simulation oil entering a rock core, the second auxiliary branch is used for simulating preparation of CO2-hydrocarbon mixed gas, the third auxiliary branch is used for simulating well opening production, and the fourth auxiliary branch is used for simulating oil gas entering the rock core. And the fourth auxiliary branch is used for simulating the confining pressure on the rock core. By means of the device, the compressibility of CO2 in the early stage of huff and puff can be improved, the miscibility of CO2 and simulated oil in the later stage of huff and puff can be enhanced, then the dissolved gas drive effect is fully played, the carrying capacity of CO2 on crude oil in a pore throat is improved, meanwhile, the competitive adsorption capacity of CO2 in organic matter can be improved by adding propane, and therefore the recovery efficiency is improved.

Description

Technical Field

[0001] The invention relates to a simulated oil production device, more specifically, to a device for simulating the use of carbon dioxide-hydrocarbon mixed gas to improve the shale oil throughput recovery rate. Background Art

[0002] In recent years, with the decline in the production of conventional oil reservoirs, shale oil reservoirs have attracted more and more attention due to their rich reserves and huge development potential. However, compared with conventional oil reservoirs, shale oil reservoirs are rich in organic matter, and nano-micron pore throats (pore diameter between 50 and 300 nm) are widely developed in the reservoirs, and the matrix porosity and permeability are also poorly developed. In addition, fluids exist in shale in various forms, including free states stored in matrix pores, microcracks and layer fractures, and adsorbed and dissolved states adsorbed on the pore surface and dissolved in organic matter (kerogen and asphalt), and the latter is more difficult to mobilize than the former. Based on the above characteristics, shale oil reservoirs are difficult to develop and the mining effect is average. It is becoming increasingly important to find suitable technologies to effectively develop shale oil reservoirs.

[0003] Horizontal wells combined with multi-stage hydraulic fracturing technology can achieve effective development of shale reservoirs on an initial scale. However, due to the complex pore structure and small pore throats of shale reservoirs, formation energy is not easy to be replenished through edge and bottom water. Oil and gas are produced only by elastic energy and dissolved gas drive, which leads to a rapid decline in formation pressure and crude oil production, and the initial recovery degree is usually less than 10%. Water injection is a common way to replenish energy, but it is not suitable for shale reservoirs because water drive has poor injection capacity, low sweep efficiency, and can cause clay minerals to expand and block small pore throats. Compared with water injection, gas injection can quickly and effectively enter tight reservoirs, but considering the strong heterogeneity and developed fractures of shale reservoirs, gas drive may cause viscous fingering or gas channeling, and the development effect is often poor. Gas injection huff and puff extracts and carries crude oil through repeated injection of gas in multiple rounds, effectively avoiding the problem of difficult control of injected fluid mobility, and is an effective shale reservoir development technology.

[0004] CO2 is a common huff-and-puff gas that has been widely used in tight oil reservoirs such as Bakken, Eagle Ford, Jiangsu, and Daqing. During the huff-and-puff process, CO2 can significantly reduce crude oil viscosity and interfacial tension, increase crude oil volume expansion, extract light components of crude oil, effectively adsorb in kerogen, and form dissolved gas drive inside the pore throat. These characteristics of CO2 are extremely beneficial to improving the recovery rate of shale oil reservoirs. However, in the process of CO2 huff-and-puff, there are also problems such as the early stage of huff-and-puff, gas can be injected but cannot be spit out, and in the later stage of huff-and-puff, oil and gas are separated, and the efficiency of gas carrying crude oil is not high. In the early stage of huff-and-puff, the oil saturation in the reservoir is high, but due to the low porosity and low permeability characteristics of shale, it is particularly difficult for crude oil to flow in the pore throat. The volume expansion of CO2 separated during depressurization production is limited, and it is difficult to play the role of dissolved gas drive. Some gas is also bound in the pore throat and difficult to return. In the later stage of huff and puff, as the oil saturation in the reservoir decreases, the reservoir gradually becomes depleted, and the CO2 separated during the depressurization production easily aggregates into a continuous gas phase and rushes to the bottom of the production well, unable to effectively carry the crude oil in the pores to flow to the bottom of the well. Therefore, in the process of CO2 huff and puff, how to increase the volume expansion of CO2, enhance the carrying capacity of CO2 for crude oil in the pore throat, and improve the desorption capacity of CO2 for adsorbed dissolved crude oil is of great significance to accelerate the efficient development of shale oil. Summary of the invention

[0005] Based on this, it is necessary to provide a device for simulating the use of carbon dioxide-hydrocarbon mixed gas to improve shale oil throughput recovery rate in response to the above technical problems.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A device for simulating the use of carbon dioxide-hydrocarbon mixed gas to improve the throughput recovery rate of shale oil, characterized in that the device for simulating the use of carbon dioxide-hydrocarbon mixed gas to improve the throughput recovery rate of shale oil comprises a main branch, the main branch is provided with a first sub-branch, a second sub-branch, a third sub-branch and a fourth sub-branch, the main branch, the first sub-branch, the second sub-branch, the third sub-branch and the fourth sub-branch are all arranged in a constant temperature box,

[0008] Among them, the first sub-branch is used to simulate the saturated simulated oil entering the core, the second sub-branch is used to simulate the preparation of CO2-hydrocarbon mixed gas, the third sub-branch is used to simulate well opening production, and the fourth sub-branch is used to simulate the confining pressure on the core.

[0009] As a preferred embodiment of the present invention, the hydrocarbon gas in the CO2-hydrocarbon mixed gas is one of methane, ethane and propane.

[0010] As a preferred embodiment of the present invention, the CO2-hydrocarbon mixed gas is in a gaseous state or a supercritical state, and the molar concentration of the hydrocarbon gas in the mixed gas is 0% to 20%.

[0011] As a preferred embodiment of the present invention, the main branch is connected in series with a vacuum pump, a third stop valve, a mixed gas storage tank, a seventh stop valve, a third three-way joint, a stainless steel high-pressure coil, a nuclear magnetic resonance imaging analyzer, a fourth three-way joint, a ninth stop valve and a first simulated oil intermediate container.

[0012] The first secondary branch is provided with a second stop valve, a first three-way joint and a core saturation tank connected in series, the first three-way joint is provided with a first pressure sensor, the core saturation tank is provided with a core, the side wall of the core saturation tank is provided with a first stop pipe, the first stop pipe is provided with a first stop valve, the end of the first stop pipe is provided with a second simulated oil intermediate container, the second simulated oil intermediate container is provided with simulated oil, and the outside of the second simulated oil intermediate container is provided with a simulated oil saturation pump,

[0013] The second secondary branch is provided with a fourth stop valve, a second three-way joint, a visual container and a mixed gas injection pump connected in series, the second three-way joint is provided with a third pressure sensor, the outer wall of the visual container is provided with a fifth stop valve pipeline and a sixth stop valve pipeline, the fifth stop valve pipeline is provided with a fifth stop valve, the sixth stop valve pipeline is provided with a sixth stop valve, the end of the fifth stop valve pipeline is provided with a hydrocarbon gas intermediate container, the hydrocarbon gas intermediate container is provided with a second pressure sensor, the hydrocarbon gas intermediate container is connected to the hydrocarbon gas injection pump through a pipeline, and the end of the sixth stop valve pipeline is provided with a CO2 storage tank,

[0014] The third auxiliary branch is provided with an eighth stop valve and an oil-gas separator connected in series.

[0015] The nuclear magnetic resonance imaging analyzer is provided with a three-axis core holder inside, and the annulus of the three-axis core holder is filled with fluorine oil.

[0016] The fourth auxiliary branch is provided with a confining pressure pump, and the confining pressure pump is connected to the nuclear magnetic resonance imaging analyzer.

[0017] As a preferred embodiment of the present invention, the first three-way joint includes a first joint, a second joint and a third joint, the second three-way joint includes a fourth joint, a fifth joint and a sixth joint, the third three-way joint includes a seventh joint, an eighth joint and a ninth joint, and the fourth three-way joint includes a tenth joint, an eleventh joint and a twelfth joint.

[0018] The first simulated oil intermediate container is connected to the tenth joint of the fourth three-way joint through a pipeline, a ninth stop valve is arranged on the pipeline between the first simulated oil intermediate container and the fourth three-way joint, the three-axis core holder is connected to the eleventh joint of the fourth three-way joint through a pipeline, and the fifth pressure sensor is connected to the twelfth joint of the fourth three-way joint through a pipeline,

[0019] The stainless steel high-pressure coil is connected to the seventh joint of the third three-way joint through a pipeline.

[0020] One end of the oil-gas separator is connected to the eighth joint of the third three-way joint through a pipeline, and one end of the oil-gas separator is connected to the outside through a pipeline. An eighth stop valve is arranged on the pipeline between the oil-gas separator and the third three-way joint.

[0021] The mixed gas storage tank is connected to the ninth joint of the third three-way joint through a pipeline, a seventh stop valve is arranged on the pipeline between the mixed gas storage tank and the third three-way joint, the visual container is connected to the fourth joint of the second three-way joint through a pipeline, the mixed gas storage tank is connected to the fifth joint of the second three-way joint, a fourth stop valve is arranged on the pipeline between the mixed gas storage tank and the second three-way joint, the third pressure sensor is connected to the sixth joint of the second three-way joint through a pipeline, the core saturation tank is connected to the first joint of the first three-way joint through a pipeline, the first pressure sensor is connected to the second joint of the first three-way joint through a pipeline, the vacuum pump is connected to the third joint of the first three-way joint through a pipeline, a second stop valve is arranged on the pipeline between the vacuum pump and the first three-way joint, the second simulated oil intermediate container is connected to the simulated oil saturation pump and the core saturation tank through a pipeline, the A first stop valve is arranged on the pipeline between the second simulated oil intermediate container and the core saturation tank, the hydrocarbon gas intermediate container is connected to the hydrocarbon gas injection pump, the second pressure sensor and the visible container through a pipeline, a fifth stop valve is arranged on the pipeline between the hydrocarbon gas intermediate container and the visible container, the mixed gas injection pump is connected to the visible container through a pipeline, the CO2 storage tank is connected to the visible container through a pipeline, a sixth stop valve is arranged on the pipeline between the CO2 storage tank and the visible container, the stainless steel high-pressure coil is connected to the three-axis core clamp through a pipeline, the confining pressure pump is connected to the three-axis core clamp through a pipeline, the three-axis core clamp is placed in a nuclear magnetic resonance imaging analyzer, the fourth pressure sensor is connected to the mixed gas storage tank through a pipeline, the vacuum pump is connected to the mixed gas storage tank through a pipeline, and a third stop valve is arranged on the pipeline between the vacuum pump and the mixed gas storage tank.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention provides a device for simulating the use of carbon dioxide-hydrocarbon mixed gas to improve the throughput recovery rate of shale oil. The device can accurately simulate the influence of carbon dioxide-hydrocarbon mixed gas on the throughput recovery rate of high shale oil, thereby guiding actual production. Through this method, the compressibility of CO2 can be improved in the early stage of throughput, and the miscibility of CO2 with simulated oil can be enhanced in the later stage of throughput, thereby giving full play to the dissolved gas drive effect and improving the carrying capacity of CO2 for crude oil in pore throats. At the same time, the addition of propane can improve the competitive adsorption capacity of CO2 in organic matter, thereby improving the recovery rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the scheme of the present invention, a brief introduction is given below to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 It is a schematic diagram of the structure of the device for simulating the use of carbon dioxide-hydrocarbon mixed gas to improve the shale oil throughput recovery rate of the present invention;

[0026] Figure 2 for Figure 1 A magnified view of region A in FIG.

[0027] Figure 3 for Figure 1 A magnified view of area B in FIG.

[0028] Figure 4 for Figure 1 A magnified view of region C in FIG.

[0029] Figure 5 for Figure 1 A magnified view of the D region in FIG.

[0030] The markings in the figure are as follows: 1. Vacuum pump; 10. Mixed gas storage tank; 101. First stop valve; 101S, First stop pipeline; 102. Second stop valve; 103. Third stop valve; 104. Fourth stop valve; 105. Fifth stop valve; 105S, Fifth stop valve pipeline; 106. Sixth stop valve; 106S, Sixth stop valve pipeline; 107. Seventh stop valve; 108. Eighth stop valve; 109. Ninth stop valve; 11. CO2 storage tank; 12. Oil-gas separator; 13. Stainless steel high-pressure coil; 14. Nuclear magnetic resonance imaging analyzer; 15. Three-axis core holder; 16. Confining pressure pump; 17. First 1. Simulated oil intermediate container; 19. Simulated oil; 2. Second simulated oil intermediate container; 20. Core; 201. First pressure sensor; 202. Second pressure sensor; 203. Third pressure sensor; 22. Fluorine oil; 3. Simulated oil saturation pump; 301. First three-way joint; 302. Second three-way joint; 303. Third three-way joint; 304. Fourth three-way joint; 4. Core saturation tank; 5. Hydrocarbon gas intermediate container; 6. Hydrocarbon gas injection pump; 7. Visible container; 9. Mixed gas injection pump; L0. Main branch; L1. First secondary branch; L2. Second secondary branch; L3. Third secondary branch; L4. Fourth secondary branch. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0032] like Figure 1 As shown, the device for simulating the use of carbon dioxide-hydrocarbon mixed gas to improve the shale oil throughput recovery rate includes a main branch L0, and the main branch L0 is provided with a first sub-branch L1, a second sub-branch L2, a third sub-branch L3 and a fourth sub-branch L4.

[0033] The main branch L0 is connected in series in sequence with a vacuum pump 1, a third stop valve 103, a mixed gas storage tank 10, a seventh stop valve 107, a third three-way connector 303, a stainless steel high-pressure coil 13, a nuclear magnetic resonance imaging analyzer 14, a fourth three-way connector 304, a ninth stop valve 109 and a first simulated oil intermediate container 17.

[0034] The first sub-branch L1 is provided with a second stop valve 102, a first three-way joint 301 and a core saturation tank 4 connected in series, the first three-way joint 301 is provided with a first pressure sensor 201, the core saturation tank 4 is provided with a core 20, the side wall of the core saturation tank 4 is provided with a first stop pipe 101S, the first stop pipe 101S is provided with a first stop valve 101, the end of the first stop pipe 101S is provided with a second simulated oil intermediate container 2, the second simulated oil intermediate container 2 is provided with simulated oil 19, and the outside of the second simulated oil intermediate container 2 is provided with a simulated oil saturation pump 3.

[0035] The second secondary branch L2 is provided with a fourth stop valve 104, a second three-way joint 302, a visual container 7 and a mixed gas injection pump 9 connected in series, the second three-way joint 302 is provided with a third pressure sensor 203, the outer wall of the visual container 7 is provided with a fifth stop valve pipeline 105S and a sixth stop valve pipeline 106S, the fifth stop valve pipeline 105S is provided with a fifth stop valve 105, the sixth stop valve pipeline 106S is provided with a sixth stop valve 106, the end of the fifth stop valve pipeline 105S is provided with a hydrocarbon gas intermediate container 5, the hydrocarbon gas intermediate container 5 is provided with a second pressure sensor 202, the hydrocarbon gas intermediate container 5 is connected to the hydrocarbon gas injection pump 6 through a pipeline, and the end of the sixth stop valve pipeline 106S is provided with a CO2 storage tank 11,

[0036] The third auxiliary branch L3 is provided with an eighth shut-off valve 108 and an oil-gas separator 12 connected in series.

[0037] A three-axis core holder 15 is disposed inside the nuclear magnetic resonance imaging analyzer 14 , and an annulus of the three-axis core holder 15 is filled with fluorine oil 22 . A confining pressure pump 16 is connected to the outside of the nuclear magnetic resonance imaging analyzer 14 .

[0038] It should be noted that the first three-way joint 301 includes a first joint 301A, a second joint 301B and a third joint 301C, the second three-way joint 302 includes a fourth joint 302A, a fifth joint 302B and a sixth joint 302C, the third three-way joint 303 includes a seventh joint 303A, an eighth joint 303B and a ninth joint 303C, and the fourth three-way joint 304 includes a tenth joint 304A, an eleventh joint 304B and a twelfth joint 304C.

[0039] The first simulated oil intermediate container 17 is connected to the tenth joint 304A of the fourth three-way joint 304 through a pipeline, a ninth stop valve 109 is arranged on the pipeline between the first simulated oil intermediate container 17 and the fourth three-way joint 304, the three-axis core clamp 15 is connected to the eleventh joint 304B of the fourth three-way joint 304 through a pipeline, the fifth pressure sensor 205 is connected to the twelfth joint 304C of the fourth three-way joint 304 through a pipeline, the stainless steel high-pressure coil 13 is connected to the seventh joint 303A of the third three-way joint 303 through a pipeline, one end of the oil-gas separator 12 is connected to the eighth joint 303B of the third three-way joint 303 through a pipeline, one end of the oil-gas separator 12 is connected to the outside through a pipeline, and the oil-gas separator The eighth stop valve 108 is arranged on the pipeline between the device 12 and the third three-way joint 303 through the pipeline, the mixed gas storage tank 10 is connected to the ninth joint 303C of the third three-way joint 303 through the pipeline, the seventh stop valve 107 is arranged on the pipeline between the mixed gas storage tank 10 and the third three-way joint 303, the visual container 7 is connected to the fourth joint 302A of the second three-way joint 302 through the pipeline, the mixed gas storage tank 10 is connected to the fifth joint 302B of the second three-way joint 302, the fourth stop valve 104 is arranged on the pipeline between the mixed gas storage tank 10 and the second three-way joint 302, the third pressure sensor 203 is connected to the sixth joint 302C of the second three-way joint 302 through the pipeline, the core saturation tank 4 ... The first pressure sensor 201 is connected to the first joint 301A of the first three-way joint 301 through a pipeline, the first pressure sensor 201 is connected to the second joint 301B of the first three-way joint 301 through a pipeline, the vacuum pump 1 is connected to the third joint 301C of the first three-way joint 301 through a pipeline, a second stop valve 102 is arranged on the pipeline between the vacuum pump 1 and the first three-way joint 301, the second simulated oil intermediate container 2 is connected to the simulated oil saturation pump 3 and the core saturation tank 4 through a pipeline, a first stop valve 101 is arranged on the pipeline between the second simulated oil intermediate container 2 and the core saturation tank 4, the hydrocarbon gas intermediate container 5 is connected to the hydrocarbon gas injection pump 6, the second pressure sensor 202 and the visual container 7 through a pipeline, the hydrocarbon gas intermediate container 5 is connected to the visual container 7, and the hydrocarbon gas intermediate container 5 is connected to the visual container 7. A fifth stop valve 105 is arranged on the pipeline between the containers 7, the mixed gas injection pump 9 is connected to the visible container 7 through a pipeline, the CO2 storage tank 11 is connected to the visible container 7 through a pipeline, a sixth stop valve 106 is arranged on the pipeline between the CO2 storage tank 11 and the visible container 7, the stainless steel high-pressure coil 13 is connected to the triaxial core holder 15 through a pipeline, the confining pressure pump 16 is connected to the triaxial core holder 15 through a pipeline, the triaxial core holder 15 is placed in the nuclear magnetic resonance imaging analyzer 14, the fourth pressure sensor 204 is connected to the mixed gas storage tank 10 through a pipeline, the vacuum pump 1 is connected to the mixed gas storage tank 10 through a pipeline, and a third stop valve 103 is arranged on the pipeline between the vacuum pump 1 and the mixed gas storage tank 10;The vacuum pump 1, the second simulated oil intermediate container 2, the simulated oil saturation pump 3, the core saturation tank 4, the hydrocarbon gas intermediate container 5, the hydrocarbon gas injection pump 6, the visual container 7, the visual window 8, the mixed gas injection pump 9, the mixed gas storage tank 10, the CO2 storage tank 11, the oil-gas separator 12, the stainless steel high-pressure coil 13, the nuclear magnetic resonance imaging analyzer 14, the three-axis core clamp 15, the confining pressure pump 16, the first simulated oil intermediate container 17, the constant temperature box 18, the first stop valve 101, and the second stop valve 102 , the third stop valve 103, the fourth stop valve 104, the fifth stop valve 105, the sixth stop valve 106, the seventh stop valve 107, the eighth stop valve 108, the ninth stop valve 109, the first pressure sensor 201, the second pressure sensor 202, the third pressure sensor 203, the fourth pressure sensor 204, the fifth pressure sensor 205, the first three-way joint 301, the second three-way joint 302, the third three-way joint 303, and the fourth three-way joint 304 are controlled in temperature by the thermostat 18. ;

[0040] The following is an explanation of the working mode of the device for simulating the use of carbon dioxide-hydrocarbon mixed gas to increase the shale oil throughput recovery rate.

[0041] The indoor experiment used to evaluate the carbon dioxide-hydrocarbon mixture gas for improving the recovery rate of shale oil includes the following steps:

[0042] (1) Saturation of the core 20 with simulated oil 19: Open the thermostat 18, set the temperature to T in the range of 33-105°C, weigh the cleaned and dried core 20 to m0, put it into the core saturation tank 4, keep all the stop valves closed, open the second stop valve 102, evacuate the core saturation tank 4 to 0.1 Pa through the vacuum pump 1, inject the simulated oil 19 into the second simulated oil intermediate container 2, close the second stop valve 102, open the first stop valve 101, and pressurize the core saturation tank 4 to the set saturation pressure through the simulated oil saturation pump 3. The pressure is P0, until the pumping volume V0 of the simulated oil saturation pump 3 does not change; the core 20 is taken out and weighed as a wet weight of m1, and is placed in the core holder 15, and the confining pressure pump 16 is used to apply confining pressure to the core 20 in the core holder 15 to a set pressure Pf; the first stop valve 101 is closed, the third stop valve 103 and the seventh stop valve 107 are opened, and the mixed gas storage tank 10, the stainless steel high-pressure coil 13 and the core holder 15 are evacuated to 0.1Pa by the vacuum pump 1, and the T2 spectrum of the saturated core 20 is tested by the nuclear magnetic resonance imaging analyzer 14;

[0043] (2) Preparation of CO2-hydrocarbon mixed gas: Open the sixth stop valve 106, inject CO2 into the visual container 7, and obtain the initial pressure P1 in the visual container 7 through the third pressure sensor 203. Calculate the amount of CO2 in the visual container 7 as n1 according to the gas state equation; Close the sixth stop valve 106, open the fifth stop valve 105, record the initial pressure P2 of the hydrocarbon gas intermediate container 5 through the second pressure sensor 202, inject the hydrocarbon gas 21 with an amount of n2 into the visual container 7 through the hydrocarbon gas injection pump 6, and observe the state of CO2 and hydrocarbon gas through the visual window 8 to prevent gas liquefaction. When the reading of the second pressure sensor 202 remains unchanged, close the fifth stop valve 105 to obtain the CO2-hydrocarbon mixed gas.

[0044] (3) The outlet pipeline is saturated with simulated oil: The pipeline between the fourth three-way joint 304 and the first simulated oil intermediate container 17 is evacuated by the vacuum pump 1. The negative pressure will cause the simulated oil 19 to be spontaneously absorbed into the outlet pipeline.

[0045] (4) Injection of CO2-hydrocarbon mixed gas: open the fourth stop valve 104, pressurize the mixed gas to the reservoir pressure through the mixed gas injection pump 9, close the fourth stop valve 104, open the seventh stop valve 107, and when the fourth pressure sensor 204 and the fifth pressure sensor 205 show the same reading, close the seventh stop valve 107 and record the pressure change through the fifth pressure sensor 205.

[0046] (5) Well production: After the stainless steel high-pressure coil is connected to the core holder and balanced for 24-120 hours, the eighth stop valve 108 is opened to start well production until the reading of the fifth pressure sensor 205 drops to 0.1 MPa. The T2 spectrum of the core 20 at the end of production is tested by the nuclear magnetic resonance imaging analyzer 14. The core 20 is taken out of the core holder 15 to obtain the final mass m2 of the core 20. The matrix recovery factor and the degree of utilization of crude oil in the large pores, medium pores and small pores of the core 20 are calculated respectively.

[0047] The matrix recovery factor fm can be calculated by formula (1):

[0048]

[0049] Wherein, m1 is the weight of the core 20 after being saturated with hexadecane, g; m2 is the weight of the core 20 after the huff and puff, g; and m0 is the weight of the core 20 after being washed and dried.

[0050] The utilization degree fT of crude oil in the large pores, medium pores and small pores of core 20 can be calculated by formula (2):

[0051]

[0052] Wherein, Spvi is the area of ​​the T2 spectrum of the core 20 after the huff and puff; Sini is the area of ​​the T2 spectrum of the core 20 after the saturation of hexadecane.

[0053] Repeat steps (2) to (5) to perform four throughput operations to obtain four throughput recovery factors.

[0054] Example 1

[0055] Select the clean and dried core 20, i.e., shale sample A. The sample parameters of the core 20 are shown in Table 1. Put it into the core saturation tank 4. After vacuuming, open the first stop valve 101, saturate the simulated oil 19 until the pressure stabilizes at 20 MPa, take it out and weigh the wet weight, calculate that the saturated simulated oil 19 is 0.811 g, put it into the core holder 15, inject fluorine oil 22 into the annulus of the core holder 15 until the confining pressure reaches 30 MPa, test the T2 spectrum of the core 20 after saturation by the nuclear magnetic resonance imaging analyzer 14, open the fourth stop valve 104 and the sixth stop valve 106, inject CO2 into the mixed gas storage tank 10 to 21 MPa, and close the fourth stop valve 104. Stop valve 104, open the seventh stop valve 107 until the fourth pressure sensor 204 and the fifth pressure sensor 205 show the same reading, close the seventh stop valve 107, balance and stabilize for 48 hours, open the eighth stop valve 108 to start well production, until the reading of the fifth pressure sensor 205 drops to 0.1MPa, test the core T2 spectrum of the core 20 after the completion of the throughput, take out the core 20 and weigh the mass of 60.542g, according to calculation, the matrix recovery factor is 24.62%, the hexadecane utilization degree in the micron (large pore), submicron (medium pore) and nanometer (small pore) pore throats of the core 20 are 30.84%, 19.51% and 13.62%, respectively.

[0056] Example 2

[0057] A clean and dried core 20, i.e., shale sample A, is selected. The sample parameters of the core 20 are shown in Table 1. The core 20 is placed in a core saturation tank 4. After vacuuming, the first stop valve 101 is opened, the saturated simulated oil 19 is stabilised to a pressure of 20 MPa, the wet weight is taken out, and the saturated simulated oil 19 is calculated to be 0.811 g. The core is placed in a core holder 15, and fluorine oil 22 is injected into the annulus of the core holder 15 until the confining pressure reaches 30 MPa. The T2 spectrum of the core 20 after saturation is tested by a nuclear magnetic resonance imaging analyser 14. The sixth stop valve 106 is opened, CO2 of a set pressure is injected into the visual container 7, the sixth stop valve 106 is closed, the fifth stop valve 105 is opened, methane of a set pressure is injected into the visual container 7, and the molar concentration of methane in the mixed gas is calculated to be 20%, and the fifth stop valve is closed. 105, open the fourth stop valve 104, inject CO2-methane mixed gas into the mixed gas storage tank 10 to 21MPa, close the fourth stop valve 104, open the seventh stop valve 107, until the fourth pressure sensor 204 and the fifth pressure sensor 205 show the same reading, close the seventh stop valve 107, balance and stabilize for 48 hours, open the eighth stop valve 108 to start well production, until the reading of the fifth pressure sensor 205 drops to 0.1MPa, test the core T2 spectrum of the core 20 after the completion of the throughput, take out the core 20 and weigh it to be 60.534g, and calculate that the matrix recovery factor is 25.47%, and the hexadecane utilization degrees in the micron (large pores), submicron (medium pores) and nanometer (small pores) pore throats of the core 20 are 40.51%, 17.33% and 8.13%, respectively.

[0058] Example 3

[0059] A clean and dried core 20, i.e., shale sample A, is selected. The sample parameters of the core 20 are shown in Table 1. The core 20 is placed in a core saturation tank 4. After vacuuming, the first stop valve 101 is opened, and the saturated simulated oil 19 is stabilized at a pressure of 20 MPa. The simulated oil 19 is taken out and weighed wetly. The saturated simulated oil 19 is calculated to be 0.811 g. The core is placed in a core holder 15. Fluorine oil 22 is injected into the annulus of the core holder 15 until the confining pressure reaches 30 MPa. The T2 spectrum of the core 20 after saturation is tested by a nuclear magnetic resonance imaging analyzer 14. The sixth stop valve 106 is opened, and CO2 of a set pressure is injected into the visual container 7. The sixth stop valve 106 is closed, and the fifth stop valve 105 is opened. Ethane of a set pressure is injected into the visual container 7. The molar concentration of ethane in the mixed gas is calculated to be 20%. The fifth stop valve 105 is closed. 105, open the fourth stop valve 104, inject CO2-ethane mixed gas into the mixed gas storage tank 10 to 21MPa, close the fourth stop valve 104, open the seventh stop valve 107, until the fourth pressure sensor 204 and the fifth pressure sensor 205 show the same reading, close the seventh stop valve 107, balance and stabilize for 48 hours, open the eighth stop valve 108 to start well production, until the reading of the fifth pressure sensor 205 drops to 0.1MPa, test the core T2 spectrum of the core 20 after the completion of the throughput, take out the core 20 and weigh it to be 60.541g, and calculate that the matrix recovery factor is 24.58%, and the hexadecane utilization degrees in the micron (large pores), submicron (medium pores) and nanometer (small pores) pore throats of the core 20 are 30.75%, 19.59% and 13.84%, respectively.

[0060] Example 4

[0061] A clean and dried core 20, i.e., shale sample A, is selected. The sample parameters of the core 20 are shown in Table 1. The core 20 is placed in a core saturation tank 4. After vacuuming, the first stop valve 101 is opened, the simulated oil 19 is saturated until the pressure stabilizes at 20 MPa, the wet weight is taken out, and the saturated simulated oil 19 is calculated to be 0.811 g. The core is placed in a core holder 15, and fluorine oil 22 is injected into the annulus of the core holder 15 until the confining pressure reaches 30 MPa. The T2 spectrum of the core 20 after saturation is tested by a nuclear magnetic resonance imaging analyzer 14. The sixth stop valve 106 is opened, and CO2 of a set pressure is injected into the visual container 7. The sixth stop valve 106 is closed, and the fifth stop valve 105 is opened. Propane of a set pressure is injected into the visual container 7. The molar concentration of propane in the mixed gas is calculated to be 20%, and the fifth stop valve is closed. 105, open the fourth stop valve 104, inject CO2-propane mixed gas into the mixed gas storage tank 10 to 21MPa, close the fourth stop valve 104, open the seventh stop valve 107, until the fourth pressure sensor 204 and the fifth pressure sensor 205 show the same reading, close the seventh stop valve 107, balance and stabilize for 48 hours, open the eighth stop valve 108 to start well production, until the reading of the fifth pressure sensor 205 drops to 0.1MPa, test the core T2 spectrum of the core 20 after the completion of the throughput, take out the core 20 and weigh it, the mass is 60.517g, and the matrix recovery factor is calculated to be 27.61%, and the hexadecane utilization degrees in the micron (large pores), submicron (medium pores) and nanometer (small pores) pore throats of the core 20 are 27.18%, 23.45% and 20.75%, respectively.

[0062] Example 5

[0063] A clean and dried core 20, namely shale sample A, is selected. The sample parameters of the core 20 are shown in Table 1. The core 20 is placed in a core saturation tank 4. After vacuuming, the first stop valve 101 is opened, the saturated simulated oil 19 is stabilised to a pressure of 20 MPa, the wet weight is taken out, and the saturated simulated oil 19 is calculated to be 0.811 g. The core is placed in a core holder 15, and fluorine oil 22 is injected into the annulus of the core holder 15 until the confining pressure reaches 30 MPa. The T2 spectrum of the core 20 after saturation is tested by a nuclear magnetic resonance imaging analyser 14. The sixth stop valve 106 is opened, and CO2 of a set pressure is injected into the visual container 7. The sixth stop valve 106 is closed, and the fifth stop valve 105 is opened. In the first and second throughput cycles, methane of a set pressure is injected into the visual container 7. The molar concentration of methane in the mixed gas is calculated to be 20%. In the third and fourth throughput cycles, a set pressure of Propane, calculate the molar concentration of propane in the mixed gas to be 20%, close the fifth stop valve 105, open the fourth stop valve 104, inject CO2-hydrocarbon mixed gas into the mixed gas storage tank 10 to 21MPa, close the fourth stop valve 104, open the seventh stop valve 107, until the fourth pressure sensor 204 and the fifth pressure sensor 205 show the same reading, close the seventh stop valve 107, balance and stabilize for 48 hours, open the eighth stop valve 108 to start well production, until the reading of the fifth pressure sensor 205 drops to 0.1MPa, test the core T2 spectrum of the core 20 after the completion of the throughput, take out the core 20 and weigh it to be 60.506g, and calculate that the matrix recovery factor is 28.93%, and the hexadecane utilization degrees in the micron (large pores), submicron (medium pores) and nanometer (small pores) pore throats of the core 20 are 38.43%, 21.68% and 15.62%, respectively.

[0064] Table 1 (core parameters)

[0065]

[0066] Table 2 (Results of shale core A huff-and-puff experiments with different hydrocarbon gases in a mixed gas with a molar concentration of 20% at 50°C and 21 MPa)

[0067]

[0068] In addition to the above embodiments, we also evaluated the throughput effects of adding several different hydrocarbon gases 21 to two cores 20, which are listed in Tables 2 and 3 respectively. It can be seen that for different cores 20, the matrix recovery rate increases to varying degrees after adding methane or propane to CO2, while the matrix recovery rate is basically similar after adding ethane, and the matrix recovery rate is between 18% and 28%. Analysis of the crude oil utilization in macropores, mesopores and small pores of different cores 20 shows that compared with pure CO2 huff and puff, CO2-methane mixed gas can effectively mobilize crude oil in macropores, but the utilization of crude oil in mesopores and small pores is weak, with the utilization of macropores ranging from 32% to 41%, while CO2-propane mixed gas can mobilize crude oil in macropores, mesopores and small pores to a large extent, with the utilization ranging from 22% to 28%, 19% to 24% and 16% to 21%, respectively, indicating that appropriately enhancing the compressibility and miscibility of CO2 is beneficial to the development of shale oil. The recovery rate of different hydrocarbon gases added to the matrix of core 20A is higher than that of core 20B, which may be related to the high kerogen content in core 20B. In addition, the addition of propane increased the matrix recovery of core 20B by 3.94%, which was 0.95% higher than that of core 20A, indicating that CO2-propane can effectively mobilize the adsorbed dissolved crude oil in kerogen. At the same time, through the recovery results of different hydrocarbon gases 21, it can be seen that the addition of propane has the best effect in improving the recovery.

[0069] Table 3 (Results of shale core B huff-and-puff experiments with different hydrocarbon gases at 20% molar concentration in the mixed gas at 50°C and 21 MPa)

[0070]

[0071] Table 4 (Results of huff-and-puff experiment of shale core A under different injection sequences of CO2-methane and CO2-propane mixed gases at 50℃ and 21MPa)

[0072]

[0073] At the same time, we also evaluated the huff and puff effects of two mixed gases, CO2-methane and CO2-propane, under different injection modes for core 20A. The experimental results are listed in Table 4. It can be seen that compared with pure CO2 huff and puff and CO2-propane / CO2-methane huff and puff, CO2-methane / CO2-propane huff and puff has the best effect, with a matrix recovery factor of 28.93%, a large pore production degree of 38.43%, a medium pore production degree of 21.68%, and a small pore production degree of 15.63%, which are 4.31%, 6.59%, 2.17% and 2.01% higher than those of pure CO2 huff and puff, respectively. This shows that injecting CO2-methane gas in the early stage of huff and puff and injecting CO2-propane gas in the later stage of huff and puff is beneficial to the development of shale oil.

[0074] It can be seen from these embodiments that, by adopting the method of the present invention, the recovery rate of shale oil injection CO2-hydrocarbon mixed gas huffing and puffing can be greatly improved compared with CO2 huffing and puffing. By adopting the injection method of injecting CO2-methane mixed gas in the early stage of huffing and puffing and injecting CO2-propane mixed gas in the late stage of huffing and puffing, not only can the energy of the production stage be increased by the strong compressibility of methane in the early stage of huffing and puffing, the crude oil in the large pores of shale can be effectively mobilized, and the role of dissolved gas drive can be fully exerted; in the late stage of huffing and puffing, the strong miscibility and strong extraction ability of propane can be used to reduce the oil interfacial tension between oil and gas, so that the mixed gas can enter the pores and small pores of shale to exploit crude oil, and the exploited crude oil can be effectively carried to the bottom of the production well. In addition, the strong competitive adsorption ability of propane is also very beneficial to the utilization of adsorbed dissolved crude oil in kerogen. The CO2-hydrocarbon mixed gas provided by the present invention selects a small molecular weight hydrocarbon gas, and after mixing with CO2, it can always maintain a gaseous and supercritical state under experimental conditions, thereby avoiding the liquefaction of the mixed gas and reducing the injection capacity and diffusion capacity in the shale oil reservoir, causing additional economic losses. The method for improving the recovery rate of shale oil by using CO2-hydrocarbon mixed gas provided by the present invention is a significant improvement over the traditional shale oil CO2 injection and injection method. In addition to being able to observe the phase state of the mixed gas through a visual container during the mixed gas configuration process, the supply of the mixed gas can be maintained through a stainless steel high-pressure coil during the well soaking process, thereby increasing the diffusion of the mixed gas in the shale oil and fully utilizing the adsorbed dissolved crude oil. In addition, the nuclear magnetic resonance technology can also accurately calculate the degree of utilization of different gases on crude oil in different pore sizes, thereby revealing the relevant properties of hydrocarbon gases in the process of developing shale oil, which can provide theoretical guidance for field experiments.

[0075] The present invention provides a device for simulating the use of carbon dioxide-hydrocarbon mixed gas to improve the throughput recovery rate of shale oil. The device can accurately simulate the influence of carbon dioxide-hydrocarbon mixed gas on the throughput recovery rate of high shale oil, thereby guiding actual production. Through this method, the compressibility of CO2 can be improved in the early stage of throughput, and the miscibility of CO2 with simulated oil can be enhanced in the later stage of throughput, thereby giving full play to the dissolved gas drive effect and improving the carrying capacity of CO2 for crude oil in pore throats. At the same time, the addition of propane can improve the competitive adsorption capacity of CO2 in organic matter, thereby improving the recovery rate.

[0076] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

[0077] Obviously, the embodiments described above are only part of the embodiments of the present application, rather than all the embodiments. The drawings provide preferred embodiments of the present application, but do not limit the patent scope of the present application.

Claims

1. A device for simulating the use of carbon dioxide-hydrocarbon mixed gas to improve shale oil throughput recovery, characterized in that: The device for simulating the use of carbon dioxide-hydrocarbon mixed gas to improve the shale oil throughput recovery rate comprises a main branch (L0), the main branch (L0) is provided with a first sub-branch (L1), a second sub-branch (L2), a third sub-branch (L3) and a fourth sub-branch (L4), the main branch (L0), the first sub-branch (L1), the second sub-branch (L2), the third sub-branch (L3) and the fourth sub-branch (L4) are all arranged in a constant temperature box (18), The first sub-branch (L1) is used to simulate the saturated simulated oil entering the core (20), the second sub-branch (L2) is used to simulate the preparation of CO2-hydrocarbon mixed gas, the third sub-branch (L3) is used to simulate well opening and production, and the fourth sub-branch (L4) is used to simulate the confining pressure on the core (20).

2. The device for simulating the use of carbon dioxide-hydrocarbon mixed gas to improve shale oil throughput recovery according to claim 1, characterized in that: The hydrocarbon gas in the CO2-hydrocarbon mixed gas is one of methane, ethane and propane.

3. The device for simulating the use of carbon dioxide-hydrocarbon mixed gas to improve shale oil throughput recovery according to claim 1, characterized in that: The CO2-hydrocarbon mixed gas is in a gaseous state or a supercritical state, and the molar concentration of the hydrocarbon gas in the mixed gas is 0% to 20%.

4. The device for simulating the use of carbon dioxide-hydrocarbon mixed gas to improve shale oil throughput recovery according to claim 1, characterized in that: The main branch (L0) is connected in series in sequence with a vacuum pump (1), a third stop valve (103), a mixed gas storage tank (10), a seventh stop valve (107), a third three-way connector (303), a stainless steel high-pressure coil (13), a nuclear magnetic resonance imaging analyzer (14), a fourth three-way connector (304), a ninth stop valve (109) and a first simulated oil intermediate container (17). The first secondary branch (L1) is provided with a second stop valve (102), a first three-way joint (301) and a core saturation tank (4) connected in series; the first three-way joint (301) is provided with a first pressure sensor (201); a core (20) is provided in the core saturation tank (4); a first stop pipe (101S) is provided on the side wall of the core saturation tank (4); the first stop pipe (101S) is provided with a first stop valve (101); a second simulated oil intermediate container (2) is provided at the end of the first stop pipe (101S); simulated oil (19) is provided in the second simulated oil intermediate container (2); a simulated oil saturation pump (3) is provided outside the second simulated oil intermediate container (2); The second secondary branch (L2) is provided with a fourth stop valve (104), a second three-way joint (302), a visual container (7) and a mixed gas injection pump (9) connected in series; the second three-way joint (302) is provided with a third pressure sensor (203); a fifth stop valve pipeline (105S) and a sixth stop valve pipeline (106S) are provided on the outer wall of the visual container (7); the fifth stop valve pipeline (105S) is provided with a fifth stop valve (105); the sixth stop valve pipeline (106S) is provided with a sixth stop valve (106); a hydrocarbon gas intermediate container (5) is provided at the end of the fifth stop valve pipeline (105S); the hydrocarbon gas intermediate container (5) is provided with a second pressure sensor (202); the hydrocarbon gas intermediate container (5) is connected to the hydrocarbon gas injection pump (6) through a pipeline; a CO2 storage tank (11) is provided at the end of the sixth stop valve pipeline (106S); The third auxiliary branch (L3) is provided with an eighth stop valve (108) and an oil-gas separator (12) connected in series. The nuclear magnetic resonance imaging analyzer (14) is provided with a three-axis core holder (15) inside, and the annulus of the three-axis core holder (15) is filled with fluorine oil (22). The fourth auxiliary branch (L4) is provided with a confining pressure pump (16), and the confining pressure pump (16) is connected to the nuclear magnetic resonance imaging analyzer (14).

5. The device for simulating the use of carbon dioxide-hydrocarbon mixed gas to improve shale oil throughput recovery rate according to claim 4, characterized in that: The first three-way joint (301) comprises a first joint (301A), a second joint (301B) and a third joint (301C); the second three-way joint (302) comprises a fourth joint (302A), a fifth joint (302B) and a sixth joint (302C); the third three-way joint (303) comprises a seventh joint (303A), an eighth joint (303B) and a ninth joint (303C); the fourth three-way joint (304) comprises a tenth joint (304A), an eleventh joint and a twelfth joint (304C); The first simulated oil intermediate container (17) is connected to the tenth joint (304A) of the fourth three-way joint (304) via a pipeline; a ninth stop valve (109) is provided on the pipeline between the first simulated oil intermediate container (17) and the fourth three-way joint (304); the three-axis core holder (15) is connected to the eleventh joint of the fourth three-way joint (304) via a pipeline; the fifth pressure sensor (205) is connected to the twelfth joint (304C) of the fourth three-way joint (304) via a pipeline; The stainless steel high-pressure coil (13) is connected to the seventh joint (303A) of the third three-way joint (303) via a pipeline. One end of the oil-gas separator (12) is connected to the eighth joint (303B) of the third three-way joint (303) through a pipeline, and one end of the oil-gas separator (12) is connected to the outside through the pipeline. An eighth stop valve (108) is arranged on the pipeline between the oil-gas separator (12) and the third three-way joint (303). The mixed gas storage tank (10) is connected to the ninth joint (303C) of the third three-way joint (303) through a pipeline, a seventh stop valve (107) is arranged on the pipeline between the mixed gas storage tank (10) and the third three-way joint (303), the visible container (7) is connected to the fourth joint (302A) of the second three-way joint (302) through a pipeline, the mixed gas storage tank (10) is connected to the fifth joint (302B) of the second three-way joint (302), a fourth stop valve (104) is arranged on the pipeline between the mixed gas storage tank (10) and the second three-way joint (302), and the third pressure sensor ( The core saturation tank (4) is connected to the first joint (301A) of the first three-way joint (301) through a pipeline, the first pressure sensor (201) is connected to the second joint (301B) of the first three-way joint (301) through a pipeline, the vacuum pump (1) is connected to the third joint (301C) of the first three-way joint (301) through a pipeline, a second stop valve (102) is arranged on the pipeline between the vacuum pump (1) and the first three-way joint (301), and the second simulated oil intermediate container (2) is connected to the simulated oil intermediate container (301) through a pipeline. The oil saturation pump (3) is connected to the core saturation tank (4); a first stop valve (101) is provided on the pipeline between the second simulated oil intermediate container (2) and the core saturation tank (4); the hydrocarbon gas intermediate container (5) is connected to the hydrocarbon gas injection pump (6), the second pressure sensor (202) and the visual container (7) through a pipeline; a fifth stop valve (105) is provided on the pipeline between the hydrocarbon gas intermediate container (5) and the visual container (7); the mixed gas injection pump (9) is connected to the visual container (7) through a pipeline; the CO2 storage tank (11) is connected to the visual container (7) through a pipeline; the CO2 storage tank (11) is connected to the visual container (7) through a pipeline; 1) and the visible container (7), a sixth stop valve (106) is arranged on the pipeline between the stainless steel high-pressure coil (13) and the three-axis core holder (15) through the pipeline, the confining pressure pump (16) is connected to the three-axis core holder (15) through the pipeline, the three-axis core holder (15) is placed in the nuclear magnetic resonance imaging analyzer (14), the fourth pressure sensor (204) is connected to the mixed gas storage tank (10) through the pipeline, the vacuum pump (1) is connected to the mixed gas storage tank (10) through the pipeline, and a third stop valve (103) is arranged on the pipeline between the vacuum pump (1) and the mixed gas storage tank (10).

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