Pressure-braising-seepage-drainage integrated experimental device and method for shale reservoir under actual temperature and pressure conditions

Abstract

The invention belongs to the field of shale oil reservoir development in the oil and gas reservoir development technology, and discloses a pressure-braising-seepage-drainage integrated experimental device and method for shale reservoir actual temperature and pressure conditions, and the device comprises a power system, a fluid supply system, a reservoir simulation system, a temperature control system and an electronic metering system; the power system is used for providing pressure for the fluid supply system; the fluid supply system is used for supplying fluid to the reservoir simulation system, and the fluid is oil in the oil saturation process or fracturing fluid in the displacement process; the reservoir simulation system is used for simulating the fracturing-soaking-imbibition-flowback integrated process of the target shale oil reservoir under the actual temperature and pressure conditions; the temperature control system is used for simulating the actual temperature of the shale reservoir; and the electronic metering system is used for measuring the oil saturation in the produced liquid. The device is resistant to high temperature and high pressure, can simulate the ultrahigh-temperature and high-pressure actual oil reservoir environment of a shale reservoir, and can realize the fracturing-soaking-imbibition-flowback integrated process considering the actual formation pressure of shale.

Description

Technical Field

[0001] The invention belongs to the field of shale oil reservoir development in oil and gas reservoir development technology, and specifically relates to a pressure-stemming-permeation-drainage integrated experimental device and method under actual temperature and pressure conditions of shale reservoirs. Background Art

[0002] my country's shale oil reserves are rich and have great development potential. Shale reservoirs have extremely low porosity and permeability, a large number of micro-nano pore throats, and extremely low natural production capacity. At present, large-scale volume fracturing technology must be used to develop shale oil reservoirs to obtain commercial production capacity. It is mainly done by adding oil displacement agents to the fracturing fluid, sending the oil displacement agents into the reservoir matrix while fracturing, and displacing the shale oil in the reservoir matrix into the fractures through the imbibition of the fracturing fluid during the well-sealing stage, thereby increasing the shale oil recovery rate on a large scale. Therefore, it is of great significance to establish an experimental device that can simulate the integrated development process of fracturing-well-sealing-imbibition-flowback under the actual temperature and pressure conditions of shale oil reservoirs for the further development of shale oil reservoirs.

[0003] At present, in the laboratory simulation of shale oil reservoir fracturing development, the fluid pressure in the core is often not considered, and shale recovery evaluation experiments are carried out on cores without fluid internal pressure. However, in the actual shale reservoir fracturing development process, there is extremely high fluid pressure in the reservoir matrix. After the fracturing fluid is injected, the formation pressure is supplemented, the matrix rock is compressed, and the pore throat size is improved; in addition, the formation pressure decreases during the backflow process, the matrix rock expands, and the pore throat size shrinks. This pressure change process has a huge impact on the flow capacity of shale oil and seriously affects the shale recovery rate. In order to solve the above problems, the present invention provides a pressure-simmering-permeation-drainage integrated experimental device and method under the actual temperature and pressure conditions of shale reservoirs. Summary of the invention

[0004] In order to overcome the problem that existing laboratories are unable to simulate the integrated process of fracturing-well soaking-imbibition-flowback under the actual formation fluid pressure of shale reservoirs, the present invention provides an integrated fracturing-well soaking-imbibition-flowback experimental device and method under the actual temperature and pressure conditions of shale reservoirs. The experimental device is resistant to high temperature and high pressure, prefabricated cracks in the core (simulating the shale reservoir after fracturing), and there is fluid pressure in the core (simulating the actual fluid pressure of the shale formation), and then the fracturing fluid injection process is carried out. After the injection is completed, well soaking and imbibition are started, and finally the fracturing fluid flowback process is simulated, which solves the problem that the integrated process of fracturing-well soaking-imbibition-flowback under formation fluid pressure cannot be simulated.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A pressure-steeping-permeation-drainage integrated experimental device under actual temperature and pressure conditions of shale reservoirs, the device comprising: a power system, a fluid supply system, a reservoir simulation system, a temperature control system, and an electronic metering system;

[0007] The power system is connected to the fluid supply system, the fluid supply system is connected to the reservoir simulation system, the fluid supply system and the reservoir simulation system are placed in the temperature control system, and the reservoir simulation system is connected to the electronic metering system;

[0008] The power system is used to provide pressure to the fluid supply system;

[0009] The fluid supply system is used to supply fluid to the reservoir simulation system, wherein the fluid is oil in the oil saturation process or fracturing fluid in the displacement process;

[0010] The reservoir simulation system is used to simulate the integrated process of fracturing-well soaking-imbibition-flowback under the actual temperature and pressure conditions of the target shale oil reservoir;

[0011] The temperature control system is used to simulate the actual temperature of the shale reservoir;

[0012] The electronic metering system is used to measure the oil saturation in the produced fluid.

[0013] Preferably, the power system comprises: a dual-cylinder constant speed and constant pressure pump, which provides power, ie, pressure, to the fluid supply system under constant speed or constant pressure conditions.

[0014] Preferably, the fluid supply system comprises: a first high temperature and high pressure resistant two-way valve, a second high temperature and high pressure resistant two-way valve and a high temperature and high pressure resistant intermediate container;

[0015] The first high temperature and high pressure resistant two-way valve controls the power system to provide power to the high temperature and high pressure resistant intermediate container, and the second high temperature and high pressure resistant two-way valve controls the outflow of fluid in the high temperature and high pressure resistant intermediate container.

[0016] Preferably, the reservoir simulation system comprises: a third high temperature and high pressure two-way valve, a first high temperature and high pressure back pressure valve, a fourth high temperature and high pressure two-way valve, a high temperature and high pressure core holder, a shale core, a fifth high temperature and high pressure two-way valve, a second high temperature and high pressure back pressure valve and a produced fluid collection device;

[0017] The third high temperature and high pressure two-way valve and the fourth high temperature and high pressure two-way valve control whether the fluid can flow to the high temperature and high pressure core holder, and the first high temperature and high pressure back pressure valve and the second high temperature and high pressure back pressure valve control the pressure of the fluid flowing into and out of the high temperature and high pressure core holder, thereby controlling the fluid pressure in the shale core;

[0018] The left end of the first high temperature and high pressure back pressure valve is connected to the fluid supply system, and the right end is connected to the left end of the high temperature and high pressure core holder, so as to simulate the fracturing fluid injection process in the actual development of shale oil reservoirs;

[0019] The right end of the high temperature and high pressure core clamp is connected to the fifth high temperature and high pressure two-way valve, and the fifth high temperature and high pressure two-way valve is connected to the second high temperature and high pressure back pressure valve to simulate the actual shale reservoir formation fluid pressure.

[0020] Preferably, the temperature control system comprises a constant temperature box, and the temperature control system ensures that the temperature of the fluid supply system and the reservoir simulation system is the same as the actual temperature of the shale oil reservoir.

[0021] Preferably, the electronic metering system includes an infrared laser instrument, an automatic data reading device and a data visualization device. The electronic metering system is connected to a produced fluid collection device in a reservoir simulation system to measure the oil saturation in the produced fluid.

[0022] The present invention also provides a pressure-simmering-permeation-drainage integrated experimental method under actual temperature and pressure conditions of shale reservoirs, which is implemented by using the aforementioned pressure-simmering-permeation-drainage integrated experimental device under actual temperature and pressure conditions of shale reservoirs, and includes the following steps:

[0023] S1. Place a shale oil-saturated shale core in a high temperature and high pressure core holder, fill a high temperature and high pressure intermediate container of a fluid supply system with shale oil, and set the pressures of the first high temperature and high pressure back pressure valve and the second high temperature and high pressure back pressure valve to the actual formation pressure of the shale reservoir;

[0024] S2, open the first high temperature and high pressure two-way valve, the second high temperature and high pressure two-way valve, the third high temperature and high pressure two-way valve, the fourth high temperature and high pressure two-way valve and the fifth high temperature and high pressure two-way valve, start the double-cylinder constant speed and constant pressure pump of the power system, and start the oil saturation process by constant speed injection. The injection speed of the double-cylinder constant speed and constant pressure pump is the experimental preset speed until the pressure in the shale core reaches the actual formation pressure of the shale reservoir, and close the third high temperature and high pressure two-way valve, the fourth high temperature and high pressure two-way valve and the fifth high temperature and high pressure two-way valve and the double-cylinder constant speed and constant pressure pump;

[0025] S3, adjusting the pressure of the first high temperature and high pressure back pressure valve to the actual fluid pressure in the fracture after the shale reservoir is fractured, so as to simulate the process of the fracturing fluid entering the reservoir matrix during the actual fracturing of the shale reservoir, and filling the high temperature and high pressure intermediate container of the fluid supply system with the fracturing fluid actually used on site;

[0026] S4, open the third high temperature and high pressure two-way valve and the fourth high temperature and high pressure two-way valve, start the double-cylinder constant speed and constant pressure pump of the power system, and inject the fracturing fluid in the high temperature and high pressure intermediate container into the shale core by the actual fluid pressure in the fracture after fracturing of the shale oil reservoir, until the injection volume of the fracturing fluid reaches the preset injection volume of the experiment, close the third high temperature and high pressure two-way valve, the fourth high temperature and high pressure two-way valve and the double-cylinder constant speed and constant pressure pump, and start the well soaking and absorption process according to the preset well soaking time of the experiment;

[0027] S5. After the well is shut down, the pressure of the first high temperature and high pressure back pressure valve is adjusted to the actual bottom hole flow pressure after the well is shut down after the fracturing development of the shale oil reservoir, and the third high temperature and high pressure two-way valve is connected to the produced fluid collection device, and the third high temperature and high pressure two-way valve and the fourth high temperature and high pressure two-way valve are opened to simulate the fracturing fluid backflow process until the pressure in the core drops to the preset pressure and the oil production no longer changes, and the experiment ends;

[0028] S6. Collect the data recorded by the data visualization device in the electronic metering system, calculate the recovery factor and draw the corresponding recovery factor curve.

[0029] Preferably, in S3, the pressure of the first high temperature and high pressure back pressure valve is adjusted to the actual fluid pressure in the fracture after the shale reservoir is fractured, so as to simulate the process of the fracturing fluid entering the reservoir matrix during the actual fracturing of the shale reservoir, including:

[0030]

[0031] Among them, p z is the injection pressure, MPa; p 0 It is the surface injection pressure of the fracturing fluid during actual construction on site, MPa; is the density of the injected fracturing fluid, kg / m 3 ; g is the acceleration due to gravity, m / s 2 ;p my is the friction along the way, MPa; p mj is the local friction, MPa; p ms is the perforation friction, MPa.

[0032] Preferably, in S6, calculating the recovery factor includes:

[0033] EOR=Vo / Vz

[0034] Wherein, EOR is the recovery factor, %; Vo is the volume of shale oil in the flowback fluid, mL; Vz is the core saturated oil volume, mL.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] On the one hand, the present invention can simulate the reservoir environment of actual formation temperature and formation pressure in shale reservoirs, solving the problem that traditional experimental devices cannot simulate actual formation pressure, and is equipped with an electronic metering system to solve the problem of low precision and large reading error of traditional produced fluid collection devices; on the other hand, the experimental device is simple to operate, and can completely simulate the entire process of fracturing-well soaking-imbibition-flowback in the actual development of shale, and can accurately predict the degree of recovery of shale cores after fracturing, providing data support for the feasibility of fracturing development of shale oil reservoirs, and solving the problem of laboratory simulation of the integrated process of fracturing-well soaking-imbibition-flowback under actual formation temperature and pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0038] Figure 1 It is a structural schematic diagram of the experimental device of the present invention;

[0039] Figure 2 It is a structural diagram of shale core;

[0040] Figure 3 This is the curve of shale oil recovery rate changing with flowback fluid volume in Example 1 of the present invention.

[0041] In the figure, a-power system, b-fluid supply system, c-reservoir simulation system, d-temperature control system, e-electronic metering system, 1-double-cylinder constant speed and constant pressure pump, 2-first high temperature and high pressure resistant two-way valve, 3-high temperature and high pressure resistant intermediate container, 4-second high temperature and high pressure resistant two-way valve, 5-third high temperature and high pressure resistant two-way valve, 6-first high temperature and high pressure back pressure valve, 7-fourth high temperature and high pressure resistant two-way valve, 8-high temperature and high pressure resistant core clamp, 9-shale core, 10-fifth high temperature and high pressure resistant two-way valve, 11-second high temperature and high pressure back pressure valve, 12-produced fluid collection device, 13-infrared laser instrument, 14-automatic data reading device, 15-data visualization device, 16-constant temperature box, 17-preset fractures, 18-steel mesh. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] Embodiment 1

[0045] like Figure 1 As shown, the embodiment of the present invention provides a pressure-steeping-permeation-drainage integrated experimental device under actual temperature and pressure conditions of shale reservoirs, the device comprising: a power system a, a fluid supply system b, a reservoir simulation system c, a temperature control system d, and an electronic metering system e;

[0046] The power system a is connected to the fluid supply system b, the fluid supply system b is connected to the reservoir simulation system c, the fluid supply system b and the reservoir simulation system c are placed in the temperature control system d, and the reservoir simulation system c is connected to the electronic metering system e;

[0047] A power system a, used for providing pressure to a fluid supply system b;

[0048] A fluid supply system b, used for supplying fluid to the reservoir simulation system c, wherein the fluid is oil in the oil saturation process or fracturing fluid in the displacement process;

[0049] Reservoir simulation system c, used to simulate the integrated process of fracturing-well soaking-imbibition-flowback under the actual temperature and pressure conditions of the target shale oil reservoir;

[0050] Temperature control system d, used to simulate the actual temperature of shale reservoir;

[0051] Electronic metering system e, used to measure the oil saturation in the produced fluid.

[0052] In this embodiment, the power system a includes: a dual-cylinder constant speed and constant pressure pump 1, which provides power, ie, pressure, to the fluid supply system under constant speed or constant pressure conditions.

[0053] In this embodiment, the fluid supply system b comprises: a first high temperature and high pressure resistant two-way valve 2, a second high temperature and high pressure resistant two-way valve 4 and a high temperature and high pressure resistant intermediate container 3;

[0054] The first high temperature and high pressure two-way valve 2 controls the power system a to provide power to the high temperature and high pressure intermediate container 3 , and the second high temperature and high pressure two-way valve 4 controls the outflow of fluid in the high temperature and high pressure intermediate container 3 .

[0055] In this embodiment, the reservoir simulation system c includes: a third high temperature and high pressure two-way valve 5, a first high temperature and high pressure back pressure valve 6, a fourth high temperature and high pressure two-way valve 7, a high temperature and high pressure core holder 8, a shale core 9, a fifth high temperature and high pressure two-way valve 10, a second high temperature and high pressure back pressure valve 11 and a produced liquid collection device 12;

[0056] The third high temperature and high pressure two-way valve 5 and the fourth high temperature and high pressure two-way valve 7 control whether the fluid can flow to the high temperature and high pressure core holder 8, and the first high temperature and high pressure back pressure valve 6 and the second high temperature and high pressure back pressure valve 11 control the pressure of the fluid flowing into and out of the high temperature and high pressure core holder 8, thereby controlling the fluid pressure in the shale core 9;

[0057] The left end of the first high temperature and high pressure back pressure valve 6 is connected to the fluid supply system b, and the right end is connected to the left end of the high temperature and high pressure core holder 8, simulating the fracturing fluid injection process in the actual development process of the shale oil reservoir; wherein, the fracturing fluid injection process in the actual development process of the shale oil reservoir is simulated, that is, the fracturing fluid is injected from the high temperature and high pressure intermediate container 3 in the fluid supply system into the shale core 9;

[0058] The right end of the high temperature and high pressure core holder 8 is connected to the fifth high temperature and high pressure two-way valve 10, and the fifth high temperature and high pressure two-way valve 10 is connected to the second high temperature and high pressure back pressure valve 11 to simulate the actual shale reservoir formation fluid pressure; wherein, simulating the actual shale reservoir formation fluid pressure includes: in the process of saturating oil, by setting the first high temperature and high pressure back pressure valve 6 and the second high temperature and high pressure back pressure valve 11 pressure to control the fluid pressure in the shale core 9. In the process of saturating oil, by setting the pressure of the first high temperature and high pressure back pressure valve 6 and the second high temperature and high pressure back pressure valve 11 to the actual fluid pressure in the shale reservoir (actual monitoring data of the oil field mine), and then starting to saturate oil, until a continuous and stable oil flow appears in the produced fluid collection device 12, it is considered that the fluid pressure in the shale core 9 reaches the shale reservoir formation fluid pressure.

[0059] like Figure 2 As shown, the shale core 9 is first pre-set with fractures 17 and then filled with sand (sand with the mesh size used in the actual fracturing process of shale oil reservoirs). After filling with sand, a steel mesh 18 with a mesh size smaller than the sand used is used to wrap the fracture surface, so as to simulate the shale fracturing reservoir, that is, the pre-fractured shale core is used to simulate the shale fracturing reservoir.

[0060] By setting the pressure of the first high temperature and high pressure back pressure valve 6 (the back pressure valve pressure can be set directly), the pressure Pz of the fluid entering the shale core 9 can be controlled, and the process of fracturing fluid entering the reservoir matrix from the cracks during the actual shale fracturing process can be simulated.

[0061] The second high temperature and high pressure back pressure valve 11 can control the fluid pressure in the shale core 9 and can simulate the actual formation pressure conditions of the shale reservoir, that is, during the oil saturation process, by setting the pressure of the second high temperature and high pressure back pressure valve 11 (the back pressure valve pressure can be directly set) to control the fluid outflow pressure in the core, the fluid pressure in the core can be controlled.

[0062] Specifically, the high-temperature and high-pressure core holder 8 in the reservoir simulation system c is equipped with a shale core sample (the core is pre-fractured and then filled with sand to simulate the reservoir after fracturing; and there is fluid pressure inside the core to simulate the actual formation pressure environment in the shale reservoir), and the left and right ends are connected to the first high-temperature and high-pressure back-pressure valve 6 to simulate the integrated process of fracturing-well soaking-imbibition-flowback under the actual temperature and pressure conditions of the target shale oil reservoir.

[0063] Simulate the integrated process of fracturing-well soaking-imbibition-flowback under the actual temperature and pressure conditions of the target shale reservoir, including:

[0064] The core with prefabricated fractures is used to simulate the shale fracturing reservoir. After the core is saturated with oil, the valve is closed after the fracturing fluid is injected into the core to simulate the well shut-in process. During the well shut-in process, the fracturing fluid displaces the crude oil in the core into the fractures through the percolation effect. After the prefabricated well shut-in time is reached, the valve is opened to start the backflow process.

[0065] Specifically, a shale core 9 with prefabricated fractures is used to simulate a fractured reservoir after shale oil reservoir fracturing. During the process of saturating the shale core 9 with oil, the pressure of the first high temperature and high pressure back pressure valve 6 and the second high temperature and high pressure back pressure valve 11 are controlled to make the fluid pressure in the shale core 9 after saturation with oil consistent with the actual fluid pressure in the shale reservoir; then, the pressure of the first high temperature and high pressure back pressure valve 6 is controlled to make the pressure of the fracturing fluid in the high temperature and high pressure intermediate container 3 when injected into the shale core 9 consistent with the pressure of the fracturing fluid flowing from the fracture to the matrix after shale oil reservoir fracturing. After the injection of the fracturing fluid is completed, the fourth high temperature and high pressure two-way valve 7 and the fifth high temperature and high pressure two-way valve 10 are closed to simulate the well soaking process after shale oil reservoir fracturing. During the well soaking process, the fracturing fluid controlled by capillary force can replace the crude oil in the core matrix into the fracture through the infiltration effect. After reaching the preset well soaking time, the pressure of the first high temperature and high pressure back pressure valve 6 is adjusted to make it consistent with the fluid pressure of the production well at the mine time, simulating the backflow process after shale oil reservoir fracturing.

[0066] In this embodiment, the temperature control system d includes a constant temperature box 16, and the temperature control system b ensures that the temperature of the fluid supply system b and the reservoir simulation system c is the same as the actual temperature of the shale oil reservoir.

[0067] In this embodiment, the electronic metering system e includes an infrared laser instrument 13, an automatic data reading device 14 and a data visualization device 15. The electronic metering system e is connected to the produced fluid collection device 12 in the reservoir simulation system c to measure the oil saturation in the produced fluid, that is, to read the oil volume in the produced fluid through infrared rays.

[0068] The experimental device is resistant to high temperature and high pressure, and can simulate the actual reservoir environment of ultra-high temperature and high pressure in shale reservoirs. It can realize the integrated process of fracturing-well soaking-imbibition-flowback that takes into account the actual formation pressure of shale, solving the problem that the laboratory cannot simulate the real formation fluid pressure of shale reservoirs.

[0069] Embodiment 2

[0070] The embodiment of the present invention provides a pressure-simmering-permeation-drainage integrated experimental method under actual temperature and pressure conditions of a shale reservoir, which is implemented by using the pressure-simmering-permeation-drainage integrated experimental device under actual temperature and pressure conditions of a shale reservoir described in Example 1, and includes the following steps:

[0071] S1, placing a shale oil-saturated shale core 9 into a high temperature and high pressure core holder 8, filling the high temperature and high pressure intermediate container 3 of the fluid supply system b with shale oil, and setting the pressures of the first high temperature and high pressure back pressure valve 6 and the second high temperature and high pressure back pressure valve 11 to the actual formation pressure of the shale reservoir;

[0072] S2, open the first high temperature and high pressure two-way valve 2, the second high temperature and high pressure two-way valve 4, the third high temperature and high pressure two-way valve 5, the fourth high temperature and high pressure two-way valve 7 and the fifth high temperature and high pressure two-way valve 10, start the double-cylinder constant speed and constant pressure pump 1 of the power system a, adopt a constant speed injection method, the injection speed of the double-cylinder constant speed and constant pressure pump 1 is the experimental preset speed, until the pressure in the shale core reaches the actual formation pressure of the shale reservoir, close the third high temperature and high pressure two-way valve 5, the fourth high temperature and high pressure two-way valve 7 and the fifth high temperature and high pressure two-way valve 10 and the double-cylinder constant speed and constant pressure pump 1;

[0073] S3, adjusting the pressure of the first high temperature and high pressure back pressure valve 6 to the actual fluid pressure in the fracture after the shale reservoir is fractured, so as to simulate the process of the fracturing fluid entering the reservoir matrix during the actual fracturing of the shale reservoir, and filling the high temperature and high pressure intermediate container 3 of the fluid supply system b with the fracturing fluid actually used on site;

[0074] S4, open the third high temperature and high pressure two-way valve 5 and the fourth high temperature and high pressure two-way valve 7, start the double-cylinder constant speed and constant pressure pump 1 of the power system a, and inject the fracturing fluid in the high temperature and high pressure intermediate container 3 into the shale core 9 by the actual fluid pressure in the seam after fracturing the shale oil reservoir by constant pressure injection, until the injection volume of the fracturing fluid reaches the experimental preset injection volume, close the third high temperature and high pressure two-way valve 5, the fourth high temperature and high pressure two-way valve 7 and the double-cylinder constant speed and constant pressure pump 1, and start the well soaking and absorption process according to the experimental preset well soaking time;

[0075] S5. After the well is shut down, the pressure of the first high temperature and high pressure back pressure valve 6 is adjusted to the actual bottom hole flow pressure after the well is shut down after the fracturing development of the shale oil reservoir, and the third high temperature and high pressure two-way valve 5 is connected to the produced fluid collection device 12, and the third high temperature and high pressure two-way valve 5 and the fourth high temperature and high pressure two-way valve 7 are opened to simulate the fracturing fluid backflow process until the pressure in the core drops to the preset pressure and the oil production no longer changes, and the experiment ends;

[0076] S6. Collect the data recorded by the data visualization device 15 in the electronic metering system e, calculate the recovery factor and draw the corresponding recovery factor curve.

[0077] In this embodiment, in S3, the pressure of the first high temperature and high pressure back pressure valve 6 is adjusted to the actual fluid pressure in the fracture after the shale reservoir is fractured, simulating the process of fracturing fluid entering the reservoir matrix during the actual fracturing of the shale reservoir, including:

[0078]

[0079] Among them, p z is the injection pressure, MPa; p 0 It is the surface injection pressure of the fracturing fluid during actual construction on site, MPa; is the density of the injected fracturing fluid, kg / m 3 ; g is the acceleration due to gravity, m / s 2 ;p my is the friction along the way, MPa; p mj is the local friction, MPa; p ms is the perforation friction, MPa.

[0080] In this embodiment, in S4, the soaking and imbibition process is started according to the preset soaking time of the experiment, including: after the soaking starts, the fracturing fluid replaces the shale oil through imbibition, and the imbibition process occurs during the soaking process (the oil and water saturation distribution field is redistributed under the imbibition effect during the soaking process).

[0081] In the actual reservoir fracturing process, after the fracturing fluid is injected into the reservoir, the production well will be closed for the well shut-in process, so that the fracturing fluid flows from the cracks to the matrix, and the crude oil at the far end of the matrix is ​​displaced by the imbibition effect. In the experimental process, after the fracturing fluid is injected into the core, the fourth high-temperature and high-pressure two-way valve 7 and the fifth high-temperature and high-pressure two-way valve 10 are closed to simulate the actual well shut-in process.

[0082] In this embodiment, in S5, the fracturing fluid backflow process is simulated, including: after the well soaking process is completed, the high temperature and high pressure two-way valve 5 and the produced fluid collection device are connected, and the third high temperature and high pressure two-way valve 5 and the fourth high temperature and high pressure two-way valve 7 are opened. Due to the fluid pressure in the core, the valve is connected to the atmospheric pressure, and the fluid in the core flows out of the valve under the action of the pressure difference.

[0083] In this embodiment, in S6, calculating the recovery factor includes:

[0084] EOR=Vo / Vz

[0085] Wherein, EOR is the recovery factor, %; Vo is the volume of shale oil in the flowback fluid, mL; Vz is the core saturated oil volume, mL.

[0086] Embodiment 3

[0087] The shale core fracturing development effect of the Z oilfield was evaluated by using a pressure-simmering-permeation-drainage integrated experimental device and method under actual temperature and pressure conditions of a shale reservoir provided in Example 1 and Example 2 of the present invention.

[0088] 1. Experimental Materials

[0089] The experimental water was simulated formation water with a salinity of 12497 mg / L. The fracturing fluid was the actual fracturing fluid provided by the Z oilfield, containing chemical oil displacement agent (mass fraction 0.35%), and the oil-water interfacial tension was 0.0023 mN / m. The experimental oil was simulated oil, which was a mixture of dehydrated and degassed crude oil from the Z oilfield and aviation kerosene, with a viscosity of 4.158 mPa·s (134.2 ℃). The experimental core was a natural shale core sample from the reservoir of the Z block, with core appearance geometric dimensions: length 10.0 cm, diameter 2.5 cm, and permeability 0.238 mD.

[0090] 2. Experimental equipment

[0091] The main equipment is, a-power system, b-fluid supply system, c-reservoir simulation system, d-temperature control system, e-electronic metering system, 1-dual-cylinder constant speed and constant pressure pump, 2-first high temperature and high pressure two-way valve, 3-high temperature and high pressure intermediate container, 4-second high temperature and high pressure two-way valve, 5-third high temperature and high pressure two-way valve, 6-first high temperature and high pressure back pressure valve, 7-fourth high temperature and high pressure two-way valve, 8-high temperature and high pressure core holder, 9-shale core, 10-fifth high temperature and high pressure two-way valve, 11-second high temperature and high pressure back pressure valve, 12-produced fluid collection device, 13-infrared laser instrument, 14-automatic data reading device, 15-data visualization device, 16-constant temperature box, all connecting wires in systems a, b, c and d are high temperature and high pressure conduits, and the connecting wires in system e are data transmission lines. The schematic diagram of the experimental device flow is shown in Figure 1 .

[0092] 3. Experimental methods

[0093] S1. Place the shale oil-saturated shale core into a high temperature and high pressure core holder 8, fill the high temperature and high pressure intermediate container of the fluid supply system with shale oil, and set the pressure of the first high temperature and high pressure back pressure valve 6 and the second high temperature and high pressure back pressure valve 11 to the actual formation pressure of the shale reservoir (the actual formation pressure of the reservoir in block Z is 62.99 MPa).

[0094] S2. Open the first, second, third, fourth and fifth high temperature and high pressure two-way valves, start the double-cylinder constant speed and constant pressure pump of the power system, and start the oil saturation process by constant speed injection. The injection speed of the double-cylinder constant speed and constant pressure pump is the experimental preset speed (0.01 ml / min), until the pressure in the shale core reaches the actual formation pressure of the shale reservoir (62.99 MPa), and then close the third, fourth and fifth high temperature and high pressure two-way valves and the double-cylinder constant speed and constant pressure pump.

[0095] S3, adjust the pressure of the first high temperature and high pressure back pressure valve 6 to 87.4 MPa ( ), which is used to simulate the process of fracturing fluid entering the reservoir matrix during the actual fracturing of shale reservoirs, and to fill the high-temperature and high-pressure resistant intermediate container of the fluid supply system with the fracturing fluid actually used on site.

[0096]

[0097] p z is the injection pressure, MPa; p 0 It is the surface injection pressure of the fracturing fluid during actual construction on site; is the density of the injected fracturing fluid, kg / m 3 ; g is the acceleration due to gravity, m / s 2 ;p my is the friction resistance along the way, Pa; p mj is the local friction, Pa; p ms is the perforation friction, Pa.

[0098] S4, open the third and fourth high temperature and high pressure two-way valves, start the double-cylinder constant speed and constant pressure pump of the power system, and use the constant pressure injection method to inject the fracturing fluid in the high temperature and high pressure intermediate container 3 into the shale core at the actual fluid pressure in the fracture after fracturing of the shale oil reservoir, until the injection volume of the fracturing fluid reaches the preset injection volume of the experiment (0.3 PV, the core pore volume is 4.54 ml, 0.3 PV=4.45*0.3=1.362 ml), close the third and fourth high temperature and high pressure two-way valves and the double-cylinder constant speed and constant pressure pump, and start the well soaking and imbibition process according to the preset well soaking time (1 h) of the experiment.

[0099] S5. After the well is shut down, the pressure of the first high-temperature and high-pressure back-pressure valve 6 is adjusted to the actual bottom hole flow pressure after the shale oil reservoir is fracturing and developed (the bottom hole flow pressure after fracturing and flowback in block Z is 30 MPa), and the third high-temperature and high-pressure two-way valve is connected to the produced fluid collection device, and the third and fourth high-temperature and high-pressure two-way valves are opened to simulate the fracturing fluid flowback process until the pressure in the core drops to the preset pressure (30 MPa), the oil production no longer changes, and the experiment ends.

[0100] S6. Collect the data recorded by the data visualization device in the electronic metering system, calculate the recovery factor and draw the corresponding recovery factor curve.

[0101] 4. Experimental results

[0102] The curve of shale oil recovery rate changing with flowback fluid volume is as follows: Figure 3 As shown in the figure, the recovery factor first increases rapidly and then increases slowly with the increase of the flowback fluid volume, and finally tends to be stable. The final shale recovery factor is 16.32%.

[0103] EOR=Vo / Vz=0.862 / 5.28=16.32%

[0104] EOR is the recovery factor, %; Vo is the volume of shale oil in the flowback fluid, mL; Vz is the core saturated oil volume, mL.

[0105] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A pressure-simmering-permeation-drainage integrated experimental device under actual temperature and pressure conditions of shale reservoirs, characterized in that: The device comprises: a power system (a), a fluid supply system (b), a reservoir simulation system (c), a temperature control system (d), and an electronic metering system (e); The power system (a) is connected to the fluid supply system (b), the fluid supply system (b) is connected to the reservoir simulation system (c), the fluid supply system (b) and the reservoir simulation system (c) are placed in the temperature control system (d), and the reservoir simulation system (c) is connected to the electronic metering system (e); The power system (a) is used to provide pressure to the fluid supply system (b); The fluid supply system (b) is used to supply fluid to the reservoir simulation system (c), wherein the fluid is oil in the oil saturation process or fracturing fluid in the displacement process; The reservoir simulation system (c) is used to simulate the integrated process of fracturing-well soaking-imbibition-flowback under the actual temperature and pressure conditions of the target shale oil reservoir; The temperature control system (d) is used to simulate the actual temperature of the shale reservoir; The electronic metering system (e) is used to measure the oil saturation in the produced fluid; The reservoir simulation system (c) comprises: a third high temperature and high pressure two-way valve (5), a first high temperature and high pressure back pressure valve (6), a fourth high temperature and high pressure two-way valve (7), a high temperature and high pressure core holder (8), a shale core (9), a fifth high temperature and high pressure two-way valve (10), a second high temperature and high pressure back pressure valve (11) and a produced fluid collection device (12); The third high temperature and high pressure two-way valve (5) and the fourth high temperature and high pressure two-way valve (7) control whether the fluid can flow to the high temperature and high pressure core holder (8), and the first high temperature and high pressure back pressure valve (6) and the second high temperature and high pressure back pressure valve (11) control the pressure of the fluid flowing into and out of the high temperature and high pressure core holder (8), thereby controlling the fluid pressure in the shale core (9); The left end of the first high temperature and high pressure back pressure valve (6) is connected to the fluid supply system (b), and the right end is connected to the left end of the high temperature and high pressure core holder (8), so as to simulate the fracturing fluid injection process in the actual development process of shale oil reservoirs; The right end of the high temperature and high pressure core holder (8) is connected to the fifth high temperature and high pressure two-way valve (10), and the fifth high temperature and high pressure two-way valve (10) is connected to the second high temperature and high pressure back pressure valve (11), so as to simulate the actual shale reservoir formation fluid pressure.

2. The device according to claim 1, characterized in that The power system (a) comprises: a double-cylinder constant speed and constant pressure pump (1) which provides power, i.e. pressure, to the fluid supply system under constant speed or constant pressure conditions.

3. The device according to claim 1, characterized in that The fluid supply system (b) comprises: a first high temperature and high pressure resistant two-way valve (2), a second high temperature and high pressure resistant two-way valve (4) and a high temperature and high pressure resistant intermediate container (3); The first high temperature and high pressure resistant two-way valve (2) controls the power system (a) to provide power to the high temperature and high pressure resistant intermediate container (3), and the second high temperature and high pressure resistant two-way valve (4) controls the outflow of fluid in the high temperature and high pressure resistant intermediate container (3).

4. The device according to claim 1, characterized in that The temperature control system (d) comprises a constant temperature box (16), and the temperature control system (b) ensures that the temperature of the fluid supply system (b) and the reservoir simulation system (c) is the same as the actual temperature of the shale oil reservoir.

5. The device according to claim 1, characterized in that The electronic metering system (e) comprises an infrared laser instrument (13), an automatic data reading device (14) and a data visualization device (15). The electronic metering system (e) is connected to a produced fluid collection device (12) in a reservoir simulation system (c) to measure the oil saturation in the produced fluid.

6. A pressure-simmering-permeation-drainage integrated experimental method under actual temperature and pressure conditions of shale reservoirs, characterized in that: The integrated pressure-steeping-permeation-drainage experimental device under the actual temperature and pressure conditions of the shale reservoir described in any one of claims 1 to 5 is implemented, comprising the following steps: S1. A shale core (9) saturated with shale oil is placed in a high temperature and high pressure core holder (8), a high temperature and high pressure intermediate container (3) of a fluid supply system (b) is filled with shale oil, and the pressures of the first high temperature and high pressure back pressure valve (6) and the second high temperature and high pressure back pressure valve (11) are both set to the actual formation pressure of the shale reservoir; S2, opening the first high temperature and high pressure two-way valve (2), the second high temperature and high pressure two-way valve (4), the third high temperature and high pressure two-way valve (5), the fourth high temperature and high pressure two-way valve (7) and the fifth high temperature and high pressure two-way valve (10), starting the double-cylinder constant speed and constant pressure pump (1) of the power system (a), and starting the oil saturation process by means of constant speed injection, the injection speed of the double-cylinder constant speed and constant pressure pump (1) being the experimental preset speed, until the pressure in the shale core reaches the actual formation pressure of the shale reservoir, and closing the third high temperature and high pressure two-way valve (5), the fourth high temperature and high pressure two-way valve (7) and the fifth high temperature and high pressure two-way valve (10) and the double-cylinder constant speed and constant pressure pump (1); S3, adjusting the pressure of the first high temperature and high pressure back pressure valve (6) to the actual fluid pressure in the fracture of the shale oil reservoir after fracturing, so as to simulate the process of fracturing fluid entering the reservoir matrix during the actual fracturing of the shale reservoir, and filling the high temperature and high pressure intermediate container (3) of the fluid supply system (b) with the fracturing fluid actually used on site; S4, opening the third high temperature and high pressure two-way valve (5) and the fourth high temperature and high pressure two-way valve (7), starting the double-cylinder constant speed and constant pressure pump (1) of the power system (a), and injecting the fracturing fluid in the high temperature and high pressure intermediate container (3) into the shale core (9) by means of constant pressure injection at the actual fluid pressure in the fracture after fracturing the shale oil reservoir, until the injection volume of the fracturing fluid reaches the injection volume preset in the experiment, closing the third high temperature and high pressure two-way valve (5), the fourth high temperature and high pressure two-way valve (7) and the double-cylinder constant speed and constant pressure pump (1), and starting the well soaking and absorption process according to the well soaking time preset in the experiment; S5, after the well is shut down, the pressure of the first high temperature and high pressure back pressure valve (6) is adjusted to the actual bottom hole flow pressure after the well is shut down after the shale oil reservoir is fracturing and developed, and the third high temperature and high pressure two-way valve (5) is connected to the produced fluid collection device (12), and the third high temperature and high pressure two-way valve (5) and the fourth high temperature and high pressure two-way valve (7) are opened to simulate the fracturing fluid backflow process until the pressure in the core drops to the preset pressure and the oil production no longer changes, and the experiment ends; S6. Collect the data recorded by the data visualization device (15) in the electronic metering system (e), calculate the recovery factor and draw a corresponding recovery factor curve.

7. The method according to claim 6, characterized in that In S3, the pressure of the first high temperature and high pressure back pressure valve (6) is adjusted to the actual fluid pressure in the fracture of the shale oil reservoir after fracturing, simulating the process of fracturing fluid entering the reservoir matrix during the actual fracturing of the shale reservoir, including: Among them, p z is the injection pressure, MPa; p0 is the ground injection pressure of the fracturing fluid during actual construction on site, MPa; is the density of the injected fracturing fluid, kg / m 3 ; g is the acceleration due to gravity, m / s 2 ;p my is the friction along the way, MPa; p mj is the local friction, MPa; p ms is the perforation friction, MPa.

8. The method according to claim 6, characterized in that In S6, calculating the recovery factor includes: EOR=Vo / Vz Wherein, EOR is the recovery factor, %; Vo is the volume of shale oil in the flowback fluid, mL; Vz is the core saturated oil volume, mL.

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