Experimental system and method for gas displacement of reservoir crude oil

Abstract

The invention discloses an experimental system and method for gas displacement of reservoir crude oil. The experimental system comprises a displacement kettle; the displacement container is arranged in the displacement kettle and used for bearing a reservoir sample, and a plurality of fluid communication holes are distributed in the periphery of the side wall of the displacement container; the under-pressure gas supply unit is configured to provide displacement gas with a preset pressure value into the displacement kettle so as to apply confining pressure to the sample and displace the sample; the collecting and metering unit is configured to collect and meter the crude oil displaced from the sample; and the control and processing unit is configured to set a preset pressure value and determine the amount of the displaced crude oil based on the metering value of the collecting and metering unit. The displacement uniformity can be improved, the shape of a sample is not limited, the amount of displaced crude oil can be accurately measured, the accuracy of mobility evaluation is improved, the displacement process under the formation pressure and temperature conditions can be simulated, and it is guaranteed that the experiment conditions conform to the actual formation conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of oil extraction experiments, and particularly relates to an experimental system and method for gas displacement of reservoir crude oil. Background Art

[0002] The Gulong shale oil in the Songliao Basin is widely distributed, with large resource and reserve amounts. The exploration and development of shale oil are important bases for the high-quality development of the Daqing Oilfield. However, the Gulong shale oil has low permeability and poor fluidity, and the exploration and development are extremely difficult. Existing technologies are difficult to apply, and it is urgent to break through the key technologies for evaluating the mobility and "four properties" of shale oil to provide a scientific basis for the large-scale effective utilization and exploitation of shale oil.

[0003] Patent CN116163707A discloses an experimental system for studying the enhanced oil recovery of shale oil by CO2, including a high-temperature and high-pressure displacement device. The high-temperature and high-pressure displacement device includes a high-precision constant-pressure and constant-speed pump, an intermediate container, a core holder, a confining pressure pump, a back-pressure valve, a produced gas-liquid metering device, a pressure sensor, and a data acquisition computer. When conducting an experiment, the core is fixed by the core holder and saturated with simulated formation oil. CO2 is injected from the core inlet. While injecting CO2, the confining pressure liquid is injected into the adjustable cavity through the liquid injection pipe by the confining pressure pump. After that, the inlet is closed for shut-in. After the shut-in is completed, the inlet pressure is quickly reduced to atmospheric pressure, and the oil production at the inlet end is recorded.

[0004] Patent CN113340928A discloses an experimental device and method for the cyclic steam stimulation of shale oil by supercritical CO2 / H2O mixed fluid. When conducting an experiment, the oil-saturated core is placed in the core holder, and the confining pressure is applied to the core holder by a hand-operated pump. The injection valve is opened, and the mixed fluid containing a certain mole fraction of water vapor prepared by a booster pump is injected into the core holder. After shut-in, the weight of the absorbent cotton is weighed, and the oil production is calculated.

[0005] It can be seen that when conducting displacement experiments in the prior art, the confining pressure is generally applied to the sample and the sample is displaced by separately injecting the confining pressure liquid and the displacement gas. In these prior art solutions, since the displacement gas usually flows to the sample from one main direction, the uniformity of the displacement process is poor, the displacement is not sufficient, and the sample needs to be made into a regular shape (usually cylindrical) that matches the core holder to fix the sample, resulting in limited sample selection and difficulties in sample preparation.

[0006] Based on this, there is still room for further improvement in the prior art. Summary of the Invention

[0007] The main object of the present invention is to provide an experimental system and method for gas displacing reservoir crude oil, so as to solve the problems of poor displacement uniformity in existing displacement experiments and the use of only samples with regular shapes.

[0008] According to one aspect of the present invention, an experimental system for gas displacing reservoir crude oil is provided, including:

[0009] A displacement kettle;

[0010] A displacement container, which is arranged in the displacement kettle and used to carry the reservoir sample, and a plurality of fluid communication holes are distributed around the side wall of the displacement container;

[0011] A pressurized gas supply unit, configured to provide a displacement gas with a predetermined pressure value into the displacement kettle to apply confining pressure to the sample and displace the sample;

[0012] A collection and metering unit, configured to collect and meter the crude oil displaced from the sample;

[0013] A control and processing unit, configured to set a predetermined pressure value and determine the amount of crude oil displaced based on the metering value of the collection and metering unit.

[0014] According to an embodiment of the present invention, the side wall of the displacement container is a mesh structure.

[0015] According to an embodiment of the present invention, the displacement kettle has a gas inlet, and the pressurized gas supply unit provides the displacement gas through the gas inlet, and the gas inlet is located at the lower side of the displacement container.

[0016] According to an embodiment of the present invention, it further includes a rotation mechanism arranged in the displacement kettle, the rotation mechanism drives the displacement container to rotate around its own axis, or the rotation mechanism is arranged to stir the displacement gas in the displacement kettle.

[0017] According to an embodiment of the present invention, the rotation mechanism includes:

[0018] A motor, which is arranged outside the bottom wall of the displacement kettle and is communicatively connected with the control and processing unit;

[0019] A rotating part, which is arranged in the displacement kettle and is located below the displacement container, and the motor drives the rotating part to rotate;

[0020] A bearing part connected to the rotating part and carrying the displacement container, or a stirring blade connected to the rotating part and located below the displacement container.

[0021] According to an embodiment of the present invention, the upper part of the displacement kettle has a gas outlet, and the collection and metering unit includes:

[0022] A liquid collection container, the liquid collection container is communicated with the gas outlet through a pipeline, and a liquid that can trap crude oil but not trap the displacement gas is placed in the liquid collection container;

[0023] A homogenizing component configured to homogenize the solution in the liquid collection container;

[0024] An oil detector configured to detect the oil concentration of the solution in the liquid collection container;

[0025] The control and processing unit is configured to calculate the crude oil amount based on the oil concentration and the volume of the solution in the liquid collection container.

[0026] According to an embodiment of the present invention, the homogenizing component is a peristaltic pump, and the peristaltic pump is communicatively connected to the control and processing unit and drives the solution in the liquid collection container to circulate.

[0027] According to an embodiment of the present invention, the displacement kettle includes a kettle body having an upper opening and a cover detachably connected to the upper opening.

[0028] According to an embodiment of the present invention, it further includes a kit disposed on the outer periphery of the displacement kettle and a heating part and a temperature measuring part embedded in the kit, and the control and processing unit is configured to control the heating part to heat the displacement kettle to a predetermined temperature value based on the detection value of the temperature measuring part.

[0029] According to an embodiment of the present invention, it further includes a heat preservation part disposed outside the kit; and / or the bottom wall of the displacement kettle is provided with a drain hole for discharging the cleaning liquid.

[0030] According to another aspect of the present invention, there is provided an experimental method for gas displacing reservoir crude oil, including:

[0031] Placing a reservoir sample in a displacement container inside the displacement kettle, wherein a plurality of fluid communication holes are distributed around the side wall of the displacement container;

[0032] Providing a displacement gas with a predetermined pressure value into the displacement kettle to apply confining pressure to the sample and displace the sample;

[0033] Collecting and measuring the crude oil displaced from the sample to determine the amount of displaced crude oil.

[0034] According to an embodiment of the present invention, the sample has a regular shape or an irregular shape.

[0035] According to an embodiment of the present invention, collecting and measuring the crude oil displaced from the sample to determine the amount of displaced crude oil includes:

[0036] After the displacement is completed, allowing the gas in the displacement kettle to enter the liquid collection container, and capturing the gaseous crude oil in the gas by the liquid in the liquid collection container;

[0037] Homogenizing the solution in the liquid collection container and detecting the oil concentration of the solution in the liquid collection container;

[0038] Calculate the crude oil quantity based on the oil concentration and the volume of the solution in the liquid collection container.

[0039] According to an embodiment of the present invention, it further includes: during the displacement process, making the displacement container carry the sample and rotate around its own axis, or stirring the displacement gas in the displacement autoclave.

[0040] According to an embodiment of the present invention, it further includes: respectively heating and detecting the temperature of the displacement autoclave through the heating part and the temperature measuring part, and controlling the heating part to heat the displacement autoclave to a predetermined temperature value based on the temperature detection value.

[0041] According to an embodiment of the present invention, it further includes: performing relevant detections on the sample after the displacement to evaluate one or more of the following properties of the reservoir: lithology, physical properties, oil-bearing property, electrical property.

[0042] In the technical solution of the present invention, a plurality of fluid communication holes are distributed around the side wall of the displacement container. The displacement gas with a predetermined pressure value entering the displacement autoclave enters the displacement container from all around through the plurality of fluid communication holes, simultaneously applying confining pressure to the sample in the displacement container and displacing the sample. Since the displacement gas flows towards the sample from all around, the uniformity of the displacement can be improved and the displacement can be ensured to be carried out fully; and, since the sample is under the action of balanced pressure from the surrounding, rather than the action of air flow in a single direction, it can be stably placed in the displacement container without being made into a regular shape matching the displacement container for fixation, that is, the shape of the sample of the present invention is not limited, and samples with regular shapes or irregular shapes can be used, thereby reducing the difficulty of sample production. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0044] Figure 1 Schematic diagram showing an experimental system for gas displacing reservoir crude oil according to an embodiment of the present invention;

[0045] Figure 2 Schematic diagram showing the structure of a displacement unit according to an embodiment of the present invention;

[0046] Figure 3 Schematic diagram showing the structure of the cover of a displacement autoclave according to an embodiment of the present invention;

[0047] Figure 4 Schematic diagram showing a partial structure of a rotating mechanism according to an embodiment of the present invention;

[0048] Figure 5 Shows a schematic structural diagram of a collection and metering unit according to an embodiment of the present invention.

[0049] Explanation of reference numerals:

[0050] 100, displacement unit; 110, displacement kettle; 111, lower flange; 112, kettle body; 113, graphite gasket; 114, cover; 115, plastic gasket; 117, upper flange; 119, handle; 120, displacement container; 130, rotation mechanism; 131, motor; 132, rotating part; 133, stirring blade; 134, positioning shaft; 135, bearing; 140, kit; 142, heating part; 144, temperature measuring part; 200, pressurized gas supply unit; 201, gas source; 203, booster pump; 205, chiller; 300, collection and metering unit; 301, liquid collection container; 302, pipeline; 303, peristaltic pump; 304, control valve; 305, oil detector; 400, control and processing unit; 401, controller; 403, temperature control module; 405, pressure control module. Detailed implementation manners

[0051] To make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the following further elaborates on the embodiments of the present invention in detail with reference to specific embodiments and the accompanying drawings.

[0052] It should be noted that all the expressions using "first" and "second" in the embodiments of the present invention are used to distinguish two entities or parameters with the same name but different, so "first" and "second" are only for the convenience of expression and should not be construed as a limitation on the embodiments of the present invention. This will not be elaborated one by one in the subsequent embodiments.

[0053] Refer to Figure 1 and Figure 2, the present invention provides an experimental system for gas displacement of reservoir crude oil, comprising: a displacement unit 100, a pressurized gas supply unit 200, a collection and measurement unit 300, and a control and processing unit 400. The displacement unit 100 includes a displacement autoclave 110 and a displacement container 120. The displacement container 120 is disposed within the displacement autoclave 110 and is used to carry a reservoir sample. There is a spacing between the outer sidewall of the displacement container 120 and the inner sidewall of the displacement autoclave 110. A plurality of fluid communication holes are distributed around the sidewall of the displacement container 120 to achieve fluid communication between the displacement autoclave 110 and the displacement container 120. The pressurized gas supply unit 200 is configured to supply a displacement gas with a predetermined pressure value into the displacement autoclave to apply confining pressure to the sample and displace the sample. The collection and measurement unit 300 is configured to collect and measure the crude oil displaced from the sample. The control and processing unit 400 is configured to set the predetermined pressure value and determine the amount of crude oil displaced based on the measurement value of the collection and measurement unit 300 to evaluate the mobility of the reservoir crude oil.

[0054] In an embodiment of the present invention, a plurality of fluid communication holes are distributed around the sidewall of the displacement container 120. The displacement gas with a predetermined pressure value entering the displacement autoclave enters the displacement container 120 from all around through the plurality of fluid communication holes, simultaneously applying confining pressure to the sample in the displacement container 120 (for example, the confining pressure can be more than 2 MPa higher than the formation fluid pressure, up to 100 MPa) and displacing the sample. Since the displacement gas flows towards the sample from all around, the uniformity of displacement can be improved and the displacement can be ensured to proceed fully; moreover, since the sample is subjected to balanced pressure from all around, rather than a single-directional air flow (in the prior art, the sample is subjected to a single-directional displacement air flow, and if the sample is not fixed, the sample will move with the air flow and cannot maintain its position), the sample can be stably placed in the displacement container without being made into a regular shape matching the displacement container for fixation. That is, the shape of the sample in the present invention is not restricted, and samples with regular or irregular shapes can be used, thereby reducing the difficulty of sample preparation. In addition, the present invention sets the predetermined pressure value and determines the amount of crude oil based on the control and processing unit 400, with a high degree of automation.

[0055] In an embodiment of the present invention, the reservoir sample can be a source rock sample, such as shale, mudstone, tight sandstone, siltstone, etc.; the displacement gas can be carbon dioxide (supercritical carbon dioxide), nitrogen, natural gas, etc.

[0056] The displacement kettle 110 and the displacement container 120 can be made of nickel-based alloy steel to ensure its strength under high temperature and high pressure. The displacement container 120 can be cylindrical or other suitable shapes. In some embodiments, a plurality of fluid communication holes are formed by punching holes on the side wall of the displacement container 120. In some embodiments, the side wall of the displacement container 120 is a mesh structure, and the mesh holes are used as fluid communication holes. For example, the displacement container 120 can be a cylindrical structure surrounded by wire mesh. The bottom wall and the top wall of the displacement container 120 can also form a plurality of fluid communication holes to further ensure that the displacement gas is in full and uniform contact with the sample.

[0057] In some embodiments, the displacement kettle 110 has a gas inlet, and the pressurized gas supply unit 200 provides displacement gas through the gas inlet, and the gas inlet is located at the lower side of the displacement container 120. In this way, the displacement gas can gradually diffuse upward from the bottom to the surrounding of the sample in the displacement container 120. In some embodiments, the pressurized gas supply unit 200 includes a gas source 201 and a booster pump 203. The gas source 201 is connected to the gas inlet of the displacement kettle 110 through a pressure-resistant pipeline, and the booster pump 203 is arranged on the pipeline to pressurize the displacement gas to a predetermined pressure value. The pressurized gas supply unit 200 may also include a chiller 205 arranged between the gas source 201 and the booster pump 203 to keep the displacement gas at a low temperature. The control and processing unit 400 controls the booster pump 203 to achieve a predetermined pressure value of the displacement gas.

[0058] refer to Figure 2 In some embodiments, the displacement kettle 110 includes a kettle body 112 having an upper opening and a cover 114 detachably connected (e.g., threaded, snap-fitted, friction-fitted, etc.) to the upper opening. When performing a displacement experiment, the cover 114 is sealed at the upper opening of the displacement kettle 110 to ensure that the displacement kettle 110 is sealed; after the displacement experiment is completed, the cover 114 is removed to take out the sample, and a cleaning liquid can also be injected through the upper opening to clean the displacement kettle 110. Figure 3 In some embodiments, the cover 114 includes, arranged from bottom to top, a lower flange 111, a graphite gasket 113, a plastic gasket 115, an upper flange 117, and a handle 119. The lower flange 111 and the upper flange 117 are connected by fasteners such as bolts, and the upper flange 117 has an external thread structure to cooperate with the internal thread structure of the kettle body 112 to achieve a detachable connection between the upper flange 117 and the kettle body 112. The graphite gasket 113 and the plastic gasket 115 are used to achieve sealing at the connection. The handle 119 is arranged on the upper flange 117, and the cover 114 is easily installed and removed by the handle 119.

[0059] refer to Figure 1 and Figure 2, in some embodiments, the displacement unit 100 further includes a kit 140 disposed on the outer periphery of the displacement kettle 110, and a heating part 142 and a temperature measuring part 144 embedded in the kit 140. The control and processing unit 400 is configured to control the heating part 142 to heat the displacement kettle 110 to a predetermined temperature value based on the detection value of the temperature measuring part 144. The present invention can set the predetermined pressure value and the predetermined temperature value of the displacement experiment process, so as to simulate the formation temperature and pressure conditions and ensure that the simulation experiment conditions are close to the actual formation situation. The kit 140 can be, for example, a steel sleeve. The heating part 142 can be, for example, a heating pipe, and a plurality of heating pipes are uniformly arranged circumferentially in the kit 140. The temperature measuring part 144 can be, for example, a thermocouple. Reference Figure 2 , in some embodiments, the displacement unit 100 further includes a heat preservation part 146 (the heat preservation part 146 is, for example, a heat preservation layer) disposed outside the kit 140, which is used to prevent heat loss and increase the smoothness of temperature control. The heat preservation part 146 can also be disposed outside the cover 114 and / or outside the bottom wall of the displacement kettle 110. In some embodiments, the bottom wall of the displacement kettle 110 is provided with a liquid discharge hole for discharging the cleaning liquid. The heat preservation part 146 and the motor 131 to be described later can also be provided with liquid discharge holes at corresponding positions to ensure the smooth discharge of the cleaning liquid.

[0060] Reference Figure 2 , in some embodiments, the displacement unit 100 further includes a rotating mechanism 130 disposed in the displacement kettle 110. The rotating mechanism 130 drives the displacement container 120 to rotate around its own axis, or the rotating mechanism 130 is configured to stir the displacement gas in the displacement kettle. By rotating the sample or stirring the displacement gas, it is further ensured that the displacement gas is evenly diffused around the sample, so as to ensure the uniformity and sufficiency of the displacement.

[0061] Reference Figure 2 and Figure 4 , the rotating mechanism 130 includes: a motor 131, which is disposed outside the bottom wall of the displacement kettle 110 and is connected to the control and processing unit 400 in communication; a rotating part 132, which is disposed in the displacement kettle 110 and is located below the displacement container 120, and the motor 131 drives the rotating part 132 to rotate. In some embodiments, the rotating mechanism 130 further includes a bearing part connected to the rotating part 132 and carrying the displacement container 120, so as to drive the displacement container 120 to rotate; or, in some other embodiments, the rotating mechanism 130 includes stirring blades 133 connected to the rotating part 132 and located below the displacement container 120, so as to stir the displacement gas below the displacement container 120. The rotating mechanism 130 can also include a positioning shaft 134 and a bearing 135. The lower end of the positioning shaft 134 is connected (for example, threadedly connected) to the bottom wall of the displacement kettle 110, and the rotating part 132 is installed on the positioning shaft 134 through the bearing 135.

[0062] Reference Figure 1 、Figure 2 and Figure 5 , in some embodiments, the upper part of the displacement kettle 110 has a gas outlet. The collection and metering unit 300 includes: a liquid collection container 301, the liquid collection container 301 is communicated with the gas outlet through a pipeline 302, and a liquid (such as water) that can trap crude oil but not trap displacement gas is contained in the liquid collection container 301; a homogenization component configured to homogenize the solution in the liquid collection container; an oil detector 305 configured to detect the oil concentration of the solution in the liquid collection container; the control and processing unit 400 is configured to calculate the crude oil amount based on the oil concentration and the volume of the solution in the liquid collection container 301. A control valve 304 is provided on the pipeline 302. After the displacement experiment is completed, by operating the control valve 304, the gas in the displacement kettle 110 (the gas at this time includes the displacement gas and the gaseous displaced crude oil) flows through the gas outlet and the pipeline to the liquid collection container 301, and the crude oil is trapped by the liquid to form a mixed solution (such as an oil-water mixture), and the displacement gas is discharged outside the liquid collection container 301. The oil detector 305 samples from the homogenized solution to detect the oil concentration of the solution. The measurement accuracy of the oil detector 305 is high, for example, it can be accurate to one in a million, so as to ensure that the finally calculated crude oil amount has high accuracy to accurately evaluate the mobility of reservoir crude oil. In some embodiments, the homogenization component is a stirring device. In some embodiments, the homogenization component is a peristaltic pump 303, and the peristaltic pump 303 is communicatively connected to the control and processing unit 400 and drives the solution in the liquid collection container 301 to circulate. The liquid collection container 301, the peristaltic pump 303, and the oil detector 305 can all be controlled by the control and processing unit 400 to achieve automatic collection and metering.

[0063] In some embodiments, the control and processing unit 400 may include a controller 401, a temperature control module 403, and a pressure control module 405 electrically connected to the controller 401. The controller 401 is electrically connected to the peristaltic pump 303, the oil detector 305, and the booster pump 203. The controller 401 receives the measurement data from the oil detector 305, controls the switching action of the peristaltic pump 303, and controls the operation of the booster pump 203. The temperature control module 403 is electrically connected to the heating unit 142 and the temperature measuring unit 144, and is used to monitor the temperature inside the displacement autoclave 110. The controller 401 includes a processor, a memory, and a communication interface electrically connected to the processor. The temperature control module 403 and the pressure control module 405 are electrically connected to the processor through the communication interface. The processor generates control instructions according to the set control parameters (including temperature value, pressure value, displacement time, etc.) and sends them to the temperature control device 403 and the pressure control module 405. The temperature control module 403 controls the heating unit 142 to work according to the set value. At the same time, the processor receives the temperature value of the displacement autoclave 110 detected by the temperature measuring unit 144, and judges whether the temperature value reaches the set temperature value. If it reaches the set temperature value, the processor controls the heating unit 142 to stop heating through the temperature control module 403. The processor forms a closed-loop control through the temperature value feedback communication of the temperature measuring unit 144, so that the temperature of the displacement autoclave 110 is always maintained within the temperature range where the set temperature value is located until the set displacement time is reached.

[0064] The present invention also provides an experimental method for gas displacement of reservoir crude oil, including:

[0065] Placing the reservoir sample in the displacement container 120 inside the displacement autoclave 110, wherein a plurality of fluid communication holes are distributed around the side wall of the displacement container 120;

[0066] Providing a displacement gas with a predetermined pressure value into the displacement autoclave 110 to apply confining pressure to the sample and displace the sample;

[0067] Collecting and measuring the crude oil displaced from the sample to determine the amount of displaced crude oil.

[0068] In some embodiments, the sample has a regular shape or an irregular shape.

[0069] In some embodiments, collecting and measuring the crude oil displaced from the sample to determine the amount of displaced crude oil includes:

[0070] After the displacement is completed, allowing the gas inside the displacement autoclave 110 to enter the liquid collection container 301, and the liquid in the liquid collection container 301 traps the gaseous crude oil in the gas;

[0071] Homogenizing the solution in the liquid collection container 301 and detecting the oil concentration of the solution in the liquid collection container 301;

[0072] Calculate the crude oil quantity based on the oil concentration and the volume of the solution in the liquid collection container 301.

[0073] In some embodiments, the experimental method further includes: during the displacement process, causing the displacement container 120 to carry the sample and rotate around its own axis, or stirring the displacement gas in the displacement autoclave 110.

[0074] In some embodiments, the experimental method further includes: heating and temperature detecting the displacement autoclave by the heating unit 142 and the temperature measuring unit 144 respectively, and controlling the heating unit 142 to heat the displacement autoclave to a predetermined temperature value based on the temperature detection value.

[0075] In some embodiments, the experimental method further includes: performing relevant detections on the sample after the displacement to evaluate one or more of the following properties of the reservoir: lithology, physical properties, oil-bearing property, and electrical property.

[0076] In some embodiments, the experimental method for supercritical CO2 displacement of shale oil includes the following steps:

[0077] Step 1, sample matching collection and experimental analysis. Weigh the shale sample and place it in the displacement container 120 in the displacement autoclave 110, and check the tightness of the displacement autoclave 110.

[0078] Step 2, set control parameters through the controller 401. The control parameters include the set temperature and the formation temperature of the sample, the set pressure and the formation pressure of the sample, the set displacement time, and automatically start the supercritical displacement system through the controller 401 to perform supercritical displacement on the sample in the displacement container 120.

[0079] Step 3, when the displacement is carried out at the set temperature and pressure values and reaches the displacement time, the controller 401 automatically stops the displacement; release the pressure around the sample in the displacement container 120 through the pressurized gas supply unit 200, and measure the concentration of the displaced oil by the oil detector 305.

[0080] Step 4, after the temperature and pressure in the displacement autoclave 110 drop to room temperature and standard atmospheric pressure respectively, open the cover 114, take out the displaced sample in the displacement container 120, and perform corresponding supporting experimental analysis.

[0081] Step 5, after the supporting experimental analysis, calculate and process the experimental data to obtain the experimental parameters of the shale reservoir before and after high-temperature and high-pressure supercritical CO2 displacement, and evaluate the mobility of shale oil and the "four properties" of the reservoir.

[0082] In some embodiments, performing matching collection and experimental analysis includes performing the following detections: porosity, permeability, rock pyrolysis, laser confocal microscopy, whole-rock minerals, scanning electron microscopy detection, etc., to evaluate the changes in the oil-bearing property, reservoir property, minerals and brittleness, and mobility of the shale reservoir before and after displacement.

[0083] In some embodiments, the working process of the high-temperature and high-pressure supercritical displacement system includes: the controller 401 starts the heating unit 142 to work through the temperature control module 403. The controller 401 receives the temperature of the displacement kettle 110 fed back and communicated by the temperature measuring unit 144 until the temperature of the displacement kettle 110 reaches the set temperature value. The controller 401 stabilizes the temperature of the displacement kettle 110 at the set temperature value through the feedback communication closed-loop control method; meanwhile, the gas source 201 is opened, and the controller 401 controls the booster pump 203 to inject pressurized CO2 into the displacement kettle 110 through the pressure-resistant pipeline, so that the pressure in the displacement container 120 reaches the set pressure value.

[0084] In summary, aiming at the problems of relatively few quantitative studies on the pore structure and mobile fluid of shale reservoirs and insufficient understanding of the objective evaluation and recovery rate of shale oil, the present invention provides an experimental system and method for displacing crude oil in shale reservoirs with high-temperature and high-pressure supercritical CO2. The system uses a large cavity made of nickel-based alloy steel as the displacement container, which has low cost and large volume and can be applied to regular and irregular samples of different sizes; by connecting the pressure-resistant pipeline inside the displacement container and adopting the method of injecting CO2 to increase the pressure of the displacement container, the mobile oil is displaced under the simulated actual underground shale temperature and pressure, and the supporting experimental parameters such as porosity, permeability, rock pyrolysis, and laser confocal of the shale reservoir before and after displacement are measured to effectively evaluate the mobility and "four properties" of the shale reservoir oil, evaluate the mobility, oil-bearing property, reservoir property, mineral and brittleness characteristics of the shale reservoir before and after displacement, and provide important parameter indicators and technical means for shale oil exploration and development.

[0085] Through the above technical solutions, the present invention has the following technical effects:

[0086] (1) Using a dynamic displacement kettle and independent heating pipes, temperature and pressure control devices, and automatic collection and metering devices as the displacement system kit, the temperature and pressure of the dynamic displacement kettle are controlled by the controller. The highest simulated temperature can reach 200 °C, and the highest simulated pressure can reach 100 Mpa, so as to realize the displacement process of simulating different shale samples under formation temperature and pressure conditions, and the experimental conditions are more in line with the actual situation of the formation;

[0087] (2) Compared with the existing displacement kettle that can only place regular samples for displacement inside, the displacement kettle of the present invention uses a displacement container placed in the displacement kettle as a sample chamber, where irregular samples of different sizes can be placed. This can solve the problem that cylindrical samples cannot be made for CO2 displacement experiments due to the developed bedding in shale. By injecting supercritical CO2 around the displacement container in the displacement kettle, the confining pressure condition of shale under formation conditions can be truly simulated; along with the rotation of the sample by the rotation mechanism or the stirring of the displacement gas, the CO2 displacement process can be made more sufficient, the displacement effect is better, and the results are more accurate.

[0088] (3) The experimental system and method accurately collect and measure the fluid displaced by the dynamic displacement kettle by the automatic collection and measurement device, and the movable oil volume of the sample can be directly obtained, providing a reliable experimental basis for the quantitative evaluation of the mobility of shale reservoirs.

[0089] (4) A heat preservation layer is provided around the dynamic displacement kettle, which can reduce the loss of the temperature of the displacement kettle. The controller cooperates with the thermocouple to control the temperature control device using a feedback communication closed-loop control strategy, effectively maintaining the temperature consistency inside the dynamic displacement kettle and improving the accuracy of the experimental results under simulated formation conditions.

[0090] (5) This method can obtain supporting experimental parameters such as porosity, permeability, rock pyrolysis, and laser confocal of shale reservoirs before and after high-temperature, high-pressure, and supercritical CO2 displacement, so as to effectively evaluate the oil mobility and "four properties" of shale reservoirs.

[0091] Those of ordinary skill in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope (including the claims) disclosed in the embodiments of the present invention is limited to these examples; under the idea of the embodiments of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and there are many other variations in different aspects of the embodiments of the present invention as described above, which are not provided in detail for the sake of brevity. Therefore, any omission, modification, equivalent replacement, improvement, etc. made within the spirit and principle of the embodiments of the present invention shall be included within the protection scope of the embodiments of the present invention.

Claims

1. An experimental system for gas displacement of reservoir crude oil, characterized in that, Comprising: Displacement kettle; Displacement container, arranged inside the displacement kettle and used for carrying reservoir samples, with a plurality of fluid communication holes distributed around the side wall of the displacement container; Pressurized gas supply unit, configured to supply displacement gas with a predetermined pressure value into the displacement kettle to apply confining pressure to the sample and displace the sample; Collection and metering unit, configured to collect and meter the crude oil displaced from the sample; Control and processing unit, configured to set the predetermined pressure value and determine the amount of crude oil displaced based on the metering value of the collection and metering unit.

2. The system according to claim 1, characterized in that, The side wall of the displacement container is a mesh structure.

3. The system according to claim 1, characterized in that, The displacement kettle has a gas inlet, and the pressurized gas supply unit provides the displacement gas via the gas inlet, and the gas inlet is located at the lower side of the displacement container.

4. The system according to claim 1, characterized in that, It further includes a rotation mechanism arranged inside the displacement kettle, the rotation mechanism drives the displacement container to rotate around its own axis, or the rotation mechanism is arranged to stir the displacement gas inside the displacement kettle.

5. The system according to claim 4, characterized in that, The rotation mechanism includes: Motor, arranged outside the bottom wall of the displacement kettle and communicatively connected to the control and processing unit; Rotating part, arranged inside the displacement kettle and located below the displacement container, and the motor drives the rotating part to rotate; Carrying part connected to the rotating part and carrying the displacement container, or stirring blades connected to the rotating part and located below the displacement container.

6. The system according to claim 1, characterized in that, The upper part of the displacement kettle has a gas outlet, and the collection and metering unit includes: Liquid collection container, the liquid collection container is communicated with the gas outlet through a pipeline, and a liquid capable of capturing crude oil but not capturing the displacement gas is placed in the liquid collection container; Homogenization component, configured to homogenize the solution in the liquid collection container; Oil detector, configured to detect the oil concentration of the solution in the liquid collection container; The control and processing unit is configured to calculate the amount of crude oil based on the oil concentration and the volume of the solution in the liquid collection container.

7. The system according to claim 6, characterized in that, The homogenization component is a peristaltic pump, and the peristaltic pump is communicatively connected to the control and processing unit and drives the solution in the liquid collection container to circulate.

8. The system according to claim 1, characterized in that, The displacement kettle includes a kettle body with an upper opening and a cover detachably connected to the upper opening.

9. The system according to claim 1, characterized in that, It further includes a kit arranged on the outer periphery of the displacement kettle and a heating part and a temperature measuring part embedded in the kit, and the control and processing unit is configured to control the heating part to heat the displacement kettle to a predetermined temperature value based on the detection value of the temperature measuring part.

10. The system according to claim 9, characterized in that, It further includes a heat preservation part arranged outside the kit; and / or the bottom wall of the displacement kettle is provided with a liquid discharge hole for discharging cleaning liquid.

11. An experimental method for gas displacement of reservoir crude oil, characterized in that, Comprising: Placing a reservoir sample in a displacement container inside a displacement kettle, wherein a plurality of fluid communication holes are distributed around the side wall of the displacement container; Providing displacement gas with a predetermined pressure value into the displacement kettle to apply confining pressure to the sample and displace the sample; Collecting and metering the crude oil displaced from the sample to determine the amount of crude oil displaced.

12. The method according to claim 11, characterized in that, The sample has a regular shape or an irregular shape.

13. The method according to claim 11, characterized in that, The collecting and metering the crude oil displaced from the sample to determine the amount of crude oil displaced includes: After the displacement is completed, the gas in the displacement kettle is allowed to enter the liquid collection container, and the gaseous crude oil in the gas is trapped by the liquid in the liquid collection container; Homogenize the solution in the liquid collection container and detect the oil concentration of the solution in the liquid collection container; Calculate the amount of crude oil based on the oil concentration and the volume of the solution in the liquid collection container.

14. The method according to claim 11, wherein, It further includes: During the displacement process, the displacement container is made to rotate around its own axis carrying the sample, or the displacement gas in the displacement kettle is stirred.

15. The method according to claim 11, wherein, It further includes: The displacement kettle is heated and its temperature is detected by a heating part and a temperature measuring part respectively, and the heating part is controlled based on the temperature detection value to heat the displacement kettle to a predetermined temperature value.

16. The method according to claim 11, wherein, It further includes: Perform relevant detections on the sample after the displacement is completed to evaluate one or more of the following properties of the reservoir: lithology, physical properties, oil-bearing property, electrical property.

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