Oil reservoir in-situ displacement physical simulation device and method

Abstract

The invention provides an oil reservoir in-situ displacement physical simulation device and method.The oil reservoir in-situ displacement physical simulation device comprises a core holder, a nuclear magnetic resonance testing mechanism, a magnetic resonance imaging mechanism, a magnetic resonance imaging mechanism, a magnetic resonance imaging mechanism, a magnetic resonance imaging mechanism and a magnetic resonance imaging mechanism, and the core holder is internally provided with a cavity used for containing a core sample with the length of at least one meter; a confining pressure loading mechanism, a resistivity testing mechanism, a pressure testing mechanism and an ultrasonic testing mechanism are also arranged on the core holder; the fluid injection unit is connected to the inlet of the core holder so as to inject fluid into the cavity of the core holder; and the pressure control unit is connected to the outlet of the core holder so as to control the pressure in the cavity. According to the invention, the problem that the in-situ displacement simulation of the low-pressure gradient of the deep part of the oil reservoir cannot be realized in the existing indoor oil reservoir in-situ displacement physical simulation experiment can be solved, and the fluid displacement rule and the remaining oil occurrence state in the real flowing process of the deep part of the oil reservoir can be researched.

Description

Technical Field

[0001] This invention relates to the field of oil and gas exploration and development technology, and in particular to an in-situ reservoir displacement physical simulation device and method. Background Technology

[0002] Currently, conventional indoor in-situ reservoir displacement physical simulation experiments generally set displacement velocities or pressure differentials to overcome end-effects, obtaining key indicators such as oil displacement efficiency and residual oil saturation. The displacement pressure differential is typically in the MPa range, meaning that the displacement pressure gradient in indoor experiments is generally greater than 1 MPa / m. These experiments can only characterize the near-wellbore flow process and are insufficient to reflect the fluid displacement patterns and residual oil occurrence state during the actual flow process at depth in the reservoir.

[0003] Different displacement pressure gradients significantly affect oil displacement efficiency and the distribution of remaining oil. Under actual reservoir conditions, due to the "pressure drop funnel" characteristic, except for a 15m radius near the wellbore, the displacement pressure gradient in most areas of the reservoir is less than 0.1 MPa / m, mainly ranging from 0.02 MPa / m to 0.03 MPa / m. Therefore, the actual in-situ waterflooding efficiency in the reservoir is likely to be significantly lower than the efficiency measured in the laboratory.

[0004] If a core displacement experiment with a displacement pressure gradient of 0.02 MPa / m to 0.03 MPa / m can be achieved to simulate the real in-situ water-drive oil recovery process in the reservoir, it will be of great significance for evaluating the effectiveness of current water-drive development of reservoirs and analyzing the microscopic residual oil distribution in the later stages of water-drive development. Summary of the Invention

[0005] The purpose of this invention is to provide an in-situ displacement physical simulation device and method for oil reservoirs, which solves the problem that current indoor in-situ displacement physical simulation experiments cannot simulate in-situ displacement of low pressure gradients in deep oil reservoirs, and enables the study of fluid displacement laws and residual oil occurrence state during the actual flow process in deep oil reservoirs.

[0006] The above-mentioned technical objectives of the present invention are mainly achieved through the following technical solutions.

[0007] On one hand, the present invention provides an in-situ reservoir displacement physical simulation device, which includes:

[0008] A core holder, wherein a cavity is formed within the core holder for accommodating a core sample with a length of at least 1 meter, the core holder is disposed within a nuclear magnetic resonance testing mechanism, and the core holder is further provided with a confining pressure loading mechanism for applying confining pressure to the core sample, a resistivity testing mechanism for measuring the axial resistivity of the core sample, a pressure testing mechanism for measuring the axial pressure difference of the core sample, and an ultrasonic testing mechanism for performing ultrasonic detection on the core sample.

[0009] A fluid injection unit is connected to the inlet of the core holder to inject fluid into the cavity of the core holder;

[0010] A pressure control unit is connected to the outlet of the core holder to control the pressure in the cavity.

[0011] In a preferred embodiment of the present invention, the core holder is configured to move relative to the nuclear magnetic resonance testing mechanism along the axial direction of the core sample to change the axial measurement position of the nuclear magnetic resonance testing mechanism.

[0012] In a preferred embodiment of the present invention, the confining pressure loading mechanism includes:

[0013] A confining pressure loading cavity is provided within the core holder, and the confining pressure loading cavity is arranged around the cavity;

[0014] A confining pressure supply pipeline is connected to the confining pressure loading chamber, and a confining pressure pump and a confining pressure valve are provided on the confining pressure supply pipeline.

[0015] In a preferred embodiment of the present invention, the resistivity testing mechanism is provided with a plurality of resistivity measurement points spaced apart along the axial direction of the core sample on the core holder, so as to obtain the resistivity gradient in the axial direction of the core sample.

[0016] In a preferred embodiment of the present invention, the pressure testing mechanism has a plurality of pressure measurement points spaced apart along the axial direction of the core sample on the core holder to obtain the pressure gradient in the axial direction of the core sample.

[0017] In a preferred embodiment of the present invention, the fluid injection unit includes:

[0018] A piston container, which is connected to the inlet of the core holder via an injection line;

[0019] A dual-cylinder constant-speed and constant-pressure pump, wherein the dual-cylinder constant-speed and constant-pressure pump is connected to the lower end of the piston container via a pipeline;

[0020] A gas supply line is connected to the upper end of the piston container, and the gas supply line is equipped with a gas source and a gas booster pump.

[0021] In a preferred embodiment of the present invention, the pressure control unit includes an outlet pipeline connected to the outlet of the core holder, and the outlet pipeline is sequentially provided with a back pressure valve, an oil-water metering mechanism, and a back pressure control mechanism.

[0022] In a preferred embodiment of the present invention, the pipelines in the fluid injection unit and the pressure control unit are wrapped with a thermal insulation layer.

[0023] On the other hand, the present invention also provides a reservoir in-situ displacement physical simulation method, which is implemented using the reservoir in-situ displacement physical simulation device described above, the reservoir in-situ displacement physical simulation method comprising:

[0024] The prepared fluid and core sample were placed in the fluid injection unit and core holder, respectively, and connected to the experimental pipeline.

[0025] The pressure control unit is used to set the pressure at the outlet of the core holder to be higher than the designed injection pressure.

[0026] Fluid is injected into the core holder using a fluid injection unit at the designed injection pressure.

[0027] When the fluid velocity in the fluid injection unit is stable, the pressure control unit is used to reduce the pressure at the outlet end of the core holder to form the designed production pressure difference for displacement. Throughout the experiment, the nuclear magnetic resonance testing mechanism is used to collect T2 spectrum, layered T2 spectrum and MRI imaging data in real time, and the resistivity testing mechanism, pressure testing mechanism and ultrasonic testing mechanism are used to collect resistivity data, pressure difference data and ultrasonic data respectively.

[0028] In a preferred embodiment of the present invention, the data acquisition process using the nuclear magnetic resonance testing apparatus includes:

[0029] The core holder is fixed inside the nuclear magnetic resonance (NMR) testing mechanism, which is used to acquire T2 spectra, layered T2 spectra, and MRI imaging data in real time to obtain wavelength, wave velocity, displacement front location, and oil saturation changes; and / or,

[0030] Along the axial direction of the core sample, the outlet end of the core holder is moved into the nuclear magnetic resonance testing mechanism until the outlet end of the core holder passes the nuclear magnetic resonance testing mechanism. During the movement, the nuclear magnetic resonance testing mechanism is used to collect T2 spectrum, layered T2 spectrum and MRI imaging data in real time to monitor the nuclear magnetic resonance signal change characteristics at different positions of the core holder at different times.

[0031] Compared with the prior art, the technical solution of the present invention has the following characteristics and advantages:

[0032] On the one hand, addressing the current difficulty in achieving in-situ displacement simulation with low pressure gradients, this invention provides a core holder capable of accommodating core samples at least 1 meter in length. Combined with a pressure testing mechanism and a pressure control unit, this enables a pressure gradient of 0.02 MPa / m to 0.03 MPa / m during the simulated displacement process. On the other hand, considering the limited coverage of magnets on existing nuclear magnetic resonance (NMR) testing mechanisms, which cannot completely cover core samples of 1 meter or more, the core holder in this invention is configured to move relative to the NMR testing mechanism along the axial direction of the core sample, thereby enabling the acquisition of NMR data along the entire axial direction of the core sample.

[0033] As described above, based on high-precision pressure control and measurement, this invention can simulate the displacement pressure gradient and displacement process under real reservoir conditions, and perform real-time dynamic monitoring of oil saturation under in-situ displacement conditions. Combined with the testing of nuclear magnetic resonance T2 spectrum, layered T2 spectrum and MRI imaging during the experiment, it can accurately characterize key injection and production information such as the displacement front position, sweep rate, migration distance and oil saturation change of the injected fluid. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0035] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way. Furthermore, the shapes and proportions of the components in the drawings are merely illustrative to aid in understanding the invention and do not specifically limit the shapes and proportions of the components. Those skilled in the art, guided by the teachings of this invention, can select various possible shapes and proportions to implement the invention according to specific circumstances.

[0036] Figure 1 This is a schematic diagram of the in-situ reservoir displacement physical simulation device described in this invention;

[0037] Figure 2 This is a schematic diagram of the core holder of the present invention being fixed and measured within the nuclear magnetic resonance testing mechanism;

[0038] Figures 3 to 6 This is a schematic diagram of the core holder described in this invention moving and measuring within the nuclear magnetic resonance testing mechanism.

[0039] Explanation of reference numerals in the attached figures:

[0040] 10. Core holder; 11. Core sample; 12. Confining pressure loading mechanism; 13. Resistivity testing mechanism; 14. Pressure testing mechanism; 15. Ultrasonic testing mechanism; 16. Nuclear magnetic resonance testing mechanism;

[0041] 20. Fluid injection unit; 21. Piston container; 22. Injection pipeline; 23. Dual-cylinder constant speed and constant pressure pump; 24. Gas supply pipeline; 25. Gas source; 26. Gas booster pump;

[0042] 30. Pressure control unit; 31. Outlet pipeline; 32. Back pressure valve; 33. Oil and water metering mechanism; 34. Back pressure control mechanism. Detailed Implementation

[0043] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0044] It should be noted that when an element is referred to as being "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only embodiments.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0046] Implementation Method 1:

[0047] This invention provides an in-situ reservoir displacement physical simulation device, such as... Figure 1As shown, it includes: a core holder 10, which has a cavity for accommodating a core sample 11 with a length of at least 1 meter. The core holder 10 is disposed within a nuclear magnetic resonance testing mechanism 16. The core holder 10 is also provided with a confining pressure loading mechanism 12 for loading confining pressure onto the core sample 11, a resistivity testing mechanism 13 for measuring the axial resistivity of the core sample 11, a pressure testing mechanism 14 for measuring the axial pressure difference of the core sample 11, and an ultrasonic testing mechanism 15 for performing ultrasonic detection on the core sample 11; a fluid injection unit 20, which is connected to the inlet of the core holder 10 to inject fluid into the cavity of the core holder 10; and a pressure control unit 30, which is connected to the outlet of the core holder 10 to control the pressure in the cavity.

[0048] The reservoir in-situ displacement physical simulation device of the present invention simulates the displacement pressure gradient and displacement process under real reservoir conditions based on high-precision pressure control and measurement. It can monitor the oil saturation in real time under the in-situ displacement state of the reservoir. Combined with the test of nuclear magnetic resonance T2 spectrum, layered T2 spectrum and MRI imaging during the experiment, it can accurately characterize key injection and production information such as the displacement front position, sweep rate, migration distance and oil saturation change of the injected fluid.

[0049] The following section will provide a detailed description of the specific structure of each part of the reservoir in-situ displacement physical simulation device described in this invention, as well as the positional relationships and pipeline connections between the parts.

[0050] The reservoir in-situ displacement physical simulation device includes a core holder 10, which is the core equipment of the entire device. The core holder 10 is used to hold the core sample 11 and is connected to various testing mechanisms to test various parameters in the simulated displacement process.

[0051] Specifically, such as Figure 1As shown, the core holder 10 has a rectangular parallelepiped structure with an internal cavity for mounting the core sample 11. The length of the cavity is greater than or equal to 1 meter, allowing the core holder 10 to hold core samples 11 with a length of 1 meter or more. The length design of the core holder 10 is determined according to the purpose of this invention. The length of the inner cavity of the core holder 10 needs to be designed to be no less than 1 meter because a longer core sample 11 is necessary to achieve precise pressure control and a lower pressure propagation speed, thereby obtaining the smaller displacement pressure difference (0.02 MPa / m-0.03 MPa / m) in this invention. If a conventional, shorter core sample 11 of about 5 cm is used, the pressure propagation is very fast, making precise pressure control impossible. Furthermore, even if a smaller pressure difference can be achieved on both sides of a short core sample 11, dividing the smaller pressure difference by the shorter core sample 11 length when calculating the pressure gradient may still result in a large pressure gradient.

[0052] like Figure 1 As shown, the core holder 10 has an inlet and an outlet at both ends that are connected to the inner cavity. The driving fluid in the simulated displacement process enters from the inlet, and the product in the simulated displacement process flows out from the outlet.

[0053] like Figure 1 As shown, the core holder 10 is placed inside the nuclear magnetic resonance (NMR) testing mechanism 16. The NMR testing mechanism 16 can perform real-time NMR T2 spectrum, layered T2 spectrum, and MRI imaging monitoring of the core sample 11 through the core holder 10. The NMR signal quantity characterizes the crude oil signal during the simulated displacement process. Therefore, key information such as the change in oil saturation and the degree of crude oil recovery within the core sample 11 can be obtained through the acquisition of NMR signals. The NMR testing mechanism 16 can be an existing device in the art, and its specific structure and testing principle will not be described in detail here.

[0054] Furthermore, such as Figure 1 As shown, the core holder 10 is equipped with a confining pressure loading mechanism 12, which is used to apply confining pressure to the outer periphery of the core sample 11 to simulate the high-pressure environment underground.

[0055] Specifically, in this embodiment, the core holder 10 is provided with a confining pressure loading chamber, which surrounds the cavity, and a confining pressure loading element is provided between the confining pressure loading chamber and the cavity; the confining pressure loading chamber is connected to a confining pressure supply pipeline, and a confining pressure pump and a confining pressure valve are provided on the confining pressure supply pipeline. The high-pressure fluid generated by the confining pressure pump enters the confining pressure loading chamber through the confining pressure supply pipeline, and the pressure is transmitted to the outer peripheral surface of the core sample 11 through the confining pressure loading element, thereby simulating the high-pressure environment underground.

[0056] Furthermore, such as Figure 1As shown, the core holder 10 is equipped with a resistivity testing mechanism 13, which is used to measure the resistivity of the core sample 11 during the simulated displacement process.

[0057] Specifically, in this embodiment, multiple resistivity measurement points are spaced apart along the axial direction of the core sample 11. Each resistivity measurement point is equipped with a resistance testing circuit, and each resistance testing circuit is connected to a multi-channel resistance meter via wires, thereby enabling the acquisition of the resistivity gradient of the core sample 11 in the axial direction. The computer software can invert the oil saturation data of the core sample 11 based on the measured resistivity data and in combination with other data.

[0058] Furthermore, such as Figure 1 As shown, the core holder 10 is equipped with a pressure testing mechanism 14, which is used to measure the pressure gradient of the core sample 11 during the simulated displacement process.

[0059] Specifically, in this embodiment, multiple pressure measurement points are spaced apart along the axial direction of the core sample 11. Each pressure measurement point is equipped with a pressure sensor, and each pressure sensor is connected to a high-precision pressure control and testing system via wires, thereby enabling the acquisition of the pressure gradient of the core sample 11 in the axial direction. On the one hand, the measured pressure gradient can be used to help determine whether the pressure difference between the two ends of the core sample 11 meets the testing requirements; on the other hand, the computer software can invert the oil saturation data of the core sample 11 based on the measured pressure gradient data and in combination with other data.

[0060] Furthermore, such as Figure 1 As shown, the core holder 10 is equipped with an ultrasonic testing mechanism 15, which is used to perform ultrasonic measurements on the core sample 11 during the simulated displacement process. The ultrasonic testing mechanism 15 can be an ultrasonic probe set at both ends of the core sample 11.

[0061] The resistivity testing mechanism 13, pressure testing mechanism 14 and ultrasonic testing mechanism 15 mentioned above are all connected to the data processing center. The data processing center can integrate and process the above data to reflect the characteristics of the core sample 11 in the simulated displacement process.

[0062] The reservoir in-situ displacement physical simulation device also includes a fluid injection unit 20, which is connected to the inlet of the core holder 10, so that the medium used in the simulated displacement process can be injected into the core holder 10.

[0063] Specifically, such as Figure 1As shown, in this embodiment, the fluid injection unit 20 includes a piston container 21, which stores a displacement medium. The piston container 21 is connected to the inlet of the core holder 10 via an injection line 22, which is equipped with a switching valve and a pressure sensor. The lower end of the piston container 21 is connected to a dual-cylinder constant-speed and constant-pressure pump 23 via a pipeline. The dual-cylinder constant-speed and constant-pressure pump 23 provides power for the fluid to flow into the core holder 10 and adjusts the pressure at the inlet of the core holder 10. The upper end of the piston container 21 is connected to a gas supply line 24, which is equipped with a gas source 25, a gas booster pump 26, a switching valve, and a pressure sensor. The gas in the gas source 25 is pressurized by the gas booster pump 26 and then enters the piston container 21 to mix with the displacement medium before entering the core holder 10.

[0064] The reservoir in-situ displacement physical simulation device also includes a pressure control unit 30, which is connected to the outlet of the core holder 10. The products in the simulated displacement process can enter the pressure control unit 30 and the pressure at the outlet of the core holder 10 can be controlled by the pressure control unit 30.

[0065] Specifically, such as Figure 1 As shown, the pressure control unit 30 includes an outlet pipeline 31 connected to the outlet of the core holder 10. The outlet pipeline 31 is sequentially equipped with a back pressure valve 32, an oil-water metering mechanism 33, and a back pressure control mechanism 34. The back pressure valve 32, in conjunction with the back pressure control mechanism 34 (usually a back pressure pump), adjusts the pressure at the outlet of the core holder 10. The oil-water metering mechanism 33 is used to meter the products in the simulated displacement process.

[0066] The structure and technical effects of the preferred embodiment of the reservoir in-situ displacement physical simulation device of the present invention will be further described below.

[0067] According to one embodiment of the present invention, such as Figures 3 to 6 As shown, the core holder 10 is configured to move relative to the nuclear magnetic resonance testing mechanism 16 along the axial direction of the core sample 11 to change the axial measurement position of the nuclear magnetic resonance testing mechanism 16.

[0068] like Figure 2 As shown, the magnet coverage of the current nuclear magnetic resonance testing mechanism 16 is limited. For core samples 11 of 1 meter or more, it can only cover a part of the axial direction of the core sample 11. Therefore, in order to obtain nuclear magnetic resonance data on the entire core sample 11, the core holder 10 is designed as a movable structure. For example, the core holder 10 is installed on an axially movable track, so that it can move axially relative to the nuclear magnetic resonance testing mechanism 16.

[0069] According to one embodiment of the present invention, the pipelines (such as injection pipeline 22, gas supply pipeline 24, outlet pipeline 31, etc.) within the fluid injection unit 20 and pressure control unit 30 are wrapped with an insulation layer. The insulation layer can prevent heat loss and ensure the phase stability of the fluid;

[0070] Implementation Method Two:

[0071] The present invention also provides a reservoir in-situ displacement physical simulation method, which is implemented using the reservoir in-situ displacement physical simulation device as described in Embodiment 1. The reservoir in-situ displacement physical simulation method includes the following steps:

[0072] Step S1: Place the prepared fluid and core sample 11 into the fluid injection unit 20 and the core holder 10 respectively, and connect the experimental pipeline;

[0073] Step S2: Use the pressure control unit 30 to set the pressure at the outlet end of the core holder 10 to be higher than the designed injection pressure;

[0074] Step S3: Inject fluid into the core holder 10 using the fluid injection unit 20 at the designed injection pressure;

[0075] Step S4: When the fluid flow rate in the fluid injection unit 20 is stable, the pressure control unit 30 is used to reduce the pressure at the outlet end of the core holder 10 to form the designed production pressure difference for displacement. Throughout the experiment, the nuclear magnetic resonance testing mechanism 16 is used to collect T2 spectrum, layered T2 spectrum and MRI imaging data in real time, and the resistivity testing mechanism 13, pressure testing mechanism 14 and ultrasonic testing mechanism 15 are used to collect resistivity data, pressure difference data and ultrasonic data respectively.

[0076] The reservoir in-situ displacement physical simulation method described in this invention simulates the displacement pressure gradient and displacement process under real reservoir conditions based on high-precision pressure control and measurement. It provides real-time dynamic monitoring of oil saturation under in-situ displacement conditions. Combined with the testing of nuclear magnetic resonance T2 spectrum, layered T2 spectrum and MRI imaging during the experiment, it can accurately characterize key injection and production information such as the displacement front position, sweep rate, migration distance and oil saturation change of the injected fluid.

[0077] The following section will describe in detail the steps of the in-situ reservoir displacement physical simulation method described in this invention.

[0078] In step S1, the appropriate displacement medium is first prepared according to experimental requirements and loaded into the piston container 21 of the fluid injection unit 20. Simultaneously, a core sample 11 with a length of at least one meter is prepared according to experimental requirements. After washing the core sample 11 with oil and salt, a vacuum is drawn and pressurized with saturated crude oil. Then, the core sample 11 is loaded into the cavity inside the core holder 10. After preparing the displacement medium and core sample 11, the pipelines between the core holder 10, the fluid injection unit 20, and the pressure control unit 30 are connected. At the same time, various loading mechanisms and testing mechanisms are connected to the core holder 10.

[0079] In step S2, after the preparation work is completed, the back pressure control mechanism 34 in the pressure control unit 30 is used to control the pressure of the back pressure valve 32 to be higher than the designed injection pressure.

[0080] In step S3, the gas booster pump 26 and the dual-cylinder constant speed and constant pressure pump 23 in the gas injection unit are turned on. Gas is injected into the piston container 21 by the gas booster pump 26 through the gas source 25 for gas injection; liquid is injected by opening the piston container 21.

[0081] In step S4, the flow rate of the dual-cylinder constant-speed and constant-pressure pump 23 is observed. When the flow rate stabilizes (achieving a stable injection state), the pressure of the back pressure valve 32 at the outlet of the core holder 10 is reduced using the back pressure control mechanism 34 to create the designed production pressure difference (0.02MPa / m-0.03MPa / m) for displacement. Throughout the simulated displacement experiment, the nuclear magnetic resonance testing mechanism 16 is used to collect real-time T2 spectrum, layered T2 spectrum, and MRI imaging data. The resistivity testing mechanism 13, pressure testing mechanism 14, and ultrasonic testing mechanism 15 arranged along the flow path are used to collect pressure difference, resistivity, and ultrasonic data.

[0082] Furthermore, the data acquisition process using the nuclear magnetic resonance testing apparatus 16 includes both fixed testing and mobile testing processes.

[0083] During fixed testing, such as Figure 2 As shown, the core holder 10 is fixed in the nuclear magnetic resonance testing mechanism 16, and the nuclear magnetic resonance testing mechanism 16 is used to collect T2 spectrum, layered T2 spectrum and MRI imaging data in real time to obtain the sweep distance, sweep velocity, displacement front position and oil saturation changes.

[0084] Because the magnet inside the nuclear magnetic resonance testing mechanism 16 cannot cover the entire core sample 11, it can only monitor the nuclear magnetic resonance signal within a core sample 11 of the same length as the magnet. Figure 2Fluid signals within the core sample between points A and B. During the experiment, real-time nuclear magnetic resonance T2 spectroscopy, layered T2 spectroscopy, and MRI imaging were performed on the core sample within the coverage area of ​​the magnet coil to obtain the following key information:

[0085] (1) Sweep distance L: When the signal quantity at point A is observed to change, it indicates that the injected fluid has reached point A. That is, the sweep distance L is the distance from the end face of core sample 11 to point A.

[0086] (2) Sweeping velocity v: The sweeping velocity v can be calculated using the injection time and sweeping distance L.

[0087] (3) Displacement leading edge position: Starting from the change in NMR signal at point A, the advancing position of the displacement leading edge can be obtained based on the changes in the NMR spectrum between points A and B obtained by the test.

[0088] (4) Changes in oil saturation: Starting from the change in NMR signal at point A, the characteristics of oil saturation change can be obtained from the changes in NMR spectrum between points A and B obtained by the test.

[0089] During mobile testing, such as Figures 3 to 6 As shown, along the axial direction of the core sample 11, the outlet end of the core holder 10 is moved into the nuclear magnetic resonance testing mechanism 16 until the outlet end of the core holder 10 passes the nuclear magnetic resonance testing mechanism 16. During the movement, the nuclear magnetic resonance testing mechanism 16 is used to collect T2 spectrum, layered T2 spectrum and MRI imaging data in real time to monitor the nuclear magnetic resonance signal change characteristics at different positions of the core holder 10 at different times.

[0090] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A physical simulation device for in-situ displacement of oil reservoirs, characterized in that, include: A core holder (10) is provided, which has a cavity for accommodating a core sample (11) with a length of at least 1 meter. The core holder (10) is located in a nuclear magnetic resonance testing mechanism (16). The core holder (10) is also provided with a confining pressure loading mechanism (12) for loading confining pressure onto the core sample (11), a resistivity testing mechanism (13) for measuring the axial resistivity of the core sample (11), a pressure testing mechanism (14) for measuring the axial pressure difference of the core sample (11), and an ultrasonic testing mechanism (15) for ultrasonic detection of the core sample (11). A fluid injection unit (20) is connected to the inlet of the core holder (10) to inject fluid into the cavity of the core holder (10); A pressure control unit (30) is connected to the outlet of the core holder (10) to control the pressure in the cavity.

2. The reservoir in-situ displacement physical simulation device according to claim 1, characterized in that, The core holder (10) is configured to move relative to the nuclear magnetic resonance testing mechanism (16) along the axial direction of the core sample (11) to change the axial measurement position of the nuclear magnetic resonance testing mechanism (16).

3. The reservoir in-situ displacement physical simulation device according to claim 1 or 2, characterized in that, The confining pressure loading mechanism (12) includes: A confining pressure loading cavity is provided in the core holder (10), and the confining pressure loading cavity is arranged around the cavity; A confining pressure supply pipeline is connected to the confining pressure loading chamber, and a confining pressure pump and a confining pressure valve are provided on the confining pressure supply pipeline.

4. The reservoir in-situ displacement physical simulation device according to claim 1 or 2, characterized in that, The resistivity testing mechanism (13) has multiple resistivity measurement points spaced apart along the axial direction of the core sample (11) on the core holder (10) to obtain the resistivity gradient in the axial direction of the core sample (11).

5. The reservoir in-situ displacement physical simulation device according to claim 1 or 2, characterized in that, The pressure testing mechanism (14) has multiple pressure measurement points spaced apart along the axial direction of the core sample (11) on the core holder (10) to obtain the pressure gradient in the axial direction of the core sample (11).

6. The reservoir in-situ displacement physical simulation device according to claim 1, characterized in that, The fluid injection unit (20) includes: A piston container (21) is connected to the inlet of the core holder (10) via an injection line (22); A dual-cylinder constant speed and constant pressure pump (23) is connected to the lower end of the piston container (21) via a pipeline; A gas supply line (24) is connected to the upper end of the piston container (21), and a gas source (25) and a gas booster pump (26) are provided on the gas supply line (24).

7. The reservoir in-situ displacement physical simulation device according to claim 1, characterized in that, The pressure control unit (30) includes an outlet line (31) connected to the outlet of the core holder (10), and the outlet line (31) is provided with a back pressure valve (32), an oil-water metering mechanism (33) and a back pressure control mechanism (34) in sequence.

8. The reservoir in-situ displacement physical simulation device according to claim 6 or 7, characterized in that, The pipelines inside the fluid injection unit (20) and the pressure control unit (30) are wrapped with a thermal insulation layer.

9. A method for in-situ reservoir displacement physical simulation, implemented using the in-situ reservoir displacement physical simulation device according to any one of claims 1-8, characterized in that, The in-situ displacement physical simulation method for oil reservoirs includes: The prepared fluid and core sample (11) were placed in the fluid injection unit (20) and the core holder (10) respectively and connected to the experimental pipeline; The pressure at the outlet end of the core holder (10) is set higher than the designed injection pressure using the pressure control unit (30); Fluid is injected into the core holder (10) using the fluid injection unit (20) at the designed injection pressure; When the fluid flow rate in the fluid injection unit (20) is stable, the pressure control unit (30) is used to reduce the pressure at the outlet end of the core holder (10) to form the designed production pressure difference for displacement. Throughout the experiment, the nuclear magnetic resonance testing mechanism (16) is used to collect T2 spectrum, layered T2 spectrum and MRI imaging data in real time, and the resistivity testing mechanism (13), pressure testing mechanism (14) and ultrasonic testing mechanism (15) are used to collect resistivity data, pressure difference data and ultrasonic data respectively.

10. The reservoir in-situ displacement physical simulation method according to claim 9, characterized in that, The data acquisition process using the nuclear magnetic resonance testing apparatus (16) includes: The core holder (10) is fixed inside the nuclear magnetic resonance testing mechanism (16), and the nuclear magnetic resonance testing mechanism (16) is used to acquire T2 spectrum, layered T2 spectrum and MRI imaging data in real time to obtain the sweep distance, sweep velocity, displacement front position and oil saturation changes; and / or, Along the axial direction of the core sample (11), the outlet end of the core holder (10) is moved into the nuclear magnetic resonance testing mechanism (16) until the outlet end of the core holder (10) passes the nuclear magnetic resonance testing mechanism (16). During the movement, the nuclear magnetic resonance testing mechanism (16) is used to collect T2 spectrum, layered T2 spectrum and MRI imaging data in real time to monitor the nuclear magnetic resonance signal change characteristics of different positions of the core holder (10) at different times.

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