Method and device for quantitatively detecting fluid mobility of unconventional resource core

Abstract

The embodiment of the present application provides a kind of unconventional resource core fluid mobility quantitative detection method and device, the method comprises: obtaining the physical property parameter of core after oil treatment;Based on the physical property parameter and the displacement pressure in the process of core oil displacement test, determine displacement pressure gradient;Under different displacement pressure gradient, the cumulative nuclear magnetic resonance T2 signal amount of fluid in core is obtained;Based on the cumulative nuclear magnetic resonance T2 signal amount under different displacement pressure gradient, the mobility of core fluid is quantitatively detected.The unconventional resource core fluid mobility quantitative detection method and device of the present application can realize the quantitative detection of core fluid mobility under different displacement pressure gradient, and the detection process is more close to resource development process, so that the test result has higher accuracy, can accurately guide production.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development technology, specifically to a method for quantitatively detecting the fluid mobility of unconventional resource cores, a device for quantitatively detecting the fluid mobility of unconventional resource cores, and a machine-readable storage medium. Background Technology

[0002] Currently, unconventional resources such as shale oil and gas, and tight oil and gas, are enormous and have become crucial strategic replacement resources. Movable fluid volume is a key parameter in reserve calculations and development plan formulation. Existing technologies typically assess reservoir fluid mobility using centrifugation, where fluid-containing rocks are centrifuged at different speeds, followed by nuclear magnetic resonance (NMR) measurements to calculate the movable fluid. However, unconventional resource reservoirs such as shale oil and gas and tight oil and gas have dense rocks with very small pore radii, averaging several hundred nanometers, with some pores only a few or tens of nanometers. The centrifugal force provided by the centrifuge is insufficient to displace the fluid within these nanometer-sized pores. If conventional centrifugation methods are used to obtain movable fluid data, the data will be very small, or even nonexistent, which does not match actual field development and cannot accurately guide production. Summary of the Invention

[0003] The purpose of this invention is to provide a method and apparatus for quantitatively detecting the mobility of fluids in unconventional resource cores. This method and apparatus solves the problem mentioned above where conventional centrifugation methods are used to obtain mobile fluid data, but the data is very small or even nonexistent, which is inconsistent with the actual development situation in the field.

[0004] To achieve the above objectives, embodiments of the present invention provide a method for quantitatively detecting the fluid mobility of unconventional resource cores, comprising:

[0005] Obtain the physical properties of the core sample after oil washing treatment;

[0006] Based on the aforementioned physical properties and the displacement pressure during the core flooding test, the displacement pressure gradient is determined.

[0007] The cumulative nuclear magnetic resonance T2 signal of fluid in the core under different displacement pressure gradients was obtained;

[0008] Based on the cumulative nuclear magnetic resonance T2 signal quantity under different displacement pressure gradients, the mobility of core fluids was quantitatively detected.

[0009] Optionally, the physical property parameter is the length of the core; the displacement pressure is the pressure difference between the inlet and outlet ends of the nuclear magnetic resonance spectrometer's holder during the oil displacement test.

[0010] Optionally, obtaining the cumulative nuclear magnetic resonance T2 signal of the fluid in the core under different displacement pressure gradients includes:

[0011] The nuclear magnetic resonance (NMR) T2 spectra and cumulative NMR T2 signal quantities of fluid in the core are acquired sequentially under different displacement pressure gradients with constant fluid volume, from smallest to largest, until the difference between the NMR T2 spectra of fluid in two adjacent cores is less than a preset difference.

[0012] Optionally, the cumulative nuclear magnetic resonance T2 signal of the fluid within the core is obtained using the following method:

[0013] Based on the nuclear magnetic resonance T2 spectrum of the fluid inside the core, the cumulative nuclear magnetic resonance T2 signal of the fluid inside the core is obtained by using the area function.

[0014] Optionally, the quantitative detection of core fluid mobility based on the cumulative nuclear magnetic resonance T2 signal quantity under different displacement pressure gradients includes:

[0015] Determine the target T2 relaxation time under different displacement pressure gradients based on the cumulative nuclear magnetic resonance T2 signal quantity under different displacement pressure gradients;

[0016] The minimum pore radius that fluid can enter under different displacement pressure gradients is determined based on the target T2 relaxation time under different displacement pressure gradients, and the minimum pore radius is used as the quantitative detection result of core fluid mobility.

[0017] Optionally, determining the target T2 relaxation time under different displacement pressure gradients based on the cumulative nuclear magnetic resonance T2 signal quantity under different displacement pressure gradients includes:

[0018] Plot the curves showing the relationship between the cumulative nuclear magnetic resonance T2 signal quantity and the T2 relaxation time under different displacement pressure gradients, where the T2 relaxation time is on a logarithmic scale.

[0019] The calculation formula is obtained by fitting the straight line segment in the curve of the cumulative nuclear magnetic resonance T2 signal quantity versus T2 relaxation time.

[0020] The maximum value of the accumulated nuclear magnetic resonance T2 signal under different displacement pressure gradients is substituted into the calculation formula to calculate the target T2 relaxation time under different displacement pressure gradients.

[0021] Optionally, the target T2 relaxation time is calculated using the following formula:

[0022]

[0023] Where Q is the maximum value of the cumulative nuclear magnetic resonance T2 signal of the fluid in the core; T is the target T2 relaxation time; k and b are fitting coefficients, which are obtained by fitting the straight line segment in the graph of the cumulative nuclear magnetic resonance T2 signal of the fluid in the core with the T2 relaxation time.

[0024] Optionally, determining the minimum pore radius that the fluid can enter under different displacement pressure gradients based on the target T2 relaxation time under different displacement pressure gradients includes:

[0025] Based on the target T2 relaxation time under different displacement pressure gradients, the minimum pore radius that the fluid can enter under different displacement pressure gradients is obtained using mercury intrusion porosimetry data.

[0026] Optionally, the minimum pore radius is calculated using the following formula:

[0027] r = T·μ

[0028] Where r is the minimum pore radius; T is the target T2 relaxation time; and μ is the conversion coefficient, determined from mercury porosimetry data.

[0029] Optionally, the fluid is shale oil, tight oil, white oil, or hydrocarbons.

[0030] A second aspect of the present invention provides a device for quantitatively detecting the fluid mobility of unconventional resource core samples, comprising:

[0031] The first acquisition module is used to acquire the physical property parameters of the core after oil washing treatment;

[0032] The determination module is used to determine the displacement pressure gradient based on the physical property parameters and the displacement pressure during the core flooding test.

[0033] The second acquisition module is used to acquire the cumulative nuclear magnetic resonance T2 signal of the fluid in the core under different displacement pressure gradients;

[0034] The detection module is used to quantitatively detect the mobility of the core fluid based on the cumulative nuclear magnetic resonance T2 signal of the fluid obtained in the core.

[0035] On the other hand, the present invention provides a machine-readable storage medium storing instructions for causing a machine to execute the unconventional resource core fluid mobility quantitative detection method described in this application.

[0036] This technical solution obtains the physical property parameters of the core after oil washing treatment, determines the displacement pressure gradient based on the physical property parameters and the displacement pressure during the core oil displacement test, obtains the cumulative nuclear magnetic resonance T2 signal of the fluid in the core under different displacement pressure gradients, and realizes the quantitative detection of the mobility of the core fluid under different displacement pressure gradients based on the obtained cumulative nuclear magnetic resonance T2 signal of the fluid in the core. Moreover, the detection process is closer to the resource development process, making the test results more accurate and able to accurately guide production.

[0037] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0038] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0039] Figure 1 This is a flowchart of the method for quantitative detection of fluid mobility in unconventional resource cores provided by the present invention;

[0040] Figure 2 This is a schematic diagram of the structure of the device for quantitative detection of fluid mobility in unconventional resource cores provided by the present invention;

[0041] Figure 3 This is a schematic diagram showing the relationship between the nuclear magnetic resonance T2 spectrum and the T2 relaxation time under different displacement pressure gradients provided by the present invention;

[0042] Figure 4 This is a schematic diagram showing the relationship between the cumulative nuclear magnetic resonance T2 signal quantity and the T2 relaxation time under different displacement pressure gradients provided by the present invention;

[0043] Figure 5 This is a schematic diagram showing the relationship between the maximum value of the cumulative nuclear magnetic resonance T2 signal and the corresponding minimum pore radius under different displacement pressure gradients provided by the present invention.

[0044] Explanation of reference numerals in the attached figures

[0045] 10 - First Acquisition Module; 20 - Determination Module; 30 - Second Acquisition Module;

[0046] 40 - Detection module. Detailed Implementation

[0047] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of the present invention.

[0048] In the embodiments of the present invention, unless otherwise stated, directional terms such as "up," "down," "left," and "right" generally refer to the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use.

[0049] The terms “first,” “second,” “third,” etc., are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0050] The terms "parallel" and "perpendicular" do not mean that the components must be absolutely parallel or perpendicular, but rather that they can be slightly tilted. For example, "parallel" simply means that its direction is more parallel than "perpendicular," not that the structure must be completely parallel, but that it can be slightly tilted.

[0051] The terms "horizontal," "vertical," and "sag" do not imply that a component must be absolutely horizontal, vertical, or sagging, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," not that the structure must be completely horizontal, but can be slightly tilted.

[0052] Furthermore, terms like "roughly" and "basically" are used to indicate that the content does not require absolute precision, but rather allows for a certain degree of deviation. For example, "roughly equal" does not simply mean absolute equality; in actual production and operation, achieving absolute "equality" is difficult, and a certain degree of deviation is generally present. Therefore, besides absolute equality, "roughly equal to" also includes the aforementioned situation where a certain degree of deviation exists. Using this as an example, in other cases, unless otherwise specified, terms like "roughly" and "basically" have similar meanings.

[0053] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0054] Figure 1 This is a flowchart of the method for quantitative detection of fluid mobility in unconventional resource cores provided by the present invention; Figure 2 This is a schematic diagram of the structure of the device for quantitative detection of fluid mobility in unconventional resource cores provided by the present invention; Figure 3 This is a schematic diagram showing the relationship between the nuclear magnetic resonance T2 spectrum and the T2 relaxation time under different displacement pressure gradients provided by the present invention; Figure 4This is a schematic diagram showing the relationship between the cumulative nuclear magnetic resonance T2 signal quantity and the T2 relaxation time under different displacement pressure gradients provided by the present invention; Figure 5 This is a schematic diagram showing the relationship between the maximum value of the cumulative nuclear magnetic resonance T2 signal and the corresponding minimum pore radius under different displacement pressure gradients provided by the present invention.

[0055] like Figure 1 As shown, this invention provides a method for quantitatively detecting the fluid mobility of unconventional resource cores, comprising:

[0056] Step 101: Obtain the physical property parameters of the core sample after oil washing treatment;

[0057] Step 102: Determine the displacement pressure gradient based on the aforementioned physical property parameters and the displacement pressure during the core flooding test;

[0058] Step 103: Obtain the cumulative nuclear magnetic resonance T2 signal of fluid in the core under different displacement pressure gradients;

[0059] Step 104: Based on the cumulative nuclear magnetic resonance T2 signal quantity under different displacement pressure gradients, the mobility of the core fluid is quantitatively detected.

[0060] Specifically, in this embodiment, the core sample can be a matrix core or a fracture core; it can be an irregular sample, simply processed into a cylindrical shape with both ends cut flat. The diameter of the cylindrical sample can be set to 2.5 cm or 3.8 cm. Before testing, the obtained core sample is washed with solvent to remove oil, then dried. After drying, nuclear magnetic resonance (NMR) measurement is performed. If an NMR signal is present, it indicates that crude oil remains in the core, and the washing process needs to be repeated until the NMR signal in the core is zero. This ensures that the core is thoroughly cleaned and free of any residual crude oil, so as not to affect the subsequent experimental results and ensure the accuracy of the detection. Secondly, the physical properties of the core samples after oil washing were measured. The samples were then loaded into the holder of the NMR spectrometer, with the core positioned in the center. Square core plugs were added to both sides of the holder and tightened. The holder was then installed on the NMR spectrometer to ensure accurate measurement of the core's NMR signal. The temperature during the testing process was set to the reservoir temperature, and the outlet of the holder was set to atmospheric pressure or reservoir pressure. The corresponding pressure of the injection pump at the inlet was also set to create a displacement pressure differential. During testing, the initial displacement pressure differential was set to a small value, such as 0.001 MPa. Each test corresponds to a displacement pressure, thus determining the displacement pressure gradient for each test. The displacement pressure and the displacement pressure... The displacement pressure gradient gradually increases with the number of detections, resulting in multiple displacement pressure gradients. Fluid is injected at a constant pressure using a pre-set injection pump. During the experiment, the fluid is ensured to be injected from the inlet, pass through the core within the holder, and exit from the outlet, where it is measured. Throughout the process, the nuclear magnetic resonance (NMR) signal of the core is continuously scanned. When the NMR signal of the core remains constant and the fluid output rate at the outlet of the holder matches the injection rate of the pump at the inlet, the fluid volume in the unconventional resource core no longer changes. The cumulative NMR T2 signal value under each displacement pressure gradient is obtained. Based on the obtained cumulative NMR T2 signal values ​​of the fluid within the core under different displacement pressure gradients, the mobility of the core fluid is quantitatively detected. Different sample types have different permeabilities, therefore the displacement pressures also differ; the lower the permeability of the core, the higher the displacement pressure value at the start of the detection.

[0061] Furthermore, the physical property parameter is the length of the core; the displacement pressure is the pressure difference between the inlet and outlet ends of the nuclear magnetic resonance spectrometer's holder during the oil displacement test.

[0062] Specifically, since the length of the core inserted into the holder of the nuclear magnetic resonance spectrometer varies, the size of the fluid path also varies, which will have a certain impact on the displacement pressure gradient. Since the core diameter is already determined, the length of the core is measured in advance before the test, and the pressure value at the outlet end of the holder is set in advance and kept unchanged according to the actual test situation. During the test, the pressure value at the inlet end is changed accordingly to form the displacement pressure, and the displacement pressure gradient is calculated.

[0063] Furthermore, the acquisition of the cumulative nuclear magnetic resonance T2 signal of the fluid within the core under different displacement pressure gradients includes:

[0064] The nuclear magnetic resonance (NMR) T2 spectra and cumulative NMR T2 signal quantities of fluid in the core are acquired sequentially under different displacement pressure gradients with constant fluid volume, from smallest to largest, until the difference between the NMR T2 spectra of fluid in two adjacent cores is less than a preset difference.

[0065] Specifically, since the pressure at the outlet of the gripper is fixed, the pressure at the inlet of the gripper needs to be changed during each test to form a displacement pressure. Following the order of increasing displacement pressure, the nuclear magnetic resonance (NMR) T2 spectrum and cumulative NMR T2 signal are obtained sequentially when the fluid volume within the core remains constant under the corresponding displacement pressure gradient. Because the displacement pressure is a variable in each test, the NMR T2 spectrum and cumulative NMR T2 signal obtained during each test are different. Therefore, the NMR T2 spectrum obtained during the test under the current displacement pressure gradient when the fluid volume within the core remains constant is compared with the NMR T2 spectrum obtained during the test under the previous displacement pressure gradient when the fluid volume within the core remains constant. If the difference between the two is less than a preset difference, it indicates that all the fluid capable of flowing within the core has already flowed, and further testing is unnecessary. The constant fluid volume within the core can be understood as the nuclear magnetic resonance signal remaining unchanged under this displacement pressure, and the fluid production rate at the outlet end being consistent with the injection rate at the inlet end. In unconventional resource cores, the fluid volume no longer changes, and subsequent displacement pressure gradients are no longer detected.

[0066] Furthermore, the cumulative nuclear magnetic resonance T2 signal of the fluid within the core was obtained using the following method:

[0067] Based on the nuclear magnetic resonance T2 spectrum of the fluid inside the core, the cumulative nuclear magnetic resonance T2 signal of the fluid inside the core is obtained by using the area function.

[0068] Specifically, in each round of testing, the nuclear magnetic resonance (NMR) T2 spectrum of the fluid within the core can be directly output from the NMR spectrometer. Then, using an area function (area integral), the cumulative NMR T2 signal of the fluid within the core is obtained, enabling quantitative detection of the fluid mobility within the core. The method of obtaining the cumulative NMR T2 signal using an area function based on the NMR T2 spectrum is a well-established and mature procedure, and will not be elaborated upon here.

[0069] Specifically, the quantitative detection of core fluid mobility based on the cumulative nuclear magnetic resonance T2 signal quantity under different displacement pressure gradients includes:

[0070] Determine the target T2 relaxation time under different displacement pressure gradients based on the cumulative nuclear magnetic resonance T2 signal quantity under different displacement pressure gradients;

[0071] The minimum pore radius that fluid can enter under different displacement pressure gradients is determined based on the target T2 relaxation time under different displacement pressure gradients, and the minimum pore radius is used as the quantitative detection result of core fluid mobility.

[0072] Specifically, in this embodiment, when the difference between the nuclear magnetic resonance T2 spectra of fluids in two adjacent cores is less than a preset difference, the nuclear magnetic resonance T2 spectra under subsequent displacement pressure gradients are no longer acquired. Instead, the target T2 relaxation time under different displacement pressure gradients is determined directly by the cumulative nuclear magnetic resonance T2 signal quantity of the fluids in the cores corresponding to the nuclear magnetic resonance T2 spectra of the fluids in the cores under different displacement pressure gradients. Then, based on the obtained target T2 relaxation time, the minimum pore radius that the fluid can enter under different displacement pressure gradients is determined as the quantitative detection result of the fluid mobility in the cores.

[0073] Furthermore, determining the target T2 relaxation time under different displacement pressure gradients based on the cumulative nuclear magnetic resonance T2 signal quantity under different displacement pressure gradients includes:

[0074] Plot the curves showing the relationship between the cumulative nuclear magnetic resonance T2 signal quantity and the T2 relaxation time under different displacement pressure gradients, where the T2 relaxation time is on a logarithmic scale.

[0075] The calculation formula is obtained by fitting the straight line segment in the curve of the cumulative nuclear magnetic resonance T2 signal quantity versus T2 relaxation time.

[0076] The maximum value of the accumulated nuclear magnetic resonance T2 signal under different displacement pressure gradients is substituted into the calculation formula to calculate the target T2 relaxation time under different displacement pressure gradients.

[0077] Specifically, in this embodiment, the cumulative NMR T2 signal intensity of fluids within the core under different displacement pressure gradients is plotted on the same coordinate system as the T2 relaxation time, with the T2 relaxation time on the horizontal axis using a logarithmic scale. Under a certain displacement pressure gradient, the cumulative NMR T2 signal intensity gradually increases as the T2 relaxation time gradually decreases; when the T2 relaxation time decreases to a certain value, the cumulative NMR T2 signal intensity no longer changes. This process reflects the gradual flow of fluid within pores of different sizes under this displacement pressure gradient: first, fluid flows in larger pores, and then fluid gradually flows in smaller pores. When the cumulative NMR T2 signal intensity remains constant, it indicates that all flowable fluid within the pores under this displacement pressure gradient has been determined. The cumulative nuclear magnetic resonance T2 signal quantity of the fluid in the core obtained at the last time was selected as a function of T2 relaxation time. A straight line segment was selected from the curve and fitted to obtain the corresponding calculation formula. This formula reflects that as the displacement pressure gradient increases, the available pore radius gradually decreases and the flowable fluid gradually increases. The maximum value of the cumulative nuclear magnetic resonance T2 signal quantity under different displacement pressure gradients was then substituted into the calculation formula to obtain the target T2 relaxation time under different displacement pressure gradients.

[0078] In another implementation, only the curve of the cumulative nuclear magnetic resonance T2 signal quantity obtained at the end as a function of T2 relaxation time can be plotted, and the calculation formula can be obtained by fitting the straight line segment in the curve. Then, the maximum value of the cumulative nuclear magnetic resonance T2 signal quantity under different displacement pressure gradients can be substituted into the calculation formula to calculate the target T2 relaxation time under different displacement pressure gradients.

[0079] Furthermore, the target T2 relaxation time is calculated using the following formula:

[0080]

[0081] Where Q is the maximum value of the cumulative nuclear magnetic resonance T2 signal of the fluid in the core; T is the target T2 relaxation time; k and b are fitting coefficients, which are obtained by fitting the straight line segment in the graph of the cumulative nuclear magnetic resonance T2 signal of the fluid in the core with the T2 relaxation time.

[0082] Furthermore, determining the minimum pore radius that the fluid can enter under different displacement pressure gradients based on the target T2 relaxation time under different displacement pressure gradients includes:

[0083] Based on the target T2 relaxation time under different displacement pressure gradients, the minimum pore radius that the fluid can enter under different displacement pressure gradients is obtained using mercury intrusion porosimetry data.

[0084] Specifically, after determining the T2 relaxation time under different displacement pressure gradients using the above scheme, the minimum pore radius that the fluid can enter under different displacement pressure gradients can be obtained using mercury intrusion porosimetry data (obtained by mercury intrusion porosimetry). The minimum pore radius is used as the quantitative detection result of the fluid mobility in the core. This minimum pore radius is determined under the condition that the fluid flows in the core, thus determining the mobile fluid in the core under different conditions, and realizing the quantitative evaluation of the fluid mobility of unconventional resource cores.

[0085] Furthermore, the minimum pore radius is calculated using the following formula:

[0086] r = T·μ

[0087] Where r is the minimum pore radius; T is the target T2 relaxation time; and μ is the conversion coefficient, determined from mercury porosimetry data.

[0088] Furthermore, the fluid is shale oil, tight oil, white oil, or hydrocarbons.

[0089] Specifically, the fluid can be shale oil or tight oil that has been filtered to remove solid impurities, or it can be white oil. It can also be high-purity hydrocarbons, such as n-pentane, n-hexane, n-heptane, n-octane, etc., or gases such as methane, ethane, propane, butane, etc.

[0090] like Figure 2 As shown, embodiments of the present invention also provide a quantitative detection device for the fluid mobility of unconventional resource cores, comprising:

[0091] The first acquisition module 10 is used to acquire the physical property parameters of the core after oil washing treatment;

[0092] The determination module 20 is used to determine the displacement pressure gradient based on the physical property parameters and the displacement pressure during the core flooding test.

[0093] The second acquisition module 30 is used to acquire the cumulative nuclear magnetic resonance T2 signal of the fluid in the core under different displacement pressure gradients.

[0094] The detection module 40 is used to quantitatively detect the mobility of the core fluid based on the acquired cumulative nuclear magnetic resonance T2 signal.

[0095] This invention also provides a machine-readable storage medium storing instructions for causing a machine to execute the unconventional resource core fluid mobility quantitative detection method described above.

[0096] Example

[0097] Sample Acquisition: Obtain shale oil samples from the target block, process the samples into cylindrical shapes, and cut both ends flat. The sample diameter is 2.54 cm and the length is 3.83 cm.

[0098] Sample washing: The sample was washed with solvent and then dried. Nuclear magnetic resonance (NMR) measurements were performed after drying to ensure the sample was completely clean and free of any residual crude oil, which could affect subsequent experimental results. The measured air permeability was 0.257 mD.

[0099] Shale core fluid mobility testing experiment: The washed oil sample was loaded into the holder of the NMR spectrometer and then into the NMR spectrometer to ensure accurate measurement of the sample's NMR signal. The experimental temperature was set to the reservoir temperature of 80℃. The outlet pressure of the holder was set to 20MPa, and the pressure of the injection pump at the inlet was set to ensure the formation of a displacement pressure differential. Initially, the displacement pressure differential was set to 0.5MPa. Based on the core length of 3.83cm, the displacement pressure gradient was calculated to be 0.13MPa / cm. Fluid, n-dodecane, was injected at a constant pressure according to the set injection pump pressure. During the experiment, the fluid was ensured to be injected from the inlet, pass through the shale core in the holder, and be produced from the outlet, where it was measured. Throughout the process, the NMR signal of the shale sample was continuously scanned. When the NMR signal of the sample remained constant, and the fluid production rate at the outlet matched the injection rate of the pump at the inlet, the fluid volume in the shale core no longer changed, and the NMR T2 spectrum of the core was recorded. Assuming a displacement pressure gradient of 0.5 MPa and a core length of 3.83 cm, the calculated displacement pressure gradient is 0.13 MPa / cm. Under this displacement pressure gradient, the NMR T2 spectrum of the fluid flowing within the core can be obtained. The cumulative NMR T2 signal of the fluid flowing within the shale core can be calculated using area integration. Increasing the inlet pressure to increase the displacement pressure gradient to 1 MPa and repeating the above steps yields the NMR T2 spectrum and cumulative NMR T2 signal of the fluid flowing within the core under a second displacement pressure gradient of 0.26 MPa / cm. This process is repeated to obtain the NMR T2 spectrum and cumulative NMR T2 signal of the fluid flowing within the core under a series of displacement pressure gradients. Nuclear magnetic resonance (NMR) T2 spectra were obtained for displacement pressure gradients of 0.52 MPa / cm, 1.04 MPa / cm, and 1.31 MPa / cm. When the displacement pressure gradient was further increased to 1.57 MPa / cm, the NMR T2 spectrum of the flowable fluid within the shale core showed little change compared to the previous displacement pressure gradient of 1.31 MPa / cm. At this point, it was considered that all flowable fluid within the shale core had flowed, and the fluid mobility testing experiment was concluded. Figure 3 The diagram shows the relationship between the T2 NMR spectrum and the T2 relaxation time under different displacement pressure gradients.

[0100] Quantitative detection method for fluid mobility in shale cores: The relationship between the cumulative nuclear magnetic resonance T2 signal quantity and T2 relaxation time under different displacement pressure gradients is plotted on the same graph, such as... Figure 4 As shown, the horizontal axis T2 relaxation time is on a logarithmic scale. Under a certain displacement pressure gradient, as the T2 relaxation time gradually decreases, the cumulative NMR T2 signal quantity gradually increases; when the T2 relaxation time decreases to a certain value, the cumulative NMR T2 signal quantity no longer changes.

[0101] By fitting the linearly increasing line segment on the cumulative NMR T2 signal curve corresponding to the maximum displacement pressure gradient of 1.57 MPa / cm, the corresponding relationship A is obtained: Where Q is the maximum value of the cumulative NMR T2 signal of the fluid in the core; T is the target T2 relaxation time. The maximum value of the cumulative NMR T2 signal under different displacement pressure gradients is substituted into the relationship A obtained under the maximum displacement pressure gradient of 1.57 MPa / cm. Using this relationship A, the target T2 relaxation time corresponding to the maximum value of the cumulative NMR T2 signal under different displacement pressure gradients is determined. The conversion relationship between relaxation time and pore radius determined using mercury intrusion porosimetry data is: r = T·180, where r is the minimum pore radius; T is the target T2 relaxation time. Converting the target T2 relaxation time into pore radius determines the minimum pore radius that shale fluid can enter under different displacement pressure gradients. Figure 5 As shown in the figure and Table 1 below:

[0102] Table 1. Variation of cumulative nuclear magnetic resonance T2 signal quantity and T2 relaxation time.

[0103]

[0104] The detection method of this invention is implemented under fluid flow conditions. Throughout the process, the fluid seeps into the unconventional resource core under the action of a pressure gradient. After the fluid flow reaches a stable state, the lower limit of the pore size at which the fluid can flow is determined. The entire process is a realistic simulation of fluid flow in unconventional resource formations, and the detection process conforms to the development process of unconventional resources, resulting in more accurate results. Furthermore, it can continuously detect fluid mobility under different displacement pressure gradients, ensuring completely consistent experimental conditions while saving a significant amount of time.

[0105] The optional embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above embodiments. Within the scope of the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical solutions of the embodiments of the present invention, and these simple modifications all fall within the protection scope of the embodiments of the present invention.

[0106] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the embodiments of the present invention will not describe the various possible combinations separately.

[0107] Those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. This program is stored in a storage medium and includes several instructions to cause a microcontroller, chip, or processor to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, a portable hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0108] Furthermore, various different implementations of the present invention can be combined arbitrarily, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed in the present invention.

Claims

1. A method for quantitatively detecting the fluid mobility of unconventional resource cores, characterized in that, include: Obtain the physical properties of the core sample after oil washing treatment; Based on the aforementioned physical properties and the displacement pressure during the core flooding test, the displacement pressure gradient is determined. The cumulative nuclear magnetic resonance T2 signal of fluids in cores under different displacement pressure gradients was obtained, including: The nuclear magnetic resonance T2 spectrum and cumulative nuclear magnetic resonance T2 signal of the fluid in the core are obtained sequentially under different displacement pressure gradients with constant fluid volume, in order from small to large displacement pressure, until the difference between the nuclear magnetic resonance T2 spectra of the fluid in two adjacent cores is less than the preset difference. Based on the cumulative nuclear magnetic resonance T2 signal quantity under different displacement pressure gradients, the mobility of core fluids was quantitatively detected, including: Plot the curves showing the relationship between the cumulative nuclear magnetic resonance T2 signal quantity and the T2 relaxation time under different displacement pressure gradients, where the T2 relaxation time is on a logarithmic scale. The calculation formula is obtained by fitting the straight line segment in the curve of the cumulative nuclear magnetic resonance T2 signal quantity versus T2 relaxation time. Substitute the maximum value of the accumulated nuclear magnetic resonance T2 signal under different displacement pressure gradients into the calculation formula to calculate the target T2 relaxation time under different displacement pressure gradients. The minimum pore radius that the fluid can enter under different displacement pressure gradients is determined based on the target T2 relaxation time under different displacement pressure gradients, and the minimum pore radius is used as the quantitative detection result of the fluid mobility in the core. The target T2 relaxation time is calculated using the following formula: in, The maximum value of the cumulative nuclear magnetic resonance T2 signal of the fluid in the core; T is the target T2 relaxation time; and The fitting coefficients are obtained by fitting the linear segments in the graph showing the cumulative nuclear magnetic resonance T2 signal quantity of the fluid in the core as a function of T2 relaxation time.

2. The method according to claim 1, characterized in that, The physical property parameter is the length of the core; the displacement pressure is the pressure difference between the inlet and outlet ends of the nuclear magnetic resonance spectrometer's holder during the oil displacement test.

3. The method according to claim 1, characterized in that, The cumulative nuclear magnetic resonance T2 signal of the fluid within the core was obtained using the following method: Based on the nuclear magnetic resonance T2 spectrum of the fluid inside the core, the cumulative nuclear magnetic resonance T2 signal of the fluid inside the core is obtained by using the area function.

4. The method according to claim 1, characterized in that, The determination of the minimum pore radius that fluid can enter under different displacement pressure gradients based on the target T2 relaxation time under different displacement pressure gradients includes: Based on the target T2 relaxation time under different displacement pressure gradients, the minimum pore radius that the fluid can enter under different displacement pressure gradients is obtained using mercury intrusion porosimetry data.

5. The method according to claim 4, characterized in that, The minimum pore radius is calculated using the following formula: in, The minimum pore radius is T; T is the target T2 relaxation time. The conversion factor was determined from mercury porosimetry data.

6. The method according to claim 1, characterized in that, The fluid is shale oil, tight oil, white oil, or hydrocarbons.

7. A quantitative detection device for the fluid mobility of unconventional resource core samples, characterized in that, include: The first acquisition module is used to acquire the physical property parameters of the core after oil washing treatment; The determination module is used to determine the displacement pressure gradient based on the physical property parameters and the displacement pressure during the core flooding test. The second acquisition module is used to acquire the cumulative nuclear magnetic resonance T2 signal of the fluid in the core under different displacement pressure gradients, including: The nuclear magnetic resonance T2 spectrum and cumulative nuclear magnetic resonance T2 signal of the fluid in the core are obtained sequentially under different displacement pressure gradients with constant fluid volume, in order from small to large displacement pressure, until the difference between the nuclear magnetic resonance T2 spectra of the fluid in two adjacent cores is less than the preset difference. The detection module is used to quantitatively detect the mobility of core fluids based on the acquired cumulative nuclear magnetic resonance T2 signal, including: Plot the curves showing the relationship between the cumulative nuclear magnetic resonance T2 signal quantity and the T2 relaxation time under different displacement pressure gradients, where the T2 relaxation time is on a logarithmic scale. The calculation formula is obtained by fitting the straight line segment in the curve of the cumulative nuclear magnetic resonance T2 signal quantity versus T2 relaxation time. Substitute the maximum value of the accumulated nuclear magnetic resonance T2 signal under different displacement pressure gradients into the calculation formula to calculate the target T2 relaxation time under different displacement pressure gradients. The minimum pore radius that the fluid can enter under different displacement pressure gradients is determined based on the target T2 relaxation time under different displacement pressure gradients, and the minimum pore radius is used as the quantitative detection result of the fluid mobility in the core. The target T2 relaxation time is calculated using the following formula: in, The maximum value of the cumulative nuclear magnetic resonance T2 signal of the fluid in the core; T is the target T2 relaxation time; and The fitting coefficients are obtained by fitting the linear segments in the graph showing the cumulative nuclear magnetic resonance T2 signal quantity of the fluid in the core as a function of T2 relaxation time.

8. A machine-readable storage medium storing instructions for causing a machine to perform the method for quantitative detection of fluid mobility in unconventional resource cores according to any one of claims 1-6 of this application.

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