Method, device and equipment for obtaining rock cores with different saturations based on nuclear magnetic resonance

Abstract

The invention provides a method, a device and equipment for acquiring cores with different saturations based on nuclear magnetic resonance, which can be applied to the technical field of carbon emission and geological storage. The method comprises the steps that nuclear magnetic resonance testing is conducted on an initial rock core, an initial peak area corresponding to a nuclear magnetic resonance spectrogram is obtained, and the initial rock core represents a rock core obtained after a to-be-detected rock core is subjected to pressure applying and water injection treatment; a target peak area is determined based on a preset saturation degree and the initial peak area, the preset saturation degree is determined based on a target saturation degree of a target rock, and the target rock represents a rock in the reservoir environment; the difference value between the initial peak area and the target peak area when gas is injected into the initial rock core is detected, and the initial peak area is larger than the target peak area; and determining a target rock core based on the difference value and a preset difference threshold value. According to the method, damage to the rock core can be reduced, nondestructive and sensitive detection is achieved, and the acquisition requirements of the rock cores with different saturations are met.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon emission and geological storage, and in particular to a method, a device and equipment for obtaining cores with different saturations based on nuclear magnetic resonance. Background Art

[0002] Carbon Capture and Storage (CCS) technology is currently recognized as the most direct and cost-effective way to reduce CO2 emissions. Deep saline aquifers are considered one of the most promising CO2 geological storage sites due to their huge CO2 storage capacity. Core flooding experiments can be used to analyze the impact of cores with different saturations on the CO2 geological storage mechanism.

[0003] The inventors found that in the related technology, the use of core flooding experiments to achieve the original saturation of rock voids under different environments has the following defects: on the one hand, due to the high temperature of related equipment (such as a hot air gun) during the core flooding experiment, part of the water in the core will evaporate, and the original saturation of the core will change; on the other hand, during the displacement experiment, there may be water in the pipeline that cannot be completely driven out by the gas. Therefore, the accuracy of the original saturation of the core calculated by the water mass collected at the outlet, the mass of the fully saturated core and the mass of the completely dry core is relatively low. Summary of the invention

[0004] In view of the above problems, the present invention provides a method, device, equipment, medium and program product for obtaining cores with different saturations based on nuclear magnetic resonance.

[0005] According to a first aspect of the present invention, there is provided a method for obtaining cores with different saturations based on nuclear magnetic resonance, comprising: performing a nuclear magnetic resonance test on an initial core to obtain an initial peak area corresponding to a nuclear magnetic resonance spectrum, wherein the initial core represents a core obtained after pressurization and water injection treatment of the core to be tested; determining a target peak area based on a preset saturation and the initial peak area, wherein the preset saturation is determined based on a target saturation of a target rock, and the target rock represents a rock under a reservoir environment; detecting a difference between the initial peak area and the target peak area when gas is injected into the initial core, wherein the initial peak area is greater than the target peak area; and determining the target core based on the difference and a preset difference threshold.

[0006] According to an embodiment of the present invention, the above-mentioned initial core is obtained by the following operations: applying pressure to the above-mentioned core to be tested to obtain a pressure core that meets a preset pressure threshold, wherein the above-mentioned pressure treatment includes confining pressure treatment and back pressure treatment; and injecting water into the above-mentioned pressure core to obtain the above-mentioned initial core.

[0007] According to an embodiment of the present invention, a nuclear magnetic resonance test is performed on an initial core to obtain an initial peak area corresponding to a nuclear magnetic resonance spectrum, including: testing the initial core to obtain a spectrum corresponding to the initial core; and determining the initial peak area based on the nuclear magnetic resonance spectrum and a reference axis corresponding to the spectrum.

[0008] According to an embodiment of the present invention, detecting the difference between the initial peak area and the target peak area when gas is injected into the initial core includes: injecting gas into the initial core using a gas injection device to displace the fluid in the initial core; and detecting the difference between the initial peak area and the target peak area during the displacement process.

[0009] According to an embodiment of the present invention, the method further includes: processing the target rock to generate a sample core meeting a preset size; and cleaning and drying the sample core using a cleaning agent to obtain the core to be tested.

[0010] According to an embodiment of the present invention, the initial core is tested to obtain a spectrum corresponding to the initial core, including: exciting the initial core with a radio frequency pulse to generate a magnetization signal; detecting a plurality of signal intensities corresponding to the magnetization signal at a plurality of time points, wherein the plurality of signal intensities are inversely proportional to the plurality of time points; and processing the initial signal corresponding to the plurality of signal intensities using a preset conversion rule to obtain the spectrum.

[0011] According to an embodiment of the present invention, the above-mentioned initial signal represents a time domain signal corresponding to a time point; the initial signal corresponding to the multiple signal intensities is processed using a preset conversion rule to obtain the above-mentioned spectrogram, including: converting the above-mentioned time domain signal using the above-mentioned preset conversion rule to obtain amplitude information and phase information corresponding to multiple frequencies; and generating the above-mentioned spectrogram based on the above-mentioned amplitude information and phase information.

[0012] According to an embodiment of the present invention, the method further comprises: processing the plurality of magnetization signals by using reverse pulses so that the strength of the magnetization signals meets a preset detection requirement.

[0013] The second aspect of the present invention provides a device for obtaining cores with different saturations based on nuclear magnetic resonance, characterized in that the device comprises: a testing module, used to perform a nuclear magnetic resonance test on an initial core to obtain an initial peak area corresponding to a nuclear magnetic resonance spectrum, wherein the initial core represents a core obtained after pressurization and water injection treatment of the core to be tested; a peak area determination module, used to determine a target peak area based on a preset saturation and the initial peak area, wherein the preset saturation is determined based on a target saturation of a target rock, and the target rock represents a rock under a reservoir environment; a detection module, used to detect the difference between the initial peak area and the target peak area when gas is injected into the initial core, wherein the initial peak area is greater than the target peak area; and a determination module, used to determine the target core based on the difference and a preset difference threshold.

[0014] A third aspect of the present invention provides an electronic device, comprising: one or more processors; a memory for storing one or more computer programs, wherein the one or more processors execute the one or more computer programs to implement the steps of the above method.

[0015] The fourth aspect of the present invention further provides a computer-readable storage medium on which a computer program or instruction is stored, and the steps of the above method are implemented when the above computer program or instruction is executed by a processor.

[0016] The fifth aspect of the present invention also provides a computer program product, including a computer program or instructions, which implement the steps of the above method when executed by a processor.

[0017] According to the method, device and equipment for obtaining cores with different saturations based on nuclear magnetic resonance provided by the present invention, an initial peak area corresponding to an initial core spectrum is obtained through nuclear magnetic resonance, thereby determining a target peak area based on the initial peak area and a preset saturation, and detecting the difference between the initial peak area and the target peak area during gas injection into the initial core, thereby obtaining a target core. Since the initial core has been pressurized and water-injected, the target core obtained based on the initial core can meet the saturation requirements of the actual reservoir environment, thereby avoiding the situation in which the accuracy of the target core acquisition result is low due to failure to consider the water loss of the core in traditional technologies. In addition, the nuclear magnetic resonance test minimizes damage to the core, achieves non-destructive and sensitive detection, and meets the needs for obtaining cores with different saturations in an actual environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above contents and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0019] Figure 1A diagram showing an application scenario of a method for obtaining cores with different saturations based on nuclear magnetic resonance according to an embodiment of the present invention;

[0020] Figure 2 A flow chart of a method for obtaining cores with different saturations based on nuclear magnetic resonance according to an embodiment of the present invention is shown;

[0021] Figure 3 Schematic diagrams of core T2 spectra according to an embodiment of the present invention are shown, wherein FIG (a) shows a two-dimensional schematic diagram of T2 spectra, and FIG (b) shows a three-dimensional schematic diagram of T2 spectra;

[0022] Figure 4 A flow chart showing another method for obtaining cores with different saturations based on nuclear magnetic resonance according to an embodiment of the present invention is shown;

[0023] Figure 5 A structural block diagram of a device for obtaining cores with different saturations based on nuclear magnetic resonance according to an embodiment of the present invention is shown;

[0024] Figure 6 A block diagram of an electronic device suitable for implementing a method for acquiring cores with different saturations based on nuclear magnetic resonance according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0025] Below, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of concepts of the present invention.

[0026] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0027] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0028] When using expressions such as "at least one of A, B, and C, etc.", they should generally be interpreted according to the meaning of the expression commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0029] In the technical solution of the present invention, the user information (including but not limited to user personal information, user image information, user device information, such as location information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved are all information and data authorized by the user or fully authorized by all parties, and the collection, storage, use, processing, transmission, provision, disclosure and application of the relevant data comply with relevant laws, regulations and standards, take necessary confidentiality measures, do not violate public order and good morals, and provide corresponding operation entrances for users to choose to authorize or refuse.

[0030] In the process of conceiving the present invention, the inventors found that in the related technology, when loading samples in the core displacement experiment in the traditional technology, the high temperature of the related equipment (such as a hot air gun) will cause part of the water in the core to evaporate, and the original saturation of the core will change; on the other hand, since there may be water in the pipeline during the displacement experiment and it cannot be completely driven out by the gas, the original saturation of the core calculated by the water mass collected at the outlet, the mass of the fully saturated core and the mass of the completely dry core has a low accuracy.

[0031] In view of this, the present invention obtains the initial peak area corresponding to the initial core spectrum through nuclear magnetic resonance, thereby determining the target peak area based on the initial peak area and the preset saturation, and detecting the difference between the initial peak area and the target peak area during the gas injection process into the initial core, thereby obtaining the target core. Since the initial core has been pressurized and water-injected, the target core obtained based on the initial core can meet the saturation requirements of the actual reservoir environment, avoiding the situation in which the accuracy of the target core acquisition result is low due to the failure to consider the water loss of the core in the traditional technology, and the nuclear magnetic resonance test minimizes the damage to the core, achieving non-destructive and sensitive detection, and meeting the acquisition needs of cores with different saturations in the actual environment.

[0032] Embodiments of the present invention provide a method, device and equipment for obtaining cores with different saturations based on nuclear magnetic resonance. The method includes performing a nuclear magnetic resonance test on an initial core to obtain an initial peak area corresponding to a nuclear magnetic resonance spectrum, wherein the initial core represents a core obtained after pressurization and water injection treatment of the core to be tested; determining a target peak area based on a preset saturation and the initial peak area, wherein the preset saturation is determined based on a target saturation of a target rock, and the target rock represents a rock under a reservoir environment; detecting the difference between the initial peak area and the target peak area when gas is injected into the initial core, wherein the initial peak area is greater than the target peak area; and determining the target core based on the difference and a preset difference threshold.

[0033] Figure 1 A diagram showing an application scenario of a method for obtaining cores with different saturations based on nuclear magnetic resonance according to an embodiment of the present invention.

[0034] like Figure 1 As shown, the application scenario according to this embodiment may include a first terminal device 101, a second terminal device 102, a third terminal device 103, a network 104, a server 105, and a detection device 106. The network 104 is used to provide a medium for a communication link between the first terminal device 101, the second terminal device 102, the third terminal device 103, and the server 105. The network 104 may include various connection types, such as wired, wireless communication links, or optical fiber cables, etc.

[0035] The detection device 106 may represent a test device for performing nuclear magnetic resonance on a rock core, and may include a nuclear magnetic resonance rock measuring instrument or a rock nuclear magnetic resonance instrument. The specific type of the device may be determined according to actual conditions and is not limited here. The detection device 106 may be connected to the server 105 via the network 104 so that the acquired relevant data is sent to the server 106 for corresponding processing.

[0036] The user can use the first terminal device 101, the second terminal device 102, and the third terminal device 103 to interact with the server 105 through the network 104 to receive or send messages, etc. Various communication client applications can be installed on the first terminal device 101, the second terminal device 102, and the third terminal device 103, such as shopping applications, web browser applications, search applications, instant messaging tools, email clients, social platform software, etc. (only for example).

[0037] The first terminal device 101, the second terminal device 102, and the third terminal device 103 may be various electronic devices having display screens and supporting web browsing, including but not limited to smart phones, tablet computers, laptop computers, desktop computers, and the like.

[0038] The server 105 may be a server that provides various services, such as a background management server (only as an example) that provides support for websites browsed by users using the first terminal device 101, the second terminal device 102, and the third terminal device 103. The background management server may analyze and process the received data such as user requests, and feed back the processing results (such as web pages, information, or data obtained or generated according to user requests) to the terminal device.

[0039] It should be noted that the method for obtaining cores with different saturations based on nuclear magnetic resonance provided in the embodiment of the present invention can generally be executed by the server 105. Accordingly, the device for obtaining cores with different saturations based on nuclear magnetic resonance provided in the embodiment of the present invention can generally be set in the server 105. The method for obtaining cores with different saturations based on nuclear magnetic resonance provided in the embodiment of the present invention can also be executed by a server or server cluster that is different from the server 105 and can communicate with the first terminal device 101, the second terminal device 102, the third terminal device 103 and / or the server 105. Accordingly, the device for obtaining cores with different saturations based on nuclear magnetic resonance provided in the embodiment of the present invention can also be set in a server or server cluster that is different from the server 105 and can communicate with the first terminal device 101, the second terminal device 102, the third terminal device 103 and / or the server 105.

[0040] It should be understood that Figure 1 The number of terminal devices, networks, detection devices and servers in the embodiment is only for illustration. Any number of terminal devices, networks, detection devices and servers may be provided according to implementation requirements.

[0041] Figure 2 A flow chart of a method for obtaining cores with different saturations based on nuclear magnetic resonance according to an embodiment of the present invention is shown.

[0042] like Figure 2 As shown, the method for obtaining cores with different saturations based on nuclear magnetic resonance in this embodiment includes operations S210 to S240.

[0043] In operation S210, a nuclear magnetic resonance test is performed on the initial core to obtain an initial peak area corresponding to the nuclear magnetic resonance spectrum, wherein the initial core represents a core obtained after the core to be tested is subjected to pressure and water injection treatment.

[0044] According to an embodiment of the present invention, the initial core may be a core that satisfies a preset saturation after pressure treatment and water injection treatment are performed on the obtained core to be tested according to actual needs and reservoir environment. In the case of generating a core that meets the preset saturation, the initial core may be tested using nuclear magnetic resonance (NMR) to obtain a nuclear magnetic resonance transverse relaxation time (T2 spectrum, T2 spectrum). It is understandable that the nuclear magnetic resonance transverse relaxation time T2 spectrum may characterize the spectrum obtained by T2 measurement of the core to be tested in the nuclear magnetic resonance device, and may reflect the size of rock voids and the distribution of hydrogen-containing fluid information. It should be noted that the peaks on the spectrum represent the components of the fluid contained in the core, and the peak area enclosed by the T2 spectrum and the reference axis may reflect the content of the hydrogen-containing fluid in the core. The initial peak area may characterize the peak area enclosed by the nuclear magnetic resonance transverse relaxation time T2 spectrum obtained by testing the initial core and the reference axis.

[0045] In operation S220, a target peak area is determined based on a preset saturation and an initial peak area, wherein the preset saturation is determined based on a target saturation of a target rock, the target rock representing a rock in a reservoir environment.

[0046] According to an embodiment of the present invention, the target saturation can characterize the original saturation of rock voids under different actual environments to meet the analysis of the impact of different saturation cores on gas geological storage technology. It is understandable that the specific preset saturation value can be determined according to the actual situation and is not limited here. The target peak area can characterize the peak area formed by the nuclear magnetic resonance transverse relaxation time T2 spectrum obtained by testing the target core corresponding to the target rock and the reference axis.

[0047] In operation S230, a difference between an initial peak area and a target peak area when gas is injected into the initial core is detected, wherein the initial peak area is greater than the target peak area.

[0048] According to an embodiment of the present invention, the gas may be a greenhouse gas, a harmful gas or other gas to be sealed based on actual conditions, and the gas includes but is not limited to carbon dioxide, fluorinated gas, sulfided gas and nitrogen oxides, which are not specifically limited herein. The difference may characterize the difference between the peak area (initial peak area) obtained during the displacement process and the target peak area by displacing the fluid in the initial core through a displacement experiment.

[0049] It is understandable that in the embodiments of the present invention, during the process of geological storage of gas in deep saline aquifers on land, as gas is continuously injected, the water in the aquifer will be driven away, and after most of the water is driven away, due to the capillary force between the rock voids, some water will still remain between the rock voids, and the percentage of the rock void volume occupied by the remaining water to the total rock void volume can be defined as the saturation of the deep saline aquifer at that moment. The saturation of the deep saline aquifer can reflect the proportion of liquid in the aquifer, which has an important impact on the potential evaluation and safety assessment of gas geological storage.

[0050] In operation S240, a target core is determined based on the difference and a preset difference threshold.

[0051] According to an embodiment of the present invention, by comparing the difference with a preset difference threshold, when the difference between the initial peak area and the target peak area is less than or equal to the preset difference threshold, the core at this time is determined as the target core. It should be noted that the preset difference threshold can be determined according to actual conditions and is not specifically limited here.

[0052] According to an embodiment of the present invention, an initial peak area corresponding to an initial core spectrum is obtained by nuclear magnetic resonance, thereby determining a target peak area based on the initial peak area and a preset saturation, and detecting the difference between the initial peak area and the target peak area during gas injection into the initial core, thereby obtaining a target core. Since the initial core has been pressurized and water-injected, the target core obtained based on the initial core can meet the saturation requirements of the actual reservoir environment, thereby avoiding the situation in which the accuracy of the target core acquisition result is low due to failure to consider the water loss in the core in the traditional technology. In addition, the nuclear magnetic resonance test minimizes damage to the core to the greatest extent, achieving non-destructive and sensitive detection, and meeting the needs for obtaining cores with different saturations in the actual environment.

[0053] According to an embodiment of the present invention, the initial core is obtained by the following operations: applying pressure to the core to be tested to obtain a pressure core that meets a preset pressure threshold, wherein the pressure treatment includes confining pressure treatment and back pressure treatment; and injecting water into the pressure core to obtain the initial core.

[0054] According to an embodiment of the present invention, considering the influence of actual formation pressure, it is necessary to perform confining pressure treatment and back pressure treatment on the obtained core to be tested (sample core) to better simulate the core behavior under actual formation pressure conditions. Furthermore, in order to obtain a core that meets a preset saturation (e.g., 100%), the core that has been subjected to pressure treatment can be subjected to water injection treatment to obtain an initial core.

[0055] In a feasible embodiment, the method of performing confining pressure treatment on the sample core may include: installing the sample core in a test chamber of a confining pressure machine (Triaxial Test Equipment) or other professional equipment, and ensuring that its position is stable; applying confining pressure to the sample core through the confining pressure equipment, and referring to the in-situ pressure (such as formation pressure or fluid static pressure), and applying a corresponding confining pressure value; gradually increasing the confining pressure to avoid sudden rupture of the sample; and monitoring the confining pressure, axial strain and other related parameters in real time until the actual formation pressure effect can be achieved.

[0056] In a feasible embodiment, the back pressure treatment can simulate the state of the core when the formation pressure changes, and can be performed after the confining pressure treatment. The back pressure treatment method may include: after the confining pressure treatment is completed, applying appropriate back pressure to simulate the actual formation conditions, and the back pressure value can be determined according to the characteristics of the formation fluid and the properties of the core; under the back pressure, a predetermined time can be maintained according to the experimental requirements so that the core reaches a stable state, and the specific time can be determined according to the actual situation; at the same time, the changes in various parameters during the back pressure process are recorded and stored, such as permeability, pore water pressure and stress-strain relationship related data, to meet the formation pressure effect in the actual environment.

[0057] According to the embodiments of the present invention, by subjecting the sample core to confining pressure and back pressure treatment, the physical and chemical environment of the actual formation can be better reproduced in the experiment, thereby improving the reliability and repeatability of the experimental results.

[0058] According to an embodiment of the present invention, a nuclear magnetic resonance test is performed on the initial core to obtain an initial peak area corresponding to the nuclear magnetic resonance spectrum, including: testing the initial core to obtain a spectrum corresponding to the initial core; and determining the initial peak area based on the nuclear magnetic resonance spectrum and a reference axis corresponding to the spectrum.

[0059] According to an embodiment of the present invention, the spectrum can characterize the time coefficient of the disappearance of coherence of nuclear spins in the transverse plane (the plane perpendicular to the external magnetic field) in the nuclear magnetic resonance test, can characterize the energy loss caused by the interaction between the spin systems, and is associated with the physical and chemical environment of the sample core. The initial peak area can characterize the area enclosed by the T2 spectrum based on the transverse relaxation time of the nuclear magnetic resonance and the reference axis (such as the horizontal axis) of the spectrum. In the T2 spectrum, the method of determining the enclosed area between the T2 spectrum and the horizontal axis includes but is not limited to numerical integration, fitting method and nuclear magnetic resonance NMR data analysis software.

[0060] According to an embodiment of the present invention, detecting the difference between the initial peak area and the target peak area when gas is injected into the initial core includes: injecting gas into the initial core using a gas injection device to displace the fluid in the initial core; and detecting the difference between the initial peak area and the target peak area during the displacement process.

[0061] According to an embodiment of the present invention, a method for detecting the difference between the initial peak area and the target peak area when gas is injected into the initial core through a displacement experiment may include: placing the core in a high-pressure closed container, and setting an appropriate gas injection pressure and flow rate; injecting gas (such as nitrogen, carbon dioxide, etc.) into the core, so that a stable pressure and flow rate can be maintained during the gas injection process, and the initial conditions of the gas injection and the amount of gas injected are recorded; during the gas injection process, the T2 spectrum of the sample core is measured regularly using an NMR instrument; after each gas injection, the T2 spectrum can be obtained, the initial peak area can be recorded, and the spectrum changes caused by changes in the gas injection amount can be detected; a threshold is set according to actual conditions, and when the initial peak area in the T2 spectrum reaches a predetermined value, and the difference between the initial peak area and the target peak area is less than or equal to the preset difference threshold, the gas injection is stopped. It can be understood that the predetermined value should be determined based on factors such as the core properties and the gas type.

[0062] According to an embodiment of the present invention, the method further includes: processing the target rock to generate a sample core meeting a preset size; and cleaning and drying the sample core using a cleaning agent to obtain a core to be tested.

[0063] According to an embodiment of the present invention, the target rock is a rock that needs to seal the gas to be sealed under an actual reservoir environment. The preset size of the sample core can be determined according to actual conditions, such as 25 mm x 50 mm, 80 mm x 50 mm, and is not specifically limited here.

[0064] In a feasible embodiment, a method for processing a target rock to generate a sample core of a preset size may include: obtaining an original rock sample, using rock processing equipment (such as a cutter, a diamond saw, a grinder, a measuring tool, a weighing device) to accurately measure the rock and mark the cutting line according to a preset sample size; using a rock cutter or a diamond saw to cut the rock along the marked line, keeping the cut surface flat and vertical; using a grinder to polish the cut core sample to make its surface smooth and reach a predetermined size and shape; and checking the size and quality of the sample to ensure that it meets the experimental requirements.

[0065] In a feasible embodiment, a method for obtaining a sample core by cleaning and drying the sample core with a cleaning agent may include: selecting a suitable cleaning agent (such as deionized water, alcohol solvents or special cleaning agents), and the selection of the cleaning agent may be determined according to the nature of the rock and the degree of contamination; soaking the sample core in the cleaning agent to remove surface dirt and impurities, and an ultrasonic cleaner may be used to enhance the cleaning effect; using a drying device (such as an oven, a vacuum drying oven or a freeze dryer), the cleaned sample core is placed in an oven, and an appropriate temperature is set (for example, between 50-80°C, specifically determined according to the rock type), and drying at an appropriate temperature for a preset time period until the sample weight is stable, indicating that the water has been completely evaporated; taking out the dried sample and placing it at room temperature to cool to avoid damage to the sample due to sudden temperature changes; weighing the dried core sample and recording the basic information of the sample (such as size, mass, etc.) as the core to be tested for subsequent experiments.

[0066] According to an embodiment of the present invention, an initial core is tested to obtain a spectrum corresponding to the initial core, including: exciting the initial core with a radio frequency pulse to generate a magnetization signal; detecting multiple signal intensities corresponding to the magnetization signal at multiple time points, wherein the multiple signal intensities are inversely proportional to the multiple time points; and processing the initial signal corresponding to the multiple signal intensities using a preset conversion rule to obtain the spectrum.

[0067] According to an embodiment of the present invention, a method for generating a T2 spectrum of an initial core using nuclear magnetic resonance may include: placing the initial core in a strong magnetic field, using a radio frequency (RF) pulse to excite the nuclear spins in the initial core, for example, using a 90-degree pulse to deflect the spins from an equilibrium state to an xy plane; after excitation, the spin system may return to an equilibrium state, generating a transverse magnetization signal, which may decay over time to form a T2 relaxation process; different signal intensities may be obtained by applying different delay times (also called echo times); after obtaining signal intensity data at multiple echo times, the signal may be processed using Fourier transform to obtain a frequency spectrum of the time domain signal, and the T2 value may be calculated by fitting the decay curve of the signal (which may be an exponential decay); and then a T2 spectrum may be drawn based on the T2 value.

[0068] Figure 3 A schematic diagram of a core T2 spectrum according to an embodiment of the present invention is shown, wherein FIG. (a) shows a two-dimensional schematic diagram of the T2 spectrum, and FIG. (b) shows a three-dimensional schematic diagram of the T2 spectrum.

[0069] like Figure 3As shown, when the preset saturation is 100%, the area enclosed by the NMR transverse relaxation time T2 spectrum corresponding to the initial core and the horizontal axis of the reference axis of the spectrum can be taken as the initial peak area 310; when the target saturation is 60%, the target peak area 320 can be determined.

[0070] According to an embodiment of the present invention, nuclear magnetic resonance is a non-destructive testing technology that can minimize physical damage to core samples and preserve the original state and structure of the rock. Using nuclear magnetic resonance to obtain the T2 spectrum of the initial core can provide information such as the distribution and size of pores in the rock. By analyzing the T2 relaxation time, the pore structure characteristics of the rock can be inferred. At the same time, the T2 spectrum can distinguish the distribution of different types of fluids in the pores. This feature is of great significance for accurately evaluating the fluid saturation and fluidity of the reservoir, and a high-resolution T2 spectrum can be obtained in a relatively short time, quickly providing physical information of the core, which is suitable for the analysis of large-scale samples; when obtaining the T2 spectrum, the experimental conditions (such as temperature, pressure, magnetic field strength, etc.) can be adjusted according to actual needs to adapt to different experimental needs, with high flexibility.

[0071] According to an embodiment of the present invention, an initial signal represents a time domain signal corresponding to a time point; the initial signal corresponding to multiple signal intensities is processed using a preset conversion rule to obtain a spectrogram, including: converting the time domain signal using a preset conversion rule to obtain amplitude information and phase information corresponding to multiple frequencies; and generating a spectrogram based on the amplitude information and phase information.

[0072] According to an embodiment of the present invention, the preset conversion rules include but are not limited to Fourier transform and Z-transform. The specific conversion method can be determined according to actual needs.

[0073] In a feasible embodiment, a method for converting a time domain signal into a frequency domain signal using a fast Fourier transform may include: sampling the signal at a uniform time interval, and the sampling frequency should satisfy the Nyquist sampling theorem to avoid aliasing; the signal center may be set near zero, and the DC component may be removed to improve the clarity of the spectrum; before performing the fast Fourier transform, a window function (such as a Hanning window, a Hamming window, etc.) may be applied to reduce the signal boundary effect, thereby reducing spectrum leakage; the discrete signal is transformed using a Fourier transform, and the existing mathematical library may usually be used for calculation, and a set of complex numbers output by the Fourier transform may represent the amplitude and phase information of different frequency components; the amplitude of each frequency component is obtained by calculating the result of the complex output, and then the phase of each frequency component is obtained by calculating the phase of the complex output; and according to the sampling frequency and the number of points of the Fourier transform, a corresponding frequency axis is generated, and the amplitude spectrum and the phase spectrum are plotted to generate a spectrogram.

[0074] According to an embodiment of the present invention, the method further includes: processing the plurality of magnetization signals using reverse pulses so that the strength of the magnetization signals meets a preset detection requirement.

[0075] According to the embodiments of the present invention, considering that in signal detection, due to various factors (such as material absorption, scattering and other physical phenomena), the signal will attenuate over time, resulting in reduced detectability, the present invention can make the signal undergo a phase reversal by applying a reverse pulse, thereby offsetting the attenuation effect to some extent. After the reverse pulse is applied, the propagation process of the signal can generate an echo, resulting in a phase reversal of the signal; after a delay, the inverted signal can propagate again and return to the receiver, in which the echo signal is opposite in phase to the original signal, which helps to enhance detection.

[0076] According to the embodiments of the present disclosure, by processing multiple magnetization signals with reverse pulses, the signal strength can be improved and background noise can be suppressed to a certain extent. The reverse pulses interfere with the noise, so that the noise components in the signal are weakened, thereby improving the signal-to-noise ratio and the accuracy of detection.

[0077] Figure 4 A flow chart of another method for obtaining cores with different saturations based on nuclear magnetic resonance according to an embodiment of the present invention is shown.

[0078] like Figure 4 As shown, the method for acquiring cores with different saturations based on nuclear magnetic resonance in this embodiment may include operations S410 to S450.

[0079] In operation S410, an initial core is obtained. After the core to be tested is clamped by a clamp, a core displacement device is placed, confining pressure and back pressure are applied (to achieve a reservoir environment), and water is injected to saturate the core until it is completely saturated (initial saturation is 100%) to obtain an initial core.

[0080] In operation S420, the initial peak area is determined. After the water injection saturation is completed, the initial core can be subjected to a nuclear magnetic resonance test to obtain a nuclear magnetic resonance T2 spectrum of the fully saturated core, and based on the nuclear magnetic resonance T2 spectrum at this time, the peak area A0 (initial peak area) in the T2 spectrum is calculated.

[0081] In operation S430, the target peak area is determined. The peak area A1 of the core nuclear magnetic resonance T2 spectrum is determined according to the target saturation (for example, 60%) and the initial saturation as shown in the following formula (1):

[0082] (1);

[0083] Among them, SW It can represent the target saturation (for example, 60%), A0 can represent the initial peak area in the T2 spectrum when the initial saturation is 100%, and A1 can represent the target peak area in the T2 spectrum of the target saturation.

[0084] In operation S440, a nuclear magnetic resonance test is performed. Gas is injected into the core holder through a gas injection pump to perform a core displacement experiment, and a nuclear magnetic resonance test is performed on the initial core at the same time.

[0085] In operation S450, the target core is determined. As the core displacement experiment proceeds, the water inside the initial core is continuously driven out, and the initial peak area in the T2 spectrum is continuously reduced. When the peak area in the nuclear magnetic resonance T2 spectrum of the core is the target peak area A1, the gas injection is stopped, and the sample preparation is completed, thereby achieving the preparation of the core with an initial saturation of 60% of the rock voids in the reservoir environment.

[0086] Based on the above method for obtaining cores with different saturations based on nuclear magnetic resonance, the present invention also provides a device for obtaining cores with different saturations based on nuclear magnetic resonance. Figure 5 The device is described in detail.

[0087] Figure 5 A structural block diagram of a device for acquiring cores with different saturations based on nuclear magnetic resonance according to an embodiment of the present invention is shown.

[0088] like Figure 5 As shown, the device for acquiring cores with different saturations based on nuclear magnetic resonance in this embodiment includes a testing module 510 , a peak area determination module 520 , a detection module 530 and a determination module 540 .

[0089] The test module 510 is used to perform a nuclear magnetic resonance test on the initial core to obtain an initial peak area corresponding to the nuclear magnetic resonance spectrum, wherein the initial core represents the core obtained after the core to be tested is subjected to pressure and water injection treatment. In one embodiment, the test module 510 can be used to perform the operation S210 described above, which will not be repeated here.

[0090] The peak area determination module 520 is used to determine the target peak area based on the preset saturation and the initial peak area, wherein the preset saturation is determined based on the target saturation of the target rock, and the target rock represents the rock in the reservoir environment. In one embodiment, the peak area determination module 520 can be used to perform the operation S220 described above, which will not be repeated here.

[0091] The detection module 530 is used to detect the difference between the initial peak area and the target peak area when the gas is injected into the initial core, wherein the initial peak area is greater than the target peak area. In one embodiment, the detection module 530 can be used to perform the operation S230 described above, which will not be repeated here.

[0092] The determination module 540 is used to determine the target core based on the difference and the preset difference threshold. In one embodiment, the determination module 540 can be used to perform the operation S240 described above, which will not be described in detail here.

[0093] According to an embodiment of the present invention, through the testing module 510, the peak area determination module 520, the detection module 530 and the determination module 540 in the device for obtaining cores with different saturations based on nuclear magnetic resonance, the initial peak area corresponding to the initial core spectrum is obtained through nuclear magnetic resonance, so as to determine the target peak area based on the initial peak area and the preset saturation, and detect the difference between the initial peak area and the target peak area during the gas injection into the initial core, so as to obtain the target core. Since the initial core has been pressurized and water-injected, the target core obtained based on the initial core can meet the saturation requirements of the actual reservoir environment, avoiding the situation in which the accuracy of the target core acquisition result is low due to the failure to consider the water loss of the core in the traditional technology, and the nuclear magnetic resonance test minimizes the damage to the core, achieves non-destructive and sensitive detection, and meets the acquisition requirements of cores with different saturations in the actual environment.

[0094] According to an embodiment of the present invention, the initial core is obtained by the following operations: applying pressure to the core to be tested to obtain a pressure core that meets a preset pressure threshold, wherein the pressure treatment includes confining pressure treatment and back pressure treatment; and injecting water into the pressure core to obtain the initial core.

[0095] According to an embodiment of the present invention, the testing module 510 includes a core testing submodule and an initial peak area determination submodule.

[0096] The core test submodule is used to test the initial core and obtain the spectrum corresponding to the initial core.

[0097] The initial peak area determination submodule is used to determine the initial peak area based on the nuclear magnetic resonance spectrum and the reference axis corresponding to the spectrum.

[0098] According to an embodiment of the present invention, the detection module 530 includes a displacement processing submodule and a difference detection submodule.

[0099] The displacement treatment submodule is used to inject gas into the initial core using gas injection equipment to perform displacement treatment on the fluid in the initial core.

[0100] The difference detection submodule is used to detect the difference between the initial peak area and the target peak area during the displacement process.

[0101] According to an embodiment of the present invention, the device further comprises a sample generating module and a core processing module.

[0102] The sample generation module is used to process the target rock and generate a sample core that meets the preset size.

[0103] The core processing module is used to clean and dry the sample core with a cleaning agent to obtain the core to be tested.

[0104] According to an embodiment of the present invention, the core testing submodule includes a signal generating unit, an intensity detecting unit and a signal processing unit.

[0105] The signal generating unit is used to excite the initial core with radio frequency pulses to generate a magnetization signal.

[0106] The intensity detection unit is used to detect multiple signal intensities corresponding to the magnetization signal at multiple time points, wherein the multiple signal intensities are inversely proportional to the multiple time points.

[0107] The signal processing unit is used to process the initial signal corresponding to the multiple signal intensities using a preset conversion rule to obtain a spectrogram.

[0108] According to an embodiment of the present invention, the initial signal represents a time domain signal corresponding to a time point; the signal processing unit includes: a signal conversion subunit and a spectrogram generation subunit.

[0109] The signal conversion subunit is used to convert the time domain signal using a preset conversion rule to obtain amplitude information and phase information corresponding to multiple frequencies.

[0110] The spectrum generating subunit is used to generate a spectrum based on the amplitude information and the phase information.

[0111] According to an embodiment of the present invention, the device further includes: a magnetization signal processing module, which is used to process multiple magnetization signals using reverse pulses so that the intensity of the magnetization signals meets preset detection requirements.

[0112] According to an embodiment of the present invention, any multiple modules of the test module 510, the peak area determination module 520, the detection module 530 and the determination module 540 can be combined in one module for implementation, or any one of the modules can be split into multiple modules. Alternatively, at least part of the functions of one or more of these modules can be combined with at least part of the functions of other modules and implemented in one module. According to an embodiment of the present invention, at least one of the test module 510, the peak area determination module 520, the detection module 530 and the determination module 540 can be at least partially implemented as a hardware circuit, such as a field programmable gate array (FPGA), a programmable logic array (PLA), a system on a chip, a system on a substrate, a system on a package, an application specific integrated circuit (ASIC), or can be implemented by hardware or firmware such as any other reasonable way of integrating or packaging the circuit, or implemented in any one of the three implementation methods of software, hardware and firmware or in a suitable combination of any of them. Alternatively, at least one of the testing module 510, the peak area determination module 520, the detection module 530 and the determination module 540 may be at least partially implemented as a computer program module, which may perform a corresponding function when executed.

[0113] Figure 6 A block diagram of an electronic device suitable for implementing a method for acquiring cores with different saturations based on nuclear magnetic resonance according to an embodiment of the present invention is shown.

[0114] like Figure 6 As shown, the electronic device 600 according to an embodiment of the present invention includes a processor 601, which can perform various appropriate actions and processes according to a program stored in a read-only memory (ROM) 602 or a program loaded from a storage part 608 to a random access memory (RAM) 603. The processor 601 may include, for example, a general-purpose microprocessor (e.g., a CPU), an instruction set processor and / or a related chipset and / or a special-purpose microprocessor (e.g., an application-specific integrated circuit (ASIC)), etc. The processor 601 may also include an onboard memory for caching purposes. The processor 601 may include a single processing unit or multiple processing units for performing different actions of the method flow according to an embodiment of the present invention.

[0115] In RAM 603, various programs and data required for the operation of electronic device 600 are stored. Processor 601, ROM 602 and RAM 603 are connected to each other via bus 604. Processor 601 performs various operations of the method flow according to the embodiment of the present invention by executing the program in ROM 602 and / or RAM 603. It should be noted that the program can also be stored in one or more memories other than ROM 602 and RAM 603. Processor 601 can also perform various operations of the method flow according to the embodiment of the present invention by executing the program stored in the one or more memories.

[0116] According to an embodiment of the present invention, the electronic device 600 may further include an input / output (I / O) interface 605, which is also connected to the bus 604. The electronic device 600 may further include one or more of the following components connected to the input / output (I / O) interface 605: an input portion 606 including a keyboard, a mouse, etc.; an output portion 607 including a cathode ray tube (CRT), a liquid crystal display (LCD), etc., and a speaker, etc.; a storage portion 608 including a hard disk, etc.; and a communication portion 609 including a network interface card such as a LAN card, a modem, etc. The communication portion 609 performs communication processing via a network such as the Internet. A drive 610 is also connected to the input / output (I / O) interface 605 as needed. A removable medium 611, such as a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, etc., is installed on the drive 610 as needed, so that a computer program read therefrom is installed into the storage portion 608 as needed.

[0117] The present invention also provides a computer-readable storage medium, which may be included in the device / apparatus / system described in the above embodiment; or may exist independently without being assembled into the device / apparatus / system. The above computer-readable storage medium carries one or more programs, and when the above one or more programs are executed, the method according to the embodiment of the present invention is implemented.

[0118] According to an embodiment of the present invention, the computer-readable storage medium may be a non-volatile computer-readable storage medium, for example, it may include but is not limited to: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof. In the present invention, the computer-readable storage medium may be any tangible medium containing or storing a program, which may be used by or in combination with an instruction execution system, an apparatus or a device. For example, according to an embodiment of the present invention, the computer-readable storage medium may include the ROM 602 and / or RAM 603 described above and / or one or more memories other than ROM 602 and RAM 603.

[0119] The embodiment of the present invention also includes a computer program product, which includes a computer program, and the computer program contains program code for executing the method shown in the flowchart. When the computer program product is run in a computer system, the program code is used to enable the computer system to implement the method for obtaining cores with different saturations based on nuclear magnetic resonance provided by the embodiment of the present invention.

[0120] The computer program executes the above functions defined in the system / device of the embodiment of the present invention when it is executed by the processor 601. According to the embodiment of the present invention, the system, device, module, unit, etc. described above can be implemented by a computer program module.

[0121] In one embodiment, the computer program may rely on tangible storage media such as optical storage devices, magnetic storage devices, etc. In another embodiment, the computer program may also be transmitted and distributed in the form of signals on a network medium, and downloaded and installed through the communication part 609, and / or installed from a removable medium 611. The program code contained in the computer program may be transmitted using any appropriate network medium, including but not limited to: wireless, wired, etc., or any suitable combination of the above.

[0122] In such an embodiment, the computer program can be downloaded and installed from the network through the communication part 609, and / or installed from the removable medium 611. When the computer program is executed by the processor 601, the above functions defined in the system of the embodiment of the present invention are performed. According to the embodiment of the present invention, the system, device, means, module, unit, etc. described above can be implemented by a computer program module.

[0123] According to an embodiment of the present invention, the program code for executing the computer program provided by the embodiment of the present invention can be written in any combination of one or more programming languages. Specifically, these computing programs can be implemented using high-level process and / or object-oriented programming languages, and / or assembly / machine languages. Programming languages ​​include, but are not limited to, Java, C++, python, "C" language or similar programming languages. The program code can be executed entirely on the user computing device, partially on the user device, partially on the remote computing device, or entirely on the remote computing device or server. In the case of a remote computing device, the remote computing device can be connected to the user computing device through any type of network, including a local area network (LAN) or a wide area network (WAN), or can be connected to an external computing device (e.g., using an Internet service provider to connect through the Internet).

[0124] The flow chart and block diagram in the accompanying drawings illustrate the possible architecture, function and operation of the system, method and computer program product according to various embodiments of the present invention. In this regard, each box in the flow chart or block diagram can represent a module, a program segment, or a part of a code, and the above-mentioned module, program segment, or a part of a code contains one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram or flow chart, and the combination of the boxes in the block diagram or flow chart can be implemented with a dedicated hardware-based system that performs a specified function or operation, or can be implemented with a combination of dedicated hardware and computer instructions.

[0125] It will be appreciated by those skilled in the art that the features described in the various embodiments of the present invention may be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in the present invention. In particular, without departing from the spirit and teachings of the present invention, the features described in the various embodiments of the present invention may be combined and / or combined in various ways. All of these combinations and / or combinations fall within the scope of the present invention.

[0126] The embodiments of the present invention are described above. However, these embodiments are only for the purpose of illustration, and are not intended to limit the scope of the present invention. Although each embodiment is described above, it does not mean that the measures in each embodiment cannot be used in combination advantageously. Without departing from the scope of the present invention, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present invention.

Claims

1. A method for obtaining cores with different saturations based on nuclear magnetic resonance, characterized in that: The method comprises: Performing a nuclear magnetic resonance test on the initial core to obtain an initial peak area corresponding to the nuclear magnetic resonance spectrum, wherein the initial core represents a core obtained after the core to be tested is subjected to pressure and water injection treatment; Determining a target peak area based on a preset saturation and the initial peak area, wherein the preset saturation is determined based on a target saturation of a target rock, the target rock representing a rock in a reservoir environment; detecting a difference between the initial peak area and the target peak area when gas is injected into the initial core, wherein the initial peak area is greater than the target peak area; Based on the difference and a preset difference threshold, a target core is determined.

2. The method according to claim 1, characterized in that The initial core is obtained by the following operations: Applying pressure to the core to be tested to obtain a pressure core that meets a preset pressure threshold, wherein the pressure treatment includes confining pressure treatment and back pressure treatment; The pressure core is subjected to water injection treatment to obtain the initial core.

3. The method according to claim 1, characterized in that Perform NMR test on the initial core to obtain the initial peak area corresponding to the NMR spectrum, including: Testing the initial core to obtain a spectrum corresponding to the initial core; The initial peak area is determined based on the nuclear magnetic resonance spectrum and a reference axis corresponding to the spectrum.

4. The method according to claim 1, characterized in that: The difference between the initial peak area and the target peak area when the detection gas is injected into the initial core includes: Injecting gas into the initial core using a gas injection device to displace the fluid in the initial core; The difference between the initial peak area and the target peak area during the displacement process is detected.

5. The method according to claim 1, characterized in that The method further comprises: Processing the target rock to generate a sample core meeting a preset size; The sample core is cleaned and dried using a cleaning agent to obtain the core to be tested.

6. The method according to claim 3, characterized in that: The initial core is tested to obtain a spectrum corresponding to the initial core, including: Exciting the initial core with a radio frequency pulse to generate a magnetization signal; detecting a plurality of signal intensities corresponding to the magnetization signal at a plurality of time points, wherein the plurality of signal intensities are inversely proportional to the plurality of time points; The initial signals corresponding to the plurality of signal intensities are processed using a preset conversion rule to obtain the spectrogram.

7. The method according to claim 6, characterized in that The initial signal represents a time domain signal corresponding to a time point; The initial signals corresponding to the plurality of signal intensities are processed using a preset conversion rule to obtain the spectrogram, including: The time domain signal is converted using the preset conversion rule to obtain amplitude information and phase information corresponding to multiple frequencies; The spectrogram is generated based on the amplitude information and the phase information.

8. The method according to claim 6, characterized in that The method further comprises: The plurality of magnetization signals are processed by using reverse pulses so that the strength of the magnetization signals meets preset detection requirements.

9. A device for obtaining core samples with different saturations based on nuclear magnetic resonance, characterized in that: The device comprises: A testing module, used to perform a nuclear magnetic resonance test on an initial core to obtain an initial peak area corresponding to a nuclear magnetic resonance spectrum, wherein the initial core represents a core obtained after pressurizing and injecting water on the core to be tested; A peak area determination module, configured to determine a target peak area based on a preset saturation and the initial peak area, wherein the preset saturation is determined based on a target saturation of a target rock, the target rock representing a rock in a reservoir environment; a detection module, configured to detect a difference between the initial peak area and the target peak area when gas is injected into the initial core, wherein the initial peak area is greater than the target peak area; A determination module is used to determine the target core based on the difference and a preset difference threshold.

10. An electronic device, comprising: one or more processors; a memory for storing one or more computer programs, It is characterized in that the one or more processors execute the one or more computer programs to implement the steps of the method according to any one of claims 1 to 8.

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