Pore ​​size distribution test method, device, equipment and storage medium for core samples

Abstract

The present application provides a method, device, equipment, and storage medium for testing the pore size distribution of a core sample. The method includes: obtaining M groups of echo point signals of the core sample under M phase encoding gradients; the M is greater than or equal to the X; according to the M groups of echo point signals, obtaining the echo point signals corresponding to each layer of the core sample; according to the echo point signals corresponding to each layer of the core sample, obtaining the T2 relaxation spectrum corresponding to each layer of the core sample; according to the T2 relaxation spectrum corresponding to each layer of the core sample, obtaining the pore size distribution of each layer of the core sample. The method of the present application can obtain the pore size distribution of different layers of the core sample, making the description of the core sample information more accurate.

Description

Technical Field

[0001] The present application relates to the field of core testing technology, and in particular to a method, device, equipment, and storage medium for testing the pore size distribution of a core sample. Background Art

[0002] Core samples refer to cylindrical rock samples taken from rocks using annular core drill bits and other coring tools according to the needs of geological exploration. Core samples often have many pores inside, and the number distribution of pores of different sizes inside is called pore size distribution. The pore size distribution of core samples is important for oil and gas geological research, so it is necessary to test the pore size of core samples. Nuclear magnetic resonance technology is often used to study the pore size distribution of core samples.

[0003] In the prior art, when the core pore size distribution is tested by the nuclear magnetic resonance method, the core sample is often tested as a whole, so the test results obtained can only reflect the overall pore size distribution of the core sample. However, the overall pore size distribution of the core sample obtained by the above method often cannot truly reflect the core pore size distribution, and it is difficult to accurately describe the core information. Summary of the invention

[0004] The present application provides a method, device, equipment and storage medium for testing the pore size distribution of a core sample, so as to solve the problem that the overall pore size distribution of the core sample obtained by the prior art cannot truly reflect the core pore size distribution and is difficult to accurately describe the core information.

[0005] In a first aspect, the present application provides a method for testing the pore size distribution of a core sample, wherein the core sample comprises X layers distributed along an axial direction, wherein X is an integer greater than or equal to 2, and the method comprises:

[0006] Acquire M groups of echo point signals of the core sample under M phase encoding gradients; wherein M is greater than or equal to X;

[0007] According to the M groups of echo point signals, the echo point signals corresponding to each layer of the core sample are obtained;

[0008] According to the echo point signal corresponding to each layer of the core sample, a T2 relaxation spectrum corresponding to each layer of the core sample is obtained;

[0009] According to the T2 relaxation spectrum corresponding to each layer of the core sample, the pore size distribution of each layer of the core sample is obtained.

[0010] Optionally, acquiring M groups of echo point signals of the core sample under M phase encoding gradients includes:

[0011] Using the pulse sequence of the core sample, performing nuclear magnetic resonance testing on the core sample under M phase encoding gradients to obtain a group of echo point signals under each phase encoding gradient;

[0012] The pulse sequence is used to characterize the parameters used by the radio frequency channel, the parameters used by the phase encoding gradient channel, and the parameters used by the signal acquisition channel; the phase encoding gradient direction is the axial direction of the core sample.

[0013] Optionally, using the pulse sequence of the core sample to perform nuclear magnetic resonance testing on the core sample under M phase encoding gradients to obtain a set of echo point signals under each phase encoding gradient includes:

[0014] Using the pulse sequence of the core sample, perform the following operations M times:

[0015] Applying a radio frequency pulse of a first angle to the core sample on a radio frequency channel so that the macroscopic magnetization intensity vector of the core sample is in a transverse plane of the static magnetic field of the nuclear magnetic resonance instrument;

[0016] In the gradient channel, applying the corresponding phase encoding gradient to the core sample, so that the core sample is in the corresponding phase encoding gradient;

[0017] On the radio frequency channel, N second-angle radio frequency pulses are applied to the core sample respectively, and on the acquisition channel, the spin echo signals of the core sample corresponding to each second-angle radio frequency pulse are acquired respectively to obtain a group of echo point signals under the corresponding phase encoding gradient; the spin echo signals corresponding to the N second-angle radio frequency pulses constitute a group of echo point signals under the phase encoding gradient, and N is an integer greater than or equal to 1.

[0018] Optionally, the gradient field strength of the phase encoding gradient and the value of X are both negatively correlated with the thickness of each layer of the core sample.

[0019] Optionally, the method further includes:

[0020] receiving pulse sequence configuration information input by a user;

[0021] A pulse sequence of the core sample is generated according to the configuration information.

[0022] Optionally, acquiring the echo point signal corresponding to each layer of the core sample according to the M groups of echo point signals includes:

[0023] The M groups of echo point signals are subjected to Fourier transformation to obtain the echo point signal corresponding to each layer of the core sample.

[0024] Optionally, the method further includes:

[0025] Output the pore size distribution of each layer of the core sample.

[0026] In a second aspect, the present application provides a pore size distribution testing device for a core sample, wherein the core sample comprises X layers distributed along an axial direction, wherein X is an integer greater than or equal to 2, and the device comprises:

[0027] A first acquisition module is used to acquire M groups of echo point signals of the core sample under M phase encoding gradients; wherein M is greater than or equal to X;

[0028] The second acquisition module: acquires the echo point signal corresponding to each layer of the core sample according to the M groups of echo point signals;

[0029] The third acquisition module: acquiring the T2 relaxation spectrum corresponding to each layer of the core sample according to the echo point signal corresponding to each layer of the core sample;

[0030] The fourth acquisition module is to obtain the pore size distribution of each layer of the core sample according to the T2 relaxation spectrum corresponding to each layer of the core sample.

[0031] In a third aspect, the present application provides an electronic device, comprising: a processor, and a memory communicatively connected to the processor;

[0032] The memory stores computer-executable instructions;

[0033] The processor executes the computer-executable instructions stored in the memory to implement the method described in any one of the first aspects.

[0034] In a fourth aspect, the present application provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer-executable instructions, and when the computer-executable instructions are executed by a processor, they are used to implement the method described in any one of the first aspects.

[0035] In a fifth aspect, the present application provides a computer program product, comprising a computer program, which, when executed by a processor, implements the method as described in any one of the first aspects.

[0036] The core sample pore size testing method, device, equipment, and storage medium provided in the present application divide the core sample into different layers by applying a phase encoding gradient to the core sample, thereby achieving the effect of obtaining the pore size distribution of the core in different layers and more accurately describing the core sample information. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0038] Figure 1 A schematic diagram of a core sample provided in an embodiment of the present application;

[0039] Figure 2 A schematic diagram of a flow chart of a core sample pore size distribution testing method provided in an embodiment of the present application;

[0040] Figure 3 A schematic diagram of all echo point signals in a group M provided in an embodiment of the present application;

[0041] Figure 4 A schematic diagram of echo point signals of different layers of a core sample provided in an embodiment of the present application;

[0042] Figure 5 A schematic diagram of the T2 relaxation spectrum corresponding to each layer of a core sample provided in an embodiment of the present application;

[0043] Figure 6 A schematic diagram of the pore size distribution of each layer of a core sample provided in an embodiment of the present application;

[0044] Figure 7 A pulse sequence schematic diagram of a core sample provided in an embodiment of the present application;

[0045] Figure 8 A schematic diagram of another method for testing the pore size distribution of core samples provided in an embodiment of the present application;

[0046] Fig. 9 A schematic diagram of the structure of a pore size distribution testing device for a core sample provided in an embodiment of the present application;

[0047] Fig.10 A schematic structural diagram of a nuclear magnetic resonance apparatus 100 provided in an embodiment of the present application.

[0048] The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0049] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0050] In order to explain the present application more clearly, some of the terms involved in the present application are explained below.

[0051] Nuclear magnetic resonance: It is a physical process in which the spin energy level of an atomic nucleus with a non-zero magnetic moment undergoes Zeeman splitting under the action of an external magnetic field, and resonantly absorbs radio frequency radiation of a certain frequency. Nuclear magnetic resonance technology is based on this principle and is a technology that obtains electromagnetic signals of matter and then determines the structure of matter.

[0052] Nuclear magnetic resonance instrument: refers to a tool that uses nuclear magnetic resonance technology to conduct qualitative or quantitative analysis on the composition and structure of various organic and inorganic substances. It is also called a nuclear magnetic resonance spectrometer.

[0053] Phase encoding gradient: a gradient magnetic field used for phase encoding. Phase is the position of a wave in its cycle at a specific moment: a measure of whether it is at a crest, trough, or somewhere in between. The phase of the spin echo signal is different under different magnetic fields, so the phase encoding gradient is a gradient magnetic field that encodes the phase of the spin echo.

[0054] Pulse sequence: When using nuclear magnetic resonance technology to test materials, the settings of related parameters such as radio frequency pulses, gradient fields and signal acquisition time and their arrangement in time sequence are called the nuclear magnetic resonance pulse sequence.

[0055] Macroscopic magnetization vector: refers to the macroscopic description of all nuclear magnetic moment vectors within a unit volume. The nuclear magnetic moment is the vector sum of the orbital magnetic moment of all protons in the nucleus and the spin magnetic moment of all boxes.

[0056] Spin echo (SE) signal: It is a signal in the magnetic resonance phenomenon that uses spin echo as the source. It is the result of the interaction between the radio frequency pulse and the nuclear magnetic moment system in the static magnetic field. Two radio frequency pulses with appropriate widths (usually 90° and 180° radio frequency pulses) act on the nuclear magnetic moment system in the static magnetic field at a certain interval. After a period of time, an induction signal will appear in the signal acquisition channel. The interval between the signal and the second radio frequency pulse is exactly equal to the interval between the pulses, just like the echo of the pulse signal, so it is called a spin echo signal. The spin echo signal is a signal that grows back after the second radio frequency pulse by re-phase the de-phased magnetization vector.

[0057] Echo point signal: Each time point at which a spin echo signal is collected is called an echo point; the corresponding spin echo signal collected at an echo point is called an echo point signal. In this application, only the center value of the spin echo signal is collected at each echo point, so the echo point signal in this application is the center value of the spin echo signal of the echo point.

[0058] Dephase: that is, the atomic nuclei change from the same phase to different phases.

[0059] Re-phase: that is, eliminating the influence of the main magnetic field inhomogeneity on the phase loss of hydrogen protons, that is, changing the atomic nuclei from different phases to the same phase.

[0060] T2 relaxation time: also known as transverse relaxation time, which is the time required for the transverse magnetization vector to decay from the maximum value to 37% or the real value of the transverse magnetization vector to lose 63%. It is a characteristic quantity that characterizes how fast the transverse magnetization vector recovers to the equilibrium state. In nuclear magnetic resonance technology, the T2 relaxation time of a substance is an important parameter for describing the microstructure and dynamic process of the substance. The spectrum composed of T2 relaxation times corresponding to spin echo signals of different amplitudes is called the T2 relaxation spectrum.

[0061] The pore size distribution of core samples plays an important role in oil and gas geological research, so it needs to be tested. Nuclear magnetic resonance technology is often used to study the pore size distribution of core samples.

[0062] Core samples have certain heterogeneity, especially those with low porosity and low permeability, whose structures are chaotic and complex and whose layers are seriously superimposed. Therefore, the pore size distribution at different positions of core samples varies greatly.

[0063] However, in the prior art, when using nuclear magnetic resonance technology to test the core pore size, the core sample is often tested as a whole, and the pore size distribution reflecting the core sample as a whole is obtained. This processing method ignores the heterogeneity of the core sample, resulting in the pore size distribution obtained being unable to reflect the pore size variation law at different positions of the core sample, that is, unable to accurately reflect the difference in pore size inside the core sample, and thus unable to accurately describe the core sample information based on the pore size distribution.

[0064] Taking into account that the core sample has a certain degree of heterogeneity, the present application proposes a testing method that can obtain the pore size distribution at different positions of the core sample. This method applies a phase encoding gradient to the core sample, thereby achieving encoding of different positions of the core sample, and then achieving testing of the pore size distribution at different positions of the core sample.

[0065] The core sample of the present application is introduced below. The core sample of the present application includes X layers distributed along the axial direction, where X is an integer greater than or equal to 2. Among them, the thickness of each of the above X layers is equal. The thickness of each layer is determined according to the actual situation during the specific setting, so as to help describe the pore size distribution at different positions of the core sample. In addition, since the core sample is layered along the axial direction, and then the pore size distribution of each layer is obtained, it has its practical use significance. Therefore, the layering direction of the core sample in the present application is the axial direction of the core sample.

[0066] Figure 1 A schematic diagram of a core sample provided in an embodiment of the present application, such as Figure 1 As shown, the core sample includes 7 layers along the axial direction, and each layer has the same thickness. Correspondingly, the subsequent core sample pore size distribution test method provided in this application can obtain the corresponding Figure 1 The pore size distribution of each layer is shown.

[0067] The execution subject of the present application may be a nuclear magnetic resonance apparatus, or other equipment connected to the nuclear magnetic resonance apparatus, such as a host computer of the nuclear magnetic resonance apparatus, or a user terminal (such as a mobile phone, a tablet, a server), or a device deployed in the cloud, such as a server. The above connection method may be a wireless or wired connection.

[0068] The following embodiments illustrate the method for testing the pore size distribution of core samples. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0069] Figure 2 A schematic diagram of a core sample pore size distribution test method provided in an embodiment of the present application, such as Figure 2 As shown, the method includes:

[0070] S101, obtaining M groups of echo point signals of a core sample under M phase encoding gradients. The above M is greater than or equal to the above X, that is, the number of layers of the core sample.

[0071] The above phase encoding gradient and core sample are layered using the same thickness unit. For example, if the thickness of each layer of the core sample is 1 cm, the thickness of the corresponding phase encoding gradient layer is also 1 cm. After the phase encoding gradient processing, the magnetic field where the phase encoding gradient is located is divided into different layers, and the corresponding core sample is also divided into different layers along the axial direction according to the same layering unit mentioned above.

[0072] Each of the above-mentioned M phase encoding gradients has a constant amplitude.

[0073] The value of M is the number of echo point signals that need to be collected to fill the K space corresponding to the core sample under the phase encoding gradient. The above K space is also called Fourier space, which is the filling space of the original data of the nuclear magnetic resonance signal with spatial positioning encoding information.

[0074] Since the spin echo signal can characterize the internal structural characteristics of the core sample, it is necessary to collect the spin echo signal of the core sample to test its pore size distribution. In this step, the filling of the K space can be achieved by acquiring M groups of echo point signals under M phase encoding gradients. Subsequently, the acquisition of the pore size distribution of different layers of the core sample can be achieved based on the M groups of echo point signals filled in the K space. Any group of echo point signals in the above-mentioned M groups of echo point signals can be expressed as S_m(n, tau). Among them, m represents the group, 1≦m≦M; n represents the echo point; tau represents the time interval from the midpoint of the pulse that causes the macroscopic transverse magnetization vector to re-phase to the midpoint of the spin echo generation time.

[0075] When the execution subject is a nuclear magnetic resonance instrument, as a possible implementation method, the nuclear magnetic resonance instrument uses a pulse sequence of a core sample to perform nuclear magnetic testing on the core sample under M phase encoding gradients, and obtains a set of echo point signals under each phase encoding gradient, that is, obtains M groups of echo point signals of the core sample under M phase encoding gradients.

[0076] When the execution subject is other equipment connected to the nuclear magnetic resonance apparatus, as another possible implementation manner, the other equipment obtains M groups of echo point signals under M phase encoding gradients collected by the nuclear magnetic resonance apparatus.

[0077] Figure 3 A schematic diagram of M groups of all echo point signals provided in an embodiment of the present application, such as Figure 3 As shown, the ordinate is the amplitude of the collected M groups of echo point signals, and the abscissa is the number of signals with different amplitudes in the collected M groups of echo point signals.

[0078] S102. Acquire the echo point signal corresponding to each layer of the core sample according to the M groups of echo point signals.

[0079] For example, the M groups of echo point signals are subjected to Fourier transform to obtain the echo point signals corresponding to each layer of the core sample. The echo point signal corresponding to any layer can be expressed as ρ(z, n×tau), where z is the axial coordinate of the core sample.

[0080] As mentioned above, M is greater than or equal to X. When M is greater than X, it means that the number of layers of the phase encoding gradient is greater than the number of layers of the core sample. Therefore, among the layers of the phase encoding gradient corresponding to the M groups of echo point signals, there will be some layers without core samples. Therefore, the echo point signals corresponding to these layers are significantly different from the echo point signals corresponding to the layers with core samples. In addition, the phase encoding gradient and the core sample are layered using the same thickness unit. That is, in the layer with the core sample, each layer of the phase encoding gradient corresponds to a layer of the core sample. Therefore, by processing these groups of echo point signals, the echo point signals corresponding to each layer of the core sample can be extracted from these groups of echo point signals.

[0081] by Figure 1 As an example, assume that the core sample is divided into 7 layers after the phase encoding gradient is applied. Figure 2 The M groups of echo point signals shown are processed according to Fourier transform to obtain the echo point signals of all layers under the phase encoding gradient. Based on the logic described above, the echo point signals of each of the 7 layers of the core sample can be obtained from the M groups of echo point signals.

[0082] Figure 4 This is a schematic diagram of echo point signals of different layers of a core sample provided in an embodiment of the present application, wherein the horizontal axis is the echo point signal acquisition time, and the horizontal axis is the echo point signal amplitude. Figure 4 As shown, corresponding to Figure 1 , the echo point signals of selected layers 1-7 correspond to Figure 1 The stratification of the core sample shown. It should be noted that the stratification in the figure is equivalent to the stratification described in this application, and this application does not distinguish between them.

[0083] S103. Obtain a T2 relaxation spectrum corresponding to each layer of the core sample according to the echo point signal corresponding to each layer of the core sample.

[0084] As mentioned above, the center value of the spin echo signal at different echo points in this application is called the echo point signal. The spectrum formed by the T2 relaxation time corresponding to the spin echo signals of different amplitudes is the T2 relaxation spectrum. Figure 4 As shown, in this step, since the T2 relaxation spectrum corresponding to each layer of the core sample can reflect the pore size distribution of each layer of the core sample, and the echo point signal corresponding to each layer of the core sample carries the T2 relaxation spectrum information corresponding to each layer, the T2 relaxation spectrum corresponding to each layer of the core sample is obtained according to the echo point signal corresponding to each layer of the core sample. The T2 relaxation spectrum corresponding to any layer can be expressed as P(z, T 2 ). Among them, T 2 That is, it indicates that the type of relaxation spectrum is T2 relaxation spectrum. The specific implementation method is referred to the prior art and will not be described in detail here.

[0085] Continue to refer to the above Figure 4 The example shown, Figure 4 The echo point signal of each of the seven layers of the core sample can characterize the amplitude change of the echo point signal collected from different layers of the core sample at different time points. According to the definition of T2 relaxation time, this change carries the T2 relaxation time information of different layers of the core sample. Therefore, based on this, the T2 relaxation spectrum corresponding to each of the seven layers of the core sample can be obtained. For example, Figure 5 A schematic diagram of the T2 relaxation spectrum corresponding to each layer of a core sample provided in an embodiment of the present application, wherein the horizontal axis is the T2 relaxation time and the vertical axis is the amplitude of the echo point signal, based on Figure 4 The T2 relaxation spectrum corresponding to each layer can be obtained as follows Figure 5 shown.

[0086] It should be understood that the T2 relaxation spectrum corresponding to each layer of the core sample can also be called the T2 relaxation spectrum corresponding to the echo point signal of each layer of the core sample.

[0087] S104. Obtain the pore size distribution of each layer of the core sample according to the T2 relaxation spectrum corresponding to each layer of the core sample.

[0088] Different structures inside the material will lead to differences in the T2 relaxation time of its internal atomic nuclei, that is, the T2 relaxation time can reflect the internal structural information of the material. Therefore, in this step, the pore size distribution of each layer of the core sample is obtained according to the T2 relaxation spectrum corresponding to each layer of the core sample. Here, there is a corresponding functional relationship between the T2 relaxation spectrum and the pore size distribution, r=f(T2). Where r is the pore size of the core, and T2 represents the relaxation time. The functional relationship between the T2 relaxation time and the pore size r can be obtained by experiment, and the specific implementation details can refer to the prior art, which will not be repeated here.

[0089] For example, Figure 6 A schematic diagram of the pore size distribution of each layer of a core sample provided in an embodiment of the present application, wherein the abscissa represents the size of the pore size of the core sample, and the ordinate represents the number of pore sizes of different sizes. Figure 6 As shown, corresponding to the above step S103 Figure 5 The T2 relaxation spectra of the 7-layer core samples are shown, and the pore size distribution of the 7-layer core samples is obtained.

[0090] The present embodiment provides a method for testing the pore size distribution of a core sample, which obtains the echo point signals of the core sample under different phase encoding gradients to fill the K space corresponding to the core sample, and processes the above echo point signals using Fourier transform to determine the echo point signals of different layers of the core sample. Furthermore, the pore size distribution of different layers of the core sample is determined based on the echo point signals of different layers of the core sample. Compared with the prior art that simply obtains the pore size distribution of the core sample as a whole, the pore size distribution testing method of the core sample provided in the present embodiment can more accurately describe the pore size distribution of the core sample.

[0091] Optionally, after obtaining the pore size distribution of each layer of the core sample, the pore size distribution of each layer of the core sample can be output, or the description information of the core sample can be further obtained based on the pore size distribution of each layer of the core sample, or it can also be used in other scenarios that require the pore size distribution of the core sample.

[0092] Taking the output of pore size distribution as an example, when the execution subject is a nuclear magnetic resonance instrument, as a possible implementation method, the nuclear magnetic resonance instrument provides a display interface for outputting the pore size distribution of each layer of the core sample, and then the nuclear magnetic resonance instrument outputs the pore size distribution of each layer of the core sample to the display interface. When the execution subject is other equipment connected to the nuclear magnetic resonance instrument, as another possible implementation method, the above other equipment provides a display interface for outputting the pore size distribution of each layer of the core sample, and outputs the pore size distribution to the interface.

[0093] When the execution subject is a nuclear magnetic resonance instrument, the nuclear magnetic resonance instrument can use the pulse sequence of the core sample to perform nuclear magnetic test on the core sample under M phase encoding gradients to obtain a set of echo point signals under each phase encoding gradient. The implementation method of this part is described in detail below.

[0094] Among them, the pulse sequence is used to characterize the parameters used by the radio frequency (RF) channel, the parameters used by the phase encoding gradient (Gradient in Phase, GPHASE) channel, and the parameters used by the signal acquisition (Acquaredsignal, ACQ) channel; the phase encoding gradient direction is the axial direction of the core sample.

[0095] Figure 7 A pulse sequence diagram of a core sample provided in an embodiment of the present application. Figure 7 As shown in the figure, from top to bottom, they are the parameters used by the RF channel, GPHASE channel, and ACQ channel.

[0096] The parameters used by the RF channel may include, for example: the angle of the RF pulse (for example, the first angle and the second angle, the figure is a schematic diagram taking the first angle as 90° and the second angle as 180° as an example), the time interval for transmitting the RF pulse (for example, tau, 2tau), and the number of RF pulse transmissions N.

[0097] The parameters used by the GPHASE channel may include, for example, the gradient field strength G and the duration t of the phase encoding gradient.

[0098] The parameters used by the ACQ channel may include, for example: the duration t of each spin echo signal acquisition ACQ , the time interval between each spin echo signal acquisition is 2tau, and the number of spin echo signal acquisitions N.

[0099] Figure 8 A schematic diagram of another core sample pore size distribution test method provided in an embodiment of the present application. Figure 8 As shown, based on the above embodiment, this embodiment will be combined with Figure 7 The method of how to use the pulse sequence of the core sample to perform nuclear magnetic resonance testing on the core sample under M phase encoding gradients to obtain a group of echo point signals under each phase encoding gradient, that is, step S101 in the above embodiment, is described.

[0100] The above-mentioned nuclear magnetic resonance testing of the core sample under M phase encoding gradients is achieved by changing the value of the gradient field strength G to change the phase encoding gradient. The gradient field strength G of the phase encoding gradient, and the number of layers X of the core sample distributed along the axial direction, are negatively correlated with the thickness of each layer of the core sample. That is, the larger the value of G, the larger the number of layers X of the core sample distributed along the axial direction, and the smaller the thickness of each layer of the core sample. It should be noted that the method of obtaining a set of echo point signals under each phase encoding gradient using the pulse sequence of the core sample is the same, and the only difference is the change of the phase encoding gradient. Therefore, the following is explained by taking one of them as an example. Step S101 may include the following steps:

[0101] Using the pulse sequence of the core sample, perform the following operation M times:

[0102] S201. In a radio frequency channel, applying a radio frequency pulse of a first angle to a core sample so that the macroscopic magnetization intensity vector of the core sample is in a transverse plane of the nuclear magnetic resonance instrument.

[0103] Continue to refer to Figure 7 The above-mentioned first-angle radio frequency pulse can be a 90° radio frequency pulse.

[0104] The direction of the external magnetic field B0 provided by the nuclear magnetic resonance instrument is the longitudinal plane, and when no radio frequency pulse is applied, the macroscopic magnetization intensity vector of the core sample is in the longitudinal plane. In this step, after applying a 90° radio frequency pulse to the core sample on the radio frequency channel, the macroscopic magnetization intensity vector of the core sample is in the transverse plane of the nuclear magnetic resonance instrument.

[0105] It should be noted that the present application does not limit the properties of the 90° RF pulse. The 90° RF pulse can be a shapeless hard pulse or a soft pulse, and those skilled in the art can set it according to actual needs.

[0106] When the 90° RF pulse is a shapeless hard pulse, the present application has a better effect when applied to the test of the pore size distribution of dense cores, and can retain more information compared to a soft pulse.

[0107] like Figure 7 As shown, the duration of the above 90° RF pulse is t 90 The 90 That is, the 90° excitation time, that is, the time required for the macroscopic magnetization intensity vector of the core sample to be in the transverse plane. 90 For example, it can be 1 second or more than ten microseconds. This time depends on the performance of the nuclear magnetic resonance instrument used, and this application does not limit it.

[0108] S202. In the gradient channel, applying the corresponding phase encoding gradient to the core sample, so that the core sample is in the corresponding phase encoding gradient.

[0109] In this step, by applying a phase encoding gradient, the encoding of different positions of the core sample can be achieved, and the stratification unit of the core sample corresponding to the phase encoding gradient is also divided into different layers, and finally the pore size distribution of different positions, i.e., different layers of the core sample can be tested. Optionally, the amplitude G of the above-mentioned phase encoding gradient ranges from 10 to 300 milliteslas / meter (mT / m). In actual application, those skilled in the art can set it according to actual conditions, and this application does not limit it. The phase encoding gradient changes according to a fixed amplitude.

[0110] In this step, the phase encoding gradient climbs to a preset amplitude of the gradient field strength G and lasts for a period of time t, and then the gradient is turned off. The above t can be, for example, 100 microseconds or 200 microseconds, which is not limited in this application.

[0111] In this step, due to the application of the phase encoding gradient, the rotation speeds of the atomic nuclei under different magnetic field strengths in the magnetic field are different, resulting in phase loss.

[0112] S203, on the radio frequency channel, apply N second-angle radio frequency pulses to the core sample respectively, and on the acquisition channel, collect the spin echo signals of the core sample corresponding to each second-angle radio frequency pulse respectively, to obtain a group of echo point signals under the corresponding phase encoding gradient; the spin echo signals corresponding to the above-mentioned N second-angle radio frequency pulses constitute a group of echo point signals under the phase encoding gradient, and N is an integer greater than or equal to 1.

[0113] In this step, the purpose of looping the above operation N times is to obtain a higher signal-to-noise ratio to make the test result more accurate.

[0114] The following is an example of applying a second-angle radio frequency pulse to a core sample and collecting the echo point signal:

[0115] like Figure 7 As shown, the radio frequency pulse of the second angle may be a 180° radio frequency pulse. By applying the 180° radio frequency pulse, the macroscopic magnetization intensity vector in the transverse plane is re-phased.

[0116] Continue to refer to Figure 7 The duration of the 180° RF pulse is t 180 The 180 That is, the 180° excitation time, i.e., the time required for the macroscopic magnetization intensity vector of the core sample to re-phase. 180 For example, it can be 1 second or more than ten microseconds. This time depends on the performance of the nuclear magnetic resonance instrument used, and this application does not limit it.

[0117] It should be noted that the present application does not limit the properties of the 180° RF pulse. The 180° RF pulse can be a shapeless hard pulse or a soft pulse, and those skilled in the art can set it according to actual needs.

[0118] When the 180° RF pulse is a shapeless hard pulse, the present application has a better effect when applied to the test of the pore size distribution of dense cores, and can retain more core sample information compared to soft pulses.

[0119] It should be noted that if Figure 7 As shown, from the above step S201, the duration of the RF pulse at the first angle applied to the core sample on the RF channel, that is, the excitation time t of 90° 90 Starting from the center moment of the step, in this step, the duration of the second angle RF pulse applied to the core sample on the RF channel, that is, the excitation time t of 180° 180 The duration is tau until the central moment of

[0120] tau=t90 / 2+t+t 180 / 2

[0121] The above t is the duration after the phase encoding gradient climbs to the preset gradient field strength amplitude G.

[0122] like Figure 7 As shown in the figure, after applying a 180° RF pulse to the core sample, the spin echo signal is collected on the ACQ acquisition channel, and the signal acquisition duration is t ACQ , the t ACQ For example, the value of 5 Microseconds and 1 second are not limited in this application.

[0123] The above-mentioned spin echo signal is the nuclear magnetic resonance spin echo signal of the core sample, which is generated by the 90° radio frequency pulse and the 180° radio frequency pulse acting on the hydrogen-containing proton spin system of the sample. The amplitude value of the spin echo signal has the characteristic of changing from weak to strong and then to weak.

[0124] It should be noted that if Figure 7 As shown, from this step, the duration of the second angle RF pulse applied to the core sample on the RF channel, that is, the excitation time t of 180° 180 Starting from the center moment of the acquisition, the duration of the acquisition of the spin echo signal on the ACQ acquisition channel in this step is t ACQ The duration is tau until the center moment of .

[0125] The above signal acquisition method is discrete acquisition, and the phase sequence only stores the signal center value.

[0126] At this point, a second-angle RF pulse is applied to the core sample once, and the echo point signal is collected. Repeat the above process N times, that is, N second-angle RF pulses are completed, and the spin echo signal of the core sample corresponding to each second-angle RF pulse is collected on the collection channel.

[0127] It should be noted that if Figure 7 As shown, in the above N repeated cycles, the cycle time interval of the 180° radio frequency pulse cyclically applied on the RF radio frequency channel is 2tau; the cycle time interval of the spin echo signal cyclically collected on the ACQ acquisition channel is 2tau.

[0128] In this step, N-point spin echo signals are acquired in sequence on the ACQ acquisition channel, and the time interval of the discrete signal at each point is 2tau.

[0129] In the ACQ acquisition channel, a group of echo point signals S_1 (n, tau) is obtained, where 1 represents the group, that is, the first group of echo point signals; 1≤n≤N.

[0130] At this point, executing S201-S203 completes the nuclear magnetic resonance test of the core sample under one phase encoding gradient. After executing step S203, you can return to executing step S201 to perform nuclear magnetic resonance testing on the core sample under the next phase encoding gradient until the nuclear magnetic resonance testing of the core sample under M phase encoding gradients is completed.

[0131] The pore size distribution test method of the core sample provided in this embodiment realizes encoding of different positions of the core sample by applying a phase encoding gradient, that is, dividing the core sample into different layers. Subsequently, by acquiring the spin echo signal of the core sample under different phase encoding gradients and performing multiple cyclic acquisition of the spin echo signal under each phase encoding gradient, not only the pore size distribution of different positions of the core sample can be obtained, but also the obtained result can be guaranteed to have a high signal-to-noise ratio.

[0132] It should be noted that the pulse sequence used by the aforementioned nuclear magnetic resonance apparatus to obtain the above-mentioned M groups of echo point signals can be pre-set in the nuclear magnetic resonance apparatus, or sent to the nuclear magnetic resonance apparatus by the host computer of the nuclear magnetic resonance apparatus, or sent to the nuclear magnetic resonance apparatus by other devices connected to the nuclear magnetic resonance apparatus, or generated by the nuclear magnetic resonance apparatus based on the pulse sequence configuration information received from the user.

[0133] Among them, the pulse sequence configuration information includes the parameters used by the above-mentioned radio frequency channel, the parameters used by the phase encoding gradient channel, and the parameters used by the signal acquisition channel. Exemplarily, as a possible implementation method, the nuclear magnetic resonance apparatus provides an operation interface to receive the pulse sequence configuration information input by the user through the operation interface. It should be noted that since the generated pulse sequence includes the setting of the phase encoding gradient, the phase pulse sequence of this application is also called the phase pulse sequence.

[0134] It should be noted that, compared with the prior art, the present application can more accurately describe the pore size information of dense cores. This is mainly reflected in the following two aspects:

[0135] First aspect:

[0136] Due to its low porosity, low permeability, high clay content, and mainly small pore distribution, the spin echo signal excited in the saturated fluid state has low amplitude and extremely fast decay (i.e., short relaxation time). Therefore, in the pore size distribution test of dense core, a large echo interval (i.e., the above-mentioned tau) will lose most of the spin echo signals in the dense core, resulting in inaccurate data analysis of the dense core.

[0137] The pore size distribution test method for core samples provided in the present application can achieve a smaller tau value, ensuring that most of the spin echo signals are not lost during the spin echo signal acquisition process, thereby ensuring the accuracy of the final dense core pore size distribution results.

[0138] Second aspect: dense cores are highly heterogeneous, and the pore size distribution at different locations varies greatly. The prior art only obtains the overall pore size distribution of dense cores, and the information description of dense cores is not accurate enough. The core sample pore size testing method provided in this application can test the pore size distribution of different layers of dense cores, and can more accurately describe the information of dense cores.

[0139] When the present application is applied to the pore size distribution test of dense core samples, the first angle radio frequency pulse and the second angle radio frequency pulse in the above embodiments are shapeless hard pulses.

[0140] Fig. 9 A schematic diagram of a pore size distribution testing device for a core sample provided in an embodiment of the present application. The core sample comprises X layers distributed along the axial direction, where X is an integer greater than or equal to 2.

[0141] like Fig. 9 As shown, the pore size distribution testing device for core samples includes: a first acquisition module 11 , a second acquisition module 12 , a third acquisition module 13 , and a fourth acquisition module 14 .

[0142] Optionally, the core sample pore size distribution testing device may include, for example, at least one of the following modules: a receiving module 15 , a generating module 16 , and an output module 17 .

[0143] The first acquisition module 11 is used to acquire M groups of echo point signals of the core sample under M phase encoding gradients; the M is greater than or equal to the X.

[0144] The second acquisition module 12 is used to acquire the echo point signal corresponding to each layer of the core sample according to the M groups of echo point signals.

[0145] The third acquisition module 13 is used to acquire the T2 relaxation spectrum corresponding to each layer of the core sample according to the echo point signal corresponding to each layer of the core sample.

[0146] The fourth acquisition module 14 is used to obtain the pore size distribution of each layer of the core sample according to the T2 relaxation spectrum corresponding to each layer of the core sample.

[0147] As a possible implementation method, the first acquisition module 11 is specifically used to use the pulse sequence of the core sample to perform nuclear magnetic resonance testing on the core sample under M phase encoding gradients to obtain a group of echo point signals under each phase encoding gradient; wherein the pulse sequence is used to characterize the parameters used by the radio frequency channel, the parameters used by the phase encoding gradient channel, and the parameters used by the signal acquisition channel; the phase encoding gradient direction is the axial direction of the core sample.

[0148] As a possible implementation, the first acquisition module 11 is specifically configured to use the pulse sequence of the core sample to perform the following operations M times:

[0149] Applying a radio frequency pulse of a first angle to the core sample on a radio frequency channel so that the macroscopic magnetization intensity vector of the core sample is in a transverse plane of the static magnetic field of the nuclear magnetic resonance instrument;

[0150] In the gradient channel, applying the corresponding phase encoding gradient to the core sample, so that the core sample is in the corresponding phase encoding gradient;

[0151] On the radio frequency channel, N second-angle radio frequency pulses are applied to the core sample respectively, and on the acquisition channel, the spin echo signals of the core sample corresponding to each second-angle radio frequency pulse are acquired respectively to obtain a group of echo point signals under the corresponding phase encoding gradient; the spin echo signals corresponding to the N second-angle radio frequency pulses constitute a group of echo point signals under the phase encoding gradient, and N is an integer greater than or equal to 1.

[0152] As a possible implementation manner, the gradient field strength of the phase encoding gradient and the value of X are negatively correlated with the thickness of each layer of the core sample.

[0153] As a possible implementation, the receiving module 15 is used to receive the pulse sequence configuration information input by the user; the generating module 16 is used to generate the pulse sequence of the core sample according to the configuration information received by the receiving module 15 .

[0154] As a possible implementation manner, the second acquisition module 12 is specifically used to perform Fourier transform on the M groups of echo point signals to obtain the echo point signal corresponding to each layer of the core sample.

[0155] As a possible implementation, the output module 17 is used to output the pore size distribution of each layer of the core sample.

[0156] The pore size distribution test device for core samples provided in the embodiment of the present application can execute the pore size distribution test method for core samples in the above method embodiment, and its implementation principle and technical effect are similar, which will not be repeated here. In specific implementation, it can be a nuclear magnetic resonance instrument, or a chip (such as a processor) of a nuclear magnetic resonance instrument, or other equipment connected to the nuclear magnetic resonance instrument, or a chip (such as a processor) of other equipment connected to the nuclear magnetic resonance instrument, etc.

[0157] Fig.10 FIG. 1 is a schematic diagram of the structure of an electronic device 100 provided in an embodiment of the present application. Fig.10 As shown, the electronic device 100 may include: at least one processor 101 and a memory 102 .

[0158] It should be noted that the electronic device may also be a nuclear magnetic resonance apparatus. When the electronic device is a nuclear magnetic resonance apparatus, it also includes hardware equipment for implementing the nuclear magnetic resonance test in the above embodiment.

[0159] The memory 102 is used to store programs. Specifically, the programs may include program codes, and the program codes include computer operation instructions.

[0160] The memory 102 may include a high-speed RAM memory, and may also include a non-volatile memory, such as at least one disk memory.

[0161] The processor 101 is used to execute the computer execution instructions stored in the memory 102 to implement the pore size distribution test method of the core sample described in the above method embodiment. The processor 101 may be a central processing unit (CPU), or an application specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present application.

[0162] The electronic device 100 may also include a communication interface 103, so that it can communicate and interact with external devices through the communication interface 103. The external device may be, for example, the aforementioned nuclear magnetic resonance apparatus, as well as other devices connected to the nuclear magnetic resonance apparatus. In specific implementation, if the communication interface 103, the memory 102 and the processor 101 are implemented independently, the communication interface 103, the memory 102 and the processor 101 may be interconnected through a bus and complete mutual communication. The bus may be an Industry Standard Architecture (ISA) bus, a Peripheral Component (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. The bus may be divided into an address bus, a data bus, a control bus, etc., but it does not mean that there is only one bus or one type of bus.

[0163] Optionally, in a specific implementation, if the communication interface 103, the memory 102 and the processor 101 are integrated on a chip, the communication interface 103, the memory 102 and the processor 101 can communicate through an internal interface.

[0164] The present application also provides a computer-readable storage medium, which may include: a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a disk or an optical disk, and other media that can store program codes. Specifically, the computer-readable storage medium stores program instructions, and the program instructions are used for the methods in the above embodiments.

[0165] The present application also provides a program product, which includes an execution instruction, which is stored in a readable storage medium. At least one processor of a computing device can read the execution instruction from the readable storage medium, and at least one processor executes the execution instruction so that the electronic device implements the pore size distribution test method of the core sample provided by the various embodiments described above.

[0166] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the invention disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary techniques in the art that are not disclosed in the present application. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present application are indicated by the following claims.

[0167] It should be understood that the present application is not limited to the precise structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. A method for testing the pore size distribution of a core sample, characterized in that: The core sample comprises X layers distributed along the axial direction, wherein X is an integer greater than or equal to 2, and the method comprises: Acquire M groups of echo point signals of the core sample under M phase encoding gradients; wherein M is greater than or equal to X; According to the M groups of echo point signals, the echo point signals corresponding to each layer of the core sample are obtained; According to the echo point signal corresponding to each layer of the core sample, a T2 relaxation spectrum corresponding to each layer of the core sample is obtained; Obtaining the pore size distribution of each layer of the core sample according to the T2 relaxation spectrum corresponding to each layer of the core sample; The step of obtaining M groups of echo point signals of the core sample under M phase encoding gradients includes: Using the pulse sequence of the core sample, performing nuclear magnetic resonance testing on the core sample under M phase encoding gradients to obtain a group of echo point signals under each phase encoding gradient; The pulse sequence is used to characterize the parameters used by the radio frequency channel, the parameters used by the phase encoding gradient channel, and the parameters used by the signal acquisition channel; the phase encoding gradient direction is the axial direction of the core sample; The method of using the pulse sequence of the core sample to perform nuclear magnetic resonance testing on the core sample under M phase encoding gradients to obtain a group of echo point signals under each phase encoding gradient includes: Using the pulse sequence of the core sample, perform the following operations M times: Applying a radio frequency pulse of a first angle to the core sample on a radio frequency channel so that the macroscopic magnetization intensity vector of the core sample is in a transverse plane of the static magnetic field of the nuclear magnetic resonance instrument; In the gradient channel, applying the corresponding phase encoding gradient to the core sample, so that the core sample is in the corresponding phase encoding gradient; On the radio frequency channel, N second-angle radio frequency pulses are applied to the core sample respectively, and on the acquisition channel, the spin echo signal of the core sample corresponding to each second-angle radio frequency pulse is acquired respectively to obtain a group of echo point signals under the corresponding phase encoding gradient; the echo point signals corresponding to the N second-angle radio frequency pulses constitute a group of echo point signals under the phase encoding gradient, and N is an integer greater than or equal to 1.

2. The method according to claim 1, characterized in that: The gradient field intensity of the phase encoding gradient and the value of X are both negatively correlated with the thickness of each layer of the core sample.

3. The method according to claim 1, characterized in that The method further comprises: receiving pulse sequence configuration information input by a user; A pulse sequence of the core sample is generated according to the configuration information.

4. The method according to any one of claims 1 to 3, characterized in that: The step of obtaining the echo point signal corresponding to each layer of the core sample according to the M groups of echo point signals includes: The M groups of echo point signals are subjected to Fourier transformation to obtain the echo point signal corresponding to each layer of the core sample.

5. The method according to any one of claims 1 to 3, characterized in that: The method further comprises: Output the pore size distribution of each layer of the core sample.

6. A pore size distribution testing device for core samples, characterized in that: The core sample comprises X layers distributed along the axial direction, wherein X is an integer greater than or equal to 2, and the device comprises: A first acquisition module is used to acquire M groups of echo point signals of the core sample under M phase encoding gradients; wherein M is greater than or equal to X; The second acquisition module is used to acquire the echo point signal corresponding to each layer of the core sample according to the M groups of echo point signals; The third acquisition module is used to acquire the T2 relaxation spectrum corresponding to each layer of the core sample according to the echo point signal corresponding to each layer of the core sample; The fourth acquisition module is used to obtain the pore size distribution of each layer of the core sample according to the T2 relaxation spectrum corresponding to each layer of the core sample; The first acquisition module is specifically used to use the pulse sequence of the core sample to perform nuclear magnetic resonance testing on the core sample under M phase encoding gradients to obtain a group of echo point signals under each phase encoding gradient; wherein the pulse sequence is used to characterize the parameters used by the radio frequency channel, the parameters used by the phase encoding gradient channel, and the parameters used by the signal acquisition channel; the phase encoding gradient direction is the axial direction of the core sample; The first acquisition module is specifically used to use the pulse sequence of the core sample to perform the following operations M times: on the radio frequency channel, applying a radio frequency pulse of a first angle to the core sample, so that the macroscopic magnetization intensity vector of the core sample is in the transverse plane of the static magnetic field of the nuclear magnetic resonance instrument; on the gradient channel, applying the corresponding phase encoding gradient to the core sample, so that the core sample is in the corresponding phase encoding gradient; on the radio frequency channel, applying N radio frequency pulses of a second angle to the core sample respectively, and on the acquisition channel, respectively acquiring the spin echo signal of the core sample corresponding to each radio frequency pulse of the second angle, to obtain a group of echo point signals under the corresponding phase encoding gradient; the echo point signals corresponding to the N radio frequency pulses of the second angle constitute a group of echo point signals under the phase encoding gradient, and N is an integer greater than or equal to 1.

7. An electronic device, characterized in that: include: A processor, and a memory communicatively connected to the processor; The memory stores computer-executable instructions; The processor executes the computer-executable instructions stored in the memory to implement the method according to any one of claims 1 to 5.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions, which are used to implement the method according to any one of claims 1 to 5 when executed by a processor.

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