A rock sample measurement system and measurement method with spatial selectivity

Abstract

The present invention discloses a rock sample measurement system and method with spatial selectivity. The present invention can obtain sampling signals of the rock sample at multiple angles. At the same time, the present invention has spatial selectivity during the rock sample measurement process and can select a rock mass area on the rock sample that does not have defects. In this way, by combining the multi-angle sampling signals and the selected rock mass area, a true rock sample signal of the rock mass area on the rock sample that does not have defects can be obtained. Finally, based on the true rock sample signal, the physical property parameters of the rock sample can be obtained. Therefore, the present invention avoids the influence of rock sample surface defects on the measurement signal, can obtain more accurate rock physical property parameter measurement results, and is suitable for large-scale application and promotion in the field of rock sample measurement.

Description

Technical Field

[0001] The present invention belongs to the field of nuclear magnetic resonance technology, and in particular relates to a rock sample measurement system and a measurement method with spatial selectivity. Background Art

[0002] As the exploration and development focus of the oil and gas industry shifts from conventional reservoirs to unconventional reservoirs, a comprehensive understanding of the rock properties and microstructure of unconventional reservoirs is of great significance for implementing efficient production construction, production increase, and production stabilization measures. Faced with the problems of diversified oil and gas storage space and the complexity of the seepage mechanism of fluids in porous rock media, traditional rock property testing and static rock microstructure description can no longer meet the research needs of oil and gas seepage and reservoir production increase. Nuclear magnetic resonance technology (NMR) is non-destructive and harmless. It can directly reflect the distribution of rock pore fluids and indirectly reflect changes in rock pore structure through resonance signals. Therefore, it has outstanding advantages in rock physical testing, pore structure characterization, and pore fluid identification.

[0003] Nuclear magnetic resonance (NMR) is sensitive to fluids and their occurrence in porous rocks, and can provide information such as oil and gas content and their occurrence. Among them, rock physical parameters are one of the important parameters for understanding the oil and gas storage conditions of oil and gas layers, dividing the physical boundaries of main layers, effective reservoirs and interlayers, and evaluating reservoirs and calculating oil and gas reserves. Therefore, NMR rock physics is an important method for oil and gas detection and has been widely used.

[0004] Existing nuclear magnetic resonance logging technologies mainly include downhole detectors and laboratory benchtop nuclear magnetic resonance instruments. Among them, downhole detectors can test in-situ cores at the bottom of the well and move to measure the physical properties of cores in different layers. However, due to hardware limitations, the logging instruments have low accuracy and low vertical resolution (generally greater than 0.5m), which can no longer meet the perforation requirements of the well site.

[0005] Laboratory benchtop nuclear magnetic resonance (NMR) instruments can be used to detect full-size rock cores, with short echo times and high test accuracy. They can also be used in conjunction with trend replacement equipment for multi-dimensional measurements. However, due to the limited effective signal receiving range of the radio frequency coil of the NMR instrument, the core samples need to be truncated. The longest sample length that can be collected cannot exceed the effective signal receiving range of the radio frequency coil. This will make it impossible to meet the needs of long-length coring sampling. Based on this, wellside core magnetic resonance measurement equipment that can measure long-length rock cores has appeared on the market. It moves the rock core through a transmission device and measures various positions of the rock core, thereby improving the vertical resolution to the level of several centimeters.

[0006] However, existing near-hole core measurement devices have the following problems: the surface of the core is easily contaminated by mud and oil, and the surface oil and gas are easily volatilized due to the huge difference in surface temperature and air pressure compared to the wellbore, and the surface of the core is easily damaged. At the same time, to prevent damage to the structure, the core cannot be processed and sampled during near-hole testing. Therefore, when performing core nuclear magnetic resonance measurements, the existing near-hole core measurement devices are easily affected by defects on the core surface, making it impossible to obtain a true rock sample signal, which in turn leads to inaccurate measurement results of the rock sample physical properties. Based on this, how to provide a rock sample measurement system and method that is not affected by defects on the core surface and can accurately obtain the true rock core signal has become an urgent problem to be solved. Summary of the Invention

[0007] The purpose of the present invention is to provide a rock sample measurement system and measurement method with spatial selectivity, so as to solve the problem that the existing technology is easily affected by defects on the surface of the core during core nuclear magnetic resonance measurement, thereby failing to obtain a true rock sample signal, and further leading to inaccurate measurement results of rock sample physical properties parameters.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] In a first aspect, a rock sample measurement system with spatial selectivity is provided, comprising:

[0010] A static magnetic field generating device, a gradient magnetic field generating device and a nuclear magnetic resonance device, wherein the static magnetic field generating device is used to generate a uniform static magnetic field, and the nuclear magnetic resonance device is electrically connected to the gradient magnetic field generating device;

[0011] The nuclear magnetic resonance device is used to control the gradient magnetic field generating device to generate a gradient magnetic field in at least one direction within the cross section of the rock sample to be measured, wherein the gradient magnetic field is located within the static magnetic field, and the rock sample to be measured is located within the gradient magnetic field;

[0012] The nuclear magnetic resonance device is used to transmit a pulse signal to the rock sample to be tested in each sampling period, and receive a plurality of echo signals generated by the rock sample to be tested when excited by the pulse signal, so as to form a sampling signal corresponding to each sampling period using the plurality of echo signals received in each sampling period, wherein the magnetic field direction of the gradient magnetic field in which the rock sample to be tested is located is different in different sampling periods, or the acquisition angle of the rock sample to be tested in the gradient magnetic field is different;

[0013] The nuclear magnetic resonance device is further used to send each sampling signal to a workstation;

[0014] The workstation is configured to obtain a cross-sectional image of the rock sample to be tested, and determine a region of interest from the cross-sectional image, wherein the region of interest is a region in the cross-sectional image where a cross section of a rock mass without defects in the rock sample to be tested is located;

[0015] The workstation is configured to obtain a first projection matrix, wherein the elements of the first projection matrix include a projection line of each projection data corresponding to each sampling signal, a length passing through a region of interest, and a length of each pixel point in a non-interest region, the projection data of any sampling signal being obtained based on each echo signal within the any sampling signal, and the non-interest region being a region in the cross-sectional image excluding the region of interest;

[0016] The workstation is further configured to generate a real rock sample signal of a rock mass without defects in the rock sample to be tested using each sampling signal and the first projection matrix, and obtain rock physical parameters of the rock sample to be tested based on the real rock sample signal.

[0017] Based on the above disclosure, the present invention adds a gradient magnetic field generating device to the traditional wellside core measurement device, wherein the gradient magnetic field generating device is used to generate a gradient magnetic field in at least one direction within the cross section of the rock sample; in this way, the nuclear magnetic resonance signal of the rock sample to be measured at different angles can be collected by adjusting the acquisition angle of the rock sample to be measured in the gradient magnetic field, or the magnetic field direction of the gradient magnetic field (equivalent to the different acquisition angles corresponding to the rock sample to be measured in each sampling period, or the different magnetic field directions of the gradient magnetic field); at the same time, the present invention excites and collects multiple echo signals at one time within a sampling period, and based on this, composes the sampling signal within the sampling period. ; Thus, sampling data at multiple angles can be obtained; after completing data acquisition, the present invention obtains a cross-sectional image of the rock sample to be tested, and determines in the image the area corresponding to the cross-section of the rock mass without defects on the rock sample to be tested; then, the present invention constructs a first projection matrix based on the projection straight line of the projection data corresponding to the echo signal in each sampling data, passing through the length of the area of ​​interest and the length of each pixel point in the non-interest area; then, the real rock sample signal of the rock mass without defects in the rock sample to be tested can be obtained based on the first projection matrix and each sampling data; finally, the rock physical parameters of the rock sample to be tested can be obtained based on the real rock sample signal.

[0018] Through the above design, the rock sample measurement system provided by the present invention can obtain sampling signals of the rock sample at multiple angles. At the same time, the present invention has spatial selectivity during the rock sample measurement process and can select a rock mass area on the rock sample that does not have defects. In this way, by combining the multi-angle sampling signals and the selected rock mass area, a true rock sample signal of the rock mass area on the rock sample that does not have defects can be obtained. Finally, based on the true rock sample signal, the physical property parameters of the rock sample can be obtained. Therefore, the present invention avoids the influence of rock sample surface defects on the measurement signal, can obtain more accurate rock physical property parameter measurement results, and is suitable for large-scale application and promotion in the field of rock sample measurement.

[0019] In one possible design, the gradient magnetic field generating device includes: a gradient power amplifier and a gradient coil, wherein the gradient coil is arranged in the static magnetic field, and the rock sample to be measured is placed in the gradient coil;

[0020] The nuclear magnetic resonance device is electrically connected to the gradient power amplifier and is used to send a gradient signal to the gradient power amplifier, wherein the gradient power amplifier is used to amplify the gradient signal and send the amplified gradient signal to the gradient coil to drive the gradient coil to generate a gradient magnetic field in at least one direction within the cross section of the rock sample to be measured.

[0021] In one possible design, when the gradient magnetic field generating device generates a gradient magnetic field in one direction within the cross section of the rock sample to be tested, the gradient magnetic field generating device further comprises: a rotating mechanism, wherein the rock sample to be tested is mounted on a rotating end of the rotating mechanism;

[0022] The nuclear magnetic resonance device is electrically connected to the rotating mechanism and is used to control the rotation of the rotating end of the rotating mechanism before starting sampling in each sampling period to adjust the collection angle of the rock sample to be tested in the gradient magnetic field;

[0023] When the gradient magnetic field generating device generates gradient magnetic fields in two directions within the cross section of the rock sample to be tested, the nuclear magnetic resonance device is used to adjust the intensity of the gradient signals in two directions within the cross section of the rock sample to be tested before starting sampling in each sampling period to change the magnetic field direction of the gradient magnetic field.

[0024] In one possible design, the pulse signal includes an excitation pulse signal and a plurality of focusing pulse signals, wherein, within any sampling period, the nuclear magnetic resonance device is used to transmit the excitation pulse signal to the rock sample to be tested, so as to excite the rock sample to be tested and obtain a rock sample signal;

[0025] The nuclear magnetic resonance device is also used to send several focusing pulse signals in sequence after transmitting the excitation pulse signal, so as to use each focusing pulse signal to flip the rock sample signal and obtain each echo signal within any sampling period, wherein the transmission interval time between the first focusing pulse signal of the several focusing pulse signals and the excitation pulse signal is TE / 2, and the transmission interval time between each focusing pulse signal is TE.

[0026] In one possible design, the nuclear magnetic resonance device includes: a nuclear magnetic resonance mechanism and a radio frequency mechanism, wherein the nuclear magnetic resonance mechanism is electrically connected to the gradient magnetic field generating device and the radio frequency mechanism, and the nuclear magnetic resonance mechanism is used to transmit the pulse signal to the rock sample to be tested through the radio frequency mechanism during each sampling cycle.

[0027] In a second aspect, a measurement method of the rock sample measurement system with spatial selectivity based on the first aspect or any possible design of the first aspect is provided, wherein the method is performed by a workstation in the rock sample measurement system with spatial selectivity, and the method comprises:

[0028] receiving a plurality of sampling signals of a rock sample to be tested sent by a nuclear magnetic resonance device, wherein any sampling signal includes a plurality of echo signals, and any echo signal is generated when the rock sample to be tested is excited by a pulse signal emitted by the nuclear magnetic resonance device;

[0029] Acquire a cross-sectional image of the rock sample to be tested, and determine a region of interest from the cross-sectional image, wherein the region of interest is a region in the cross-sectional image where a cross section of a rock mass without defects in the rock sample to be tested is located;

[0030] Obtaining a first projection matrix, wherein elements in the first projection matrix include a projection line of each projection data corresponding to each sampling signal, a length passing through a region of interest, and a length of each pixel point in a non-region of interest, wherein the projection data of any sampling signal is obtained based on each echo signal within the any sampling signal, and the non-region of interest is a region in the cross-sectional image excluding the region of interest;

[0031] Based on each sampling signal and the first projection matrix, a real rock sample signal of a rock mass without defects in the rock sample to be tested is generated, and based on the real rock sample signal, the rock physical parameters of the rock sample to be tested are obtained.

[0032] In one possible design, generating a real rock sample signal of a rock mass without defects in the rock sample to be tested based on each sampling signal and the first projection matrix includes:

[0033] Performing one-dimensional inverse Fourier transform processing on each sampling signal to obtain a one-dimensional inverse Fourier transform processing result of each sampling signal;

[0034] Constructing a second projection matrix based on the one-dimensional inverse Fourier transform processing results of each sampling signal;

[0035] constructing a rock sample signal model of a target rock mass using the first projection matrix and the second projection matrix, wherein the target rock mass is a rock mass without defects in the rock sample to be measured;

[0036] An iterative solution process is performed on the rock sample signal model to obtain a real rock sample signal of the target rock mass after the iterative solution process.

[0037] In a possible design, the rock sample signal model is:

[0038] min||AX-P|| 2 +λ1||X||+λ2||X|| TV (1)

[0039] In the above formula (1), A represents the first projection matrix, P represents the second projection matrix, X represents the pixel matrix, λ1, λ2 represent regularization factors, |||| represents the second norm, |||| TV represents the total variation distance, wherein the pixel matrix includes the true rock sample signal of the region of interest at the sampling moment corresponding to each echo signal, and the true rock sample signal of each pixel point in each non-region of interest at the sampling moment corresponding to each echo signal. The non-region of interest is the area remaining after removing the region of interest from the cross-sectional image, and the true rock sample signal of the target rock mass is determined based on the true rock sample signal of the region of interest at the sampling moment corresponding to each echo signal.

[0040] In one possible design, the first projection matrix is:

[0041]

[0042] In the above formula (2), α(θ1,H,N) represents the length of the projection line of the H-th projection data corresponding to the first sampling signal passing through the N-th pixel point in the non-interested area, and α(θ M ,H,N) represents the length of the projection line of the H-th projection data corresponding to the M-th sampling signal passing through the N-th pixel point in the non-interested area, α(θ M,H,t) represents the length of the projection line of the Hth projection data corresponding to M sampling signals passing through the region of interest, where H represents the total number of projection data corresponding to any sampling signal, N represents the total number of pixels in the non-interested region, θ M represents the coding gradient angle or the acquisition angle of the rock sample to be measured within the sampling period corresponding to the M-th sampling signal, and the coding gradient angle is determined according to the magnetic field direction of the gradient magnetic field within the sampling period corresponding to the M-th sampling signal;

[0043] The one-dimensional inverse Fourier transform processing result of any sampling signal includes a plurality of projection data of the any sampling signal and a modulus value of each projection data relative to each echo signal in the any sampling signal, and the second projection matrix is:

[0044]

[0045] In the above formula (3), p(θ1,H,E) represents the modulus of the H-th projection data corresponding to the first sampling signal relative to the E-th echo signal, and p(θ M ,H,E) represents the modulus value of the Hth projection data corresponding to the Mth sampling signal relative to the Eth echo signal, where E represents the total number of echo signals in any sampling signal.

[0046] In a possible design, the length of the projection line of the Hth projection data corresponding to the Mth sampling signal passing through the Nth pixel point in the non-interested region is calculated using the following method:

[0047] Performing gridding processing on the cross-sectional image to obtain a gridded image, wherein each grid in the gridded image represents a pixel point;

[0048] The equation of the projection line of the H-th projection data corresponding to the M-th sampling signal is calculated using the following formula (4):

[0049]

[0050] In the above formula (4), x and y represent the horizontal and vertical coordinates of each point on the projection line corresponding to the H-th projection data;

[0051] Using the straight line equation, the coordinates of the intersection of the projection straight line and the grid corresponding to the Nth pixel point are calculated, and based on the calculated intersection coordinates, the length of the projection straight line of the Hth projection data corresponding to the Mth sampling signal passing through the Nth pixel point in the non-interested area is determined.

[0052] In the third aspect, a rock sample measurement with spatial selectivity is provided. Taking the device as an electronic device as an example, it includes a memory, a processor and a transceiver that are communicatively connected in sequence, wherein the memory is used to store computer programs, the transceiver is used to send and receive messages, and the processor is used to read the computer program and execute the measurement method as described in the second aspect or any possible design of the second aspect.

[0053] In a fourth aspect, a storage medium is provided, on which instructions are stored. When the instructions are run on a computer, the measurement method according to the second aspect or any possible design of the second aspect is executed.

[0054] In a fifth aspect, a computer program product comprising instructions is provided, which, when the instructions are executed on a computer, causes the computer to execute the measurement method according to the second aspect or any possible design of the second aspect.

[0055] Beneficial effects:

[0056] (1) The rock sample measurement system provided by the present invention can obtain sampling signals of rock samples at multiple angles. At the same time, the present invention has spatial selectivity during the rock sample measurement process and can select rock areas without defects on the rock sample. In this way, by combining the multi-angle sampling signals and the selected rock area, the real rock sample signal of the rock area without defects on the rock sample can be obtained. Finally, the physical properties of the rock sample can be obtained based on the real rock sample signal. Therefore, the present invention avoids the influence of rock sample surface defects on the measurement signal, can obtain more accurate rock physical property parameter measurement results, and is suitable for large-scale application and promotion in the field of rock sample measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 A schematic diagram of a first structural embodiment of a rock sample measurement system with spatial selectivity provided by an embodiment of the present invention;

[0058] Figure 2 A schematic diagram of a second structure of a rock sample measurement system with spatial selectivity provided by an embodiment of the present invention;

[0059] Figure 3 A schematic diagram of a first magnetic resonance acquisition sequence of a rock sample measurement system with spatial selectivity provided by an embodiment of the present invention;

[0060] Figure 4 A schematic diagram of a second magnetic resonance acquisition sequence of a rock sample measurement system with spatial selectivity provided by an embodiment of the present invention;

[0061] Figure 5 A schematic diagram of a cross-sectional image provided by an embodiment of the present invention;

[0062] Figure 6A schematic diagram of a first projection matrix provided in an embodiment of the present invention;

[0063] Figure 7 A schematic flow chart of the steps of a measurement method based on a rock sample measurement system with spatial selectivity provided by an embodiment of the present invention;

[0064] Figure 8 A schematic structural diagram of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0065] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the present invention will be briefly introduced below in conjunction with the drawings and the description of the embodiments or the prior art. Obviously, the following description of the structure of the drawings is only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention.

[0066] It should be understood that although the terms "first," "second," etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element can be referred to as a second element, and similarly, a second element can be referred to as a first element without departing from the scope of the exemplary embodiments of the present invention.

[0067] It should be understood that the term "and / or" that may appear in this document is merely a description of the association relationship between associated objects, indicating that three relationships may exist. For example, A and / or B may indicate three situations: A exists alone, B exists alone, and A and B exist at the same time. The term " / and" that may appear in this document describes another type of association object relationship, indicating that two relationships may exist. For example, A / and B may indicate two situations: A exists alone, and A and B exist alone. In addition, the character " / " that may appear in this document generally indicates that the previous and subsequent associated objects are in an "or" relationship.

[0068] Example:

[0069] See also Figures 1 to 6As shown, the rock sample measurement system with spatial selectivity provided in this embodiment may include, but is not limited to: a static magnetic field generator, a gradient magnetic field generator, a nuclear magnetic resonance device, and a workstation, wherein the workstation is electrically connected to the nuclear magnetic resonance device, and the nuclear magnetic resonance device is electrically connected to the gradient magnetic field generator; in a specific application, the static magnetic field generator is used to generate a uniform static magnetic field (optionally, the static magnetic field generator may be, but is not limited to, a permanent magnet or a superconducting magnet), and the nuclear magnetic resonance device is used to control the gradient magnetic field generator to generate a gradient magnetic field in at least one direction within the cross section of the rock sample to be measured, and the gradient magnetic field is located within the static magnetic field, and the rock sample to be measured is located within the gradient magnetic field; based on this, the static magnetic field and the gradient magnetic field, in combination with the nuclear magnetic resonance device, can realize nuclear magnetic resonance measurement of the rock sample to be measured.

[0070] In specific implementation, this embodiment is equivalent to adding a gradient magnetic field with a variable gradient on the basis of a traditional wellside core measurement device to collect sampling signals of the rock sample to be measured at different angles. Specifically, the nuclear magnetic resonance device is used to transmit a pulse signal to the rock sample to be measured in each sampling period, and receive a plurality of echo signals generated by the rock sample to be measured when excited by the pulse signal, so as to use the plurality of echo signals received in each sampling period to form a sampling signal corresponding to each sampling period. Furthermore, for example, in different sampling periods, the magnetic field direction of the gradient magnetic field in which the rock sample to be measured is different, or the collection angle of the rock sample to be measured in the gradient magnetic field is different. In this way, it is equivalent to using the nuclear magnetic resonance device to control the magnetic field direction of the gradient magnetic field in each sampling period, or the collection angle of the rock sample to be measured in the gradient magnetic field, so that the collection angle in each sampling period is different, so as to obtain sampling signals of the rock sample to be measured at multiple angles.

[0071] In a specific embodiment, the pulse signal includes an excitation pulse signal and a plurality of refocusing pulse signals, wherein, within any sampling period, the nuclear magnetic resonance device is used to transmit the excitation pulse signal to the rock sample to be tested to excite the rock sample to be tested and obtain a rock sample signal; and the nuclear magnetic resonance device is further used to send a plurality of refocusing pulse signals in sequence after transmitting the excitation pulse signal, so as to use each refocusing pulse signal to flip the rock sample signal and obtain each echo signal within any sampling period; thus, within any sampling period, the nuclear magnetic resonance device first uses the excitation pulse to excite the rock sample signal, and then uses a plurality of refocusing pulse signals in sequence to flip the rock sample signal, thereby obtaining an echo signal corresponding to each refocusing pulse signal; then, the collected echo signals are used to form a sampling signal corresponding to the sampling period, and based on the sampling signals corresponding to each sampling period, a true rock sample signal of a rock mass without defects in the rock sample to be tested is obtained (the specific generation process of the true rock sample signal is described in detail below in this embodiment).

[0072] In this embodiment, the transmission interval time between the first re-focusing pulse signal among several re-focusing pulse signals and the excitation pulse signal is TE / 2, and the transmission interval time between each re-focusing pulse signal is TE (TE represents echo time); of course, the transmission interval time between the aforementioned pulse signals can be specifically set according to actual use and is not specifically limited here.

[0073] See also Figure 1 and Figure 2 As shown, the specific composition structure of the aforementioned rock sample measurement system is disclosed below:

[0074] First, the gradient magnetic field generating device may include, but is not limited to, a gradient power amplifier and a gradient coil, wherein, for example, the gradient coil is arranged in the static magnetic field, and the rock sample to be measured is placed in the gradient coil; further, for example, the gradient coil is arranged at the two poles of a permanent magnet or a superconducting magnet, and the rock sample to be measured is placed in the area enclosed by the gradient coil, thereby realizing nuclear magnetic resonance measurement under the action of the static magnetic field and the gradient magnetic field.

[0075] At the same time, the nuclear magnetic resonance device is electrically connected to the gradient power amplifier for sending a gradient signal to the gradient power amplifier, wherein the gradient power amplifier is used to amplify the gradient signal and send the amplified gradient signal to the gradient coil to drive the gradient coil to generate a gradient magnetic field in at least one direction within the cross section of the rock sample to be measured; in specific applications, for example, but not limited to, the gradient magnetic field can be generated in the X direction, Y direction, or X and Y directions on the cross section; at the same time, the Y direction can be but not limited to the vertical direction, the Z direction is the axial direction of the rock sample to be measured, and the X direction is the direction perpendicular to the YZ plane, wherein the schematic diagram of the aforementioned X direction and Y direction can be seen in Figure 1 As shown; in this way, by generating gradient magnetic fields in different directions of the cross section, the acquisition angle of each nuclear magnetic resonance acquisition can be adjusted, thereby obtaining nuclear magnetic resonance sampling signals of the rock sample to be tested at multiple angles.

[0076] Optionally, the following discloses one specific structure of the aforementioned nuclear magnetic resonance device:

[0077] In specific applications, for example, a nuclear magnetic resonance device may include, but is not limited to: a nuclear magnetic resonance mechanism and a radio frequency mechanism, wherein the nuclear magnetic resonance mechanism is electrically connected to the gradient magnetic field generating device and the radio frequency mechanism, and the nuclear magnetic resonance mechanism is used to transmit the pulse signal to the rock sample to be tested through the radio frequency mechanism in each sampling period, and to send a gradient signal to a gradient power amplifier to generate the aforementioned gradient magnetic field; in this way, it is equivalent to the nuclear magnetic resonance mechanism sending a pulse signal to the radio frequency mechanism in each sampling period, and after being processed by the radio frequency mechanism, the processed pulse signal is sent to the rock sample to be tested, so as to excite the rock sample to be tested under the action of the static magnetic field and the gradient magnetic field to obtain a number of echo signals.

[0078] In this embodiment, the aforementioned nuclear magnetic resonance mechanism may be, but is not limited to, a nuclear magnetic resonance spectrometer.

[0079] Optional, see Figure 1 and Figure 2 As shown, the radio frequency mechanism may include, but is not limited to: a radio frequency power amplifier, a transceiver conversion module, a preamplifier and a radio frequency probe, wherein the radio frequency probe is located in the gradient magnetic field, and the coil in the radio frequency probe is a spiral coil. In this way, the rock sample to be tested can be placed in the spiral coil, and then the radio frequency probe is placed in the area surrounded by the gradient coil (see Figure 1 and Figure 2 As shown), the rock sample to be tested is placed in the static magnetic field and the gradient magnetic field at the same time.

[0080] In a specific implementation, the connection structure of the aforementioned electronic components is as follows:

[0081] See also Figure 1 and Figure 2 As shown, for example, the RF probe is electrically connected to the preamplifier through the transceiver conversion module, and the input end of the RF power amplifier is electrically connected to the transmitting end of the nuclear magnetic resonance mechanism, wherein the output end of the RF power amplifier is electrically connected to the transceiver conversion module, and the preamplifier is also electrically connected to the receiving end of the nuclear magnetic resonance mechanism.

[0082] Thus, the excitation principle of the radio frequency transmission pulse of the measurement system provided in this embodiment is:

[0083] When it is necessary to transmit a pulse to the rock sample to be tested, the nuclear magnetic resonance spectrometer sends a radio frequency transmission pulse (i.e., the aforementioned pulse signal) to the radio frequency power amplifier through its corresponding transmission channel. After the radio frequency transmission pulse is amplified by the radio frequency power amplifier, it is sent to the radio frequency probe via the transceiver conversion module and transmitted to the rock sample to be tested by the spiral tube coil in the radio frequency probe.

[0084] When it is necessary to receive magnetic resonance signals, the radio frequency device is first adjusted from the transmitting state to the receiving state through the transceiver conversion module. Then, the radio frequency probe is used to receive the nuclear magnetic resonance echo signal generated by the excitation of the rock sample to be tested. Finally, after being amplified by the preamplifier, it is transmitted to the magnetic resonance spectrometer, and then received by the magnetic resonance spectrometer and transmitted to the workstation.

[0085] At the same time, as explained above, the gradient magnetic field generating device is capable of generating a gradient magnetic field in at least one direction on the cross section of the rock sample to be tested. When the gradient magnetic field is generated in only one direction, the rock sample to be tested needs to be rotated to adjust the acquisition angle. When the gradient magnetic field is generated in two directions, the intensity of the gradient signal in the two directions needs to be adjusted to change the direction of the magnetic field, thereby collecting signals of the rock sample to be tested at different angles.

[0086] Specifically, for example, when the gradient magnetic field generating device generates a gradient magnetic field in one direction within the cross-section of the rock sample to be tested (such as the X direction or the Y direction), the gradient magnetic field generating device further includes: a rotating mechanism, wherein the rock sample to be tested is mounted on the rotating end of the rotating mechanism; in this way, the nuclear magnetic resonance device can be electrically connected to the rotating mechanism so as to control the rotation of the rotating end of the rotating mechanism before starting sampling in each sampling cycle to adjust the collection angle of the rock sample to be tested in the gradient magnetic field.

[0087] In one possible design, the rotating mechanism may include, but is not limited to, a drive motor and a rotating assembly (e.g., a rotating shaft), wherein the nuclear magnetic resonance spectrometer is electrically connected to the controlled end of the drive motor, and the output end of the drive motor is connected to the rotating assembly to drive the rotating assembly to rotate; and the rotation direction is, for example, the z-axis direction, see Figure 1 shown.

[0088] Of course, if the gradient magnetic field generating device generates gradient magnetic fields in two directions within the cross section of the rock sample to be measured, the nuclear magnetic resonance device is used to adjust the intensity of the gradient signal in two directions within the cross section of the rock sample to be measured before sampling in each sampling period to change the magnetic field direction of the gradient magnetic field; that is, in this case, the gradient generating device does not need to be provided with a rotating mechanism. Its structural diagram can be seen in Figure 2 shown.

[0089] Based on the above description, the following describes the nuclear magnetic resonance sampling process of the rock sample to be tested using the above two structures.

[0090] When the gradient magnetic field generator generates a gradient magnetic field in only one direction (i.e., in any direction within the cross section of the rock sample to be tested, generally in the X or Y direction), the nuclear magnetic resonance spectrometer first controls the gradient magnetic field generator to generate a constant gradient magnetic field in one direction, which remains unchanged throughout the acquisition process. At the same time, the nuclear magnetic resonance spectrometer also controls the radio frequency mechanism to emit a 90-degree excitation pulse signal to excite the signal of the rock sample to be tested. After TE / 2 time, the first refocusing pulse signal is emitted, and then the nth refocusing pulse is emitted every TE time. The function of the refocusing pulse is to flip the excited rock sample signal so that its phase refocuses to form an echo signal, and the center of the echo signal is at a time TE / 2 from the refocusing pulse.

[0091] During the signal collection stage, the nuclear magnetic resonance spectrometer controls the RF probe and the transceiver conversion module to collect echo signals. The center of the signal receiving window is located at the center of the echo, that is, at a time TE / 2 away from the refocusing pulse, and E refocusing pulses need to be applied in each repetition cycle, and a total of E echo signals are collected (E is generally several hundred to more than one hundred thousand); in this way, the collected E refocusing pulses can be used to form the sampling signal of the current sampling period.

[0092] After collecting the last echo signal in the current sampling period, the nuclear magnetic resonance spectrometer needs to control the rotation mechanism to drive the rock sample to rotate to the specified angle θ, and then start the rock sample signal excitation and signal collection in the next sampling period; in this way, the above process is repeated continuously to obtain the sampling signal in each sampling period; further, the sampling process of the above echo signal (i.e., magnetic resonance acquisition sequence) can be referred to Figure 3 shown.

[0093] Similarly, when the gradient magnetic field generating device generates gradient magnetic fields in two directions (i.e., gradient magnetic fields are generated in both the X and Y directions within the cross section of the rock sample to be measured), the nuclear magnetic resonance spectrometer controls the gradient magnetic field generating device to generate gradient magnetic fields in the aforementioned X and Y directions, and controls the intensities of the gradient X and gradient Y so that the direction of the synthesized gradient magnetic field forms an angle θ with the X-axis, and each sampling period (TR) causes the angle θ between the gradient magnetic field and the X-axis to change, thereby forming a rotating gradient magnetic field.

[0094] During the signal transmission stage: the nuclear magnetic resonance spectrometer controls the radio frequency mechanism to transmit a 90-degree excitation pulse to stimulate the signal of the rock sample to be tested; then, after TE / 2 time, the first refocusing pulse is transmitted; then, the nth refocusing pulse signal is transmitted every TE time until all refocusing pulse signals are transmitted.

[0095] During the signal receiving stage, the nuclear magnetic resonance spectrometer controls the radio frequency probe and the transceiver conversion module to collect echo signals. The center of the signal receiving window is located at the center of the echo, that is, the moment TE / 2 away from the focusing pulse, and G focusing pulses need to be applied in each repetition cycle, and a total of G echoes are collected, where G is generally several hundred to more than one hundred thousand.

[0096] After acquiring the last echo signal in the current sampling period, the nuclear magnetic resonance spectrometer needs to adjust the intensity of the gradient signal in the X and Y directions to adjust the angle θ between the magnetic field direction of the synthesized gradient magnetic field and the X axis; then, the rock sample signal excitation and signal acquisition of the next sampling period can be started; further, when the gradient magnetic field is generated in two directions, the sampling process of the above echo signal (i.e., the magnetic resonance acquisition sequence) can be referred to. Figure 4 shown.

[0097] Therefore, the difference between the first measurement system and the second measurement system is that the first measurement system only generates a gradient magnetic field in one direction, making the gradient system simpler and also reducing the space of the gradient coil, thereby reducing the gap between the magnets and reducing the weight of the magnets. Furthermore, the gradient magnetic field is only generated in one direction and is constant, which is not affected by eddy currents, residual magnetism, etc., thereby improving measurement accuracy. The second measurement system has gradient magnetic fields in two directions, which makes sequence development more flexible.

[0098] After completing the acquisition of the nuclear magnetic resonance signals of the rock sample to be tested, the nuclear magnetic resonance device can send each sampling signal to the workstation, and the workstation can measure the rock sample to be tested based on the aforementioned sampling signals.

[0099] The workflow of the workstation is as follows:

[0100] The workstation is used to obtain a cross-sectional image of the rock sample to be tested and determine a region of interest from the cross-sectional image, wherein the region of interest is a cross-sectional area of ​​the rock mass without defects in the rock sample to be tested, and is located in the cross-sectional image. In this embodiment, the region of interest is pre-set in the workstation, and is generally a concentric circle of the cross section of the rock sample (e.g., if the diameter of the cross section is 10 cm, a concentric circle with a diameter of 6 cm can be taken as the region of interest). Figure 5 As shown, Figure 5 The shaded area is the region of interest (i.e. Figure 5 xt in, Figure 5 The concentric circles are not listed in the region of interest, which is only for illustration). Figure 5 The area other than the xt area is the non-interest area; and the aforementioned defects may include, but are not limited to, contamination, damage, and / or oil and gas volatilization. Thus, the aforementioned operation is equivalent to screening out the cross-section of the rock mass that is not contaminated, damaged, and / or has oil and gas volatilization from the rock sample to be tested, thereby facilitating the subsequent measurement of the real rock sample signal corresponding to the rock mass in the interest area based on the sampling signal.

[0101] In this embodiment, the length of the projection line corresponding to the projection data, which passes through the aforementioned region of interest in the aforementioned cross-sectional image, and the length of each pixel point outside the region of interest in the image are calculated by obtaining the number of projection data corresponding to each echo signal in each sampling signal. Then, a first projection matrix is ​​constructed based on the aforementioned lengths. Finally, a real rock sample signal of a rock mass without defects on the rock sample to be tested can be generated based on the first projection matrix and each sampling signal.

[0102] That is, the aforementioned workstation is also used to obtain a first projection matrix, wherein the elements in the first projection matrix include the projection straight line of each projection data corresponding to each sampling signal, the length passing through the region of interest, and the length of each pixel point in the non-interest region. The projection data of any sampling signal is obtained based on each echo signal within the any sampling signal, and the non-interest region is the region in the cross-sectional image excluding the region of interest.

[0103] In this embodiment, the first projection matrix may be, but is not limited to, the following formula (2).

[0104]

[0105] In the above formula (2), α(θ1,H,N) represents the length of the projection line of the H-th projection data corresponding to the first sampling signal passing through the N-th pixel point in the non-interested area, and α(θ M,H,N) represents the length of the projection line of the H-th projection data corresponding to the M-th sampling signal passing through the N-th pixel point in the non-interested area, α(θ M ,H,t) represents the length of the projection line of the Hth projection data corresponding to M sampling signals passing through the region of interest, where H represents the total number of projection data corresponding to any sampling signal, N represents the total number of pixels in the non-interested region, θ M It represents the coding gradient angle or the acquisition angle of the rock sample to be tested within the sampling period corresponding to the M-th sampling signal, and the coding gradient angle is determined according to the magnetic field direction of the gradient magnetic field within the sampling period corresponding to the M-th sampling signal. In this embodiment, the coding gradient angle is the angle between the magnetic field direction of the gradient magnetic field and the X direction in the cross section.

[0106] In one possible design, the aforementioned first projection matrix represents the result of weighted accumulation of pixel values ​​in the cross-sectional image corresponding to the projection lines of each projection data in the sampling signal at the angle θ when the rock sample to be measured is rotated to the angle θ (i.e., when a gradient magnetic field in only one direction is generated) or the encoding gradient is rotated to the angle θ (when a gradient magnetic field in two directions is generated).

[0107] Meanwhile, the specific calculation process of the length of the projection line of the H-th projection data corresponding to the M-th sampling signal passing through the N-th pixel point in the non-interested region disclosed below can be, but is not limited to, as shown below:

[0108] Step 1: The workstation performs gridding processing on the cross-sectional image to obtain a gridded image, wherein each grid in the gridded image represents a pixel point; optionally, the gridded image can be referred to Figure 6 shown.

[0109] Step 2: The workstation uses the following formula (4) to calculate the linear equation of the projection line of the Hth projection data corresponding to the Mth sampling signal.

[0110]

[0111] In the above formula (4), x and y represent the horizontal coordinate and vertical coordinate of each point on the projection line corresponding to the H-th projection data.

[0112] Assuming that there are 100 projection data in the Mth sampling signal, H is 100, and the equation of the projection line corresponding to the first projection data is:

[0113]

[0114] In this way, the linear equation of the projection line corresponding to the first projection data can be obtained based on the above formula (4); of course, the linear equations of the projection lines of the remaining projection data are calculated in the same process as the above example and will not be repeated here.

[0115] After obtaining the straight line equation of the projection line of the H-th projection data corresponding to the M-th sampling signal, the straight line equation can be used to find the intersection of the straight line and the grid corresponding to the N-th pixel point. Then, based on the intersection point, the length of the straight line passing through the N-th pixel point can be calculated; the above process is shown in the third step below.

[0116] Step 3: The workstation calculates the intersection coordinates of the projection line and the grid corresponding to the Nth pixel using the straight line equation, and determines the length of the projection line of the Hth projection data corresponding to the Mth sampling signal passing through the Nth pixel in the non-interested area based on the calculated intersection coordinates; see Figure 6 As shown, Figure 6 The P(θ, h) in the equation represents each projection data (the h-th projection data). Figure 6 The dotted lines in the figure represent the projected lines. Taking the lower rightmost projected line as an example, it has two intersection points with the lower rightmost grid in the image. Therefore, based on the linear equation of the lower rightmost projected line and the linear equation of the corresponding line constituting the lower rightmost grid, the intersection point between the lower rightmost projected line and the lower rightmost grid is calculated; then, using the coordinates of the two intersection points, the distance between the two intersection points is calculated, and this distance is the length of the lower rightmost projected line passing through the pixel corresponding to the lower rightmost grid; of course, the calculation principle of the length of each other projected line passing through other pixels is the same as the above example and will not be repeated here.

[0117] After obtaining the first projection matrix based on the above method, the workstation can combine the various sampling signals to obtain the real rock sample signal of the rock mass corresponding to the area of ​​interest.

[0118] The workstation is further configured to generate a real rock sample signal of a rock mass without defects in the rock sample to be tested using each sampling signal and the first projection matrix, and to obtain rock physical parameters of the rock sample to be tested based on the real rock sample signal. In this embodiment, examples of rock physical parameters include, but are not limited to, rock pore structure, pore fluid, occurrence state, and the like.

[0119] Furthermore, one method disclosed below for the workstation to generate a real rock sample signal of a rock mass without defects in the rock sample to be tested based on the first projection matrix and each sampling signal may be, but is not limited to, as follows:

[0120] Step 1: The workstation performs one-dimensional inverse Fourier transform processing on each sampling signal to obtain a one-dimensional inverse Fourier transform processing result of each sampling signal; in this embodiment, the one-dimensional inverse Fourier transform processing result of any sampling signal may include, but is not limited to, a number of projection data of the any sampling signal, and the modulus value of each projection data relative to each echo signal in the any sampling signal; of course, the aforementioned one-dimensional inverse Fourier transform processing is a commonly used technology in the field of signal processing, and its principle will not be repeated here.

[0121] Step 2: The workstation constructs a second projection matrix based on the one-dimensional inverse Fourier transform processing results of each sampling signal. In specific applications, the second projection matrix is ​​mainly constructed by using the modulus value of each projection data relative to each echo signal. The second projection matrix can be, but is not limited to, as shown in the following formula (3).

[0122]

[0123] In the above formula (3), p(θ1,H,E) represents the modulus of the H-th projection data corresponding to the first sampling signal relative to the E-th echo signal (of course, it is the E-th echo signal in the first sampling signal), p(θ M ,H,E) represents the modulus value of the Hth projection data corresponding to the Mth sampling signal relative to the Eth echo signal (it is the Eth echo signal in the Mth sampling signal), where E represents the total number of echo signals in any sampling signal.

[0124] After constructing the second projection matrix based on the one-dimensional inverse Fourier transform results of each sampling signal, the first projection matrix and the second projection matrix can be used to construct a rock sample signal model of the rock mass without defects; the model construction process is shown in step three below.

[0125] Step 3: Use the first projection matrix and the second projection matrix to construct a rock sample signal model of the target rock mass, wherein the target rock mass is a rock mass without defects in the rock sample to be tested; in specific applications, the rock sample signal model can be, but is not limited to, as shown in the following formula (1).

[0126] min||AX-P|| 2 +λ1||X||+λ2||X|| TV (1)

[0127] In the above formula (1), A represents the first projection matrix, P represents the second projection matrix, X represents the pixel matrix, λ1, λ2 represent regularization factors, || || represents the second norm, || || TVrepresents the total variation distance, wherein the pixel matrix includes the true rock sample signal of the region of interest at the sampling moment corresponding to each echo signal, and the true rock sample signal of each pixel point in each non-region of interest at the sampling moment corresponding to each echo signal. The non-region of interest is the area remaining after removing the region of interest from the cross-sectional image, and the true rock sample signal of the target rock mass is determined based on the true rock sample signal of the region of interest at the sampling moment corresponding to each echo signal.

[0128] In this embodiment, the pixel matrix X can be expressed as:

[0129]

[0130] In the above formula (5), x(N, R) represents the real rock sample signal of the Nth pixel point in the non-interested area at the time corresponding to the Rth echo signal in the echo signal set, and x(t, R) represents the real rock sample signal of the interested area at the time corresponding to the Rth echo signal. The echo signal set includes all echo signals in each sampling signal, and R represents the total number of echo signals in the echo signal set.

[0131] Of course, each element in the aforementioned pixel matrix is ​​a quantity to be determined; thus, the pixel matrix can be solved according to the aforementioned model, wherein the solving process is shown in the following step 4.

[0132] Step 4: Iteratively solve the rock sample signal model to obtain the real rock sample signal of the target rock mass after the iterative solution process. In this embodiment, the optimal solution of the aforementioned model is solved, that is, the pixel matrix when the entire formula (1) is minimized is the optimal solution. Therefore, in the obtained pixel matrix, the real rock sample signal of the area of ​​interest can be obtained, which can be used as the real rock sample signal of the target rock mass.

[0133] Thus, through the aforementioned steps 1 to 4, a true rock sample signal of a rock sample without defects in the rock sample to be tested can be obtained; and then, based on the true rock sample signal, the rock physical property parameters of the rock sample to be tested can be obtained.

[0134] In this embodiment, the last row of the pixel matrix represents the real rock sample signal of the rock sample without defects in the rock sample to be tested. In this way, the relaxation spectrum is inverted and the rock physical parameters of the rock sample to be tested can be determined based on the inversion results.

[0135] Optionally, for example but not limited to, the following formula (6) may be used to perform relaxation spectrum inversion.

[0136]

[0137] In the above formula (6), τ1 to τE represents the echo time (where E is the total number of echo signals in the echo signal set), T2(1) to T2(Y) are the inversion sampling time points of the relaxation spectrum, which are distributed in an exponential form, with a total of Y. That is the inversion result to be solved, and s is the column vector of the aforementioned real rock sample signal, that is, the column vector composed of the last row elements in the pixel matrix.

[0138] Therefore, the relaxation spectrum inversion result can be obtained through the above formula (6), and the above rock physical parameters can be obtained based on the inversion result.

[0139] Therefore, through the detailed description of the rock sample measurement system with spatial selectivity, the present invention can obtain sampling signals of the rock sample at multiple angles; at the same time, the present invention has spatial selectivity in the rock sample measurement process and can select rock areas without defects on the rock sample; thus, by combining the multi-angle sampling signals and the selected rock area, the true rock sample signal of the rock area without defects on the rock sample can be obtained; finally, based on the true rock sample signal, the physical properties of the rock sample can be obtained; thus, the present invention avoids the influence of rock sample surface defects on the measurement signal, can obtain more accurate rock physical property parameter measurement results, and is suitable for large-scale application and promotion in the field of rock sample measurement.

[0140] In one possible design, see Figure 7 As shown, the second aspect of this embodiment provides a measurement method of a rock sample measurement system with spatial selectivity based on the first aspect of the embodiment, wherein, for example, the method is executed by a workstation in the rock sample measurement system, and the method may include but is not limited to the following steps S1 to S4.

[0141] S1. Receive a plurality of sampling signals of a rock sample to be tested sent by a nuclear magnetic resonance device, wherein any sampling signal includes a plurality of echo signals, and any echo signal is generated when the rock sample to be tested is excited by a pulse signal emitted by the nuclear magnetic resonance device.

[0142] S2. Obtain a cross-sectional image of the rock sample to be tested, and determine a region of interest from the cross-sectional image, wherein the region of interest is a cross-sectional area of ​​a rock mass without defects in the rock sample to be tested, and is located in the cross-sectional image.

[0143] S3. Obtain a first projection matrix, wherein the elements in the first projection matrix include the projection straight line of each projection data corresponding to each sampling signal, the length passing through the region of interest, and the length of each pixel point in the non-interest region, the projection data of any sampling signal is obtained based on each echo signal within the any sampling signal, and the non-interest region is the region in the cross-sectional image excluding the region of interest.

[0144] S4. Based on each sampling signal and the first projection matrix, a true rock sample signal of a rock mass without defects in the rock sample to be tested is generated, and based on the true rock sample signal, the rock physical parameters of the rock sample to be tested are obtained. In this embodiment, the true rock sample signal can be calculated by, for example but not limited to, the following steps S41 to S44.

[0145] S41. Perform one-dimensional inverse Fourier transform processing on each sampling signal to obtain a one-dimensional inverse Fourier transform processing result of each sampling signal.

[0146] S42. Construct a second projection matrix based on the one-dimensional inverse Fourier transform processing results of each sampling signal.

[0147] S43. Construct a rock sample signal model of a target rock mass using the first projection matrix and the second projection matrix, wherein the target rock mass is a rock mass without defects in the rock sample to be measured.

[0148] S44. Perform an iterative solution process on the rock sample signal model to obtain a true rock sample signal of the target rock mass after the iterative solution process. In a specific application, the rock sample signal model may be, but is not limited to, the following formula (1):

[0149] min||AX-P|| 2 +λ1||X||+λ2||X|| TV (1)

[0150] In the above formula (1), A represents the first projection matrix, P represents the second projection matrix, X represents the pixel matrix, λ1, λ2 represent regularization factors, |||| represents the second norm, || || TV represents the total variation distance, wherein the pixel matrix includes the true rock sample signal of the region of interest at the sampling moment corresponding to each echo signal, and the true rock sample signal of each pixel point in each non-region of interest at the sampling moment corresponding to each echo signal. The non-region of interest is the area remaining after removing the region of interest from the cross-sectional image, and the true rock sample signal of the target rock mass is determined based on the true rock sample signal of the region of interest at the sampling moment corresponding to each echo signal.

[0151] At the same time, the first projection matrix is:

[0152]

[0153] In the above formula (2), α(θ1,H,N) represents the length of the projection line of the H-th projection data corresponding to the first sampling signal passing through the N-th pixel point in the non-interested area, and α(θM ,H,N) represents the length of the projection line of the H-th projection data corresponding to the M-th sampling signal passing through the N-th pixel point in the non-interested area, α(θ M ,H,t) represents the length of the projection line of the Hth projection data corresponding to M sampling signals passing through the region of interest, where H represents the total number of projection data corresponding to any sampling signal, N represents the total number of pixels in the non-interested region, θ M represents the coding gradient angle or the acquisition angle of the rock sample to be measured within the sampling period corresponding to the M-th sampling signal, and the coding gradient angle is determined according to the magnetic field direction of the gradient magnetic field within the sampling period corresponding to the M-th sampling signal;

[0154] The one-dimensional inverse Fourier transform processing result of any sampling signal includes a plurality of projection data of the any sampling signal and a modulus value of each projection data relative to each echo signal in the any sampling signal, and the second projection matrix is:

[0155]

[0156] In the above formula (3), p(θ1,H,E) represents the modulus of the H-th projection data corresponding to the first sampling signal relative to the E-th echo signal, and p(θ M ,H,E) represents the modulus value of the Hth projection data corresponding to the Mth sampling signal relative to the Eth echo signal, where E represents the total number of echo signals in any sampling signal.

[0157] In addition, for example, the length of the projection line of the Hth projection data corresponding to the Mth sampling signal passing through the Nth pixel point in the non-interested region is calculated using the following steps S44a to S44c.

[0158] S44a. Gridding the cross-sectional image to obtain a gridded image, wherein each grid in the gridded image represents a pixel point.

[0159] S44b. Use the following formula (4) to calculate the linear equation of the projection line of the H-th projection data corresponding to the M-th sampling signal.

[0160]

[0161] In the above formula (4), x and y represent the horizontal and vertical coordinates of each point on the projection line corresponding to the H-th projection data;

[0162] S44c. Calculate the coordinates of the intersection of the projection line and the grid corresponding to the Nth pixel point using the straight line equation, and determine the length of the projection line of the Hth projection data corresponding to the Mth sampling signal passing through the Nth pixel point in the non-interested area based on the calculated intersection coordinates.

[0163] The working process, working details and technical effects of the method provided in the second aspect of this embodiment can be found in the first aspect of the embodiment and will not be repeated here.

[0164] like Figure 8 As shown, the third aspect of this embodiment provides a rock sample measuring device with spatial selectivity. Taking the device as an electronic device as an example, it includes: a memory, a processor and a transceiver that are communicatively connected in sequence, wherein the memory is used to store computer programs, the transceiver is used to send and receive messages, and the processor is used to read the computer program and execute the measurement method described in the second aspect of the embodiment.

[0165] For example, the memory may include, but is not limited to, random access memory (RAM), read-only memory (ROM), flash memory, first-in first-out memory (FIFO), and / or first-in last-out memory (FILO); specifically, the processor may include one or more processing cores, such as a quad-core processor, an octa-core processor, etc. The processor may be implemented in at least one hardware form selected from DSP (Digital Signal Processing), FPGA (Field-Programmable Gate Array), and PLA (Programmable Logic Array). Furthermore, the processor may include a main processor and a coprocessor. The main processor is a processor for processing data in an awake state, also known as a CPU (Central Processing Unit); and the coprocessor is a low-power processor for processing data in a standby state.

[0166] In some embodiments, the processor may be integrated with a GPU (Graphics Processing Unit), which is responsible for rendering and drawing the content to be displayed on the display screen. For example, the processor may be, but is not limited to, a microprocessor of the STM32F105 series, a reduced instruction set computer (RISC) microprocessor, an X86 architecture processor, or a processor with an integrated embedded neural network processing unit (NPU); the transceiver may be, but is not limited to, a wireless fidelity (WIFI) wireless transceiver, a Bluetooth wireless transceiver, a general packet radio service technology (GPRS) wireless transceiver, a ZigBee protocol (a low-power local area network protocol based on the IEEE802.15.4 standard, ZigBee) wireless transceiver, a 3G transceiver, a 4G transceiver, and / or a 5G transceiver. In addition, the device may also include, but is not limited to, a power module, a display screen, and other necessary components.

[0167] The working process, working details and technical effects of the electronic device provided in this embodiment can be found in the first and second aspects of the embodiment, and will not be repeated here.

[0168] The fourth aspect of this embodiment provides a storage medium storing instructions containing the measurement method described in the second aspect of the embodiment, that is, the storage medium stores instructions, and when the instructions are run on a computer, the measurement method described in the second aspect of the embodiment is executed.

[0169] The storage medium refers to a carrier for storing data, which may include but is not limited to a floppy disk, an optical disk, a hard disk, a flash memory, a USB flash drive and / or a memory stick, and the computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device.

[0170] The working process, working details and technical effects of the storage medium provided in this embodiment can be found in the second aspect and the first aspect of the embodiment, and will not be repeated here.

[0171] The fifth aspect of this embodiment provides a computer program product containing instructions, which, when executed on a computer, causes the computer to execute the measurement method described in the second aspect of the embodiment, wherein the computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device.

[0172] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A rock sample measurement system with spatial selectivity, characterized in that: include: A static magnetic field generating device, a gradient magnetic field generating device and a nuclear magnetic resonance device, wherein the static magnetic field generating device is used to generate a uniform static magnetic field, and the nuclear magnetic resonance device is electrically connected to the gradient magnetic field generating device; The nuclear magnetic resonance device is used to control the gradient magnetic field generating device to generate a gradient magnetic field in at least one direction within the cross section of the rock sample to be measured, wherein the gradient magnetic field is located within the static magnetic field, and the rock sample to be measured is located within the gradient magnetic field; The nuclear magnetic resonance device is used to transmit a pulse signal to the rock sample to be tested in each sampling period, and receive a plurality of echo signals generated by the rock sample to be tested when excited by the pulse signal, so as to form a sampling signal corresponding to each sampling period using the plurality of echo signals received in each sampling period, wherein the magnetic field direction of the gradient magnetic field in which the rock sample to be tested is located is different in different sampling periods, or the acquisition angle of the rock sample to be tested in the gradient magnetic field is different; The nuclear magnetic resonance device is further used to send each sampling signal to a workstation; The workstation is configured to obtain a cross-sectional image of the rock sample to be tested, and determine a region of interest from the cross-sectional image, wherein the region of interest is a region in the cross-sectional image where a cross section of a rock mass without defects in the rock sample to be tested is located; The workstation is configured to obtain a first projection matrix, wherein the elements of the first projection matrix include a projection line of each projection data corresponding to each sampling signal, a length passing through a region of interest, and a length of each pixel point in a non-interest region, the projection data of any sampling signal being obtained based on each echo signal within the any sampling signal, and the non-interest region being a region in the cross-sectional image excluding the region of interest; The workstation is further configured to generate a real rock sample signal of a rock mass without defects in the rock sample to be tested using each sampling signal and the first projection matrix, and to obtain rock physical parameters of the rock sample to be tested based on the real rock sample signal; A workstation, configured to perform one-dimensional inverse Fourier transform processing on each sampling signal to obtain a one-dimensional inverse Fourier transform processing result of each sampling signal; A workstation configured to construct a second projection matrix based on a one-dimensional inverse Fourier transform processing result of each sampling signal; A workstation configured to construct a rock sample signal model of a target rock mass using the first projection matrix and the second projection matrix, wherein the target rock mass is a rock mass without defects in the rock sample to be tested; The workstation is used to perform iterative solution processing on the rock sample signal model to obtain the real rock sample signal of the target rock mass after the iterative solution processing.

2. A rock sample measurement system with spatial selectivity according to claim 1, characterized in that: The gradient magnetic field generating device comprises: a gradient power amplifier and a gradient coil, wherein the gradient coil is arranged in the static magnetic field, and the rock sample to be measured is placed in the gradient coil; The nuclear magnetic resonance device is electrically connected to the gradient power amplifier and is used to send a gradient signal to the gradient power amplifier, wherein the gradient power amplifier is used to amplify the gradient signal and send the amplified gradient signal to the gradient coil to drive the gradient coil to generate a gradient magnetic field in at least one direction within the cross section of the rock sample to be measured.

3. The rock sample measurement system with spatial selectivity according to claim 2, characterized in that: When the gradient magnetic field generating device generates a gradient magnetic field in one direction within the cross section of the rock sample to be tested, the gradient magnetic field generating device further comprises: a rotating mechanism, wherein the rock sample to be tested is mounted on a rotating end of the rotating mechanism; The nuclear magnetic resonance device is electrically connected to the rotating mechanism and is used to control the rotation of the rotating end of the rotating mechanism before starting sampling in each sampling period to adjust the collection angle of the rock sample to be tested in the gradient magnetic field; When the gradient magnetic field generating device generates gradient magnetic fields in two directions within the cross section of the rock sample to be tested, the nuclear magnetic resonance device is used to adjust the intensity of the gradient signals in two directions within the cross section of the rock sample to be tested before starting sampling in each sampling period to change the magnetic field direction of the gradient magnetic field.

4. The rock sample measurement system with spatial selectivity according to claim 1, characterized in that: The pulse signal includes an excitation pulse signal and a plurality of focusing pulse signals, wherein, in any sampling period, the nuclear magnetic resonance device is used to transmit the excitation pulse signal to the rock sample to be tested, so as to excite the rock sample to be tested and obtain a rock sample signal; The nuclear magnetic resonance device is also used to send several focusing pulse signals in sequence after transmitting the excitation pulse signal, so as to use each focusing pulse signal to flip the rock sample signal and obtain each echo signal within any sampling period, wherein the transmission interval time between the first focusing pulse signal of the several focusing pulse signals and the excitation pulse signal is TE / 2, and the transmission interval time between each focusing pulse signal is TE.

5. The rock sample measurement system with spatial selectivity according to claim 1, characterized in that: The nuclear magnetic resonance device includes: a nuclear magnetic resonance mechanism and a radio frequency mechanism, wherein the nuclear magnetic resonance mechanism is electrically connected to the gradient magnetic field generating device and the radio frequency mechanism, and the nuclear magnetic resonance mechanism is used to transmit the pulse signal to the rock sample to be tested through the radio frequency mechanism during each sampling period.

6. A measurement method based on the rock sample measurement system with spatial selectivity according to any one of claims 1 to 5, characterized in that: The method is performed by a workstation in the rock sample measurement system with spatial selectivity, and the method includes: receiving a plurality of sampling signals of a rock sample to be tested sent by a nuclear magnetic resonance device, wherein any sampling signal includes a plurality of echo signals, and any echo signal is generated when the rock sample to be tested is excited by a pulse signal emitted by the nuclear magnetic resonance device; Acquire a cross-sectional image of the rock sample to be tested, and determine a region of interest from the cross-sectional image, wherein the region of interest is a region in the cross-sectional image where a cross section of a rock mass without defects in the rock sample to be tested is located; Obtaining a first projection matrix, wherein elements in the first projection matrix include a projection line of each projection data corresponding to each sampling signal, a length passing through a region of interest, and a length of each pixel point in a non-region of interest, wherein the projection data of any sampling signal is obtained based on each echo signal within the any sampling signal, and the non-region of interest is a region in the cross-sectional image excluding the region of interest; Based on each sampling signal and the first projection matrix, a real rock sample signal of a rock mass without defects in the rock sample to be tested is generated, and based on the real rock sample signal, the rock physical parameters of the rock sample to be tested are obtained.

7. The method according to claim 6, characterized in that Generating a real rock sample signal of a rock mass without defects in the rock sample to be tested based on each sampling signal and the first projection matrix, including: Performing one-dimensional inverse Fourier transform processing on each sampling signal to obtain a one-dimensional inverse Fourier transform processing result of each sampling signal; Constructing a second projection matrix based on the one-dimensional inverse Fourier transform processing results of each sampling signal; constructing a rock sample signal model of a target rock mass using the first projection matrix and the second projection matrix, wherein the target rock mass is a rock mass without defects in the rock sample to be measured; An iterative solution process is performed on the rock sample signal model to obtain a real rock sample signal of the target rock mass after the iterative solution process.

8. The method according to claim 7, characterized in that The rock sample signal model is: （1） In the above formula (1), represents the first projection matrix, represents the second projection matrix, represents the pixel matrix, represents the regularization factor, represents the two-norm, represents the total variation distance, wherein the pixel matrix includes the true rock sample signal of the region of interest at the sampling moment corresponding to each echo signal, and the true rock sample signal of each pixel point in each non-region of interest at the sampling moment corresponding to each echo signal. The non-region of interest is the area remaining after removing the region of interest from the cross-sectional image, and the true rock sample signal of the target rock mass is determined based on the true rock sample signal of the region of interest at the sampling moment corresponding to each echo signal.

9. The method according to claim 8, characterized in that The first projection matrix is: （2） In the above formula (2), It represents the length of the projection line of the H-th projection data corresponding to the first sampling signal passing through the N-th pixel point in the non-interested area. It represents the length of the projection line of the H-th projection data corresponding to the M-th sampling signal passing through the N-th pixel point in the non-interested area, represents the length of the projection line of the H-th projection data corresponding to M sampling signals passing through the region of interest, where H represents the total number of projection data corresponding to any sampling signal, and N represents the total number of pixels in the non-region of interest. represents the coding gradient angle or the acquisition angle of the rock sample to be measured within the sampling period corresponding to the M-th sampling signal, and the coding gradient angle is determined according to the magnetic field direction of the gradient magnetic field within the sampling period corresponding to the M-th sampling signal; The one-dimensional inverse Fourier transform processing result of any sampling signal includes a plurality of projection data of the any sampling signal and a modulus value of each projection data relative to each echo signal in the any sampling signal, and the second projection matrix is: （3） In the above formula (3), It represents the modulus of the H-th projection data corresponding to the first sampling signal relative to the E-th echo signal. represents the modulus of the Hth projection data corresponding to the Mth sampling signal relative to the Eth echo signal, where E represents the total number of echo signals in any sampling signal.

10. The method according to claim 8, characterized in that The length of the projection line of the H-th projection data corresponding to the M-th sampling signal passing through the N-th pixel point in the non-interested area is calculated using the following method: Performing gridding processing on the cross-sectional image to obtain a gridded image, wherein each grid in the gridded image represents a pixel point; The linear equation of the projection line of the H-th projection data corresponding to the M-th sampling signal is calculated using the following formula (4); （4） In the above formula (4), x and y represent the horizontal and vertical coordinates of each point on the projection line corresponding to the Hth projection data; Using the straight line equation, the coordinates of the intersection of the projection straight line and the grid corresponding to the Nth pixel point are calculated, and based on the calculated intersection coordinates, the length of the projection straight line of the Hth projection data corresponding to the Mth sampling signal passing through the Nth pixel point in the non-interested area is determined.

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