A method of measuring anisotropy of acoustic wave velocity and resistivity in shales

Abstract

The application discloses a method for measuring the anisotropy of acoustic wave velocity and resistivity of bedded shale, which comprises the following steps: 1, obtaining a core sample; 2, marking a line on the core sample and arranging two groups of acoustic-electric transceiving probes on the lateral surface of the core sample; 3, overlapping the line with the axis of one group of acoustic-electric transceiving probes as an initial orientation, placing a top column on the core sample, and then applying triaxial stress to the core sample; 4, measuring the resistance and acoustic wave velocity of the core sample at the initial orientation; 5, rotating the core sample for multiple times, repeating steps 3 and 4, and measuring the resistance and acoustic wave velocity of each group of acoustic-electric transceiving probes at different angles; 6, calculating the average resistance and average acoustic wave velocity of the core sample at different angles; and 7, calculating the resistivity anisotropy coefficient and acoustic wave anisotropy coefficient of the core sample at different angles. The application solves the technical problems of few measuring directions, high sample consumption and obvious influence of lithological heterogeneity in the prior art.

Description

Technical Field

[0001] This invention relates to the field of rock physics experimental technology, specifically to a method for measuring the acoustic velocity and resistivity anisotropy of layered shale. Background Technology

[0002] Rock acoustic wave velocity and resistivity are important physical information in geophysics. Measuring these parameters under laboratory conditions is a crucial tool in geophysical research and forms the basis for quantitative evaluation of mineral resources such as oil and gas. Unconventional reservoirs, such as shale, exhibit strong anisotropy in their acoustic wave velocity and resistivity; that is, the measured acoustic wave velocity and resistivity differ in different directions, posing challenges to mineral resource evaluation. Therefore, it is necessary to measure the anisotropy of formation rock acoustic wave velocity and resistivity under laboratory conditions.

[0003] There are currently two main types of experimental methods for measuring the anisotropy of acoustic velocity and resistivity in formations:

[0004] like Figure 1 As shown, the first type involves processing cubic rock samples and measuring the acoustic velocity and resistivity of the rock samples in the X, Y, and Z directions. However, the limitation of this type of method is that the sample can only be measured in a limited number of directions, specifically acoustic velocity and resistivity in three directions, and the relative positional relationship of the three directions is fixed.

[0005] like Figure 2 As shown, the second type involves drilling conventional plunger cores (1-inch diameter cylindrical cores) in different directions from outcrop rocks or full-diameter core samples. These plunger cores from different directions are then placed in a conventional holder for acoustic velocity and resistivity measurements. This approach allows for flexible selection of measurement directions and arbitrary number of cores. However, it has two main drawbacks: firstly, it consumes a large number of cores, resulting in high costs for downhole coring. Secondly, the acoustic velocity and resistivity measurements are obtained from different core samples. When the formation rocks exhibit strong heterogeneity, the lithological differences between samples can be significant (e.g., shale may contain scattered pyrite, and the pyrite content in different plunger samples may vary considerably). Therefore, the differences caused by lithological heterogeneity in the final measurement results may mask the anisotropy caused by factors such as bedding orientation.

[0006] In addition, the patent document with the publication number CN107037129A discloses a rock anisotropy measuring clamp and a measuring method thereof, which mainly comprises a base, a guide rail, a sliding block, a pushing part, a fixing part, a pressure gauge and a sound wave receiving device, an angle adjusting device and an angle pointer are arranged on the pushing part, and a displacement scale line is arranged on the base, which can measure the sound wave anisotropy characteristics of the core at different angles and can more truly reflect the physical response of the rock in the actual formation. Figure 3 As shown in the prior art, the angle adjusting device changes the vibration direction of the transverse wave of the sound wave in the core during the propagation process, but it does not change the propagation direction of the sound wave in the core. For the measurement of the longitudinal wave of the sound wave, the technology will fail because the propagation direction and the vibration direction of the longitudinal wave are both the axial direction of the core, and the change of the angle does not change the propagation path of the sound wave, so the final measurement result cannot effectively reflect the rock and anisotropy. SUMMARY

[0007] The purpose of the present application is to overcome the above-mentioned problems existing in the prior art, and to provide a method for measuring the anisotropy of the sound wave velocity and the resistivity of the bedded shale. The present application can change the propagation direction of the sound wave in the core sample by adjusting the angle of the core sample during the measurement, so that the sound wave velocity and the resistivity anisotropy can be measured from multiple directions on the same core sample. This not only effectively reflects the differences in the propagation of the sound wave in the rock along different directions, but also solves the technical problems of the prior art, such as the small number of measurement directions, the large number of samples consumed and the significant influence of lithological heterogeneity.

[0008] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows:

[0009] A method for measuring the anisotropy of the sound wave velocity and the resistivity of the bedded shale, characterized in that it comprises the following steps:

[0010] Step 1: Obtain a cylindrical core sample from the bedded shale, and ensure that the anisotropy of the rock physical parameters can be reflected on the end face of the core sample;

[0011] Step 2: Position the core sample on the measuring seat, and set a mark line passing through the center of the core sample on the top surface of the core sample, and then set two groups of mutually perpendicular sound and electric transceiving probes on the side surface of the core sample, each group of sound and electric transceiving probes comprising sound and electric transmitting probes and sound and electric receiving probes symmetrically arranged on both sides of the core sample, and the axis of each group of sound and electric transceiving probes is perpendicular to and intersects with the axis of the core sample;

[0012] Step 3: Overlapping the mark line with the axis of one set of acoustic-electric transceiver probes as the initial orientation, placing a top pillar on the top surface of the core sample, and applying triaxial stress to the core sample from X, Y, and Z directions through the top pillar and the two sets of acoustic-electric transceiver probes respectively;

[0013] Step 4: Measuring the core sample through the two sets of acoustic-electric transceiver probes to obtain the resistance and acoustic wave speed when the axis overlaps with the mark line, and to obtain the resistance and acoustic wave speed when the axis is perpendicular to the mark line;

[0014] Step 5: Removing the triaxial stress, removing the top pillar and acoustic-electric transceiver probes, and rotating the core sample multiple times, repeating steps 3 and 4 after each rotation to obtain the resistance and acoustic wave speed of each set of acoustic-electric transceiver probes at each angle;

[0015] Step 6: Calculating the average resistance and average acoustic wave speed of the core sample at each angle based on the resistance and acoustic wave speed measured by the two sets of acoustic-electric transceiver probes at the same angle relative to the mark line;

[0016] Step 7: Calculating the resistivity anisotropy coefficient of the core sample at each angle based on the average resistance at each angle and the average resistance when the acoustic-electric transceiver probes are perpendicular to the mark line, and calculating the acoustic wave anisotropy coefficient of the core sample at each angle based on the average acoustic wave speed at each angle.

[0017] In step 6, the calculation method of the resistivity anisotropy coefficient is:

[0018]

[0019] wherein, α 电( θ) is the resistivity anisotropy coefficient of the core sample at θ angle, r(θ) is the average resistivity of the core sample at θ angle, r 90 is the average resistivity of the core sample when the acoustic-electric transceiver probes are perpendicular to the mark line, R(θ) is the average resistance of the core sample at θ angle, R 90 is the average resistance of the core sample when the acoustic-electric transceiver probes are perpendicular to the mark line, and K is a constant of the core sample.

[0020] In step 6, the calculation method of the acoustic wave anisotropy coefficient is:

[0021]

[0022] wherein, α 声(θ) is the acoustic anisotropy coefficient of the core sample at the angle θ, V(θ) is the average acoustic wave velocity of the core sample at the angle θ, V0 is the average acoustic wave velocity of the core sample when the axis line overlaps with the marker line, Δt(θ) is the time difference of the acoustic wave signal from the acoustic emission transmitter probe to the acoustic receiving probe of the core sample at the angle θ, Δt0 is the time difference of the acoustic wave signal from the acoustic emission transmitter probe to the acoustic receiving probe of the core sample when the axis line overlaps with the marker line, and D is the diameter of the core sample.

[0023] In step 1, the axis direction of the core sample is parallel to the bedding plane of the bedded shale.

[0024] In step 2, the measuring seat comprises a circular base disc and four limiting clamps uniformly fixed on the base disc, the four limiting clamps are distributed at 90° to each other, and the distance from the four limiting clamps to the center of the base disc is equal and equal to the radius of the core sample.

[0025] In step 2, the inner side of the limiting clamps is an arc surface with a curvature radius equal to the radius of the core.

[0026] In step 2, any acoustic emission transmitter probe / acoustic receiving probe is located between two adjacent limiting clamps, and the acoustic emission transmitter probe / acoustic receiving probe and the limiting clamps are placed at 45° to each other.

[0027] In step 2, a plurality of straight lines passing through the center of the base disc are marked on the base disc, and the straight lines are distributed at equal angles.

[0028] In step 2, the angle between the straight lines passing through the center of the base disc is 10°-20°.

[0029] In step 3, the outer diameter of the top column is smaller than the outer diameter of the core sample.

[0030] The advantages of the present application are as follows:

[0031] 1. Compared with the prior art, the present application can reduce the sampling consumption of the core sample, can measure the anisotropy of acoustic wave and resistivity from multiple directions on one core sample, greatly reduces the number of rock samples required for experiments, and reduces the sampling consumption. Overall, compared with the traditional prior art, the present application can obtain more abundant and accurate acoustic wave velocity and resistivity anisotropy information based on fewer core samples, has higher practicality, and has higher innovation. Moreover, the measurement results of the present application can reflect the anisotropy difference of acoustic wave propagation speed in different directions, and are suitable for both longitudinal waves and transverse waves.

[0032] 2. The present application improves the accuracy of experimental results, because the rock physical responses in different directions obtained by experiments are all from the same sample, and the anisotropy coefficients obtained are almost not affected by the lithological heterogeneity of the sample, while the anisotropy coefficients of rock physical responses in different directions measured by different core samples in the prior art are easily affected by the difference in mineral composition of the sample.

[0033] 3. The experimental orientation of this invention is flexible and variable. During the experiment, the rock core can be placed arbitrarily according to the experimenter's ideas to obtain different measurement orientations, and can be adjusted at any time. In contrast, the azimuth angle that can be examined by existing technologies is determined at the time of sampling, which is fixed and unchangeable, and has poor flexibility. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure used in the existing technology for measuring rock anisotropy based on cubic cores;

[0035] Figure 2 This is a schematic diagram of the structure used in the existing technology to measure rock anisotropy using several plunger cores.

[0036] Figure 3 A schematic diagram illustrating the direction of sound wave propagation during measurement using existing techniques.

[0037] Figure 4 This is a flowchart of the present invention;

[0038] Figure 5 This is a schematic diagram of the core sample used in this invention;

[0039] Figure 6 This is a schematic diagram of the measuring seat in this invention;

[0040] Figure 7 This is a schematic diagram of the structure during measurement according to the present invention;

[0041] Figure 8 This is a planar schematic diagram showing the direction of sound wave propagation during the measurement process of this invention;

[0042] Figure 9 This is a three-dimensional schematic diagram of the direction of sound wave propagation during measurement according to the present invention;

[0043] Figure 10 This is a graph showing the variation of resistivity anisotropy coefficient, longitudinal wave anisotropy coefficient and transverse wave anisotropy coefficient of the core sample with angle during measurement.

[0044] The markings in the figure are: 1. Core sample, 2. Base plate, 3. Limiting clip, 4. Top column, 5. Acoustic-electric transceiver probe, 6. Straight line through the center of the circle. Detailed Implementation

[0045] Example 1

[0046] like Figure 4 As shown, this embodiment provides a method for measuring the anisotropy of acoustic velocity and resistivity in layered shale, which includes the following steps:

[0047] Step 1: Drill a 1.5 inch (or other size) cylindrical core sample from a full diameter core or outcrop rock of a bedded shale, and make sure that the anisotropy of petrophysical parameters can be reflected on the end surface of the core sample. For example, as shown in FIG. 1, for a bedded anisotropic shale, the axial direction of the core sample should be parallel to the bedding plane of the bedded shale. Figure 5

[0048] Step 2: Set up a non-conductive measuring seat, and place the core sample on the measuring seat, and set a center-crossing mark line on the top surface of the core sample. For a bedded shale, it is recommended that the mark line be parallel to the bedding plane, or the mark line be consistent with the wellbore direction of the horizontal well in the target layer of the study area.

[0049] Then set two sets of mutually perpendicular acoustic-electric transceiver probes on the side surface of the core sample, each set of acoustic-electric transceiver probes including an acoustic-electric transmitting probe and an acoustic-electric receiving probe, the acoustic-electric transmitting probe and the acoustic-electric receiving probe of each set of acoustic-electric transceiver probes being symmetrically arranged on the two sides of the core sample, the axis of the acoustic-electric transmitting probe and the axis of the acoustic-electric receiving probe in each set of acoustic-electric transceiver probes coinciding, and the axes of the two being perpendicular to the axis of the core sample.

[0050] It should be noted that the four acoustic-electric probes (two acoustic-electric transmitting probes and two acoustic-electric receiving probes) in the two sets of acoustic-electric transceiver probes are distributed at 90° to each other, between the opposite acoustic-electric transmitting probe and the acoustic-electric receiving probe, the acoustic-electric transmitting probe generates an acoustic wave pulse signal, and the time difference from the acoustic wave transmission to the acoustic wave signal received by the acoustic-electric receiving probe is recorded, and based on the ratio of the core diameter to the recorded time difference, the acoustic wave speed of the core sample in the direction can be obtained. In addition, the resistance can be measured directly by an impedance analyzer to measure the resistance between the acoustic-electric transmitting probe and the acoustic-electric receiving probe.

[0051] Step 3: Rotate the core sample, overlap the mark line with the axis of one of the sets of acoustic-electric transceiver probes as the initial orientation, and then place a top column on the top surface of the core sample, the outer diameter of the top column being smaller than the outer diameter of the core sample; after placing the top column, the top column and the two sets of acoustic-electric transceiver probes are used to apply triaxial stress to the core sample from the X, Y, and Z directions, respectively.

[0052] Step 4: Measure the core sample by the two sets of acoustic-electric transceiver probes to obtain the resistance and acoustic wave speed when the axis overlaps the mark line, and the resistance and acoustic wave speed when the axis is perpendicular to the mark line.

[0053] Since two sets of acoustic-electric transceiver probes are provided in the embodiment, two resistance values and two acoustic wave speed values can be measured at the initial orientation, specifically, the resistance value and the acoustic wave speed value when the axis of one of the sets of acoustic-electric transceiver probes overlaps the mark line, and the resistance value and the acoustic wave speed value when the axis of the other set of acoustic-electric transceiver probes is perpendicular to the mark line. ​

[0054] Step 5: Remove the triaxial stress, remove the top column and the acoustic and electric transceiver probe, and then rotate the core sample in multiple times. After each rotation, repeat steps 3 and 4 to obtain the resistance and acoustic wave speed of each set of acoustic and electric transceiver probes at each angle.

[0055] This step is based on two sets of acoustic and electric transceiver probes. After each rotation of the core sample, two resistance values and two acoustic wave speed values can also be measured. Since the two sets of acoustic and electric transceiver probes are perpendicular to each other, only need to rotate the core sample by 90 degrees, that is, change the overlap of the marker line with the axis of the first set of acoustic and electric transceiver probes to the second set of acoustic and electric transceiver probes, and at the same time the marker line will be perpendicular to the first set of acoustic and electric transceiver probes. The rotation from 90 to 180 degrees will repeat the rotation from 0 to 90 degrees, so in the actual measurement process, the core sample is rotated in multiple times, each rotation is 10-30 degrees. Of course, according to the actual needs, each rotation can also be 5 degrees, 45 degrees or other angles, etc.

[0056] Step 6: According to the resistance and acoustic wave speed measured by the two sets of acoustic and electric transceiver probes at the same angle relative to the marker line, respectively calculate the average resistance and average acoustic wave speed of the core sample at each angle.

[0057] It should be noted that the average resistance in this step is calculated according to the resistance measured by the two sets of acoustic-electric transceiving probes at the same angle relative to the marker line, and the average acoustic wave speed is calculated according to the acoustic wave speed measured by the two sets of acoustic-electric transceiving probes at the same angle relative to the marker line. For example, when the core sample is rotated by 30 degrees, the angle of the first set of acoustic-electric transceiving probes relative to the marker line is 30 degrees, and the angle of the second set of acoustic-electric transceiving probes relative to the marker line is 60 degrees. At this time, the first set of acoustic-electric transceiving probes measures the resistance and acoustic wave speed at 30 degrees, and the second set of acoustic-electric transceiving probes measures the resistance and acoustic wave speed at 60 degrees. After rotating the core sample by 30 degrees again, the angle of the first set of acoustic-electric transceiving probes relative to the marker line is 60 degrees, and the angle of the second set of acoustic-electric transceiving probes relative to the marker line is 30 degrees. At this time, the first set of acoustic-electric transceiving probes measures the resistance and acoustic wave speed at 60 degrees, and the second set of acoustic-electric transceiving probes measures the resistance and acoustic wave speed at 30 degrees. Then the average resistance at 30 degrees is calculated by averaging the resistance measured by the first set of acoustic-electric transceiving probes at 30 degrees and the resistance measured by the second set of acoustic-electric transceiving probes at 30 degrees, and the average resistance at 60 degrees is calculated by averaging the resistance measured by the first set of acoustic-electric transceiving probes at 60 degrees and the resistance measured by the second set of acoustic-electric transceiving probes at 60 degrees. The average acoustic wave speed at 30 degrees is calculated by averaging the acoustic wave speed measured by the first set of acoustic-electric transceiving probes at 30 degrees and the acoustic wave speed measured by the second set of acoustic-electric transceiving probes at 30 degrees, and the average acoustic wave speed at 60 degrees is calculated by averaging the acoustic wave speed measured by the first set of acoustic-electric transceiving probes at 60 degrees and the acoustic wave speed measured by the second set of acoustic-electric transceiving probes at 60 degrees. Based on this, the accuracy of the measurement results can be effectively improved

[0058] Step 7: Calculate the resistivity anisotropy coefficient of the core sample at each angle according to the average resistance at each angle and the average resistance when the acoustic-electric transceiving probe is perpendicular to the marker line, and calculate the acoustic wave anisotropy coefficient of the core sample at each angle according to the average acoustic wave speed at each angle.

[0059] In actual measurement, the acoustic wave propagation direction of the method Figure 8 , 9 is shown in the figure, which is completely different from the acoustic wave propagation method shown in the prior art Figure 3 , so that the present application can obtain more abundant and accurate acoustic wave speed and resistivity anisotropy information based on less core sample, and the measurement results can also reflect the anisotropy difference of acoustic wave propagation speed in different directions, which is suitable for both longitudinal waves and transverse waves.

[0060] Example 2

[0061] Based on example 1, the calculation method of the resistivity anisotropy coefficient and the calculation method of the acoustic wave anisotropy coefficient are further limited in this embodiment. Specifically,

[0062] For resistivity anisotropy coefficient, although the core sample is not a cross-section uniform medium in the measurement direction, the shape of the rock is exactly the same in each direction, and therefore, the resistivity r and resistance R can be expressed as r = KR. When the size and shape of the electrode and the contact surface of the core sample, and the size and shape of the core sample are fixed, K is a constant. Therefore, the resistivity anisotropy coefficient can be directly obtained from the measured resistance, and the calculation method is:

[0063]

[0064] wherein a 电 (0) is the resistivity anisotropy coefficient of the core sample at angle 0, r(0) is the average resistivity of the core sample at angle 0, r 90 is the average resistivity of the core sample when the acoustic-electric transceiver probe is perpendicular to the marker line, R(0) is the average resistance of the core sample at angle 0, R 90 is the average resistance of the core sample when the acoustic-electric transceiver probe is perpendicular to the marker line, and K is a constant of the core sample.

[0065] Similarly, the calculation method of acoustic anisotropy coefficient is:

[0066]

[0067] wherein a 声( (0) is the acoustic anisotropy coefficient of the core sample at angle 0, V(0) is the average acoustic velocity of the core sample at angle 0, V0 is the average acoustic velocity of the core sample when the axis is overlapped with the marker line, At(0) is the time difference of acoustic signal from the acoustic-electric transmitting probe to the acoustic-electric receiving probe of the core sample at angle 0, At0 is the time difference of acoustic signal from the acoustic-electric transmitting probe to the acoustic-electric receiving probe of the core sample when the axis is overlapped with the marker line, and D is the diameter of the core sample.

[0068] Example 3

[0069] As shown in Figure 4 , the present embodiment provides a method for measuring acoustic velocity and resistivity anisotropy of bedded shale, which comprises the following steps:

[0070] Step 1: Drill a 1.5-inch (or other size) cylindrical core sample from a full-diameter core or outcrop rock of bedded shale, and ensure that the anisotropy of petrophysical parameters can be reflected on the end surface of the core sample. For example, as shown in Figure 5 , for bedded anisotropic shale, the axial direction of the core sample should be parallel to the bedding plane of the bedded shale.

[0071] Step 2: Set up a non-conductive measuring seat, place the core sample on the measuring seat, and set a marker line through the center on the top surface of the core sample. For bedding shale, it is recommended that the marker line be parallel to the bedding plane, or that the marker line be consistent with the wellbore orientation of the horizontal well of the target layer in the study area.

[0072] Then, two sets of mutually perpendicular acoustic and electrical transceiver probes are set on the side of the core sample. Each set of acoustic and electrical transceiver probes includes an acoustic and electrical transmitting probe and an acoustic and electrical receiving probe. The acoustic and electrical transmitting probes of each set of acoustic and electrical transceiver probes are symmetrically set on both sides of the core sample. The axis of the acoustic and electrical transmitting probe in each set of acoustic and electrical transceiver probes coincides with the axis of the acoustic and electrical receiving probe, and both axes intersect perpendicularly with the axis of the core sample.

[0073] like Figure 6 As shown, the measuring base in this embodiment includes a circular base plate and four limiting clips uniformly fixed on the base plate. The four limiting clips are distributed at 90° to each other, and the distances from the center of the base plate to the four limiting clips are equal and equal to the radius of the core sample. Any acoustic emission probe / acoustic receiving probe is located between two adjacent limiting clips, and the four acoustic probes (two acoustic emission probes and two acoustic receiving probes) and the four limiting clips are placed at 45° to each other. Furthermore, to better confine the core sample, the inner side of each limiting clip is designed as an arc surface with a radius of curvature equal to the radius of the core sample.

[0074] Step 3: As Figure 7 As shown, the core sample is rotated, and the marker line is aligned with the axis of one set of acoustic and electrical transceivers as the initial orientation. Then, a top column is placed on the top surface of the core sample, with the outer diameter of the top column being smaller than that of the core sample. After placing the top column, triaxial stress is applied to the core sample from the X, Y, and Z directions through the top column and the two sets of acoustic and electrical transceivers.

[0075] Step 4: Measure the core sample using two sets of acoustic transceiver probes to obtain the resistance and acoustic velocity when the axis overlaps with the marker line, and the resistance and acoustic velocity when the axis is perpendicular to the marker line.

[0076] Step 5: Remove the triaxial stress, remove the top column and acoustic transceiver probe, and then rotate the core sample multiple times. Repeat steps 3 and 4 after each rotation to obtain the resistance and sound velocity of each set of acoustic transceiver probes at each angle.

[0077] Step 6: Based on the resistance and acoustic velocity measured by the two sets of acoustic transceiver probes at the same angle relative to the marker line, calculate the average resistance and average acoustic velocity of the core sample at each angle. The calculation method is the same as that in Example 2 and will not be repeated here.

[0078] Step 7: Calculate the resistivity anisotropy coefficient of the core sample at each angle according to the average resistivity at each angle and the average resistivity when the acoustic-electric transducer is perpendicular to the marker line, and calculate the acoustic anisotropy coefficient of the core sample at each angle according to the average acoustic velocity at each angle.

[0079] Embodiment 4

[0080] As shown in Figure 4 , the embodiment provides a method for measuring the acoustic velocity and resistivity anisotropy of bedded shale, which comprises the following steps:

[0081] Step 1: Drill a 1.5-inch (or other size) cylindrical core sample from a full-diameter core of bedded shale or outcrop rock, and ensure that the anisotropy of petrophysical parameters can be reflected on the end face of the core sample. For example, as shown in Figure 5 , for bedded anisotropic shale, the axial direction of the core sample should be parallel to the bedding plane of the bedded shale.

[0082] Step 2: Set up a non-conductive measuring seat, and place the core sample on the measuring seat in a limited manner. Set a marker line passing through the center on the top surface of the core sample. For bedded shale, it is recommended that the marker line be parallel to the bedding plane, or that the marker line be consistent with the wellbore orientation of the horizontal well in the target layer of the study area. Then set two sets of mutually perpendicular acoustic-electric transducer probes on the side surface of the core sample, each set of acoustic-electric transducer probe comprising an acoustic-electric transmitting probe and an acoustic-electric receiving probe. The acoustic-electric transmitting probe and the acoustic-electric receiving probe of each set of acoustic-electric transducer probe are symmetrically arranged on the two sides of the core sample, and the axis of the acoustic-electric transmitting probe and the axis of the acoustic-electric receiving probe in each set of acoustic-electric transducer probe coincide, and both axes are perpendicular to the axis of the core sample.

[0083] As shown in Figure 6 , the measuring seat in the embodiment comprises a circular base disc and four limiting clamps uniformly fixed on the base disc. The four limiting clamps are distributed at 90° to each other, and the distance from the four limiting clamps to the center of the base disc is equal and equal to the radius of the core sample. Any acoustic-electric transmitting probe / acoustic-electric receiving probe is located between the two adjacent limiting clamps, and the four acoustic-electric probes (two acoustic-electric transmitting probes and two acoustic-electric receiving probes) and the four limiting clamps are placed at 45° to each other. In addition, in order to better limit the core sample, the inner side of the limiting clamps is provided with an arc surface with a curvature radius equal to the radius of the core.

[0084] Step 3: As shown in Figure 7As shown, the core sample is rotated, a mark line is overlapped with the axis of one set of the acoustic and electric transceiving probes as the initial orientation, and then a top pillar is placed on the top surface of the core sample, the outer diameter of the top pillar being smaller than that of the core sample.

[0085] Step 4: The core sample is measured by the two sets of acoustic and electric transceiving probes to obtain the resistance and acoustic wave velocity when the axis is overlapped with the mark line, and to obtain the resistance and acoustic wave velocity when the axis is perpendicular to the mark line.

[0086] Step 5: The triaxial stress is removed, the top pillar and the acoustic and electric transceiving probes are removed, and the core sample is rotated for multiple times, after each rotation, steps 3 and 4 are repeated to obtain the resistance and acoustic wave velocity of each set of acoustic and electric transceiving probes at each angle.

[0087] Step 6: The average resistance and average acoustic wave velocity of the core sample at each angle are calculated according to the resistance and acoustic wave velocity measured by the two sets of acoustic and electric transceiving probes at the same angle relative to the mark line. The calculation method is the same as that in Example 2, and is not repeated here.

[0088] Step 7: The resistivity anisotropy coefficient of the core sample at each angle is calculated according to the average resistance at each angle and the average resistance when the acoustic and electric transceiving probes are perpendicular to the mark line, and the acoustic wave anisotropy coefficient of the core sample at each angle is calculated according to the average acoustic wave velocity at each angle.

[0089] In step 2 of the embodiment, in order to facilitate the adjustment of the angle of the core when placing the core to achieve accurate measurement of different azimuth angles, a plurality of equal-angle-distributed straight lines passing through the center of the circle are engraved on the base plate, the angle between any two adjacent straight lines is 10°-20°, and preferably 15°. Of course, the angle is only used as a reference when rotating the core sample, and it can also be other angles.

[0090] Example 5

[0091] The applicant also verified the application by the method described in Example 4 as follows:

[0092] The applicant obtained a layer of rational shale cylindrical sample from a well in Sichuan Basin, the sample has a diameter of 1.5 inches, and parallel bedding planes can be seen on the end surface of the cylinder. The acoustic wave and resistivity anisotropy of the sample were measured by the method described in the application, the triaxial pressure was set to 1 MPa during the measurement, the measurement angle interval was 10°, a mark line parallel to the bedding plane was drawn on the end surface, and the resistivity anisotropy coefficient, the longitudinal wave and the transverse wave anisotropy coefficient of the core sample were obtained after the measurement as shown in the following table. Figure 10 ​

[0093]

[0094] By Figure 10 And the above table, at the initial angle, i.e., the rotation angle is 0°, the sample's P-wave and S-wave velocity is maximum, and the resistivity is minimum, because the sound wave propagates fastest along the bedding, and the resistivity in the bedding direction is minimum. When the rotation angle is 90°, the sample's P-wave and S-wave velocity is minimum, and the resistivity is maximum, because the sound wave propagates slowest perpendicular to the bedding, and the resistivity in the direction perpendicular to the bedding is maximum. Therefore, the anisotropy coefficient of P-wave and S-wave velocity decreases from 1 to 0.787 and 0.740, respectively, as the rotation angle increases from 0° to 90°, and the anisotropy coefficient of resistivity increases from 0.135 to 1 as the rotation angle increases from 0° to 90°. The experimental law conforms to the rock physics theory cognition, and confirms the correctness and feasibility of the present application.

[0095] The above is only a specific embodiment of the present application, any feature disclosed in the specification can be replaced by other equivalent or similar purpose replacement features, unless specifically described; all features disclosed, or steps in all methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A method for measuring the anisotropy of acoustic wave velocity and resistivity in layered shale, characterized in that... Includes the following steps: Step 1: Obtain cylindrical core samples from the bedding shale and ensure that the anisotropy of rock physical parameters can be reflected on the end face of the core sample; Step 2: Place the core sample on the measuring base and mark the center of the circle on the top surface of the core sample. Then, set two sets of mutually perpendicular acoustic and electrical transceiver probes on the side of the core sample. Each set of acoustic and electrical transceiver probes includes an acoustic and electrical transmitting probe and an acoustic and electrical receiving probe symmetrically arranged on both sides of the core sample. The axis of each set of acoustic and electrical transceiver probes intersects the axis of the core sample perpendicularly. Step 3: Overlap the marker line with the axis of one set of acoustic and electrical transceivers as the initial orientation, place a top column on the top surface of the core sample, and apply triaxial stress to the core sample from the X, Y, and Z directions respectively through the top column and the two sets of acoustic and electrical transceivers. Step 4: Measure the core sample using two sets of acoustic transceiver probes to obtain the resistance and acoustic velocity when the axis overlaps with the marker line, and the resistance and acoustic velocity when the axis is perpendicular to the marker line. Step 5: Remove the triaxial stress, remove the top column and acoustic transceiver probe, and then rotate the core sample multiple times. Repeat steps 3 and 4 after each rotation to obtain the resistance and sound velocity of each set of acoustic transceiver probes at each angle. Step 6: Based on the resistance and sound velocity measured by the two sets of acoustic transceiver probes at the same angle relative to the marker line, calculate the average resistance and average sound velocity of the core sample at each angle. Step 7: Calculate the resistivity anisotropy coefficient of the core sample at each angle based on the average resistance at each angle and the average resistance when the acoustic transceiver probe is perpendicular to the marker line. Calculate the acoustic anisotropy coefficient of the core sample at each angle based on the average acoustic velocity at each angle. In step 6, the method for calculating the resistivity anisotropy coefficient is as follows: in, For core samples in Resistivity anisotropy coefficient at an angle For core samples in Average resistivity at angle, This represents the average resistivity of the core sample when the acoustic-electric transceiver probe is perpendicular to the marker line. For core samples in Average resistance at an angle, This represents the average resistance of the core sample when the acoustic-electric transceiver probe is perpendicular to the marker line. For the core sample, is a constant. In step 6, the method for calculating the anisotropy coefficient of the sound wave is as follows: in, For core samples in The anisotropy coefficient of acoustic waves at an angle, For core samples in The average velocity of sound at an angle, The average acoustic velocity of the core sample when the axis overlaps with the marker line. For core samples in The time difference between the acoustic wave signal at an angle and the acoustic wave signal traveling from the acoustic transmitting probe to the acoustic receiving probe. This represents the time difference in acoustic signal transmission from the acoustic emission probe to the acoustic reception probe when the core sample's axis overlaps with the marker line. The diameter of the core sample is given.

2. The method for measuring the anisotropy of acoustic wave velocity and resistivity in layered shale according to claim 1, characterized in that: In step 1, the axial direction of the core sample is parallel to the bedding plane of the bedding shale.

3. The method for measuring the acoustic velocity and resistivity anisotropy of layered shale according to claim 1, characterized in that: In step 2, the measuring seat includes a circular base plate and four limiting clips evenly fixed on the base plate. The four limiting clips are distributed at 90° to each other, and the distance between the four limiting clips and the center of the base plate is equal and equal to the radius of the core sample.

4. The method for measuring the anisotropy of acoustic wave velocity and resistivity in layered shale according to claim 3, characterized in that: In step 2, the inner side of the limiting card is an arc surface with a radius of curvature equal to that of the rock core.

5. The method for measuring the acoustic velocity and resistivity anisotropy of layered shale according to claim 3, characterized in that: In step 2, any acoustic transmitting probe / acoustic receiving probe is located between two adjacent limit cards, and the acoustic transmitting probe and the limit card are placed at 45° to each other.

6. The method for measuring the anisotropy of acoustic wave velocity and resistivity in layered shale according to claim 1, characterized in that: In step 2, the base plate is engraved with several straight lines passing through the center of the circle, which are distributed at equal angles.

7. The method for measuring the anisotropy of acoustic wave velocity and resistivity in layered shale according to claim 6, characterized in that: In step 2, the angle between the straight line passing through the center of the circle on the base plate is 10°-20°.

8. The method for measuring the anisotropy of acoustic wave velocity and resistivity in layered shale according to claim 1, characterized in that: In step 3, the outer diameter of the top column is smaller than the outer diameter of the core sample.

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