Sound wave measurement method for rock debris in oil-based mud and sound wave logging instrument

Abstract

The invention discloses a sound wave measurement method for rock debris in oil-based mud and a sound wave logging instrument. The sound wave measurement method comprises the following steps: screening a rock debris sample with a millimeter-scale particle size and at least one relatively flat contact surface from the oil-based mud returned from a drilling well; sequentially numbering the rock debris samples and establishing a sample information table; cleaning the rock debris samples in batches; measuring the thickness d of the rock debris sample; collecting the first wave arrival time sum of the longitudinal wave and the transverse wave through a sound wave measurement system, and respectively calculating the longitudinal wave speed and the transverse wave speed; converting the longitudinal wave velocity and the transverse wave velocity into longitudinal wave time difference and transverse wave time difference; removing abnormal values; the method can effectively support underground stratum acoustic parameter inversion and logging analysis, and has good field adaptability and engineering application value.

Description

Technical Field

[0001] This invention relates to the field of geophysical exploration technology, and in particular to a method for measuring rock cuttings in oil-based drilling mud and an acoustic logging instrument. Background Technology

[0002] Rock cuttings in oil-based drilling mud refer to drilling cuttings generated during oil and gas drilling operations using drilling mud formulated with mineral oil as the continuous phase. Offshore oil and gas exploration faces challenges in coring, making the acquisition of rock cuttings acoustic velocity parameters (including P-wave and S-wave velocities) a critical problem for efficient evaluation of formation mechanical parameters. Traditional methods involve resin encapsulation of rock cuttings, followed by curing and polishing before measurement. This method is time-consuming (at least 24 hours) and cannot meet the needs of rapid rock cuttings testing. Furthermore, on-site measurements are affected by factors such as oil-based drilling mud contamination, irregular sample morphology, and measurement delays, all of which interfere with the measurement of rock cuttings acoustic velocity parameters, resulting in low accuracy and efficiency. Therefore, a method is needed to meet the requirements of on-site measurements and achieve high accuracy and efficiency. Summary of the Invention

[0003] (a) Technical issues

[0004] The purpose of this invention is to provide a method and instrument for acoustic measurement of rock cuttings in oil-based drilling mud, which overcomes interference from factors such as oil-based mud contamination when performing acoustic measurement of rock cuttings in oil-based drilling mud at the drilling site, and has high measurement accuracy and efficiency.

[0005] (II) Technical Solution

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for acoustic measurement of rock cuttings in oil-based drilling mud includes the following steps:

[0008] Oil-based mud cuttings with a particle size of millimeters were screened from the oil-based mud returned from drilling as cuttings samples. The cuttings samples had at least one relatively flat contact surface.

[0009] The rock cuttings samples were numbered sequentially according to well section, depth and collection time, and a sample information table was created.

[0010] Rock cuttings samples were cleaned in batches using an ultrasonic cleaner, and fluorescence testing was performed after cleaning.

[0011] The thickness of rock cutting samples that have passed fluorescence testing is automatically measured using a laser sensor rangefinder. And record it in the sample information table;

[0012] A sonic measurement system sends longitudinal and transverse waves toward the rock cutting sample, and the arrival time of the first wave of the longitudinal wave as it passes through the thickness of the rock cutting sample is collected. The first wave arrival time when the shear wave passes through the thickness of the rock debris sample And calculate the longitudinal wave velocity respectively. and transverse wave velocity ,

[0013] ;

[0014] ;

[0015] P-wave velocity and transverse wave velocity Converted to P-wave time difference and transverse wave time difference ,

[0016] ;

[0017] ;

[0018] In the above formula, The rock cuttings samples are numbered 1, 2, 3...N; The longitudinal wave zero-delay reference time for the acoustic wave measurement system. The zero-delay reference time for the transverse wave of the acoustic wave measurement system;

[0019] Data consistency was compared based on the P-wave and S-wave transit times of rock cuttings samples at the same depth, and outlier values ​​were removed.

[0020] P-wave velocity after removing outliers transverse wave velocity P-wave time difference and transverse wave time difference Record the information in the sample information table and output it.

[0021] Furthermore, the sample mean values ​​of the P-wave transit time for each rock cutting sample were calculated. and sample standard deviation The sample mean of transverse wave time difference and sample standard deviation ,

[0022] , ;

[0023] , ;

[0024] In the above formula, The rock cuttings samples are numbered 1, 2, 3...N;

[0025] when or If the abnormal values ​​are determined to be due to micro-cracks inside the rock cuttings sample or operational errors, they will be discarded.

[0026] Furthermore, the relative standard deviation of the P-wave time difference is calculated separately. The relative standard deviation of the transverse wave time difference ,

[0027] ;

[0028] ;

[0029] when or At that time, the measurement process or rock cutting samples are checked.

[0030] Furthermore, the longitudinal wave zero-delay reference time and transverse wave zero-delay reference time The acquisition process includes:

[0031] A standard aluminum block with known thickness, longitudinal wave velocity, and transverse wave velocity is clamped in the acoustic wave measurement system;

[0032] By sending longitudinal and transverse waves to a standard aluminum block and measuring the corresponding propagation speeds, the zero-delay reference time for the longitudinal wave can be obtained. and transverse wave zero-delay reference time .

[0033] Furthermore, the cleaning process for rock cuttings samples includes:

[0034] Dividing grooves are set in the ultrasonic cleaner, and rock cutting samples are placed into different dividing grooves according to their numbers;

[0035] Add anhydrous alcohol to the separator;

[0036] The ultrasonic cleaner is set to an ultrasonic frequency of 40kHz, an output power of 200W, and a cleaning time of 1 minute.

[0037] After cleaning, rock fragments that are solidified and have no obvious residue on the surface are used as measurement samples.

[0038] Furthermore, the arrival time of the first wave when the longitudinal wave passes through the thickness of the rock debris sample was determined. The first wave arrival time when the shear wave passes through the thickness of the rock debris sample The process includes:

[0039] The acoustic measurement system sequentially emits longitudinal and transverse waves toward the rock cutting sample.

[0040] Acquire longitudinal wave and transverse wave waveform data using an oscilloscope;

[0041] Eliminating noise and interference waveforms based on Wiener filtering and mode decomposition algorithms;

[0042] Analysis of wave arrival positions in longitudinal and transverse wave waveform data based on threshold detection or cross-correlation algorithms;

[0043] The arrival time of the first P-wave is obtained based on the arrival position. The arrival time of the first wave of a transverse wave .

[0044] An acoustic logging instrument that applies the acoustic measurement method for cuttings in oil-based mud as described above includes an acoustic measurement system and an ultrasonic cleaner. The acoustic measurement system includes a laser rangefinder, a pressure sensor, an oscilloscope, and a clamp for holding the cuttings sample.

[0045] (III) Beneficial Effects

[0046] Rock cuttings samples with a particle size in the millimeter range (generally 1-3 mm) and at least one relatively flat contact surface are selected to ensure good formation representativeness, suitability for acoustic measurement, and ease of cleaning. Furthermore, they are numbered according to well section, depth, and acquisition time for easier data processing and output. The oil-based drilling mud is quickly cleaned using an ultrasonic cleaner, minimizing interference during measurement. The thickness of the samples is then measured using a laser sensor rangefinder. Simultaneously, by measuring the arrival times of the first longitudinal and transverse waves using an acoustic system, and combining this with the zero-delay reference time of the acoustic measurement system to eliminate time errors, a higher-precision longitudinal wave velocity can be obtained. and transverse wave velocity Simultaneously converted into P-wave time difference and transverse wave time difference The measurement data of multiple cuttings samples at the same depth were compared for consistency, and abnormal values ​​were removed. A sample information table integrating comprehensive parameters such as well section, depth, acquisition time, P-wave velocity, S-wave velocity, P-wave transit time, and S-wave transit time was generated and output. As a result, the error of P-wave transit time and S-wave transit time measured in oil-based environment was significantly reduced, which can effectively support the inversion of downhole formation acoustic parameters and logging analysis. Moreover, the measurement method has good field adaptability and engineering application value. Attached Figure Description

[0047] Figure 1 This is a schematic flowchart of the acoustic wave measurement method of the present invention;

[0048] Figure 2This is a logic block diagram of the acoustic wave measurement method of the present invention. Detailed Implementation

[0049] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0050] See Figures 1-2 As shown, an embodiment of the present invention proposes a method for acoustic measurement of rock cuttings in oil-based drilling mud. Specifically, the method is applied to an acoustic logging instrument, which includes an acoustic measurement system and an ultrasonic cleaner. The acoustic measurement system includes a laser rangefinder, a pressure sensor, an oscilloscope, and a clamp for holding the rock cuttings sample, forming an integrated instrument that can measure the longitudinal and transverse wave parameters of rock cuttings samples in real time at the drilling site. The internal integrated software system and electrical control can be implemented using existing technologies by those skilled in the art. The key is to integrate mature instruments and unify their control and operation. This embodiment primarily utilizes an acoustic logging instrument to create a real-time, fast, highly accurate, and efficient method for measuring the acoustic parameters of rock cuttings samples, facilitating the widespread application of field measurement.

[0051] Specifically, it includes the following steps:

[0052] S100. Select oil-based mud cuttings with a particle size of millimeters from the oil-based mud returned from drilling as cuttings samples. The cuttings samples shall have at least one relatively flat contact surface.

[0053] At the drilling site, rock cuttings samples from oil-based drilling mud are screened. Rock cuttings samples with a particle size range of 1mm-3mm have good formation representativeness and are suitable for sonic measurements. They also remove non-native impurities such as wellbore debris and drill string fragments, ensuring sample purity and representativeness, which guarantees the accuracy of subsequent measurements. Furthermore, rock cuttings samples should have at least one relatively flat contact surface; a smooth contact surface can also reduce measurement errors to some extent. The screening process can be carried out using an automatic particle size analyzer or manually using tools such as vernier calipers for rapid measurement. Dimensional precision is not required during screening; samples within the 1mm to 3mm range are sufficient.

[0054] The relatively flat contact surface is designed to form a stable and comprehensive contact with the plane under a light vertical pressure of approximately 1 N, thus meeting the requirements for acoustic wave coupling.

[0055] S200. Number the rock cuttings samples sequentially according to well section, depth and collection time, and establish a sample information table.

[0056] The final output data needs to be applicable and meet engineering application requirements. Rock cuttings samples are numbered by well section, depth, and acquisition time to facilitate correlation of subsequent measurement data and improve the applicability of the final data. The numbering can be used to create batch sample numbers based on well section, depth, and acquisition time; samples from the same well section, depth, and acquisition time use the same numbering system, employing natural numbers.

[0057] S300: Batch cleaning of rock cutting samples is performed using an ultrasonic cleaner, and fluorescence testing is conducted after cleaning.

[0058] Because the rock cuttings samples are covered with oil-based mud, they need to be thoroughly cleaned to avoid interference from the mud during the measurement process. Specifically, an ultrasonic cleaner is used for cleaning. The cleaning process for the rock cuttings samples includes:

[0059] First, a separator is set up in the ultrasonic cleaner. Based on the number of the rock cutting samples, they are placed into different separators. The separator can prevent the numbering of the rock cutting samples from being confused.

[0060] Then add anhydrous alcohol to the separator. Anhydrous alcohol has a good cleaning effect on oil-based mud and evaporates quickly, allowing it to dry rapidly.

[0061] Then set the ultrasonic cleaner's ultrasonic frequency to 40kHz, output power to 200W, and cleaning time to 1 minute.

[0062] Finally, after cleaning, rock fragments that are consolidated and have no obvious residue on the surface are used as measurement samples.

[0063] After cleaning, the cleaning effect is evaluated to facilitate the classification and processing of the cleaned rock cuttings samples, specifically in three scenarios:

[0064] 1) It is solidified and has no obvious residue on the surface, so it can be directly used for acoustic testing.

[0065] 2) It is solidified, but there are obvious residues on the surface, requiring further cleaning.

[0066] 3) The rock fragments are scattered, so the rock fragments samples need to be reselected and cleaned. The broken samples cannot be compressed and shear wave data cannot be obtained, so the samples need to be reselected.

[0067] Rock cuttings samples that meet the measurement requirements are clamped in the sonic logging instrument to form a relative position. Specifically, the clamping force is detected by a pressure sensor to be 1N, so as to avoid damage and measurement results caused by excessive clamping force.

[0068] The sample loading system was calibrated under no-load conditions to ensure that the actual applied pressure value matched the set pressure value, and the linearity of the pressure sensor output was verified. Compared with the traditional manual pressing or counterweight loading mode, the clamping method can provide controllable pressure parameters for all rock cutting samples, which can ensure the coupling between the rock cutting sample and the probe and avoid sample damage, thus ensuring the stability and comparability of the test results.

[0069] S400: Automatically measures the thickness of rock cutting samples that have passed fluorescence testing using a laser sensor rangefinder. And record it in the sample information table, thickness The unit is mm, and the thickness is measured using a non-contact method, which ensures thickness accuracy.

[0070] Before measuring the thickness, the laser sensor rangefinder needs to be calibrated. Under no-load conditions, the laser rangefinder should be zeroed to ensure the system reference and the accuracy of the thickness measurement reference. The laser sensor measurement accuracy is approximately ±0.3mm.

[0071] S500: Longitudinal and transverse waves are sent toward the rock cutting sample via an acoustic measurement system, and the arrival time of the first wave of the longitudinal wave as it passes through the thickness of the rock cutting sample is collected. The first wave arrival time when the shear wave passes through the thickness of the rock debris sample And calculate the longitudinal wave velocity respectively. and transverse wave velocity ,

[0072] ;

[0073] ;

[0074] S600, longitudinal wave velocity and transverse wave velocity Converted to P-wave time difference and transverse wave time difference ,

[0075] ;

[0076] ;

[0077] In the above formula, The rock cuttings samples are numbered 1, 2, 3...N; The longitudinal wave zero-delay reference time for the acoustic wave measurement system. This is the zero-delay reference time for the transverse wave in the acoustic wave measurement system.

[0078] Among them, the longitudinal wave zero-delay reference time and transverse wave zero-delay reference time The acquisition process includes:

[0079] A standard aluminum block with known thickness, longitudinal wave velocity, and transverse wave velocity is clamped in the acoustic wave measurement system;

[0080] By sending longitudinal and transverse waves to a standard aluminum block and measuring the corresponding propagation speeds, the zero-delay reference time for the longitudinal wave can be obtained. and transverse wave zero-delay reference time .

[0081] This eliminates the influence of the probe's inherent delay, ensuring that the measurement results are the true results of the rock cuttings sample measurement, thus improving accuracy.

[0082] Furthermore, the arrival time of the first wave when the longitudinal wave passes through the thickness of the rock debris sample was determined. The first wave arrival time when the shear wave passes through the thickness of the rock debris sample The process includes:

[0083] The acoustic measurement system sequentially emits longitudinal and transverse waves toward the rock cutting sample, with the longitudinal wave emission frequency at 1000 kHz and the transverse wave emission frequency at 500 kHz.

[0084] Longitudinal and transverse wave waveforms were acquired using an oscilloscope. The oscilloscope was used for waveform data acquisition, with a longitudinal wave sampling frequency of 500 kHz and a transverse wave sampling frequency of 250 kHz. The sampling rate was 1 MHz, and the waveforms were superimposed 128 times, laying the foundation for capturing high signal-to-noise ratio waveforms.

[0085] Noise and interference waveforms are eliminated based on Wiener filtering and mode decomposition algorithms. The combined algorithm of Wiener filtering and mode decomposition can effectively eliminate waveform noise, separate interference components, purify P-wave and S-wave signals, and preserve the characteristics of the first wave leading edge, thus laying a solid signal foundation for wave arrival time measurement.

[0086] The arrival positions of P-wave and S-wave waveforms are analyzed based on threshold detection or cross-correlation algorithms. Threshold detection can quickly capture the first wave's initiation time using amplitude thresholds, while cross-correlation algorithms can achieve precise matching and positioning based on waveform similarity. Both algorithms are adaptable to different scenarios and work together to ensure the accuracy and reliability of the first wave arrival time measurement for P-waves and S-waves.

[0087] The aforementioned built-in algorithms are all integrated into the system to process the transverse and longitudinal wave waveform data acquired by the oscilloscope.

[0088] Finally, the arrival time of the first P-wave is obtained based on the arrival position. The arrival time of the first wave of a transverse wave .

[0089] The corresponding P-wave velocities were obtained by measuring the numbered rock cutting samples in sequence. transverse wave velocity P-wave time difference and transverse wave time difference However, some data may be affected by factors such as internal fractures in the rock cuttings sample, resulting in significant deviations in the measurement results. Direct output would affect the application, so it is necessary to remove abnormal data to ensure that the measurement data reflects the most accurate data from the rock cuttings sample.

[0090] S700, P-wave transit time based on rock cuttings samples at the same depth Shear wave time difference Perform a data consistency comparison and remove outlier values.

[0091] Rock cuttings samples from the same depth should have relatively consistent P-wave and S-wave transit times. Data with large differences should be screened out, and the P-wave and S-wave transit time data of multiple rock cuttings samples from the same depth that have been measured should be compared for consistency.

[0092] The following methods can be used to specifically filter out abnormal data:

[0093] Calculate the sample mean of the P-wave transit time for each rock cutting sample. and sample standard deviation The sample mean of transverse wave time difference and sample standard deviation ,

[0094] , ;

[0095] , ;

[0096] In the above formula, The numbering system is for the rock cuttings samples, numbered 1, 2, 3...N. This number represents the number of P-wave and S-wave time difference data selected from the same depth. The selected samples can be renumbered, and the numbers will be different from those recorded in the sample information table. Only the data needs to be numbered. Subsequently, all data can be removed by matching the numbers with the actual numbers of the rock cuttings samples.

[0097] Specifically, when or If any abnormal value is found due to micro-cracks inside the rock cutting sample or operational error, it will be removed. After calculating the sample mean and sample standard deviation of the P-wave transit time data and S-wave transit time data at the same depth, each data point will be judged in turn. If any one of the P-wave transit time or S-wave transit time is abnormal, the corresponding measurement parameter of the entire rock cutting sample will be removed.

[0098] Furthermore, the relative standard deviation of the P-wave time difference is calculated separately. The relative standard deviation of the transverse wave time difference ,

[0099] ;

[0100] ;

[0101] when or At that time, the measurement process or rock cutting samples are checked.

[0102] If the relative standard deviation is large, the entire measurement process or the rock cutting sample needs to be re-checked. It is possible that there was an error in the measurement process or that the selection of the rock cutting sample was incorrect. It is necessary to start the process from the rock cutting sample screening again or adjust the measurement process.

[0103] The above method can be used to filter out abnormal data in the measured P-wave and S-wave time differences.

[0104] S800, P-wave velocity after removing outliers transverse wave velocity P-wave time difference and transverse wave time difference Record the information in the sample information table and output it.

[0105] The final applicable data is consistent. All data parameters are recorded in the sample information table and then output for application in engineering practice. The longitudinal wave waveform data and the transverse wave waveform data can also be output along with the above parameters.

[0106] This process forms a complete workflow for screening, cleaning, measuring, removing abnormal data, and generating sample information tables for cuttings samples. It enables high-precision measurement of shear wave time difference and longitudinal wave time difference of cuttings samples at the drilling site, and finally generates a one-to-one corresponding sample information table. It is suitable for engineering applications such as logging acoustic logging, cuttings mechanical parameter inversion, and fine reservoir evaluation.

[0107] Using the above-described method for measuring rock cuttings in oil-based drilling mud, rapid on-site measurements can be achieved using acoustic logging instruments.

[0108] The definitions and units of the relevant parameters mentioned in this invention are as follows:

[0109] Longitudinal waves pass through the first First wave arrival time (μs) for each rock cutting sample thickness;

[0110] Longitudinal waves pass through the first First wave arrival time (μs) for each rock cutting sample thickness;

[0111] : No. P-wave velocity of each rock cuttings sample, m / s;

[0112] : No. Shear wave velocity of each rock cutting sample, m / s;

[0113] : No. The thickness of each rock fragment sample, in mm;

[0114] : No. P-wave transit time of each rock cuttings sample, μs / m;

[0115] : No. Shear wave transit time of each rock cuttings sample, μs / m;

[0116] The rock cuttings samples are numbered and numbered 1, 2, 3...N;

[0117] : The sample average of the P-wave transit time of N rock cuttings samples, in μs / m;

[0118] : Sample standard deviation of P-wave transit time for N rock cuttings samples; μs / m;

[0119] : The sample average of the shear wave transit time of N rock cuttings samples, in μs / m;

[0120] : Sample standard deviation of shear wave transit time for N rock cuttings samples; μs / m;

[0121] : Relative standard deviation of P-wave time difference, %

[0122] : Relative standard deviation of transverse wave time difference, %.

[0123] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0124] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0125] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method of measuring acoustic waves in oil-based muds, characterized in that, The method comprises the following steps: Screening millimeter-sized oil-based mud cuttings from oil-based mud returned from a well as a cutting sample, the cutting sample having at least one relatively flat contact surface; Sequentially numbering the cutting sample according to a well section, depth and collection time and establishing a sample information table; Batch cleaning the cutting sample by an ultrasonic cleaner and performing fluorescence inspection after cleaning; Automatically measuring the thickness of a rock sample that has passed a fluorescence test by a laser sensor range finder and recording in a sample information table; The acoustic wave measurement system sends a longitudinal wave and a transverse wave toward the debris sample, respectively collects a first wave arrival time of the longitudinal wave when passing through the thickness of the debris sample and a first wave arrival time of the transverse wave when passing through the thickness of the debris sample , and respectively calculates a longitudinal wave velocity and a transverse wave velocity , ； ； Convert the longitudinal wave velocity and the transverse wave velocity to the longitudinal wave transit time and the transverse wave transit time , ； ； In the above formula, is the number of the rock sample, and is 1, 2, 3, …, N; is the longitudinal wave zero delay reference time of the acoustic wave measurement system, is the transverse wave zero delay reference time of the acoustic wave measurement system; P-wave interval transit times of the same depth-based cuttings samples S-wave interval transit times Data consistency comparison was made and abnormal values were eliminated; P-wave velocity after removing abnormal values S-wave velocity P-wave interval and S-wave interval Recorded in the sample information table and output.

2. The method of claim 1, wherein, Sample mean of P-wave slowness for each sample of cuttings and sample standard deviation Sample mean of S-wave slowness for each sample of cuttings and sample standard deviation , ， ； ， ； In the above formula, is the number of the rock sample, and is 1, 2, 3, …, N; When or If so, it is determined that the abnormal value is caused by micro-fracture in the sample or operation error, and is removed.

3. The method of claim 2, wherein, The relative standard deviation of the P-wave time difference and the relative standard deviation of the S-wave time difference , ； ； When or a check is made on the measurement process or sample of the cuttings sample.

4. The method of claim 1, wherein, Longitudinal wave zero delay reference time and shear wave zero delay reference time The acquisition process comprises: Clamping a standard aluminum block with a known thickness, longitudinal wave speed and transverse wave speed in a sound wave measurement system; The longitudinal wave and the transverse wave are respectively sent to a standard aluminum block, and the corresponding propagation speeds are measured to obtain the longitudinal wave zero delay reference time and the transverse wave zero delay reference time .

5. The method of claim 1, wherein, The cleaning process of the cutting sample comprises: Setting separate grooves in the ultrasonic cleaner, and respectively placing the cutting samples in different grooves based on the numbering of the cutting samples; Adding anhydrous alcohol into the separate grooves; Setting an ultrasonic frequency of the ultrasonic cleaner to 40 kHz, an output power to 200 W and a cleaning time to 1 min; After cleaning, taking the cutting sample in a consolidated state and without obvious surface residues as a measurement sample.

6. The method of claim 1, wherein, the first arrival time of a compressional wave as it travels through the thickness of the cuttings sample and the first arrival time of a shear wave as it travels through the thickness of the cuttings sample the process comprising: Respectively emitting longitudinal waves and transverse waves toward the cutting sample by the sound wave measurement system; Collecting longitudinal wave waveform data and transverse wave waveform data by an oscilloscope; Eliminating noise and interference waveforms based on a Wiener filter and a modal decomposition algorithm; Analyzing a wave arrival position of the longitudinal wave waveform data and the transverse wave waveform data based on a threshold detection or cross-correlation algorithm; acquiring the first arrival time of the P-wave and the first arrival time of the S-wave based on the arrival positions , respectively .

7. An acoustic logging apparatus for use in oil-based mud acoustic formation evaluation according to any one of claims 1 to 6, characterized in that: The method comprises a sound wave measurement system and an ultrasonic cleaner, the sound wave measurement system comprising a laser range finder, a pressure sensor, an oscilloscope and a clamp for clamping the cutting sample.

Images