Method for extracting longitudinal and transverse wave time difference by using conventional sound wave data and application thereof

Abstract

The invention relates to a method for extracting longitudinal and transverse wave time difference through conventional sound wave data and application of the method, and belongs to the technical field of oil exploration. The method comprises the following steps that waveform standardization is conducted on a conventional sound wave data collecting instrument, and a standardized waveform is obtained; performing de-gaining on the obtained standardized waveform to obtain a double-transmitting and four-receiving de-gaining waveform; combining the obtained double-transmitting and four-receiving de-gain waveforms into a single-transmitting and eight-receiving waveform; processing the obtained single-transmitting eight-receiving waveform by adopting a time-slowness correlation method, and extracting a longitudinal and transverse wave time difference; the invention further provides application of the method in production of equipment for oil-gas exploration or development, compared with the prior art, the information utilization rate of conventional sound wave data is increased, the longitudinal wave time difference of the stratum can be calculated more accurately, and the transverse wave time difference can also be calculated.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil exploration, and particularly relates to a method for extracting longitudinal and transverse wave time differences by using conventional acoustic wave data and its application. Background Art

[0002] Acoustic logging is one of the commonly used logging methods in the technical field of oil exploration. Conventional acoustic logging establishes an artificial sound field in the well through an acoustic wave transmitter, and emits acoustic pulses with a certain sound power, certain direction and frequency characteristics into the well. The propagation of acoustic waves in the well is related to the properties of the fluid in the well and the formation near the wellbore. An acoustic wave receiver is placed at a sufficient distance from the acoustic wave transmitter. Since the mud can only undergo volumetric deformation and cannot undergo shear deformation, it can only propagate longitudinal waves and cannot propagate transverse waves. When the first arrival signal is received by the array receiver during the downward propagation in the wellbore and surrounding formations, after receiving the signal, the system converts the received acoustic analog signal into a digital signal, and uses methods such as the finite element method to convert the digital signal into an acoustic wave time difference value.

[0003] According to the above content, it can be seen that conventional acoustic logging generally calculates only the longitudinal wave time difference through the first arrival method. This method only uses the first arrival information, and the subsequent transverse wave information is not utilized at all. However, transverse waves play an important role in oil exploration and can provide more accurate information on formation lithology, fractures and caves, permeability, etc., which helps to evaluate oil and gas reserves and development value. The absence of transverse waves will result in insufficient utilization of data. Secondly, this method of only calculating the longitudinal wave time difference has very high requirements for the accuracy of the first arrival time. Inaccurate identification of the first arrival will lead to large errors in the calculation of the longitudinal wave time difference. Therefore, it is particularly important to use the waveform morphological information of longitudinal and transverse waves to calculate the longitudinal and transverse wave time differences to improve the accuracy of logging and make full use of logging data.

[0004] CN107679614B discloses a real-time extraction method for acoustic wave slowness based on particle swarm optimization, which mainly solves the problems of large computational complexity and low accuracy in calculating acoustic wave slowness by the traditional STC algorithm. The implementation process is as follows: (1) Given the arrival time of the first wave of a certain mode wave and the range of acoustic wave slowness; (2) Initialize the population; (3) Calculate the fitness value of the particle; (4) Update the historical highest fitness value of the particle and the global historical highest fitness value of the population; (5) Update the position of the particle; (6) Determine whether the algorithm meets the termination condition. If it meets, stop the iteration; otherwise, go to step (3). This invention uses the particle swarm optimization algorithm based on population random search to extract acoustic wave slowness, without the need for traversal search of time and slowness. And this algorithm is a global optimization method, greatly reducing the computational complexity of the program and being able to quickly and accurately extract the formation acoustic wave slowness. This invention provides a new slowness extraction method, improving the accuracy of obtaining acoustic wave slowness. However, since this method solves problems through a new algorithm and has a relatively large improvement, its popularization still requires time.

[0005] CN114263456A discloses a method and device for real-time calculating formation compressional and shear wave slownesses. The method includes: using downhole circuits to read and analyze the waveform of the logging while drilling (LWD) quadrupole, and obtaining the formation shear wave slowness and the correlation coefficient according to the analysis result of the LWD quadrupole waveform; using downhole circuits to read and analyze the full waveform of the LWD monopole, and obtaining the control interval of the compressional wave according to the compressional and shear wave slowness ratio. Then, obtaining the formation compressional wave slowness and the correlation coefficient according to the control interval and the analysis result of the LWD monopole full waveform; uploading the obtained formation shear wave slowness and the correlation coefficient, and the formation compressional wave slowness and the correlation coefficient to the surface system. The surface system constructs a Gaussian pulse function based on the obtained formation shear wave slowness and the correlation coefficient, and the formation compressional wave slowness and the correlation coefficient, and obtains the formation compressional and shear wave slowness projection curves; and correcting the obtained formation compressional and shear wave slowness projection curves to obtain accurate formation compressional and shear wave slowness projection curves. This invention conducts targeted analysis and optimization on the measurement of the shear wave slowness of the formation. Although there is some correlation between the slowness itself and the formation physical properties characterized by the acoustic wave slowness, it cannot replace the role of the acoustic wave slowness.

[0006] Therefore, if an adjustment and optimization for extracting the compressional and shear wave slownesses based on the acoustic wave data of the current acoustic logging method can be provided to make it better reflect the formation physical properties, it is one of the key research issues for those skilled in the art. Summary of the Invention

[0007] In view of the problem in the prior art that the acoustic wave data of conventional acoustic logging cannot be fully utilized to extract shear wave slowness information to further improve the accuracy of acoustic logging, the present invention provides a method and application for extracting longitudinal and shear wave slownesses by using conventional acoustic data. By changing the data recording method of conventional acoustic waves and the method of calculating slownesses, on the basis of the original acoustic data acquisition volume, the longitudinal wave slowness and shear wave slowness of the formation are extracted simultaneously.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A method for extracting longitudinal and shear wave slownesses by using conventional acoustic data, comprising the following steps:

[0010] S1. Standardize the waveform of the acquisition instrument for conventional acoustic data to obtain a standardized waveform;

[0011] S2. De-gain the standardized waveform obtained in step S1 to obtain a de-gained waveform of double transmitter and four receivers;

[0012] S3. Combine the de-gained waveform of double transmitter and four receivers obtained in step S2 into a single transmitter and eight receivers waveform;

[0013] S4. Process the single transmitter and eight receivers waveform obtained in step S3 by using the time-slowness correlation method (STC) to extract the longitudinal and shear wave slownesses.

[0014] Preferably, the standardization in step S1 is achieved according to the cable delay curve (TRMST).

[0015] More preferably, the standardization includes the following steps:

[0016] Adjust the waveform data before the cable delay time and assign waveform attributes.

[0017] Even more preferably, the method for adjusting the waveform data before the cable delay time is:

[0018] According to the cable delay curve (TRMST), modify the starting time of waveform recording to 0 μs, and assign 0 to the waveform amplitude values that are not collected.

[0019] Even further preferably, the waveform attributes include sampling interval, number of recording points, and source distance:

[0020] Preferably, the source distances of the de-gained standardized waveforms in step S2 are: 3 ft and 5 ft.

[0021] More preferably, the formula for de-gaining is as follows:

[0022] TRMWV_NG = TRMWV / 10 0.15*TRMGN

[0023] In the formula, TRMWV_NG is the waveform amplitude value after gain removal, TRMWV is the waveform amplitude value obtained from logging, and TRMGN is the gain value of the waveform.

[0024] Preferably, the gain-removed waveforms of the dual transmitter and four receivers in step S2 include the waveform data of single transmitter and four receivers with a source distance of 3 ft and the waveform data of single transmitter and four receivers with a source distance of 5 ft.

[0025] More preferably, the receiving source distances of the waveform data of single transmitter and four receivers with a source distance of 3 ft are 3 ft, 3.5 ft, 4 ft, and 4.5 ft;

[0026] the receiving source distances of the waveform data of single transmitter and four receivers with a source distance of 5 ft are 5 ft, 5.5 ft, 6.0 ft, and 6.5 ft.

[0027] Preferably, the method of merging in step S3 is: combining and recording the waveforms of one depth point in sequence according to the source distances of 3 ft, 3.5 ft, 4.0 ft, 4.5 ft, 5.0 ft, 5.5 ft, 6.0 ft, and 6.5 ft.

[0028] Preferably, the waveform of the single transmitter and eight receivers in step S3 has a source distance of 3 ft.

[0029] More preferably, the receiving source distances of the single transmitter and eight receivers are 3 ft, 3.5 ft, 4 ft, 4.5 ft, 5 ft, 5.5 ft, 6.0 ft, and 6.5 ft.

[0030] Preferably, the time-slowness correlation method in step S4 includes the following steps:

[0031] ① Filter the waveform to obtain a waveform signal;

[0032] ② Use a time window to scan the waveform signal obtained in step ① in the time domain and slowness domain, calculate the correlation coefficients respectively, and the slowness value corresponding to the point with the maximum local correlation coefficient is the formation slowness of the current depth point.

[0033] Preferably, the extraction method in step S4 includes the following steps:

[0034] ① Perform filtering using band-pass filtering, with a minimum frequency of 4 kHz and a maximum frequency of 26 kHz, to obtain a waveform signal;

[0035] ② Use a time window with a length of 320 μs, an initial slowness of 40 μs / ft, a final slowness of 200 μs / ft, a slowness step of 2 μs / ft, an initial time of 300 μs, a final time of 1200 μs, and a step of 100 μs to scan the acoustic waveform signal obtained in step ① in the time domain and the slowness domain, and calculate the correlation coefficients respectively. The two points with the largest local correlation coefficients correspond to the longitudinal wave travel time difference and the shear wave travel time difference of the formation respectively.

[0036] The present invention also provides an application of the method for extracting the longitudinal and shear wave travel time differences using the conventional acoustic wave data as described above in the production of equipment for oil and gas exploration or development.

[0037] The present invention also provides a device for oil and gas exploration and development, and extracts the longitudinal and shear wave travel time differences by the method for extracting the longitudinal and shear wave travel time differences using the conventional acoustic wave data provided by the present invention.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] By changing the data recording method of the conventional acoustic wave and the method for calculating the travel time difference, the present invention extracts the longitudinal wave travel time difference and the shear wave travel time difference of the formation simultaneously on the basis of the original acoustic wave data acquisition volume; improves the information utilization rate of the conventional acoustic wave data, and can not only calculate the longitudinal wave travel time difference of the formation more accurately, but also calculate the shear wave travel time difference. Description of the Drawings

[0040] Figure 1 It is a flow chart of the method for extracting the longitudinal and shear wave travel time differences using the conventional acoustic wave data of the present invention;

[0041] Figure 2 It is a waveform example diagram before gain removal in step S2 of the embodiment of the present invention;

[0042] Figure 3 It is a waveform example diagram after gain removal in step S2 of the embodiment of the present invention;

[0043] Figure 4 It is a schematic diagram of the instrument structure of the waveform of double transmitter and four receivers and the waveform of single transmitter and eight receivers in step S3 of the embodiment of the present invention;

[0044] Figure 4 The left 5700 conventional acoustic wave instrument structure in it is a schematic diagram of the waveform instrument structure of double transmitter and four receivers;

[0045] Figure 4 The right virtual array acoustic wave instrument structure in it is a schematic diagram of the waveform instrument structure of single transmitter and eight receivers;

[0046] Figure 5 It is a waveform diagram of double transmitter and four receivers with a source distance of 3 ft in step S3 of the embodiment of the present invention;

[0047] Figure 6It is the waveform diagram of dual transmitter and four receivers with a source distance of 5 ft in step S3 of the embodiment of the present invention;

[0048] Figure 7 It is the waveform diagram of single transmitter and eight receivers with a source distance of 3 ft in step S3 of the embodiment of the present invention;

[0049] Figure 8 It is the schematic diagram of shear wave travel time and compressional wave travel time obtained by using the time-slowness correlation method STC to extract the shear wave travel time and compressional wave travel time of the combined array waveform in step S4 of the embodiment of the present invention. Detailed implementation manners

[0050] Embodiment A method for extracting shear wave travel time and compressional wave travel time by using conventional acoustic wave data

[0051] In step S1, standardize the waveform data: according to the cable delay time, assign the waveform data before the cable delay time to 0 us; according to the instrument acquisition parameters, assign waveform attributes. Using the instrument of the 5700 logging system, the sampling interval for source distances of 3 ft and 5 ft is 8 us, and the number of recorded points is 185, and the standardized waveforms of 3 ft and 5 ft can be obtained.

[0052] In step S2, for the waveforms of 3 ft and 5 ft, according to the gain curve, de-gain the measured waveforms to restore the amplitude of the original waveforms, and obtain the waveforms after the true amplitude;

[0053] The formula for de-gaining is as follows:

[0054] TRMWV_NG = TRMWV / 10 0.15*TRMGN

[0055] In the formula, TRMWV_NG is the waveform amplitude value after de-gaining, TRMWV is the waveform amplitude value obtained by logging, and TRMGN is the waveform gain value;

[0056] The de-gained waveforms of dual transmitter and four receivers include the single transmitter and four receivers waveform data with a source distance of 3 ft and the single transmitter and four receivers waveform data with a source distance of 5 ft.

[0057] In step S3, combine the two groups of waveforms of 3 ft and 5 ft into an array waveform of single transmitter and eight receivers with a source distance of 3 ft;

[0058] The receiving source distances of the single transmitter and four receivers waveform data with a source distance of 3 ft are 3 ft, 3.5 ft, 4 ft, and 4.5 ft;

[0059] The receiving source distances of the single transmitter and four receivers waveform data with a source distance of 5 ft are 5 ft, 5.5 ft, 6.0 ft, and 6.5 ft;

[0060] The merging method is to combine and record the waveforms of a depth point in sequence at source offsets of 3 ft, 3.5 ft, 4.0 ft, 4.5 ft, 5.0 ft, 5.5 ft, 6.0 ft, and 6.5 ft;

[0061] The receiver source offsets for single-shot eight-receiver are 3 ft, 3.5 ft, 4 ft, 4.5 ft, 5 ft, 5.5 ft, 6.0 ft, and 6.5 ft.

[0062] At step S4, use the time-slowness correlation method STC to extract the longitudinal and transverse wave time differences of the combined array waveform;

[0063] The extraction method includes:

[0064] ① Filter using band-pass filtering with a minimum frequency of 4 kHz and a maximum frequency of 26 kHz to obtain a waveform signal;

[0065] ② Use a time window with a length of 320 μs, a starting slowness of 40 μs / ft, an ending slowness of 200 μs / ft, a slowness step size of 2 μs / ft, a starting time of 300 μs, an ending time of 1200 μs, and a step size of 100 μs to scan the acoustic waveform signal obtained in step ① in the time domain and slowness domain, calculate the correlation coefficients respectively, and the two points with the maximum local correlation coefficients correspond to the longitudinal and transverse wave time differences of the formation respectively.

[0066] Figure 2 and 3 is a schematic diagram of the formation waveform before and after de-gain in the embodiment of the present invention. During the logging process, in order to avoid signal attenuation during data transmission, the recorded waveform is generally amplified, that is, gain. In actual waveform processing, the waveform needs to be restored through a formula to de-gain and restore the true waveform of the formation.

[0067] Figure 4 is a schematic diagram of the instrument structure for combining the waveforms of dual-shot four-receiver with source offsets of 3 ft and 5 ft into single-shot eight-receiver in the embodiment of the present invention. The source offsets of single-shot four-receiver with a source offset of 3 ft are: 3 ft, 3.5 ft, 4 ft, 4.5 ft, and the waveforms are as Figure 5 shown; the source offsets of single-shot four-receiver with a source offset of 5 ft are: 5 ft, 5.5 ft, 6.0 ft, 6.5 ft, and the waveforms are as Figure 6 shown. Therefore, the waveforms can be combined into a receiver with a source offset of 3 ft and 8 receivers, and the waveforms are as Figure 7 shown.

[0068] Figure 8It shows that in step S4 of the embodiment of the present invention, the longitudinal wave time difference and the shear wave time difference are obtained by using array waveform STC processing. First, band-pass filtering is performed with a minimum frequency of 4 KHZ and a maximum frequency of 26 KHZ. Then, a time window with a length of 320 us, a starting slowness of 40 us / ft, an ending slowness of 200 us / ft, a slowness step size of 2 us / ft, a starting time of 300 us, an ending time of 1200 us, and a step size of 100 us is used to scan the acoustic wave waveform signal in the time domain and the slowness domain, and the correlation coefficients are calculated respectively. The two dots with the largest local correlation coefficients correspond to the longitudinal wave slowness and the shear wave slowness of the formation (i.e., the longitudinal wave time difference and the shear wave time difference).

[0069] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than limiting the protection scope of the present invention. Any simple modification or equivalent replacement of the technical solution of the present invention by those of ordinary skill in the art does not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A method for extracting the travel times of compressional and shear waves using conventional acoustic wave data, characterized in that It includes the following steps: S1. Standardize the waveform of the acquisition instrument for conventional acoustic wave data to obtain a standardized waveform. S2. De-gain the standardized waveform obtained in step S1 to obtain a de-gained waveform of dual-source four-receiver. S3. Combine the de-gained waveform of dual-source four-receiver obtained in step S2 into a single-source eight-receiver waveform. S4. Process the single-source eight-receiver waveform obtained in step S3 using the time-slowness correlation method to extract the longitudinal and transverse wave time differences.

2. The method according to claim 1, characterized in that: The standardization described in step S1 is achieved according to the cable delay curve.

3. The method according to claim 2, characterized in that: The standardization includes the following steps: Adjust the waveform data before the cable delay time and assign waveform attributes.

4. The method according to claim 3, characterized in that: The method for adjusting the waveform data before the cable delay time is: According to the cable delay curve, modify the starting time of the waveform record to 0 μs and assign 0 to the waveform amplitude values that are not collected.

5. The method according to claim 3, characterized in that: The waveform attributes include sampling interval, number of recorded points, and source distance.

6. The method according to claim 1, characterized in that: The source distances of the de-gained standardized waveform in step S2 are: 3 ft and 5 ft.

7. The method according to claim 6, characterized in that: The formula for de-gaining is as follows: TRMWV_NG = TRMWV / 10 0.15*TRMGN In the formula, TRMWV_NG is the waveform amplitude value after de-gaining, TRMWV is the waveform amplitude value obtained from logging, and TRMGN is the waveform gain value.

8. The method according to claim 1, characterized in that: The de-gained waveform of dual-source four-receiver in step S2 includes the single-source four-receiver waveform data with a source distance of 3 ft and the single-source four-receiver waveform data with a source distance of 5 ft.

9. The method according to claim 8, characterized in that: The receiving source distances of the single-source four-receiver waveform data with a source distance of 3 ft are 3 ft, 3.5 ft, 4 ft, and 4.5 ft. The receiving source distances of the single-source four-receiver waveform data with a source distance of 5 ft are 5 ft, 5.5 ft, 6.0 ft, and 6.5 ft.

10. The method according to claim 1, characterized in that: The method for combination in step S3 is: Combine and record the waveforms at one depth point in sequence according to the source distances of 3 ft, 3.5 ft, 4.0 ft, 4.5 ft, 5.0 ft, 5.5 ft, 6.0 ft, and 6.5 ft.

11. The method according to claim 1, characterized in that: The waveform of the single-source eight-receiver waveform in step S3 with a source distance of 3 ft; the receiving source distances of the single-source eight-receiver are 3 ft, 3.5 ft, 4 ft, 4.5 ft, 5 ft, 5.5 ft, 6.0 ft, and 6.5 ft.

12. The method according to claim 1, characterized in that: The time-slowness correlation method described in step S4 includes the following steps: ① Filter the waveform to obtain a waveform signal. ② Use a time window to scan the waveform signal obtained in step ① in the time domain and slowness domain, calculate the correlation coefficients respectively, and the slowness value corresponding to the point with the maximum local correlation coefficient is the formation slowness at the current depth point.

13. The method according to claim 1, characterized in that: The method for processing described in step S4 includes the following steps: ① Use band-pass filtering for filtering, with a minimum frequency of 4 kHz and a maximum frequency of 26 kHz, to obtain a waveform signal. ② Use a time window with a length of 320 μs, a starting slowness of 40 μs / ft, an ending slowness of 200 μs / ft, a slowness step size of 2 μs / ft, a starting time of 300 μs, an ending time of 1200 μs, and a step size of 100 μs to scan the acoustic wave waveform signal obtained in step ① in the time domain and slowness domain, calculate the correlation coefficients respectively, and the two points with the maximum local correlation coefficients respectively correspond to the longitudinal wave time difference and transverse wave time difference of the formation.

14. Application of the method according to any one of claims 1 - 13 in the production of equipment for oil and gas exploration and development.

15. An equipment for oil and gas exploration or development, characterized in that Extract the longitudinal and transverse wave time differences by the method according to any one of claims 1-13.

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