A combined longitudinal and transverse wave sliding scan acquisition method

Abstract

This invention belongs to the field of natural gas exploration technology and specifically discloses a combined sliding scanning acquisition method for P- and S-waves. The method sequentially follows the following steps: S1. Establishing a unified exchange database for vibroseis parameters for three wave sources; S2. Determining the sliding time parameter based on the principle of minimizing harmonic interference noise; S3. Verifying the rationality of the sliding time design using actual data; and S4. Using different status identifiers to distinguish and monitor the status of combined P- and S-wave sliding excitation points. This invention achieves a breakthrough from single P-wave to combined sliding scanning with three wave sources, and can avoid missed shots in combined sliding scanning acquisition of P-waves, SH-waves, and SV-waves.

Description

Technical Field

[0001] The present invention belongs to the technical field of natural gas exploration, and relates to a method for longitudinal and shear wave exploration, in particular to a longitudinal and shear wave combined sliding scanning acquisition method. Background Art

[0002] As total natural gas consumption climbs, China's total natural gas imports are increasing year by year. To discover more natural gas resources, reduce external dependence, and ensure energy security, my country has gradually increased its efforts in natural gas exploration.

[0003] Many gas-bearing structures have been discovered in the Qaidam Basin. Years of exploration practice and research results have shown that the main underground target layer in the main gas-producing area is the Quaternary Q 1+2 The target layer is buried at a depth of 800-2000m in the loose sandstone low-tectonic amplitude structure, and the gas layer is relatively shallow. Due to the influence of gas absorption attenuation, the longitudinal wave profile generally has the seismic anomaly phenomenon of "low speed, low frequency and phase axis pull-down", resulting in the low-amplitude structure in the "gas cloud area" not being imaged.

[0004] Seismic exploration in the main gas-producing areas of the Qaidam Basin began in the 1990s. Conventional 2D, high-resolution 2D, high-precision 2D, and high-density 3D seismic surveys were conducted in the region. However, P-wave exploration alone proved difficult to identify gas anomalies and image low-amplitude structures. Converted-wave 2D and 3D explorations were attempted in 2006 and 2009, respectively. The quality of low-amplitude structural data in the "gas cloud zone" was significantly improved. However, converted-wave data could not fully recover the low-amplitude structures within the complex "gas cloud zone," and substantial breakthroughs in natural gas exploration remained elusive. In 2017, Oriental Geophysical Company developed the new BV300S shear-wave controllable seismometer. This first-of-its-kind acquisition of 800 km of high-density, wide-band P- and S-wave data was conducted in the region. High-quality, broadband S-wave data were obtained for the first time, resulting in encouraging progress in delineating the boundaries of the low-amplitude "gas cloud zone" and reconstructing the structures within it. In 2019, Oriental Geophysical Company improved and upgraded the performance of the shear wave vibrator and developed the EV56S, further exploring the feasibility of conducting nine-component longitudinal and transverse wave 3D acquisition tests in the area. In 2019, Qinghai Oilfield Company deployed nine-component longitudinal and transverse wave 3D in the area, covering an area of 82.08 km. 2 The Qinghai Geophysical Exploration Department of Oriental Geophysical Company is responsible for the specific implementation of this project, which marks the world's first industrial application of nine-component longitudinal and transverse waves.

[0005] With the widespread adoption of P- and S-wave exploration technologies, substantial progress has been made in S-wave acquisition, and considerable experience has been accumulated. Efficient acquisition technology is a key component of S-wave acquisition operations. However, while there is currently relatively mature technical support for efficient acquisition of single P-wave sliding scanning, including hardware, software, and quality control, there is still a lack of technology for combined sliding scanning using three wave sources: P-wave (P), S-wave (SH), and S-wave (SV). Summary of the Invention

[0006] The purpose of the present invention is to provide a combined sliding scanning acquisition method for longitudinal and shear waves, which can improve field construction efficiency while obtaining high-quality longitudinal and shear wave single-shot records.

[0007] In order to achieve the above-mentioned purpose, the technical solutions adopted by the present invention are as follows:

[0008] A combined longitudinal and transverse wave sliding scanning acquisition method is performed in the following order:

[0009] S1. Establish a unified exchange database for the three types of vibroseis parameters;

[0010] The three wave sources are P wave, SH wave and SV wave;

[0011] S2. Determine the sliding time parameter based on the principle of minimum harmonic interference noise;

[0012] S3. Use actual data to verify the rationality of sliding time design;

[0013] S4. Use different status identifiers to distinguish and mark the status of the monitoring longitudinal and transverse wave combined sliding excitation point.

[0014] As a limitation, step S1 is performed in the following order:

[0015] S11. Establish a unified library of key parameters and sliding scanning parameters for the three types of wave source vibroseis;

[0016] S12, identify and code P-wave, SH-wave and SV-wave vibroseis database processing types;

[0017] In this step, the three types of wave source database processing are identified and coded: ① The P-wave, SH-wave and SV-wave controllable source exchange database is named; ② The P-wave, SH-wave and SV-wave controllable source exchange database is coded; ③ The tape number for storing the single-shot record of the P-wave, SH-wave and SV-wave controllable source excitation is coded; ④ The starting file number for storing the single-shot record of the P-wave, SH-wave and SV-wave controllable source excitation data is coded.

[0018] As a further limitation, step S2 is performed in the following order:

[0019] S21. Investigate and analyze the energy values and energy ratios recorded by three wave source excitations and three component receptions;

[0020] S211, passive random noise recordings at different time periods with the same receiving arrangement in the field and single shot recordings with three wave sources received at the same shot point and the same arrangement;

[0021] S212, selecting a fixed time window distribution to separate the random noise record and the single shot record into wave components, statistically analyzing the energy values and energy ratios of the effective wave and the interference wave, and drawing an energy histogram;

[0022] S213, energy statistics are analyzed using absolute amplitude, where the energy statistics formula is as follows:

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029] Where, E Z 、E X 、E Y Respectively represent the average absolute amplitude value of the fixed time window or the whole shot record of the Z, X, and Y components, that is, the energy value; the unit is voltage microvolt, that is, μv;

[0030] Represents the amplitude value of the jth sample point of the i-th channel of the Z, X, and Y components, that is, the energy value; the unit is voltage microvolt, that is, μv;

[0031] λ x / z ,λ y / z ,λ x / y Represent the X / Z, Y / Z, and X / Y component energy ratios respectively;

[0032] N x Indicates the total number of channels participating in the statistical time window or full shot record; N t Indicates the total number of sample points participating in the statistical time window or full shot record; N t Indicates the total number of sample points participating in the statistical time window or full shot record;

[0033] S22. Quantitatively design the sliding time based on the principle that the fundamental wave is not affected by the second harmonic.

[0034] As a further limitation, step S3 is performed in the following order:

[0035] S31. Design two sets of P-wave sources, two sets of SH-wave sources, and two sets of SV-wave sources, and conduct test data acquisition with different sliding times on the same section and the same number of coverage test production lines;

[0036] S32, stacking and migrating the single shot records of pure wave components YY, XX, and ZZ to form an imaging section;

[0037] S33. Extract the target signal-to-noise ratio for different sliding time profiles and plot the sliding time versus profile signal-to-noise ratio to evaluate the impact of different excitation source harmonics on the imaging profile and verify the rationality of the theoretically designed sliding time.

[0038] S34. Extract vibroseis QC data, statistically analyze the acquisition time, draw a superposition diagram of the signal-to-noise ratio and time effect of different sliding time sections, and select the optimal sliding time.

[0039] As a further limitation, step S4 includes the following process:

[0040] S41, extracting the tape number code and the shot point pile number from the track header of the data recorded by the vibroseis excitation of the P wave, SH wave and SV wave and generating the acquired shot point list data;

[0041] S42, automatically generating a P-wave, SH-wave, and SV-wave vibroseis excitation point status database based on the theoretical observation system SPS data and the acquired shot point list data;

[0042] S43. Design six status point colors to identify the point collection status and display them on a plan view.

[0043] Due to the adoption of the above technical solution, the present invention has achieved the following technical advancements compared with the prior art:

[0044] (1) The existing wired seismic acquisition instrument system can only set up a database of vibroseis sliding scanning parameters for a single wave source, and cannot realize the joint sliding scanning construction of three wave sources (P wave, SH wave and SV wave). In the construction of nine-component longitudinal and shear wave seismic acquisition projects, the sliding construction of P wave, SH wave and SV wave vibroseis is carried out separately. Due to the limitations of the number of vibroseis groups and ground electronic equipment, the acquisition efficiency is low. To address this problem, the design of the wired seismic acquisition instrument system database can lay the foundation for the implementation of subsequent methods.

[0045] (2) The present invention uses P-wave, SH-wave, and SV-wave sources for joint sliding and creates a Swath database of unified sliding parameters for the three different wave sources in the host system of the wired seismic acquisition instrument, achieving a breakthrough from single longitudinal wave to three wave source joint sliding scanning;

[0046] (3) When designing the parameters of conventional single longitudinal wave sliding scan, both the excitation source and the receiver are single components, and it is relatively simple to determine the sliding time parameters; when collecting longitudinal and transverse waves by sliding scan, there are the following major problems: 1) Each excitation has three component records and the excitation energy values of each source are inconsistent, and the harmonic strength is also inconsistent; 2) The scanning length and recording length of SH waves and SV waves are relatively long; 3) The travel time of the P wave record and the SH wave and SV wave record target layer is not uniform. The present invention effectively solves the above problems by investigating and analyzing the energy values and energy ratios of the three wave source excitations and the three-component receiving records, and quantitatively designing the sliding time based on the principle that the fundamental wave is not affected by the second harmonic;

[0047] (4) The existing wired seismic acquisition instrument system can only monitor the firing status of a single longitudinal wave excitation point (the shot point that has been acquired is red, and the shot point that has not been acquired is green). When the longitudinal and shear waves are jointly acquired by sliding scanning, it is difficult to identify which wave has been excited and which has not been excited when the controllable vibrator excites the P wave, SH wave and SV wave at the same shot point, which easily leads to missed shots. The present invention adds a function module for the acquisition of excitation points by the joint sliding scanning of longitudinal and shear waves to the existing real-time monitoring software point quality control module, thereby achieving a breakthrough from the single longitudinal wave to the three wave source joint excitation point quality control, avoiding the missed shots phenomenon in the joint sliding scanning acquisition of P wave, SH wave and SV wave.

[0048] The present invention belongs to the technical field of natural gas exploration and can improve field construction efficiency while obtaining high-quality longitudinal and shear wave single-shot records. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0050] In the attached figure:

[0051] Figure 1 Schematic diagram of database design according to an embodiment of the present invention. DETAILED DESCRIPTION

[0052] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention and are not used to limit the present invention.

[0053] Embodiment A method for collecting longitudinal and transverse wave combined sliding scanning

[0054] This embodiment is carried out in the following order:

[0055] S1, such as Figure 1 As shown, an exchange database of unified three types of wave source vibroseis parameters is established;

[0056] The three wave sources are P wave, SH wave and SV wave;

[0057] First, a unified library of key parameters and sliding scanning parameters for the three types of wave sources is established;

[0058] Secondly, identify and code the P-wave, SH-wave and SV-wave vibroseis database processing types;

[0059] In this step, in order to facilitate the wired seismic acquisition instrument system to distinguish the P-wave, SH-wave and SV-wave vibroseis excitation single-shot records, the three wave source database processing types are identified and coded: ① The P-wave, SH-wave and SV-wave vibroseis exchange databases are named: Pwave, SHwave, SVwave; ② The P-wave, SH-wave and SV-wave vibroseis exchange databases are coded: 1, 2, 3; ③ The P-wave, SH-wave and SV-wave vibroseis excitation single-shot record storage tape numbers are coded: 1, 2, 3; ④ The P-wave, SH-wave and SV-wave vibroseis excitation single-shot record storage data starting file numbers are 100001, 20001, and 300001; the file number arrangement is based on the total number of excitation shots of the three waves + the number of wasted shots in the work area project, and a reasonable starting file number is set while ensuring that the three wave file numbers are not repeated;

[0060] In this embodiment, the total number of exciting shots + wasted shots of the three types of waves accounts for 20% of the total number of shots;

[0061] S2. Determine the sliding time parameter based on the principle of minimum harmonic interference noise;

[0062] S21. Investigate and analyze the energy values and energy ratios recorded by three wave source excitations and three component receptions;

[0063] In this step, the problem of multiple excitation sources and multi-component energy differences in the joint sliding scanning of longitudinal and transverse waves is addressed. First, passive random noise recordings and single-shot recordings of the three wave sources received at the same shot point and the same arrangement are recorded in different time periods in the field with the same receiving arrangement. Then, a fixed time window distribution is selected to divide the random noise recordings and single-shot recordings into wave components, and the energy values and energy ratios of the effective waves and interference waves are statistically analyzed, and an energy histogram is drawn. Furthermore, based on energy analysis, it can be determined that the Z component has the strongest energy, followed by X, and then Y. The Z component is nearly twice the energy of the X and Y components, which means that the longitudinal wave has a greater interference effect on the transverse wave, while the transverse wave has a smaller interference effect on the longitudinal wave. Energy statistics are analyzed using absolute amplitude, and the energy statistics formula is as follows:

[0064]

[0065]

[0066]

[0067]

[0068]

[0069]

[0070] Where, E Z 、E X 、E Y Respectively represent the average absolute amplitude value of the fixed time window or the whole shot record of the Z, X, and Y components, that is, the energy value; the unit is voltage microvolt, that is, μv;

[0071] Represents the amplitude value of the jth sample point of the i-th channel of the Z, X, and Y components, that is, the energy value; the unit is voltage microvolt, that is, μv;

[0072] λ x / z ,λ y / z ,λ x / y Represent the energy ratios of X / Z, Y / Z, and X / Y components respectively; N x Indicates the total number of channels participating in the statistical time window or full shot record; N t Indicates the total number of sample points participating in the statistical time window or full shot record; N t Indicates the total number of sample points participating in the statistical time window or full shot record;

[0073] S22. Quantitatively design the sliding time based on the principle that the fundamental wave is not affected by the second harmonic

[0074] When the vibrator transmits a scanning signal to the earth, the ground force signal transmitted to the surface is a fundamental signal and a harmonic signal. The harmonic always appears after the fundamental wave. The harmonic and the fundamental wave form a complex signal with a duration equal to the scanning length. This complex signal is received by the acquisition system after passing through the radar. The second harmonic has the strongest energy and has the greatest impact on the seismic records related to the vibrator. Its harmonic formula is as follows

[0075]

[0076] Where S k (t) represents the kth harmonic signal record of the vibrator; A k (t) represents the amplitude value of the kth harmonic signal recorded by the vibrator; f s Represents the start and end frequencies of the vibrator scanning signal, in Hz; f e Represents the end frequency of the vibrator scanning signal, in Hz; T d Represents the length of the vibrator scanning signal, in seconds;

[0077] When sliding scanning is used for efficient acquisition, the sliding time is greater than the listening time and less than or equal to the scanning signal length + the recording length. The formula is as follows:

[0078]

[0079] Where, T h represents the sliding time length of the vibrator, in seconds; T l Represents the listening time, that is, the recording length, in seconds; H max Represents the maximum target layer depth in the work area, in meters; V s Represents the shear wave velocity corresponding to the maximum target layer depth in the work area, in m / s;

[0080] The second harmonic energy is relatively strong, and has a greater impact on the effective interference of the target layer. To ensure that the fundamental signal of the previous shot is not affected by the second harmonic signal of the subsequent shot, the formula is derived according to the harmonic time-frequency domain theory formula:

[0081]

[0082] S3. Use actual data to verify the rationality of sliding time design;

[0083] S31. Design two sets of P-wave sources, two sets of SH-wave sources, and two sets of SV-wave sources, and conduct test data acquisition with different sliding times on the same section and the same number of coverage test production lines;

[0084] S32, stacking and migrating the single shot records of pure wave components YY, XX, and ZZ to form an imaging section;

[0085] S33. Extract the target signal-to-noise ratio for different sliding time profiles and plot the sliding time versus profile signal-to-noise ratio to evaluate the impact of different excitation source harmonics on the imaging profile and verify the rationality of the theoretically designed sliding time.

[0086] S34. Extract vibroseis QC data, statistically analyze the acquisition time, draw a superposition diagram of the signal-to-noise ratio and time effect of different sliding time sections, and select the optimal sliding time;

[0087] S4. Use different color status markers to monitor the status of the combined longitudinal and transverse wave sliding excitation point

[0088] S41, extracting the tape number code and the shot point pile number from the track header of the data recorded by the vibroseis excitation of the P wave, SH wave and SV wave and generating the acquired shot point list data;

[0089] S42, automatically generating a P-wave, SH-wave, and SV-wave vibroseis excitation point status database based on the theoretical observation system SPS data and the acquired shot point list data;

[0090] In this embodiment, in the vibroseis excitation point status database, the acquired state is represented by 1, and the unacquired state is represented by 0;

[0091] S43. Design six status point colors to identify the point collection status and display them on a plan view.

[0092] This embodiment has been actually explored and applied in the nine-component three-dimensional seismic exploration of P- and S-waves in the main gas-producing area of the Qaidam Basin. This area is a natural gas-rich area in the Qaidam Basin. Joint exploration of P- and S-waves was adopted. The nine-component P- and S-wave combined sliding scanning parameters of the area were qualitatively and quantitatively designed through this embodiment. Two groups of P-wave, SH-wave, and SV-wave sources were used in the three-dimensional P- and S-waves. After 61 days, 118,050 shots were completed, with an average daily efficiency of 1,937 shots. Using traditional methods, the average daily shot was about 1,400 shots. It can be seen that the method implemented in this embodiment can improve efficiency by 30%, and at the same time, high-quality S-wave data can be obtained, achieving the goal of improving the quality and efficiency of the project.

Claims

1. A longitudinal and transverse wave combined sliding scanning acquisition method, characterized in that: Follow these steps in order: S1. Establish a unified exchange database for the three types of vibroseis parameters; The three wave sources are P wave, SH wave and SV wave; S2. Determine the sliding time parameter based on the principle of minimum harmonic interference noise; S3. Use actual data to verify the rationality of sliding time design; S4. Using different status identifiers to distinguish and mark the status of the monitoring longitudinal and transverse wave combined sliding excitation point; Step S2 is performed in the following order: S21. Investigate and analyze the energy values and energy ratios recorded by three wave source excitations and three component receptions; S211, passive random noise recordings at different time periods with the same receiving arrangement in the field and single shot recordings with three wave sources received at the same shot point and the same arrangement; S212, selecting a fixed time window distribution to separate the random noise record and the single shot record into wave components, statistically analyzing the energy values and energy ratios of the effective wave and the interference wave, and drawing an energy histogram; S213, energy statistics are analyzed using absolute amplitude, where the energy statistics formula is as follows: Where, E Z 、E X 、E Y Respectively represent the average absolute amplitude value of the fixed time window or the whole shot record of the Z, X, and Y components, that is, the energy value; the unit is voltage microvolt, that is, μv; Represents the amplitude value of the jth sample point of the i-th channel of the Z, X, and Y components, that is, the energy value; the unit is voltage microvolt, that is, μv; λ x / z ,λ y / z ,λ x / y Represent the X / Z, Y / Z, and X / Y component energy ratios respectively; N x Indicates the total number of channels participating in the statistical time window or full shot record; N t Indicates the total number of sample points participating in the statistical time window or full shot record; N t Indicates the total number of sample points participating in the statistical time window or full shot record; S22. Quantitatively design the sliding time based on the principle that the fundamental wave is not affected by the second harmonic.

2. A longitudinal and transverse wave combined sliding scanning acquisition method according to claim 1, characterized in that: Step S1 is performed in the following order: S11. Establish a unified library of key parameters and sliding scanning parameters for the three types of wave source vibroseis; S12, identify and code P-wave, SH-wave and SV-wave vibroseis database processing types; In this step, the three types of wave source database processing are identified and coded: ① Name the P-wave, SH-wave and SV-wave controllable source exchange database; ② Code the P-wave, SH-wave and SV-wave controllable source exchange database; ③ Code the tape number for storing the single-shot record of the P-wave, SH-wave and SV-wave controllable source excitation; ④ Code the starting file number for the single-shot record storage data of the P-wave, SH-wave and SV-wave controllable source excitation.

3. The method for collecting longitudinal and transverse wave combined sliding scans according to claim 1, characterized in that: Step S3 is performed in the following order: S31. Design two sets of P-wave sources, two sets of SH-wave sources, and two sets of SV-wave sources, and conduct test data acquisition with different sliding times on the same section and the same number of coverage test production lines; S32, stacking and migrating the single shot records of pure wave components YY, XX, and ZZ to form an imaging section; S33. Extract the target signal-to-noise ratio for different sliding time profiles and plot the sliding time versus profile signal-to-noise ratio to evaluate the impact of different excitation source harmonics on the imaging profile and verify the rationality of the theoretically designed sliding time. S34. Extract vibroseis QC data, statistically analyze the acquisition time, draw a superposition diagram of the signal-to-noise ratio and time effect of different sliding time sections, and select the optimal sliding time.

4. A longitudinal and shear wave combined sliding scanning acquisition method according to claim 3, characterized in that: The step S4 includes the following process: S41, extracting the tape number code and the shot point pile number from the track header of the data recorded by the vibroseis excitation of the P wave, SH wave and SV wave and generating the acquired shot point list data; S42, automatically generating a P-wave, SH-wave, and SV-wave vibroseis excitation point status database based on the theoretical observation system SPS data and the acquired shot point list data; S43. Design six status point colors to identify the point collection status and display them on a plan view.

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