A "black triangle" noise attenuation method based on controllable source force signal

Abstract

The application provides a "black triangle" noise attenuation method based on a controllable source force signal, relates to the field of seismic exploration, and aims at the problems of serious "black triangle" noise of the controllable source on loose ground and great difficulty in indoor noise removal. The "black triangle" noise of the controllable source can be suppressed by applying the controllable source force signal, removing noise of different causes in different ways.

Description

Technical Field

[0001] This invention relates to the field of seismic exploration, specifically to a "black triangle" noise attenuation method based on controllable source force signals. Background Technology

[0002] Due to the influence of excitation conditions, controllable source data from loose surfaces exhibit significant "black triangle" noise. This noise is characterized by high energy, large range, wide bandwidth, and no linearity, which severely affects the signal-to-noise ratio of seismic data. Moreover, conventional noise suppression techniques are insufficient to effectively remove this noise, posing considerable challenges to subsequent seismic data interpretation and inversion.

[0003] To address the strong energy noise in seismic data, geophysicists have proposed various noise suppression methods. Most of these methods are based on wavefield characteristics for filtering. Yilmaz et al. employed a high-pass filtering method based on low-frequency characteristics, Karsli et al. used Wiener filtering and FK filtering techniques for noise suppression, respectively, and Deighan et al. utilized the time-frequency analysis characteristics of wavelet transform to perform wavelet transform on seismic traces and filter the low-frequency region to suppress noise. In 2019, Liu Xiheng et al. proposed using seismic data feature extraction techniques to obtain signal and noise characteristics, and finally using these characteristics to remove noise. In 2021, Wang Lixin et al. developed a controllable source scattering surface wave interferometry prediction and matching subtraction technique based on shot-receiver seismic interference and mode matching subtraction.

[0004] Compared to explosive seismic sources, controlled-source seismic acquisition offers advantages such as safety, environmental friendliness, efficiency, and economy. Furthermore, its excitation parameters are controllable, making controlled-source acquisition a future trend in seismic exploration. However, controlled-source seismic data still suffers from several shortcomings, including noise interference, frequency band issues, and phase limitations. The strong nonlinear interference noise generated by controlled-source excitation manifests as a full-band "black triangle" high-energy noise in the gather, especially in loose surface areas where the noise energy is even stronger and the signal-to-noise ratio is lower. Currently, suppression of this "black triangle" noise is based on wavefield characteristic analysis and achieved through filtering, which inevitably damages the effective signal.

[0005] In view of the problems existing in the current technology, it is necessary to find a "black triangle" noise attenuation method based on controllable seismic source force signal. Summary of the Invention

[0006] This invention addresses the problems existing in the prior art by providing a method for attenuating "black triangle" noise based on controllable seismic source force signals. This method applies controllable seismic source force signals and uses different denoising methods to remove noise of different causes, thereby achieving the suppression of controllable seismic source "black triangle" noise.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] This invention provides a noise attenuation method, comprising the following steps:

[0009] 1) Collect the original correlation records of controlled source seismic data. First, perform conjugate function convolution of the controlled source excited wavelet ω0(t) on the original correlation records, and then divide by the modulus of ω0(t) to obtain the mother record;

[0010] 2) Statistically analyze the average amplitude value of the seismic traces and remove the mechanical noise E'(t) generated by the controllable source excitation in the master record whose amplitude value is more than ten times the average amplitude;

[0011] 3) Continue to remove controllable source noise from the controllable source mother record that is similar to well shot excitation noise, and obtain a mother record that only contains the influence of mechanical system and near-surface factors;

[0012] 4) Let p0(t) be the distortion factor of the mechanical and hydraulic systems of the controllable seismic source, and p1(t) be the correlation factor near the Earth's surface. Calculate the conjugate functions of p0(t) and p1(t) respectively.

[0013] 5) Combine the records obtained in step 3) which include the influence of mechanical systems and near-surface factors with those obtained in step 4). The denoised master record is obtained by performing a convolution and then dividing by the modulus of p0(t) and p1(t).

[0014] 6) The denoised master record is convolved with the wavelet excited by the controllable source to obtain the relevant record of the controllable source, thus achieving "black triangle" noise attenuation.

[0015] Furthermore, the calculation formula for the mother record mentioned in step 1) is as follows:

[0016] S1(t)=ω0(t)*e(t)*p0(t)*p1(t)+n′(t) Formula (1);

[0017] Wherein, S1(t) is the mother record; ω0(t) represents the wavelet excited by the controllable source; e(t) represents the formation impulse response; p0(t) is the distortion factor of the mechanical and hydraulic system of the controllable source; p1(t) is the correlation factor near the surface; and n′(t) consists of the controllable source noise similar to the well shot excitation noise and the mechanical noise generated when the controllable source is excited.

[0018] Furthermore, the calculation formula for the record containing the influence of mechanical systems and near-surface factors mentioned in step 3) is as follows:

[0019] S2(t)=ω0(t)*e(t)*p0(t)*p1(t) Formula (2);

[0020] S2(t) is the parent record that includes only the influence of mechanical systems and near-surface factors.

[0021] Furthermore, the distortion factor mentioned in step 4) is obtained by recording the diaphragm signal and trigger signal of the controllable source.

[0022] Specifically, the distortion factor in step 4) is obtained as follows: the trigger signal is the controllable source excitation wavelet ω0(t), the vibrating plate signal of the controllable source is the field-recorded controllable source force signal ω0′(t), the field-recorded controllable source force signal ω0′(t) is convolved with the conjugate function of the field-recorded controllable source force signal ω0′(t) and the controllable source excitation wavelet ω0(t), and then divided by the modulus of ω0(t) to obtain the distortion factor p0(t).

[0023] Furthermore, the relevant near-surface factors mentioned in step 4) are obtained through surface Q-value surveys.

[0024] Specifically, the method for obtaining the near-surface correlation factor in step 4) is as follows: the conjugate function of the record ω0″(t) obtained from the surface Q-value survey and the force signal ω0′(t) is used, and then divided by the modulus of ω0′(t) to obtain the near-surface correlation factor p1(t).

[0025] Among them, the surface Q value, also known as the surface quality factor, reflects the quality factor of the surface's physical characteristics of seismic absorption and attenuation.

[0026] Furthermore, the calculation of the denoised master record in step 5) includes the following steps:

[0027] Combine equation (2) with Performing convolution yields:

[0028]

[0029] That is, ω0(t)*e(t)×[|p0(t)| 2 ×|p1(t)| 1 Equation (4);

[0030] Dividing equation (4) by the moduli of p0(t) and p1(t) yields: S3(t) = ω0(t) * e(t) (Equation (5));

[0031] Where S3(t) is the mother record after denoising.

[0032] Furthermore, the calculation formula for convolving the denoised master record with the wavelet excited by the controllable source in step 6) is as follows:

[0033] S4(t)=ω0(t)*e(t)*ω0(t) Formula (6);

[0034] Wherein, S4(t) is the relevant record of the controllable source after denoising.

[0035] Furthermore, n′(t) = n′1(t) + n′2(t) + ... + n′ N (t)+E'(t);

[0036] Where, n′1(t) + n′2(t) + ... + n′ N (t) represents the controllable source noise similar to that generated by well drilling, and E′(t) represents the mechanical noise generated during controllable source excitation; where n′1(t)~n′ N (t) includes one or more of surface wave noise, multiple wave noise, linear interference noise, random noise, and environmental noise, where N is a positive integer.

[0037] The technical effects achieved by this invention are:

[0038] This invention proposes a novel approach to suppressing "black triangle" noise. Starting from the causes of "black triangle" noise formation in controlled-source seismic records, this method fully utilizes force signals to suppress noise in the master record. This study categorizes noise in controlled-source records into three types: controlled-source mechanical noise, controlled-source noise similar to well-shot noise, and controlled-source-related noise generated by mechanical and hydraulic systems and near-surface noise. By attenuating mechanical noise through large-value removal, removing well-shot-like noise using well-shot denoising techniques, and suppressing controlled-source-related noise using the conjugate function of the mechanical distortion factor and the near-surface correlation factor, the "black triangle" noise from controlled-source seismic records is effectively suppressed. Attached Figure Description

[0039] Figure 1 The original related records of controlled-source earthquake data;

[0040] Figure 2 For the original mother record;

[0041] Figure 3 To remove high-amplitude mechanical noise contained in the records, (a) is before mechanical noise removal, (b) is after mechanical noise removal, and (c) is the removed mechanical noise;

[0042] Figure 4 To remove surface waves contained in the record, where (a) is before surface wave removal, (b) is after surface wave removal, and (c) is the surface wave removed;

[0043] Figure 5 To generate wavelets using a controllable seismic source;

[0044] Figure 6 This refers to the controllable source force signal recorded in the field;

[0045] Figure 7This is a schematic diagram of the surface Q-value survey;

[0046] Figure 8 The data before and after the "black triangle" noise attenuation are compared. (a) is the superimposed record before attenuation, and (b) is the superimposed record after attenuation. Detailed Implementation

[0047] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0048] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention.

[0049] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0050] Example 1

[0051] Step 1: As Figure 5 As shown, find the conjugate function of the wavelet ω0(t) excited by the controllable source;

[0052] Step 2: Compare the conjugate function of the controlled source-excited wavelet ω0(t) with the original correlation record of the controlled source ( Figure 1 Each path in the sequence is convolved, and then divided by the modulus of the wavelet ω0(t) excited by the controllable source, to obtain the original mother record before correlation. Figure 2 );

[0053] The specific calculation formula for the above parent record is as follows:

[0054] S1(t)=ω0(t)*e(t)*p0(t)*p1(t)+n′(t) Formula (1);

[0055] Wherein, S1(t) is the mother record; ω0(t) represents the wavelet excited by the controllable source, e(t) represents the formation impulse response, p0(t) is the distortion factor of the mechanical and hydraulic system of the controllable source, p1(t) is the correlation factor near the surface, and n′(t) consists of the controllable source noise similar to the well shot excitation noise and the mechanical noise generated when the controllable source is excited;

[0056] Among them, n′(t)=n′1(t)+E′(t);

[0057] In this embodiment, n′1(t) is surface wave noise (controllable source noise similar to well shot excitation noise), and E′(t) is the mechanical noise generated when the controllable source is excited.

[0058] Step 3: Within a time window of 2000ms-8000ms, the average amplitude is calculated for every 21 seismic traces. Seismic traces with amplitude values ​​exceeding 10 times the average amplitude are removed to eliminate mechanical noise from strong amplitudes. Figure 3 ), thus obtaining the master record after eliminating mechanical noise;

[0059] Step 4: Use a high-pass filter to suppress surface wave noise with frequencies below 8Hz. Figure 4 The mother record after suppressing the surface wave is obtained, and the calculation formula is as follows:

[0060] S2(t)=ω0(t)*e(t)*p0(t)*p1(t) Formula (2);

[0061] Step 5: Combine the conjugate function of the controlled source-excited wavelet ω0(t) with the field-recorded controlled source force signal ω0′(t)... Figure 6 The distortion factor p0(t) of the hydraulic and mechanical system is obtained by convolution and then divided by the modulus of the wavelet ω0(t) excited by the controllable source.

[0062] Step 6: Convolve the conjugate function of the distortion factor with each path in the mother record, and then divide by the modulus of the hydraulic and mechanical system distortion factor to obtain the mother record after eliminating the influence of the hydraulic and mechanical system.

[0063] Step 7: Convolve the conjugate function of the field-recorded controllable source force signal ω0′(t) with the downhole record ω0″(t) from the surface Q-value survey, and then divide by the modulus of the field-recorded controllable source force signal ω0′(t) to obtain the near-surface correlation factor p1(t); see the schematic diagram of the surface Q-value survey for details. Figure 7 ;

[0064] Step 8: Convolve the conjugate function of the near-surface correlation factor with each trace in the mother record, and then divide by the modulus of the near-surface correlation factor to obtain the mother record with near-surface influence eliminated;

[0065] The specific calculation formulas for steps six and eight are as follows: (2) and... Performing convolution yields:

[0066]

[0067] That is, ω0(t)*e(t)×[|p0(t)| 2 ×|p1(t)| 2 Equation (4);

[0068] Dividing equation (4) by the moduli of p0(t) and p1(t) yields: S3(t) = ω0(t) * e(t) (Equation (5));

[0069] Where S3(t) is the mother record after denoising.

[0070] Step Nine: Convolve the denoised master record with the wavelet excited by the controllable source to obtain the controllable source correlation record after "black triangle" noise attenuation, thus achieving "black triangle" noise attenuation. For a detailed comparison of data before and after "black triangle" noise attenuation, see [link to relevant documentation]. Figure 8 .

[0071] The formula for calculating the convolution between the denoised master record and the wavelet excited by the controllable source is as follows:

[0072] S4(t)=ω0(t)*e(t)*ω0(t) Formula (6);

[0073] Wherein, S4(t) is the relevant record of the controllable source after denoising.

[0074] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A noise attenuation method, characterized in that: Includes the following steps: 1) Collect the raw correlation records of controlled-source seismic data, and first generate a controlled-source excited wavelet on the raw correlation records. The conjugate function convolution, then divided by The model is used to obtain the mother record; 2) Statistically analyze the average amplitude value of the seismic traces and discard those that are not valid. Mechanical noise generated when a controlled vibration source with an amplitude greater than ten times the average amplitude is excited. ; 3) Continue to remove controllable source noise from the controllable source mother record that is similar to well shot excitation noise, and obtain a mother record that only contains the influence of mechanical and hydraulic systems and near-surface factors; 4) The distortion factor of the mechanical and hydraulic systems of the controllable seismic source is denoted as... The relevant factors near the Earth's surface are denoted as Find them separately , conjugate function ; 5) Combine the records obtained in step 3) which include the effects of mechanical and hydraulic systems and near-surface factors with those obtained in step 4). Perform convolution, then divide by and The model is used to obtain the denoised mother record; 6) Convolve the denoised master record with the wavelet excited by the controllable source to obtain the relevant record of the controllable source, thereby achieving "black triangle" noise attenuation; The distortion factor in step 4) is determined as follows: the trigger signal is the excitation wavelet. The vibrating plate signal of the controllable source signal is the controllable source force signal recorded in the field. Controllable source force signals recorded in the field Wavelet excited by a controllable source The conjugate function convolution, then divided by The modulus, i.e., the distortion factor, is obtained. ; The method for obtaining the near-surface correlation factors mentioned in step 4) is as follows: using records obtained from surface Q-value surveys. Controlled source force signals recorded in the field The conjugate function convolution, then divided by By using the model, relevant factors near the Earth's surface can be obtained. .

2. The noise attenuation method according to claim 1, characterized in that: The formula for calculating the mother record in step 1) is as follows: Equation (1); in, Record for the mother; This indicates that a controllable seismic source can excite a wavelet. Indicates the formation impulse response, It is the distortion factor of the mechanical and hydraulic systems of a controllable seismic source. These are near-surface related factors. It consists of controlled source noise similar to well shot excitation noise and mechanical noise generated during controlled source excitation.

3. The noise attenuation method according to claim 1, characterized in that: The calculation formula for the record containing the effects of mechanical and hydraulic systems and near-surface factors mentioned in step 3) is as follows: ； in, The parent record contains only the effects of mechanical and hydraulic systems and near-surface factors.

4. The noise attenuation method according to claim 1, characterized in that: The distortion factor mentioned in step 4) is obtained by recording the vibrating plate signal and trigger signal of the controllable source.

5. The noise attenuation method according to claim 1, characterized in that: The relevant near-surface factors mentioned in step 4) are obtained through surface Q-value surveys.

6. The noise attenuation method according to claim 1, characterized in that: Step 5) describes the calculation of the denoised master record, which includes the following steps: Combine equation (2) with By performing convolution, we obtain: Equation (3); Right now Equation (4); Divide equation (4) by and The square of the modulus is obtained as follows: Equation (5); in, To complete the denoised master record.

7. The noise attenuation method according to claim 1, characterized in that: The calculation formula for convolving the denoised master record with the wavelet excited by the controllable source, as described in step 6), is as follows: Equation (6); in, This is a record of the controllable seismic source after noise reduction.

8. The noise attenuation method according to claim 2, characterized in that: ； in, This is a controllable source noise similar to the noise generated by well drilling. The mechanical noise generated during controlled vibration source excitation; where, It includes one or more of the following: surface wave noise, multiple wave noise, linear interference noise, random noise, and environmental noise, where N is a positive integer.

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