Quality evaluation method for seismic data

Abstract

The invention belongs to the field of seismic data analysis and evaluation in oil-gas exploration and development, and particularly relates to a seismic data quality evaluation method. The method comprises the following steps: calculating a full-band signal-to-noise ratio of a seismic signal of each seismic recording channel of synthetic seismic recording channel set data; averaging the full-band signal-to-noise ratios of the obtained seismic signals of all the seismic recording channels to obtain a signal-to-noise ratio calculation value of the seismic data; and evaluating the quality of the seismic data according to the signal-to-noise ratio calculation value. Wherein the method for calculating the signal-to-noise ratio of the seismic signal of the ith seismic recording channel comprises the following steps of: calculating the signal-to-noise ratio of the seismic signal of each frequency of the seismic recording channel; and taking the energy value of the seismic signal of each frequency of the seismic recording channel as a weight, and carrying out weighted summation on the obtained signal-to-noise ratio of the seismic signal of each frequency. By adopting the method, the accuracy and confidence of the evaluation result can be greatly improved.

Description

Technical Field

[0001] The invention belongs to the field of seismic data analysis and evaluation in oil and gas exploration and development, and specifically relates to a method for evaluating the quality of seismic data. Background Art

[0002] The signal-to-noise ratio and fidelity of seismic data are important indicators that characterize the quality and reliability of seismic data, and are the most essential attributes of the quality of seismic data. Without the signal-to-noise ratio and fidelity, seismic data loses its value and significance, and it is even more impossible to evaluate other attributes of seismic data. Accurately evaluating the signal-to-noise ratio and resolution of seismic data has far-reaching significance in evaluating seismic acquisition effects, monitoring the processing process, and applying the results. In the field acquisition stage, accurate signal-to-noise ratio fidelity evaluation can detect problems in the first place, improve measures in a timely manner, improve acquisition effects, and avoid major exploration errors. In the seismic processing stage, the rationality of processing methods and parameters can be accurately grasped. In the application stage, the general rules of seismic data support for regional exploration and development can be summarized through the analysis and evaluation of signal-to-noise ratio and fidelity, thereby improving the success rate of exploration and development. Existing seismic data evaluation methods usually only evaluate the quality and reliability of seismic data through the signal-to-noise ratio of seismic data, and the accuracy and confidence of the evaluation results are low.

[0003] In practice, there are certain difficulties in the accurate quantitative evaluation of the signal-to-noise ratio of seismic data. The main reason is that the existing signal-to-noise ratio calculation methods have uncertain factors in the actual seismic data analysis, and the signal-to-noise ratio estimation is limited by many factors, and the estimation results of different methods vary greatly. There is almost no quantitative research on fidelity. The Chinese invention patent specification with application publication number CN110673210A discloses a method for quantitative analysis and evaluation of the signal-to-noise ratio of seismic raw data. This method quantitatively calculates the energy intensity of high, medium and low frequencies for single-shot records collected in the field, takes the energy of the dominant frequency band as the signal energy of the original data, and the high and low end frequency bands as the energy of the noise. The two are divided to obtain the signal-to-noise ratio of the data. This method is a frequency domain estimation method, which is suitable for describing the distribution of the signal-to-noise ratio of field single-shot data in the spatial plane at the field collection site, so as to achieve preliminary evaluation and control of the quality of the original seismic data; since the noise of the seismic signal and the frequency of the effective signal may overlap, the signal-to-noise ratio calculated by this method is of low precision and inaccurate estimation, resulting in low accuracy and low confidence in the evaluation results of the quality and reliability of the seismic data; in addition, the method of this patent only evaluates the quality and reliability of the seismic data through the signal-to-noise ratio of the seismic data. The evaluation method is single and not comprehensive enough, resulting in low accuracy of the evaluation results.

[0004] In September 1990, the paper "Quantitative Estimation of Signal-to-Noise Ratio of Seismic Records" by Huo Zhijian and Fu Dandan, published in the Journal of Jianghan Petroleum Institute, discussed in detail the method of obtaining the signal-to-noise ratio using correlation analysis and statistical averaging. However, when this method is used, a large calculation deviation occurs when the signal-to-noise ratio of each frequency point is inconsistent; in addition, the above method uses a fixed-channel correlation technique, that is, the first channel in the record channel set is correlated with the subsequent records. This calculation implies that the signal-to-noise ratio of the first channel is very high, or it is a pure signal. The risk of this calculation is that if the noise in the first channel is large, it is equivalent to treating the noise as a signal, which is very unfavorable for the estimation of the signal-to-noise ratio. For data with a large number of channels and large amplitude changes, the obtained signal-to-noise ratio data will have large errors. Summary of the invention

[0005] The object of the present invention is to provide a method for evaluating the quality of seismic data, so as to solve the problem of low accuracy and confidence of the evaluation results when evaluating the quality and reliability of seismic data.

[0006] In order to solve the above technical problems, the present invention provides a method for evaluating the quality of seismic data, which is characterized by comprising:

[0007] 1) Calculate the full-band signal-to-noise ratio of the seismic signal of each seismic record track of the synthetic seismic record track gather data; wherein the method for calculating the signal-to-noise ratio of the seismic signal of the i-th seismic record track is:

[0008] Calculating the signal-to-noise ratio of the seismic signal of each frequency of the seismic recording track, and then obtaining the signal-to-noise ratio of the seismic signal of each frequency of the seismic recording track;

[0009] The energy value of the seismic signal of each frequency of the seismic recording track is used as a weight, and the signal-to-noise ratio of the seismic signal of each frequency is weighted and summed to obtain the full-band signal-to-noise ratio of the seismic signal of the seismic recording track.

[0010] 2) Calculate the average of the full-band signal-to-noise ratios of all seismic signals of all seismic recording channels to obtain the calculated signal-to-noise ratio value of the seismic data; and then evaluate the quality of the seismic data based on the calculated signal-to-noise ratio value.

[0011] The beneficial effects are as follows: the seismic signal of the seismic recording channel has a limited bandwidth (such as 5Hz-55Hz), and the signal-to-noise ratio corresponding to the seismic signal at each frequency point may be inconsistent. Therefore, the method of the present invention calculates the signal-to-noise ratio corresponding to the seismic signal of the seismic recording channel at each frequency point respectively, and performs weighted summation on the signal-to-noise ratio corresponding to each frequency point, so that the full-band signal-to-noise ratio of the seismic signal of the single seismic recording channel obtained is more accurate, thereby improving the accuracy and confidence of the evaluation result of the quality of the seismic data; when calculating the signal-to-noise ratio of the seismic data, the method of the present invention no longer uses the fixed channel correlation technology. For seismic data with a large number of channels and large amplitude changes, the full-band signal-to-noise ratio of each seismic signal is calculated and the average is calculated, and the average is used as the calculated value of the signal-to-noise ratio of the seismic data, thereby improving the accuracy of the calculated signal-to-noise ratio of the seismic data; the quality and reliability of the seismic data are evaluated based on the average, which can greatly improve the accuracy and confidence of the evaluation result.

[0012] Preferably, the signal-to-noise ratio of the seismic signal of the i-th seismic recording track with a frequency of f is calculated by combining the seismic signals of its adjacent seismic recording tracks, and its expression is:

[0013]

[0014] Where f is the frequency, μ is i (f) represents the signal-to-noise ratio of the signal with frequency f in the effective signal of the seismic signal of the i-th seismic recording channel, X in (f) represents the seismic signal with frequency f at the nth sampling point of the i-th seismic recording channel, represents the conjugate of the seismic signal with frequency f at the nth sampling point of the i-th seismic trace, It represents the conjugate of the seismic signal with frequency f at the nth sampling point of the jth seismic trace, and the jth seismic trace is adjacent to the ith seismic trace.

[0015] Preferably, if the i-th seismic recording track is not located at an edge position, two full-band signal-to-noise ratios are calculated based on the signals of its two adjacent seismic recording tracks, and the two signal-to-noise ratios are averaged to obtain the full-band signal-to-noise ratio of the seismic signal of the i-th seismic recording track.

[0016] Its beneficial effects are as follows: a seismic trace located in the middle position will have two adjacent seismic traces, and the signal-to-noise ratios calculated based on the two adjacent seismic traces are not equal. By calculating the signal-to-noise ratio of the seismic trace located in the middle position based on the two adjacent seismic traces and finding the average, the accuracy of the calculated signal-to-noise ratio is further improved, thereby further improving the accuracy and confidence of the evaluation results for evaluating the quality and reliability of seismic data.

[0017] Preferably, after obtaining the calculated value of the signal-to-noise ratio, the true value of the signal-to-noise ratio of the actual seismic data is obtained by combining the relationship between the calculated value of the signal-to-noise ratio of the preset synthetic seismic record data and the true value of the signal-to-noise ratio, and then the quality of the seismic data is evaluated based on the true value of the signal-to-noise ratio of the actual seismic data.

[0018] The beneficial effect is that since there is a certain deviation between the calculated value of the signal-to-noise ratio of seismic data and its true value, after obtaining the calculated value of the signal-to-noise ratio, the relationship curve between the calculated value of the signal-to-noise ratio and the true value of the signal-to-noise ratio can be used to quickly obtain the true value of the signal-to-noise ratio of the seismic data, and the quality of the seismic data is evaluated based on the true value of the signal-to-noise ratio, further improving the accuracy and confidence of the evaluation result. In addition, the method of the present invention can realize the quantitative calculation of the true signal-to-noise ratio of seismic data.

[0019] Preferably, the method for obtaining the relationship data diagram between the calculated signal-to-noise ratio value and the true value of the signal-to-noise ratio of the synthetic seismic record gather data is:

[0020] Adding different proportions of noise to synthetic seismic records containing only effective seismic signals to form synthetic seismic records with different signal-to-noise ratios;

[0021] The calculated signal-to-noise ratio values ​​of synthetic seismic record data with different signal-to-noise ratios are obtained respectively, and then the relationship between the calculated signal-to-noise ratio value of the synthetic seismic record stacking data and the true value of the signal-to-noise ratio is obtained.

[0022] Preferably, it also includes: after calculating the true value of the signal-to-noise ratio of the actual seismic data, determining the fidelity of the actual seismic data according to a preset relationship between the signal-to-noise ratio and fidelity of the actual seismic data, and then evaluating the quality of the seismic data based on the fidelity of the actual seismic data.

[0023] The beneficial effects are as follows: the signal-to-noise ratio and fidelity of seismic data are important indicators of the quality and reliability of seismic data, and are the most essential attributes of the quality of seismic data. The method of the present invention evaluates the quality of seismic data based on the data of the two dimensions of signal-to-noise ratio and fidelity at the same time, further improving the accuracy and confidence of the evaluation results.

[0024] Preferably, the method for obtaining the relationship between the signal-to-noise ratio and fidelity of actual seismic data comprises the following steps:

[0025] A, obtain the synthetic seismic trace with only effective seismic signals;

[0026] B, adding different proportions of noise to the acquired synthetic seismic record traces to form synthetic seismic records with different signal-to-noise ratios;

[0027] C, respectively superimposing synthetic seismic records with different signal-to-noise ratios to obtain synthetic seismic record superposition data with different signal-to-noise ratios;

[0028] D. The mutual correlation coefficients between the synthetic seismic record stacking data and the synthetic seismic record traces with different signal-to-noise ratios are obtained respectively; the value of the mutual correlation coefficient is used as the value of the fidelity, and then the relationship between the signal-to-noise ratio of the synthetic seismic record and its fidelity is obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a flow chart of the method steps of the present invention;

[0030] Figure 2 It is a schematic diagram of a process of obtaining a relationship diagram between the signal-to-noise ratio and fidelity of a synthetic seismic record according to the present invention;

[0031] Figure 3 is a schematic diagram of a wavelet;

[0032] Figure 4 It is a schematic diagram of the spectrum and phase corresponding to the zero-phase wavelet and the minimum-phase wavelet;

[0033] Figure 5 It is a schematic diagram of the reflection coefficient distribution of the present invention;

[0034] Figure 6 It is a schematic diagram of the result of the convolution operation;

[0035] Figures 7 to 10 It is a schematic diagram of synthetic seismic record gathers with four different signal-to-noise ratios;

[0036] Fig.11 is a graph showing the relationship between the correlation coefficient between the synthetic seismic record stacking data and the synthetic seismic record trace and the signal-to-noise ratio of the synthetic seismic record;

[0037] Fig.12 It is a data diagram showing the relationship between the calculated signal-to-noise ratio value of synthetic seismic record gather data and its true signal-to-noise ratio value;

[0038] Fig.13 It is a curve diagram showing the relationship between the calculated signal-to-noise ratio value and the true value of the signal-to-noise ratio of the synthetic seismic record gather data;

[0039] Fig.14 This is a schematic diagram of the evaluation results of the quality of actual seismic data in a certain work area. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0041] Example of a method for evaluating the quality of seismic data:

[0042] like Figure 1 As shown, the quality evaluation method of seismic data of the present invention comprises the following steps:

[0043] like Figure 2 As shown, in step one, a relationship diagram between the signal-to-noise ratio and fidelity of synthetic seismic records is obtained.

[0044] 1.1) Select seismic wavelet;

[0045] According to the type of earthquake data, select the appropriate earthquake wavelet. The schematic diagram of the wavelet is as follows Figure 3 As shown. Zero-phase wavelets are selected for both vibrator and deconvolution seismic data, and minimum-phase wavelets are selected for explosive data. The frequency of the wavelet is equal to the dominant frequency of the data being evaluated. The seismic wavelet uses the OMSBY wavelet, which has a frequency range of 0-60 Hz and a dominant frequency of 18-22 Hz. The zero-phase wavelet and its corresponding spectrum and phase, as well as the minimum-phase wavelet and its corresponding spectrum and phase are shown in Figure 4 As shown, the thin line in the figure represents the zero-phase wavelet, and the thick line represents the minimum phase wavelet.

[0046] 1.2) Design reflection coefficient sequence;

[0047] like Figure 5 As shown in the figure, in the reflection sequence design, the amplitude is kept single and the sequence is whitened to facilitate quantitative analysis. The reflection coefficient sequence is whitened (the number of positive and negative reflection coefficients is equal), the maximum interval of the reflection coefficient sequence does not exceed 150ms, and five reflection coefficient combinations are taken to form the reflection coefficient sequence, as shown in Table 1:

[0048] Table 1

[0049]

[0050] By making the amplitude of the reflection coefficient sequence single, the sequence whitening, and the maximum interval between the reflection coefficient sequences not exceeding 150ms, quantitative analysis is facilitated.

[0051] 1.3) Generate and output a synthetic seismic trace containing only valid seismic signals through convolution operation;

[0052] The result of the convolution operation is as follows Figure 6 The synthetic seismic traces generated are pure signal seismic traces. After the synthetic seismic traces are generated, they are copied according to the work area data to form a gather data slightly larger than the number of coverages.

[0053] 1.4) adding noise of different proportions to the synthetic seismic record traces to form synthetic seismic records with different signal-to-noise ratios and outputting synthetic seismic record trace gathers with different signal-to-noise ratios;

[0054] During the noise addition process, the signal energy remains constant and the noise ratio = 1 / snr. After adding noise to the synthetic seismic record, it is output as a signal-to-noise ratio seismic record gather. The synthetic seismic record gathers with different signal-to-noise ratios are shown in the following figure. Figures 7 to 10 shown.

[0055] The added noise is random white noise, which has a spectral whitening feature in the frequency range of 0-80Hz. When synthesizing synthetic seismic record gathers with different signal-to-noise ratios, the seismic signal energy (amplitude) remains unchanged, that is, the energy of the signal in all signal-to-noise ratio gathers is fixed. The synthesis of different signal-to-noise ratio gathers follows the following formula: T = 500 (S + N / SNR). Among them, T is the synthetic seismic trace, S is the pure signal synthetic trace (output of step 4), N is random white noise, and SNR is the signal-to-noise ratio. The coefficient of 500 is to ensure the accuracy of the data in actual seismic data processing.

[0056] In the synthetic seismic records with different signal-to-noise ratios, the differences between the signal-to-noise ratios of all synthetic seismic records with the closest signal-to-noise ratios are not equal. The signal-to-noise ratio ranges from 0.0001 to 100. For the convenience of drawing and analysis, the SNR value is taken as the logarithm LOGSNR with a base of 10. The signal-to-noise ratio design table is shown in Table 2:

[0057] Table 2

[0058] SNR LOGSNR SNR LOGSNR SNR LOGSNR SNR LOGSNR SNR LOGSNR 0.0001 -4.00000 0.07 -1.09691 0.09 -1.04575 3.70 0.56820 9.00 0.95424 0.001 -3.00000 0.08 -1.09691 1.00 0.00000 4.00 0.60206 9.50 0.97772 0.002 -2.04575 0.09 -1.04575 1.20 0.07918 4.50 0.65321 10.00 1.00000 0.005 -2.00000 0.10 -1.00000 1.40 0.14612 5.00 0.69897 12.00 1.07918 0.009 -1.69896 0.20 -0.69897 1.60 0.20411 5.50 0.74036 14.00 1.14612 0.010 -1.52287 0.30 -0.52287 1.80 0.25527 6.00 0.77815 16.00 1.20412 0.020 -1.39794 0.40 -0.39794 2.00 0.30103 6.50 0.81291 18.00 1.25527 0.030 -1.30103 0.50 -0.30103 2.35 0.37106 7.00 0.84509 20.00 1.30103 0.040 -1.22184 0.60 -0.22184 2.70 0.43136 7.50 0.87506 40.00 1.60205 0.050 -1.15490 0.70 -0.15490 3.00 0.47712 8.00 0.90309 60.00 1.77815 0.060 -1.09691 0.80 -0.09691 3.35 0.52504 8.50 0.92941 100.0 2.00000

[0059] 1.5) Superimposing synthetic seismic records with different signal-to-noise ratios respectively and outputting synthetic seismic record superposition data with different signal-to-noise ratios;

[0060] 1.6) Cross-correlating the synthetic seismic record stacking data with different signal-to-noise ratios with the synthetic seismic record traces, and obtaining the correlation coefficient between the synthetic seismic record stacking data with different signal-to-noise ratios and the synthetic seismic record traces;

[0061] 1.7) Using the numerical value of the correlation coefficient as the numerical value of the fidelity, obtain the relationship data between the signal-to-noise ratio of the synthetic seismic record stacking data and the correlation coefficient in step 1.6), and output the relationship diagram between the correlation coefficient in step 1.6) and the signal-to-noise ratio of the synthetic seismic record, that is, the relationship diagram between the signal-to-noise ratio of the synthetic seismic record and its fidelity.

[0062] The relationship between the output synthetic seismic record stacking data and the synthetic seismic record trace and the signal-to-noise ratio of the synthetic seismic record is shown in the figure below: Fig.11 shown.

[0063] Step 2: Obtain a curve diagram showing the relationship between the calculated signal-to-noise ratio value and the true value of the signal-to-noise ratio of the synthetic seismic record gather data.

[0064] The specific method for obtaining the relationship data diagram between the calculated signal-to-noise ratio value and the true signal-to-noise ratio value of the synthetic seismic record gather data is as follows: for synthetic seismic record gather data with different signal-to-noise ratios and known signal-to-noise ratios, the calculated signal-to-noise ratio values ​​are obtained respectively, and then the relationship data diagram between the calculated signal-to-noise ratio value and the true signal-to-noise ratio value of the synthetic seismic record gather data is generated as shown in FIG. Fig.12 As shown. The uncertainty error of the calculation is eliminated, and the relationship curve between the calculated signal-to-noise ratio value and the true value of the signal-to-noise ratio is obtained by curve fitting the relationship data diagram between the calculated signal-to-noise ratio value and the true value of the signal-to-noise ratio of the synthetic seismic record gather data. Fig.13 shown.

[0065] The method to obtain the calculated value of the signal-to-noise ratio of synthetic seismic record gather data is:

[0066] The full-band signal-to-noise ratio of the seismic signal of each seismic record track of the synthetic seismic record track gather data is calculated respectively and the average is calculated. The average is the signal-to-noise ratio of the synthetic seismic record track gather data.

[0067] The method for calculating the signal-to-noise ratio of the seismic signal of the i-th seismic recording channel is:

[0068] 1) Calculate the signal-to-noise ratio of the seismic signal of each frequency of the seismic recording track by combining the seismic signals of the seismic tracks adjacent to the seismic recording track, and then obtain the signal-to-noise ratio of the seismic signal of each frequency of the seismic recording track; the signal-to-noise ratio calculation expression of the seismic signal of a certain frequency of the i-th seismic recording track is as follows:

[0069]

[0070] Where f is the frequency, μ is i (f) represents the signal-to-noise ratio of the signal with frequency f in the effective signal of the seismic signal of the i-th seismic recording channel, X in (f) represents the seismic signal with frequency f at the nth sampling point of the i-th seismic recording channel, represents the conjugate of the seismic signal with frequency f at the nth sampling point of the i-th seismic trace, It represents the conjugate of the seismic signal with frequency f at the nth sampling point of the jth seismic trace.

[0071] The derivation process of formula (1) is as follows:

[0072] 2.1.1) The actual seismic signal is the sum of the effective signal and the noise signal, so the seismic signal of the i-th seismic recording channel can be expressed as:

[0073] X i (n) = S1(n) + Ni(n) (2)

[0074] Wherein: Xi is the seismic signal of the ith seismic recording channel, Si is the effective signal of the seismic signal of the ith seismic recording channel, Ni is the noise signal of the seismic signal of the ith seismic recording channel, and n=1, 2, 3, ... is the sampling point number.

[0075] When sampling the seismic signal of the i-th seismic recording channel, sampling starts from time 0. Assuming the sampling interval is dt, the expression of the sampling time of the n-th sampling point is:

[0076] t n =(n-1)*dt (3)

[0077] 2.1.2) Derive and simplify the expression of the autocorrelation coefficient of the seismic signal of the ith seismic recording channel, and derive and simplify the expression of the mutual correlation coefficient between the seismic signal of the ith seismic recording channel and the seismic signals of the adjacent seismic recording channels.

[0078] The autocorrelation function expression of the seismic signal of the i-th seismic recording channel is:

[0079]

[0080] Where: Σ represents the summation calculation, X in is the seismic signal of the ith seismic record at the nth sampling point, S in is the effective signal of the seismic signal of the ith seismic record at the nth sampling point, N in The noise signal of the seismic signal of the i-th seismic record at the n-th sampling point, is the conjugate function of the seismic signal of the ith seismic trace at the nth sampling point, is the conjugate function of the effective signal of the seismic signal of the ith seismic trace at the nth sampling point, is the conjugate function of the noise signal of the seismic signal of the i-th seismic record at the n-th sampling point; Represents the autocorrelation function of the i-th seismic signal.

[0081] Since the noise signal is not correlated with the effective signal, that is, XCORR(S, N) = 0, equation (4) can be transformed into the following expression:

[0082]

[0083] In the formula, Σ represents the summation calculation, X in is the seismic signal of the ith seismic record at the nth sampling point, S in is the effective signal of the seismic signal of the ith seismic record at the nth sampling point, N in is the noise signal of the seismic signal of the i-th seismic recording channel, is the conjugate function of the seismic signal of the ith seismic trace at the nth sampling point, is the conjugate function of the effective signal of the seismic signal of the ith seismic trace at the nth sampling point, The conjugate function of the noise signal of the seismic signal of the i-th seismic trace at the n-th sampling point; represents the autocorrelation function of the seismic signal of the ith seismic trace; represents the effective signal energy of the i-th seismic recording channel; It represents the noise signal energy of the i-th seismic record channel, and n is the sampling point number.

[0084] The expression of the cross-correlation function between the seismic signal of the i-th seismic recording track and the seismic signal of the adjacent seismic recording track j is:

[0085]

[0086] Where: Σ represents the summation calculation, ∑ n {X in X jn} represents the cross-correlation function between the seismic signal of the i-th seismic recording channel and the seismic signal of the j-th seismic recording channel, X in is the seismic signal of the ith seismic record at the nth sampling point, S in The effective signal of the seismic signal of the i-th seismic record at the n-th sampling point, N in is the noise signal of the seismic signal of the ith seismic record at the nth sampling point, is the conjugate function of the seismic signal of the jth seismic trace at the nth sampling point, is the conjugate function of the effective signal of the seismic signal of the jth seismic trace at the nth sampling point, The conjugate function of the noise signal of the seismic signal of the jth seismic trace at the nth sampling point.

[0087] Because the noise signal is random noise, the autocorrelation function value of the noise signal is 0, and the cross-correlation function value between different noise signals is also 0. Then, equation (6) can be transformed, and the transformed expression is as follows:

[0088]

[0089] In the formula, S in is the effective signal of the seismic signal of the ith seismic record at the nth sampling point, is the conjugate function of the effective signal of the seismic signal of the jth seismic recording channel at the nth sampling point, Σ represents the summation calculation, Represents the cross-correlation function between the seismic signal of the i-th seismic recording channel and the seismic signal of the j-th seismic recording channel.

[0090] The signal-to-noise ratio μ of the seismic signal with frequency f on the ith seismic recording channel i The expression of (f) is:

[0091] In the formula,

[0092] From formula (5) and formula (7), we can get:

[0093]

[0094]

[0095] Substituting equation (9) and equation (10) into equation (8), we can obtain:

[0096]

[0097] In formula (8) to formula (11), μ i (f is the signal-to-noise ratio of the seismic signal with frequency f of the i-th seismic recording channel, N in (f) is the noise signal of the seismic signal with frequency f at the nth sampling point of the ith seismic record, S in (f) is the effective signal of the seismic signal with frequency f at the nth sampling point of the ith seismic recording channel, X in (f) is the seismic signal with frequency f at the nth sampling point of the ith seismic recording channel, is the conjugate function of the seismic signal with frequency f at the nth sampling point of the ith seismic trace, It is the conjugate function of the seismic signal with frequency f at the nth sampling point of the jth seismic trace.

[0098] 2) Taking the energy value of the seismic signal of each frequency of the seismic recording track as the weight, the signal-to-noise ratio of the seismic signal of each frequency is weighted and summed to obtain the full-band signal-to-noise ratio of the seismic signal of the seismic recording track. The expression of the full-band signal-to-noise ratio is:

[0099]

[0100] In formula (12), SNR(i) represents the full-band signal-to-noise ratio of the seismic signal of the i-th seismic recording channel, Q i (f) represents the energy value of the seismic signal with frequency f of the seismic recording channel, μ i (f) represents the signal-to-noise ratio of the seismic signal with a frequency of f in the i-th seismic recording channel, where f represents the frequency of the seismic signal, f1, f2, ... f nThey respectively represent the different frequencies of the seismic signal of the i-th seismic recording channel.

[0101]

[0102] In formula (13), Q i (f) represents the energy value of the seismic signal with frequency f of the seismic recording trace, X i (f) represents the seismic signal with frequency f at the nth sampling point of the i-th seismic recording channel, Represents the conjugate of the seismic signal with frequency f at the nth sampling point of the i-th seismic trace.

[0103] There are multiple frequency points in the seismic signal of a seismic recording track, and the signal-to-noise ratio corresponding to the seismic signal at each frequency point may be inconsistent. Therefore, the method of the present invention calculates the signal-to-noise ratio of the seismic signal of the seismic recording track at each frequency point respectively, and performs weighted summation on the signal-to-noise ratio corresponding to each frequency point, so that the full-band signal-to-noise ratio of the seismic signal of a single seismic recording track obtained is more accurate, thereby improving the accuracy and confidence of the evaluation results of the quality and reliability of the seismic data.

[0104] If the i-th seismic trace is a seismic trace located at an edge position, the calculation can be performed directly according to the above two steps; if the i-th seismic trace is not located at an edge position, it has two adjacent seismic traces, and the two signal-to-noise ratios calculated based on the signals of its two adjacent seismic traces are not equal in size. The full-band signal-to-noise ratio of the seismic signal of the i-th seismic trace is obtained by taking the average of the two signal-to-noise ratios.

[0105] There will be two adjacent seismic traces in the middle position. The signal-to-noise ratios calculated based on the two adjacent seismic traces are not equal. By calculating the signal-to-noise ratio of the seismic trace in the middle position based on the two adjacent seismic traces and finding the average, the accuracy of the calculated signal-to-noise ratio is further improved, thereby further improving the accuracy and confidence of the evaluation results of the quality and reliability of the seismic data.

[0106] Step three, obtaining the calculated signal-to-noise ratio value of the actual seismic data and the synthetic seismic record gather data corresponding to the actual seismic data based on the actual seismic data.

[0107] The method for obtaining the calculated value of the signal-to-noise ratio of the actual seismic data is the same as the method for obtaining the calculated value of the signal-to-noise ratio of the synthetic seismic record gather data in step 2, and will not be repeated here.

[0108] Step 4: According to the calculated value of the signal-to-noise ratio of the actual seismic data, the true value of the signal-to-noise ratio of the actual seismic data is obtained by combining the relationship data diagram between the calculated value of the signal-to-noise ratio of the synthetic seismic record gather data and the true value of the signal-to-noise ratio.

[0109] Step 5: Calculate the fidelity value of the actual seismic data based on the true value of the signal-to-noise ratio of the actual seismic data and the relationship diagram between the signal-to-noise ratio and fidelity of the synthetic seismic record gather data.

[0110] Step six, generating a signal-to-noise ratio and fidelity evaluation report of the actual seismic data based on the true value of the signal-to-noise ratio and the fidelity value of the actual seismic data, and then evaluating the quality and reliability of the seismic data based on the signal-to-noise ratio and fidelity evaluation report of the actual seismic data.

[0111] like Fig.14 As shown, when evaluating the quality of actual seismic data of a certain work area, the method of the present invention is first used to calculate the fidelity and signal-to-noise ratio of the actual seismic data of the certain work area, and then the quality and reliability of the actual seismic data of the work area are evaluated based on the fidelity and signal-to-noise ratio.

[0112] The method of the present invention no longer uses the fixed-channel correlation technology when calculating the signal-to-noise ratio of seismic data. For seismic data with a large number of channels and large amplitude changes, the full-band signal-to-noise ratio of each seismic signal is calculated and the average is calculated, and the average is used as the calculated signal-to-noise ratio value of the seismic data, thereby improving the accuracy of the calculated signal-to-noise ratio of the seismic data; since there will be a certain deviation between the calculated signal-to-noise ratio value of the seismic data and its true value, after obtaining the calculated signal-to-noise ratio value, the relationship curve diagram between the calculated signal-to-noise ratio value and the true signal-to-noise ratio value can be used to quickly obtain the true signal-to-noise ratio value of the seismic data; after obtaining the true signal-to-noise ratio value, the fidelity of the actual seismic data can be quickly determined according to the preset relationship diagram between the signal-to-noise ratio and the fidelity of the actual seismic data; thus, the quality of the seismic data is evaluated based on the data of the two dimensions of signal-to-noise ratio and fidelity, which greatly improves the accuracy and confidence of the evaluation result.

Claims

1. A method for evaluating the quality of seismic data, characterized in that: include: 1) Calculate the full-band signal-to-noise ratio of the seismic signal of each seismic record track of the synthetic seismic record track gather data; wherein the method for calculating the signal-to-noise ratio of the seismic signal of the i-th seismic record track is: Calculating the signal-to-noise ratio of the seismic signal of each frequency of the seismic recording track, and then obtaining the signal-to-noise ratio of the seismic signal of each frequency of the seismic recording track; The energy value of the seismic signal of each frequency of the seismic recording track is used as a weight, and the signal-to-noise ratio of the seismic signal of each frequency is weighted and summed to obtain the full-band signal-to-noise ratio of the seismic signal of the seismic recording track. 2) Calculate the average of the full-band signal-to-noise ratios of all seismic signals of all seismic recording channels to obtain a calculated signal-to-noise ratio value of the seismic data; and then evaluate the quality of the seismic data based on the calculated signal-to-noise ratio value.

2. The method for evaluating the quality of seismic data according to claim 1, characterized in that: The signal-to-noise ratio of the seismic signal with a frequency of f on the i-th seismic recording channel is calculated by combining the seismic signals of its adjacent seismic recording channels, and its expression is: Where f is the frequency, μ is i (f) represents the signal-to-noise ratio of the signal with frequency f in the effective signal of the seismic signal of the i-th seismic recording channel, X in (f) represents the seismic signal with frequency f at the nth sampling point of the i-th seismic recording channel, represents the conjugate of the seismic signal with frequency f at the nth sampling point of the i-th seismic trace, It represents the conjugate of the seismic signal with frequency f at the nth sampling point of the jth seismic trace, and the jth seismic trace is adjacent to the ith seismic trace.

3. The method for evaluating the quality of seismic data according to claim 2, characterized in that: If the i-th seismic recording track is not located at the edge position, two full-band signal-to-noise ratios are calculated based on the signals of its two adjacent seismic recording tracks, and the two signal-to-noise ratios are averaged to obtain the full-band signal-to-noise ratio of the seismic signal of the i-th seismic recording track.

4. The method for evaluating the quality of seismic data according to claim 1, wherein: After obtaining the calculated signal-to-noise ratio value, the true signal-to-noise ratio value of the actual seismic data is obtained by combining the relationship between the calculated signal-to-noise ratio value of the preset synthetic seismic record data and the true signal-to-noise ratio value, and then the quality of the seismic data is evaluated based on the true signal-to-noise ratio value of the actual seismic data.

5. The method for evaluating the quality of seismic data according to claim 4, characterized in that: The method for obtaining the relationship between the calculated signal-to-noise ratio value and the true value of the signal-to-noise ratio of synthetic seismic record gather data is: Adding different proportions of noise to synthetic seismic records containing only effective seismic signals to form synthetic seismic records with different signal-to-noise ratios; The calculated signal-to-noise ratio values ​​of synthetic seismic record data with different signal-to-noise ratios are obtained respectively, and then the relationship between the calculated signal-to-noise ratio value of the synthetic seismic record stacking data and the true value of the signal-to-noise ratio is obtained.

6. The method for evaluating the quality of seismic data according to claim 4 or 5, characterized in that: Also includes: After the true value of the signal-to-noise ratio of the actual seismic data is obtained, the fidelity of the actual seismic data is determined based on the preset relationship between the signal-to-noise ratio and fidelity of the actual seismic data, and then the quality of the seismic data is evaluated based on the fidelity of the actual seismic data.

7. The method for evaluating the quality of seismic data according to claim 6, characterized in that: The method for obtaining the relationship between the signal-to-noise ratio and fidelity of the actual seismic data The following steps are involved: A, obtain the synthetic seismic trace with only effective seismic signals; B, adding different proportions of noise to the acquired synthetic seismic record traces to form synthetic seismic records with different signal-to-noise ratios; C, respectively superimposing synthetic seismic records with different signal-to-noise ratios to obtain synthetic seismic record superposition data with different signal-to-noise ratios; D, respectively obtain the mutual correlation coefficients between the synthetic seismic record stacking data and the synthetic seismic record traces with different signal-to-noise ratios; The value of the mutual correlation coefficient is used as the value of the fidelity, and then the relationship between the signal-to-noise ratio of the synthetic seismic record and its fidelity is obtained.

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