Five-dimensional phase difference cross-correlation multi-scale geological body interpretation method and device

Abstract

The present invention provides a five-dimensional phase difference cross-correlation multi-scale geological body interpretation method, which comprises: using frequency-divided multi-scale phase analysis, transforming seismic signals into the frequency domain to obtain multi-scale phase information, and then performing normalization processing to obtain normalized complex seismic traces; based on the normalized complex seismic traces, considering the geological body trend, respectively calculating the phase difference cross-correlation along different spatial directions; selecting the maximum value of the phase difference in the phase difference cross-correlation calculation result to approximately characterize the final result of the discontinuity measurement perpendicular to the structural trend. Compared with the traditional phase correlation algorithm, the present invention has a multi-scale feature in the result, can reflect the abnormal structure of a specific scale, avoid the influence of high-frequency random noise, highlight more geological detail information, and can also fuse or compare the results of different scales to obtain higher resolution results, and study the change characteristics of different scales, which can accurately describe the distribution of underground structural anomalies.

Description

Technical Field

[0001] The present invention relates to the field of signal processing and exploration geophysical interpretation technology in geology, and in particular to a five-dimensional phase difference cross-correlation multi-scale geological body interpretation method and device. Background Art

[0002] Coherence is an effective method for identifying underground structures and can be used as a quality control (QC) indicator in data acquisition and processing. The first three generations of coherence algorithms were calculated based on the eigenvalues ​​of the cross-correlation, similarity, and covariance matrices, respectively. Traditional coherence algorithms are mainly based on the geometric average results of coherence along the main survey line and the connecting survey line, or the coherence of seismic traces in two adjacent elliptical or rectangular areas. Therefore, coherence exhibits good anti-noise performance. However, the discontinuous expression of coherence is essentially a multi-channel averaging effect, which is generally a comprehensive reflection of the discontinuity of the geological body. Therefore, in deep imaging of seismic data, coherence is not sensitive to weak and hidden reflection signals. In addition, due to the multiple addition and multiplication operations of multiple channels, it is less efficient in terms of calculation speed.

[0003] Another conventional seismic feature identification attribute is phase. Traditional phase attributes are one by one. Compared with the coherent algorithm, the relatively simple calculation mode significantly improves the calculation efficiency. In addition, the phase attribute is more sensitive to subtle changes. However, the traditional phase attribute does not involve any geological or structural constraints and is prone to noise.

[0004] In 2019, Yuan proposed the geosteering phase attribute, which combines the advantages of traditional coherence and phase attributes. The phase body attributes in different directions are obtained by calculating the correlation coefficients of adjacent superimposed phase traces along different spatial directions, and extracting the directional phase information from the obtained complex covariance matrix. Then, the maximum phase attributes are compared, which can better characterize the entire outline and spatial extension direction of the geological anomaly, and increase the accuracy and credibility of seismic interpretation. Therefore, the geosteering phase attribute can identify the boundaries of geological bodies such as faults, river channels, and caves, and improve the noise resistance.

[0005] However, the discontinuity of seismic images is obtained through the cross-correlation operation between multiple channels, while increasing the dimension of the geological structure trend. Therefore, compared with conventional coherence, the computational cost is much more expensive for large earthquake data. In addition, Wang proposed a frequency-division-based geosteering coherence attribute for deep stratum feature characterization. These attributes can effectively select and utilize the phase components of favorable frequency bands, so that geological discontinuities of different scales can be identified and the influence of random noise can be reduced. However, the increased frequency dimension brings more computational burden and more expensive computational cost. In short, the application effect of existing technologies will be limited by many factors such as geological background, seismic data quality, and computational efficiency, and the scope of application is also small, so more in-depth research and discussion is needed.

[0006] Therefore, the present invention provides a five-dimensional phase difference cross-correlation multi-scale geological body interpretation method and device. Summary of the invention

[0007] To solve the above problems, the present invention provides a five-dimensional phase difference cross-correlation multi-scale geological body interpretation method, which comprises the following steps:

[0008] Step 1: Using frequency-divided multi-scale phase analysis, the seismic signal is transformed into the frequency domain to obtain multi-scale phase information, and then normalized to obtain a normalized complex seismic trace;

[0009] Step 2: Based on the normalized complex seismic traces, considering the direction of the geological body, the phase difference cross-correlation is calculated along different spatial directions respectively;

[0010] Step 3: Select the maximum value of the phase difference in the phase difference cross-correlation calculation results to approximately represent the final result of the discontinuity measurement perpendicular to the structural trend.

[0011] According to one embodiment of the present invention, in step 1, the seismic signal is transformed into the frequency domain by the following formula:

[0012] G f (a,b,ω)=∫f(t)g a (tb)e -iωt dt

[0013] Where f(t) is the seismic signal, is the basis function. Here, Gaussian function is selected as the basis function, a>0, b>0, ω is the angular frequency, t is the time, g a (tb) is the locally varying window function, parameter b is used to move the window function to cover the entire time domain, e -iωt It is a simple harmonic.

[0014] According to an embodiment of the present invention, in step 1, the normalized complex seismic trace is obtained by the following formula:

[0015]

[0016] Where f is the frequency, represents the normalized complex seismic trace, including phase information, It represents the phase information that changes with frequency. Different frequency phases can highlight geological bodies of different scales or thicknesses.

[0017] According to an embodiment of the present invention, in step 2, for a spatial direction, the phase difference cross-correlation result is calculated by the following steps:

[0018] Determine two spatial directions adjacent to and behind the current spatial direction, which are called the front adjacent spatial direction and the rear adjacent spatial direction respectively;

[0019] Performing difference processing on the normalized seismic traces of the previous adjacent spatial direction and the current spatial direction and taking the absolute value to obtain a first phase difference;

[0020] Performing difference processing on the normalized seismic traces of the subsequent adjacent spatial direction and the current spatial direction and taking the absolute value to obtain a second phase difference;

[0021] Based on the first phase difference and the second phase difference, a phase difference cross-correlation calculation result corresponding to the current spatial direction is calculated using a phase difference cross-correlation formula.

[0022] According to an embodiment of the present invention, the step 2 specifically includes the following steps:

[0023] At least four spatial directions are selected to respectively calculate the phase difference cross-correlation, wherein the selected four directions are 0°, 45°, 90°, and 135° respectively.

[0024] According to an embodiment of the present invention, in step 2, the phase difference cross-correlation is calculated by the following formula:

[0025]

[0026] in, and It represents the phase difference between two adjacent normalized seismic traces. The superscript du (u = 1, 2, ... U) represents the U-th spatial direction. The subscript k represents the k-th normalized complex seismic trace as the center trace. represents the normalized complex seismic trace, f represents frequency, t represents time, |·| represents absolute value, Represents the phase difference cross-correlation superposition result within a time window containing M sampling points.

[0027] According to an embodiment of the present invention, in step three, the maximum value of the phase difference is selected from the phase difference cross-correlation calculation results by the following formula:

[0028]

[0029] Among them, max(·) means taking the maximum value, which is a nonlinear operator; Represents the phase difference cross-correlation calculation result in the U-th spatial direction.

[0030] According to one embodiment of the present invention, the method further comprises:

[0031] Phase difference cross-correlation calculation is performed by optimizing the frequency, so as to highlight the geological abnormal structures of a specific scale in a targeted manner, and the influence of random noise on the calculation results is avoided by discarding higher frequency information.

[0032] According to another aspect of the present invention, a storage medium is provided, which contains a series of instructions for executing the method steps as described in any one of the above.

[0033] According to another aspect of the present invention, a five-dimensional phase difference cross-correlation multi-scale geological body interpretation device is provided, and five-dimensional phase difference cross-correlation multi-scale geological body interpretation is performed by the method described in any one of the above items, and the device comprises:

[0034] The first module is used to transform the seismic signal into the frequency domain by using the multi-scale phase analysis of frequency division to obtain the multi-scale phase information and then perform normalization processing to obtain the normalized complex seismic trace;

[0035] The second module is used to calculate the phase difference cross-correlation along different spatial directions based on the normalized complex seismic traces and considering the geological body trend;

[0036] The third module is used to select the maximum value of the phase difference in the phase difference cross-correlation calculation results to approximately represent the final result of the discontinuity measurement perpendicular to the structural trend.

[0037] The five-dimensional phase difference cross-correlation multi-scale geological body interpretation method and device provided by the present invention have the following technical effects:

[0038] (1) Considering that the traditional coherent algorithm has a good ability to identify underground structures and has good noise resistance, the multiple addition and multiplication operations between multiple channels greatly increase the calculation cost, especially for larger seismic data. The present invention replaces the addition and multiplication between multiple channels with simple addition and subtraction operations of adjacent channel phase differences, thereby improving the calculation efficiency, saving calculation costs, and making the scope of application of the invention wider.

[0039] (2) Most existing coherence and phase technologies fail to fully utilize the prior signals and frequency information contained in the geology itself, so the calculated results will lack a lot of useful information. The five-dimensional phase difference cross-correlation technology of the present invention organically integrates the structural trend with multi-scale phase information, and has a strong ability to extract deep weak reflection signals, so that the underground anomaly information obtained is more comprehensive and rich. It can also effectively avoid the influence of high-frequency random noise on the calculation results, and is suitable for the detection of small-scale abnormal structures in deep exploration with low signal-to-noise ratio.

[0040] (3) After obtaining the results of multiple frequencies, the present invention can also fuse the phase difference cross-correlation results of different scales to obtain a more comprehensive abnormal structure of the underground; or by comparing the results of different frequencies, the relative thickness changes of the river channel can be studied. This information will provide certain guidance for the evolution of crustal structure and the fine prediction of reservoirs, and has great research value.

[0041] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0043] Figure 1 A flow chart of a five-dimensional phase difference cross-correlation multi-scale geological body interpretation method according to an embodiment of the present invention is shown;

[0044] Figure 2 A flow chart of a five-dimensional phase difference cross-correlation multi-scale geological body interpretation method according to another embodiment of the present invention is shown;

[0045] Figure 3a -3c shows the reflection coefficients with amplitudes of 1 and -1, the reflection coefficients with amplitudes of 2 and -2, and the reflection coefficients with amplitudes of 3 and -3 according to an embodiment of the present invention;

[0046] Figure 3d The seismic records obtained by convolving three groups of reflection coefficients with 30 Hz Ricker wavelets according to one embodiment of the present invention are shown;

[0047] Figure 3e shows the phase difference cross-correlation attribute calculated from the unnormalized seismic trace according to one embodiment of the present invention;

[0048] Figure 3f shows the phase difference cross-correlation attribute calculated from the normalized seismic trace according to one embodiment of the present invention;

[0049] Figure 4a The figure shows the display mode of normalized Ricker wavelets with different phases in a unit circle according to an embodiment of the present invention;

[0050] Figure 4b shows the difference between the phase of the zero-phase wavelet and the 60°-phase wavelet according to one embodiment of the present invention;

[0051] Figure 5a A schematic diagram of two sub-waves with identical waveforms and opposite polarities according to an embodiment of the present invention is shown;

[0052] Figure 5b The result of the phase difference of two sub-waves with the same waveform and opposite polarity according to one embodiment of the present invention is shown;

[0053] Figure 5c The results of phase correlation of two wavelets with identical waveforms and opposite polarities according to one embodiment of the present invention are shown;

[0054] Figure 6a -6b shows an alternative diagram and an enlarged diagram of the difference between the 0° and 60° wavelet phases converted into the sum of the 60° and 30° wavelet phase differences and the 30° and 0° wavelet phase differences according to one embodiment of the present invention;

[0055] Figure 7a The Ricker wavelets with phases of 0°, 30°, and 60° according to one embodiment of the present invention are shown;

[0056] Figure 7b The results obtained by respectively calculating the phase cross-correlation and the phase difference cross-correlation according to one embodiment of the present invention are shown;

[0057] Figure 7c The results obtained by adding 5% noise to three phase wavelets according to an embodiment of the present invention are shown;

[0058] Figure 7d The results obtained by calculating the phase cross-correlation and the phase difference cross-correlation of the noisy Ricker wavelet according to one embodiment of the present invention are shown;

[0059] Figure 8a -8d shows a slice of the phase difference cross-correlation result calculated along the directions of 0°, 45°, 90° and 135° of the three-dimensional numerical river channel model according to one embodiment of the present invention;

[0060] Figure 9a shows a seismic signal according to an embodiment of the present invention;

[0061] Figure 9b shows the instantaneous phase obtained by Hilbert transform according to one embodiment of the present invention;

[0062] Fig.9c shows a time-frequency phase spectrum obtained by Gabor transformation according to an embodiment of the present invention;

[0063] Fig.10a A high reflectivity layer according to one embodiment of the present invention is shown;

[0064] Fig.10b -10c shows the reflection coefficients with amplitudes of 1 and -1 according to one embodiment of the present invention;

[0065] Fig.10d It shows a Ricker wavelet with a length of 61ms and a main frequency of 30Hz according to an embodiment of the present invention;

[0066] Fig.10e The three-dimensional synthetic seismic data according to one embodiment of the present invention is shown in a slice along a layer at t=100 ms;

[0067] Fig.11a -11c shows the phase cross-correlation time slices in the case of no noise, 5% noise and 10% noise according to one embodiment of the present invention;

[0068] Fig.12a -12c shows the phase difference cross-correlation time slices in the case of no noise, 5% noise and 10% noise according to one embodiment of the present invention;

[0069] Fig.13a A conventional C3 coherence result diagram of a target layer of actual data of a western deep layer according to an embodiment of the present invention is shown;

[0070] Fig.13b The target layer geosteering phase attribute slice along the layer according to one embodiment of the present invention is shown;

[0071] Fig.13c The target layer phase difference cross-correlation attribute along the layer slice according to one embodiment of the present invention is shown;

[0072] Fig.14a-14c shows the slices along the layer for the five-dimensional phase difference cross correlation of the full frequency band, 13 Hz and 33 Hz according to one embodiment of the present invention; and

[0073] Fig.15 A structural block diagram of a five-dimensional phase difference cross-correlation multi-scale geological body interpretation device according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0074] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0075] Coherence is one of the conventional attributes that describes discontinuities in seismic images. Coherence is usually calculated by using weighted cross-correlation coefficients between multiple seismic traces, so it has a certain ability to resist noise. However, this also brings a large computational cost and poor imaging effect for weak reflection signals. Another attribute for detecting discontinuities in underground seismic images is phase. Compared with the coherence attribute, phase is more sensitive to subtle changes and is calculated one trace at a time. Therefore, it has higher computational efficiency but lacks robustness, especially when dealing with seismic data with low signal-to-noise ratio. Based on the advantages of each of the above attributes, the geosteering phase attribute proposed by Yuan selectively calculates the cross-correlation coefficients along different spatial directions while considering the constraints of the geological structure strike. It shows higher robustness and highlights the discontinuity characteristics of deep weak signals. However, with the continuous increase in the scale of seismic data, the cross-correlation calculation along different spatial directions will lead to expensive computational costs.

[0076] In the prior art, phase superposition is a coherent algorithm based on complex seismic trace analysis that is not affected by amplitude. A complex seismic trace S(t) is usually constructed by a real seismic trace s(t) and its imaginary part obtained by Hilbert transform. Each complex seismic trace S(t) is determined by a unique seismic trace s(t). S(t) is usually written as amplitude A(t) and phase The form is as shown in formula (1):

[0077]

[0078] Where H[] represents the Hilbert transform, A(t) and Also called envelope and instantaneous phase. The complex seismic trace S(t) can be regarded as a vector of length A(t) rotating around a certain time axis in the complex plane as time changes.

[0079] Since the phase attribute is more sensitive to small changes, in order to make full use of the sensitivity of the phase attribute, the above formula is normalized to eliminate the influence of amplitude and obtain the normalized complex seismic trace, as shown in formula (2):

[0080]

[0081] The normalized complex seismic trace obtained in this way only contains phase information, and the modulus is 1. Then the phase superposition of the normalized complex seismic trace can be expressed as:

[0082]

[0083] Where N represents the number of points involved in the calculation (the size of the selected time window). When the two signals are completely correlated, the value is 1; when the two signals are completely uncorrelated, the value is 0. ps The value of (t) is between 0 and 1.

[0084] Phase superposition is used as a coherent measurement to determine the similarity at each sampling point, which is expressed by equation (4):

[0085]

[0086] and e iω(t) The phase superposition at N sampling points is used to measure the similarity at the time delay τ. This is to ensure that when the two are completely correlated, the final calculation result is 1. However, this formula has some problems. When the two signals are exactly the same but opposite in polarity, the calculated result is 0, which is not what we want. A value of 0 should indicate that the two signals are completely unrelated. Therefore, the above formula is modified to obtain the final calculation formula for phase cross-correlation:

[0087]

[0088] When the signals are completely correlated, the value of the second term in the formula is 0; when the signals are anti-correlated, the value of the first term in the formula is 0; when the signals are uncorrelated, the final result is a smaller value.

[0089] In order to solve the problems in the prior art, the present invention greatly reduces the computational cost of the algorithm and improves the computational efficiency by simply calculating the phase difference between adjacent complex seismic channels instead of the mutual correlation coefficient between multiple seismic channels, especially for larger seismic data. In addition, the phase difference along different spatial directions is selectively calculated to identify hidden, weak or deep reflection signals, so that underground discontinuities can be better identified. At the same time, by considering the direction of the geological body and the frequency dimension, the 3D seismic data is expanded to 5D seismic data. The increase in dimension enables the seismic data information to be fully mined, and the underground structural features can be better identified by effectively combining geological guidance, frequency and phase, especially in detecting the distribution of geological anomalies in deep exploration in larger work areas.

[0090] Figure 1 A flow chart of a five-dimensional phase difference cross-correlation multi-scale geological body interpretation method according to an embodiment of the present invention is shown.

[0091] like Figure 1 As shown, in step S101, the seismic signal is transformed into the frequency domain by using the frequency-divided multi-scale phase analysis to obtain multi-scale phase information, which is then normalized to obtain a normalized complex seismic trace.

[0092] In one embodiment, in step S101, the seismic signal is transformed into the frequency domain by the following formula:

[0093] G f (a,b,ω)=∫f(t)g a (tb)e -iωt dt

[0094] Where f(t) is the seismic signal, is the basis function. Here, Gaussian function is selected as the basis function, a>0, b>0, ω is the angular frequency, t is the time, g a (tb) is the locally varying window function, parameter b is used to move the window function to cover the entire time domain, e -iωt It is a simple harmonic.

[0095] In one embodiment, in step S101, the normalized complex seismic trace is obtained by the following formula:

[0096]

[0097] Where f is the frequency, represents the normalized complex seismic trace, including phase information, It represents the phase information that changes with frequency. Different frequency phases can highlight geological bodies of different scales or thicknesses.

[0098] like Figure 1 As shown, in step S102, based on the normalized complex seismic traces and taking into account the geological body strike, the phase difference cross-correlations are calculated along different spatial directions.

[0099] In one embodiment, in step S102, for a spatial direction, a phase difference cross-correlation result is calculated by the following steps:

[0100] S1021. Determine two spatial directions that are adjacent to and behind the current spatial direction, which are referred to as the front adjacent spatial direction and the rear adjacent spatial direction, respectively.

[0101] S1022, performing difference processing on the normalized seismic traces of the previous adjacent spatial direction and the current spatial direction, and taking the absolute value to obtain a first phase difference.

[0102] S1023, performing difference processing on the normalized seismic traces in the subsequent adjacent spatial direction and the current spatial direction and taking the absolute value to obtain a second phase difference;

[0103] S1024. Based on the first phase difference and the second phase difference, obtain a phase difference cross-correlation calculation result corresponding to the current spatial direction by using a phase difference cross-correlation formula.

[0104] In one embodiment, in step S102, at least four spatial directions are selected to respectively calculate the phase difference cross-correlation, wherein the selected four directions are 0°, 45°, 90°, and 135° respectively.

[0105] In one embodiment, in step S102, the phase difference cross-correlation is calculated by the following formula:

[0106]

[0107]

[0108] in, and It represents the phase difference between two adjacent normalized seismic traces. The superscript du (u = 1, 2, ... U) represents the U-th spatial direction. The subscript k represents the k-th normalized complex seismic trace as the center trace. represents the normalized complex seismic trace, f represents frequency, t represents time, |·| represents absolute value, Represents the phase difference cross-correlation superposition result within a time window containing M sampling points.

[0109] In step S101 and step S102, the influence of the geological structure trend is taken into account, and the multi-scale phase information obtained by frequency division is fully utilized to expand the original 3D seismic data into 5D seismic data. The resolution of the calculated phase difference cross-correlation result will be very high, and the highlighted geological anomaly information will be richer and more comprehensive.

[0110] like Figure 1 As shown, in step S103, the maximum value of the phase difference is selected from the phase difference cross-correlation calculation results to approximately represent the final result of the discontinuity measurement perpendicular to the structural trend.

[0111] Specifically, the strike of the underground anomaly is certain, and the phase difference along different spatial directions is usually different. Usually, the phase difference along the direction perpendicular to the structural strike is the largest, while when parallel to the structural strike, the phase difference is very small. Therefore, the maximum value of the phase difference is selected in multiple spatial directions to approximately characterize the final result of the discontinuity measurement perpendicular to the structural trend.

[0112] In one embodiment, in step S103, the maximum value of the phase difference is selected from the phase difference cross-correlation calculation results by the following formula:

[0113]

[0114] Among them, max(·) means taking the maximum value, which is a nonlinear operator; Represents the phase difference cross-correlation calculation result in the U-th spatial direction.

[0115] In order to improve the noise resistance of the traditional phase cross-correlation algorithm in the prior art, the present invention proposes a phase difference cross-correlation algorithm, and expands 3D seismic data into 5D seismic data by combining factors such as geological steering and frequency, which can better identify the characteristics of underground geological bodies of different scales while improving the calculation efficiency. And it is tested using different phase wavelets.

[0116] In summary, the present invention can eliminate the influence of amplitude, make full use of the characteristics of phase sensitivity to micro-structures, and perform dimensionality-upgrading processing on seismic data by increasing the frequency dimension (vertical multi-scale) and the geological body direction dimension (lateral multi-scale), so as to more fully mine the seismic data information, and can more clearly detect abnormal structures of different scales underground, especially for the characteristics of weak signals and strong noise in deep exploration, and use simple phase addition and subtraction operations to replace multiple addition and multiplication operations in traditional coherent algorithms, thereby improving the calculation efficiency, thereby providing powerful technical means for the structural evolution of deep strata, identification of special geological bodies such as fault rivers, sand body distribution and reservoir prediction, and the application field is very wide.

[0117] Compared with the previous traditional phase correlation algorithm, the results of the present invention have multi-scale characteristics, can reflect abnormal structures of a specific scale, avoid the influence of high-frequency random noise, highlight more geological detail information, and can also fuse or compare the results of different scales to obtain higher-resolution results, and study the change characteristics of different scales, so as to accurately describe the distribution of underground structural anomalies.

[0118] Figure 2 A flow chart of a five-dimensional phase difference cross-correlation multi-scale geological body interpretation method according to another embodiment of the present invention is shown.

[0119] like Figure 2As shown in the figure, the post-stack migration data is first cleaned and preprocessed, and then the full-band post-stack migration seismic signal is Gabor transformed to obtain multi-scale phase information, and then the influence of amplitude is eliminated to obtain a normalized complex seismic trace containing only phase information. Considering the influence of the geological body structural strike on the phase result, the phase difference cross-correlation between adjacent normalized complex seismic traces is calculated along the different structural strike directions, and finally the maximum value of the phase difference in each direction is selected to approximate as an attribute for detecting the discontinuity of the underground geological body. In order to better characterize the underground stratigraphic characteristics, the phase difference cross-correlation results can be analyzed, the characteristic frequency can be optimized, and the geological abnormal structures of a specific scale can be highlighted in a targeted manner. It is also possible to consider fusing the phase difference cross-correlation results of different frequencies to detect more detailed information. Finally, by combining high-precision logging data information and manually interpreted geological profiles, a comprehensive reservoir prediction and evaluation from multiple angles is carried out.

[0120] Specifically, since the phase attribute is related to structural continuity, the phase will change dramatically at the structural mutation point and is not affected by the reflection strength. If the strata in the study area have good continuity, the phase difference between the two seismic traces should be very small. On the contrary, if there are faults, cracks and other structures in the study area, the phase difference should be very large. Therefore, firstly, in the phase difference cross-correlation calculation method provided by the present invention, the phase difference between two adjacent normalized seismic traces is selected as the attribute to measure discontinuity, as shown in formula (6):

[0121] Z k (t)=|θ k+1 (t)-θ k (t)| (6)

[0122] In order to test the influence of normalization on the phase difference cross-correlation results, the amplitudes of 1 and -1 ( Figure 3a ), 2, -2( Figure 3b ) and 3, -3( Figure 3c ) The three sets of reflection coefficients are convolved with the 30Hz Ricker wavelet to obtain earthquake records with the same waveform but different amplitudes ( Figure 3d ). The calculations were performed using the unnormalized and normalized seismic traces, and the results are as follows: Figure 3e As shown in 3f, it can be seen from the two figures that when not normalized, the cross-correlation attribute is greatly affected by the amplitude, and normalization can eliminate the influence of the amplitude. Therefore, in the subsequent calculation, the present invention selects the normalized complex seismic trace for calculation.

[0123] Since the modulus of the normalized complex seismic trace is 1, the complex seismic traces of different phases (taking Ricker wavelet as an example) can be represented by vectors within the unit circle, as shown in Figure 4(a). The due east direction represents zero phase, and the counterclockwise direction represents 30°, 60°, 90°, 120°, 150°, and 180° phase wavelets. Then, when the difference between two wavelets of different phases is obtained, it is actually the line connecting the ends of the two vectors, such as the line connecting the ends of the two vectors (0° and 60° phase Ricker wavelets) shown in Figure 4(b), which represents the difference between the phases of the zero phase wavelet and the 60° phase wavelet.

[0124] However, if the phase difference between the two channels is simply used for calculation, there will be a problem: the Ricker wavelets with phases of 0° and 180° are actually two wavelets with the same waveform and opposite polarity. If only the phase difference is calculated, the result is 2, as shown in Figure 5. Figure 5(a) shows two wavelets with the same waveform and opposite polarity, and Figure 5(b) shows the phase difference between the two. This is inconsistent with the expected result. However, when formula (5) is applied to obtain the phase correlation, the result is -1, indicating that the two wavelets are anti-correlated with each other. Figure 5(c) shows the phase correlation result.

[0125] Therefore, in order to increase the noise resistance of the calculation results and avoid the above problems, the present invention selects three adjacent seismic traces, and the seismic traces on both sides are subtracted from the middle seismic trace respectively. The obtained phase difference is then subjected to traditional cross-correlation operation, that is, the sum of the phase differences of the three traces is used to represent the phase difference between the original two traces. As shown in FIG6 , the difference between the 0° and 60° wavelet phases can be converted into the sum of the 60° and 30° wavelet phase differences and the 30° and 0° wavelet phase differences. FIG6 (b) is an enlarged display. The specific formulas are shown in formulas (7) and (8):

[0126]

[0127]

[0128] in, Represents the phase difference cross-correlation superposition result within a time window containing M sampling points, where M is usually 11.

[0129] In order to test the noise resistance of the two algorithms, three phase wavelets of 0°, 30°, and 60° were selected to perform phase cross-correlation and phase difference cross-correlation calculations before and after adding 5% noise, and the corresponding results were obtained, as shown in Figure 2. Figure 7a As shown in Figure 7d, it can be found that the phase difference cross-correlation provided by the present invention has better noise resistance than the phase cross-correlation in the prior art.

[0130] Geological structures all have a certain direction, but traditional coherence algorithms do not use this prior information. If the structural direction can be incorporated into the phase cross-correlation algorithm, unexpected results will be obtained. Figure 8(a) , 8(b) , 8(c), and 8(d) are slices of the phase difference cross-correlation results calculated along the 0°, 45°, 90°, and 135° directions of the three-dimensional numerical river channel model. It can be seen that each direction can highlight the structural anomaly perpendicular to the direction. If the phase cross-correlation calculation is performed along the strike of the structure, the obtained results can fully and comprehensively display the detailed information of the structure. Therefore, the present invention expands the 3D seismic data into 4D seismic data by increasing the dimension of the geological body distribution direction.

[0131] Time-frequency analysis is one of the important means of signal analysis and processing. In response to different problems, scholars have proposed dozens of time-frequency analysis methods, which can be roughly divided into linear time-frequency transform, quadratic frequency transform, etc. As a commonly used linear transform for spectrum analysis, the Gabor transform is mainly used in this invention, which is expressed as follows:

[0132] G f (a,b,ω)=∫f(t)g a (tb)e -iωt dt (9)

[0133] in, is a Gaussian function, where a>0, b>0, ga(tb) is a locally varying window function, and parameter b is used to move the window function to cover the entire time domain.

[0134] At present, amplitude spectrum is slightly more widely used, while phase spectrum is difficult to use in seismic interpretation due to its complexity and has not been well utilized. Many frequency division coherence methods that have been developed now also mostly use multi-scale amplitude spectrum information for calculation. Therefore, few people can effectively use the multi-scale phase information obtained by frequency division to calculate coherence bodies.

[0135] Figure 9(a) is an actual seismic signal, Figure 9(b) is the instantaneous phase obtained by Hilbert transform, i.e., the phase used by traditional complex coherence technology, and Figure 9(c) is the time-frequency phase spectrum obtained by Gabor transform of the seismic signal. It can be seen that the phase spectrum has multi-scale characteristics. Therefore, the present invention selects Gabor transform, which has a simple algorithm, high computational efficiency, and takes into account both time resolution and frequency resolution, and can provide multi-scale phase information.

[0136] In summary, the influence of structural strike on coherence results is discussed, and an example analysis is given to further illustrate that strike is an important factor that cannot be ignored in phase difference cross-correlation calculations; then the time-frequency phase spectrum obtained by Gabor transform is discussed, and its multi-scale characteristics are effectively utilized and integrated into the calculation of geological steering coherence, which improves the accuracy of the calculation results.

[0137] In order to verify the application effect of the method of the present invention, a set of 3D numerical models and a set of actual data bodies of deep strata in a certain area in western my country were used to test the five-dimensional phase difference cross-correlation technology of the present invention.

[0138] Figure 10 shows the 3D numerical model synthesis process. The size of the numerical model is 300ms*201Crosslines*201Inlines. The reflection coefficient model setting process is as follows: Reflection coefficients with values ​​of 1 and -1 are placed at t=100ms and t=110, respectively. Figure 10(b) , 10(c) In order to prevent the appearance of zero value in the synthetic model, a strong reflection coefficient layer is placed at t = 95ms, as shown in Figure 10(a). The reflection coefficient model is convolved with a Ricker wavelet with a length of 61ms and a main frequency of 30Hz (Figure 10(d)) to obtain 3D synthetic seismic data, where the slice along the layer at t = 100ms is shown in Figure 10(e).

[0139] In order to illustrate that phase difference cross correlation has better noise resistance than phase cross correlation, these two algorithms are applied to the numerical models with no noise, 5% noise, and 10% noise, respectively. The results are shown in the figure below. Fig.11a -11c, Fig.12a As shown in Figure 12c, it can be clearly seen from the figure that the phase difference cross-correlation has a higher noise resistance.

[0140] Figure 13(a) is a traditional C3 coherence result of the target layer of actual data from a western deep layer. It can be seen from the figure that some faults and river channels are developed, but due to the influence of the surrounding strong amplitude, the characteristics of small faults and small river channels are difficult to observe. Figure 13(b) is a slice of the target layer geosteering phase attribute along the layer. Compared with the traditional C3 coherence, the geosteering phase attribute can better characterize the river channel boundary (especially the place indicated by the rectangular box in the figure). Figure 13(c) is a slice of the target layer phase difference cross-correlation attribute along the layer. It can be seen that it has a similar ability to characterize the geological body boundary as the geosteering phase attribute, but its calculation efficiency is significantly higher than that of the geosteering phase attribute. The calculation time of the geosteering phase is about 43.29h, while the calculation time of the phase difference cross-correlation is only 0.23h, which greatly improves the calculation speed.

[0141] Figure 14(a) , 14(b)14(c) and 14(c) are the five-dimensional phase difference cross-correlation results corresponding to the full frequency band, 13Hz (low frequency) and 53Hz (high frequency) obtained by the present invention, respectively. It can be seen that the results corresponding to different frequencies can highlight specific abnormal structures. The low frequency has a better imaging effect for the southern river channel, while the high frequency has a better imaging effect for the northern fault and the fracture zone around the fault. The signal-to-noise ratio and resolution of the phase difference cross-correlation results are generally good.

[0142] In summary, the five-dimensional phase difference cross-correlation multi-scale geological body interpretation framework provided by the present invention is used, and a set of 3D numerical models and a set of three-dimensional seismic data bodies from deep layers in a certain area in western my country are tested. The calculated results show that this method can accurately predict underground anomalies, thereby conducting a comprehensive prediction and evaluation of reservoirs, so as to achieve the purpose of reducing the risk of oil and gas reservoir prediction.

[0143] The present invention can perform phase difference cross-correlation calculation by optimizing the frequency, so as to highlight the geological abnormal structure of a specific scale in a targeted manner, and discard the higher frequency information to avoid the influence of random noise on the calculation results. In addition, the introduction of frequency increases the dimension, which is helpful for the mining of seismic information, which is very beneficial for the detection of deep abnormal structures. Finally, it is also possible to consider fusing the phase difference cross-correlation results obtained at different frequencies to detect more detailed information underground.

[0144] The present invention is mainly based on the traditional phase cross-correlation technology. In order to better increase the noise resistance of the algorithm, a phase difference cross-correlation algorithm is proposed, and the 3D seismic data is expanded into 5D seismic data in combination with factors such as geological guidance and frequency, which can better identify the characteristics of geological bodies of different scales underground. The influence of structural trend on the results is discussed. And an example analysis is given to illustrate that structural trend is an important factor that cannot be ignored in phase difference cross-correlation calculation. And compared with the traditional algorithm, the present invention has a good advantage in identifying micro-structural boundaries of different scales, and has good noise resistance and high calculation efficiency.

[0145] The present invention also provides a storage medium, which contains a series of instructions for executing the method steps of the five-dimensional phase difference cross-correlation multi-scale geological body interpretation method.

[0146] Fig.15 The structure block diagram of a five-dimensional phase difference cross-correlation multi-scale geological body interpretation device according to an embodiment of the present invention is shown. Fig.15 As shown, the five-dimensional phase difference cross-correlation multi-scale geological body interpretation device 1500 includes a first module 1501, a second module 1502 and a third module 1503.

[0147] The first module 1501 is used to utilize frequency-divided multi-scale phase analysis to transform the seismic signal into the frequency domain to obtain multi-scale phase information and then perform normalization processing to obtain a normalized complex seismic trace.

[0148] The second module 1502 is used to calculate the phase difference cross-correlation along different spatial directions based on the normalized complex seismic traces and taking into account the direction of the geological body.

[0149] The third module 1503 is used to select the maximum value of the phase difference in the phase difference cross-correlation calculation results to approximately represent the final result of the discontinuity measurement perpendicular to the structural trend.

[0150] In summary, the five-dimensional phase difference cross-correlation multi-scale geological body interpretation method and device provided by the present invention have the following technical effects:

[0151] (1) Considering that the traditional coherent algorithm has a good ability to identify underground structures and has good noise resistance, the multiple addition and multiplication operations between multiple channels greatly increase the calculation cost, especially for larger seismic data. The present invention replaces the addition and multiplication between multiple channels with simple addition and subtraction operations of adjacent channel phase differences, thereby improving the calculation efficiency, saving calculation costs, and making the scope of application of the invention wider.

[0152] (2) Most existing coherence and phase technologies fail to fully utilize the prior signals and frequency information contained in the geology itself, so the calculated results will lack a lot of useful information. The five-dimensional phase difference cross-correlation technology of the present invention organically integrates the structural trend with multi-scale phase information, and has a strong ability to extract deep weak reflection signals, so that the underground anomaly information obtained is more comprehensive and rich. It can also effectively avoid the influence of high-frequency random noise on the calculation results, and is suitable for the detection of small-scale abnormal structures in deep exploration with low signal-to-noise ratio.

[0153] (3) After obtaining the results of multiple frequencies, the present invention can also fuse the phase difference cross-correlation results of different scales to obtain a more comprehensive abnormal structure of the underground; or by comparing the results of different frequencies, the relative thickness changes of the river channel can be studied. This information will provide certain guidance for the evolution of crustal structure and the fine prediction of reservoirs, and has great research value.

[0154] It should be understood that the embodiments disclosed in the present invention are not limited to the specific structures, processing steps or materials disclosed herein, but should be extended to equivalent substitutions of these features understood by ordinary technicians in the relevant field. It should also be understood that the terms used herein are only used for the purpose of describing specific embodiments and are not meant to be limiting.

[0155] The "one embodiment" or "embodiment" mentioned in the specification means that the specific features, structures or characteristics described in conjunction with the embodiment are included in at least one embodiment of the present invention. Therefore, the phrases "one embodiment" or "embodiment" appearing in various places throughout the specification do not necessarily refer to the same embodiment.

[0156] Although the embodiments disclosed in the present invention are as above, the contents described are only embodiments adopted for facilitating the understanding of the present invention and are not intended to limit the present invention. Any technician in the technical field to which the present invention belongs can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in the present invention, but the patent protection scope of the present invention shall still be subject to the scope defined in the attached claims.

Claims

1. A five-dimensional phase difference cross-correlation multi-scale geological body interpretation method, characterized in that: The method comprises the following steps: Step 1: Using frequency-divided multi-scale phase analysis, the seismic signal is transformed into the frequency domain to obtain multi-scale phase information, and then normalized to obtain a normalized complex seismic trace; Step 2: Based on the normalized complex seismic traces, considering the direction of the geological body, the phase difference cross-correlation is calculated along different spatial directions respectively; Step 3: Select the maximum value of the phase difference in the phase difference cross-correlation calculation results to approximately represent the final result of the discontinuity measurement perpendicular to the structural trend; In the step 2, for a spatial direction, the phase difference cross-correlation result is calculated by the following steps: determining two spatial directions adjacent to the current spatial direction, which are respectively called the front adjacent spatial direction and the rear adjacent spatial direction; performing difference processing on the normalized seismic traces of the front adjacent spatial direction and the current spatial direction and taking the absolute value to obtain a first phase difference; Performing difference processing on the normalized seismic traces of the subsequent adjacent spatial direction and the current spatial direction and taking the absolute value to obtain a second phase difference; Based on the first phase difference and the second phase difference, a phase difference cross-correlation calculation result corresponding to the current spatial direction is calculated by using a phase difference cross-correlation formula; In the step 2, the phase difference cross-correlation is calculated by the following formula: in, and It represents the phase difference between two adjacent normalized seismic traces. The superscript du represents the u-th spatial direction, where u = 1, 2, ... U. The subscript k represents the k-th normalized complex seismic trace as the center trace. represents the normalized complex seismic trace, f represents frequency, t represents time, |·| represents absolute value, Represents the phase difference cross-correlation superposition result within a time window containing M sampling points.

2. The five-dimensional phase difference cross-correlation multi-scale geological body interpretation method according to claim 1, characterized in that: In step 1, the seismic signal is transformed into the frequency domain by the following formula: G f (a,b,ω)=∫f(t)g a (t-b)e -iωt dt Where f(t) is the seismic signal, is the basis function. Here, Gaussian function is selected as the basis function, a>0, b>0, ω is the angular frequency, t is the time, g a (tb) is the locally varying window function, parameter b is used to move the window function to cover the entire time domain, e -iωt It is a simple harmonic.

3. The five-dimensional phase difference cross-correlation multi-scale geological body interpretation method according to claim 1, characterized in that: In the step 1, the normalized complex seismic trace is obtained by the following formula: Where f is the frequency, represents the normalized complex seismic trace, including phase information, It represents the phase information that changes with frequency. Different frequency phases can highlight geological bodies of different scales or thicknesses.

4. The five-dimensional phase difference cross-correlation multi-scale geological body interpretation method according to claim 1, characterized in that: In the step 2, the following steps are specifically included: At least four spatial directions are selected to respectively calculate the phase difference cross-correlation, wherein the selected four directions are 0°, 45°, 90°, and 135° respectively.

5. The five-dimensional phase difference cross-correlation multi-scale geological body interpretation method according to claim 1, characterized in that: In step 3, the maximum phase difference is selected from the phase difference cross-correlation calculation results using the following formula: Among them, max(·) means taking the maximum value, which is a nonlinear operator; Represents the phase difference cross-correlation calculation result in the u-th spatial direction.

6. The five-dimensional phase difference cross-correlation multi-scale geological body interpretation method according to claim 1, characterized in that: The method further comprises: Phase difference cross-correlation calculation is performed by optimizing the frequency, so as to highlight the geological abnormal structures of a specific scale in a targeted manner, and the influence of random noise on the calculation results is avoided by discarding higher frequency information.

7. A storage medium, characterized in that: It contains a series of instructions for executing the method steps as claimed in any one of claims 1 to 6.

8. A five-dimensional phase difference cross-correlation multi-scale geological body interpretation device, characterized in that: The five-dimensional phase difference cross-correlation multi-scale geological body interpretation is performed by the method according to any one of claims 1 to 6, and the device comprises: The first module is used to transform the seismic signal into the frequency domain by using the multi-scale phase analysis of frequency division to obtain the multi-scale phase information and then perform normalization processing to obtain the normalized complex seismic trace; The second module is used to calculate the phase difference cross-correlation along different spatial directions based on the normalized complex seismic traces and considering the geological body trend; The third module is used to select the maximum value of the phase difference in the phase difference cross-correlation calculation results to approximately represent the final result of the discontinuity measurement perpendicular to the structural trend.

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