A seismic inversion method and system for eliminating the strong reflection shielding effect

Abstract

The present invention relates to a seismic inversion method for eliminating strong reflection shielding effects, and the method includes: acquiring post-stack seismic data and logging wave impedance curves, and performing well-seismic calibration; obtaining de-shielded seismic data based on the seismic data; obtaining a pseudo-wave impedance curve based on the logging wave impedance curve to match the synthetic seismic record and the de-shielded seismic data; obtaining pseudo-wave impedance inversion data based on the de-shielded seismic data and the pseudo-wave impedance curve; and carrying out comprehensive reservoir interpretation based on the pseudo-wave impedance inversion data. The present invention specifically eliminates and weakens the influence of strong reflection energy shielding and Gibbs effects, and can improve the resolution of seismic inversion and the accuracy of reservoir prediction.

Description

Technical Field

[0001] The invention belongs to the technical field of interpretation of seismic data in petroleum geophysical exploration, and in particular relates to a seismic inversion method and system for eliminating strong reflection shielding effect. Background Art

[0002] There are often some rock formations in the underground strata, such as coal seams, source rocks, volcanic rocks, etc., which have a large impedance difference with the surrounding rocks, forming strong reflections on the seismic profile. The stronger the seismic reflection energy, the more dramatic the change in wave impedance between strata. When the wave impedance of the strata on both sides of the strong reflection interface changes too dramatically, discontinuity is shown.

[0003] Due to the limitations of seismic trace and wavelet length, seismic sampling rate and seismic inversion frequency band, the Gibbs phenomenon is easily generated near such discontinuous boundaries. The Gibbs effect causes severe oscillations in the seismic inversion results near the strong reflection interface. At the same time, the wave impedance difference between the rock layers is very small inside the strata above and below the strong reflection interface. This wave impedance difference is much smaller than the oscillation caused by the Gibbs phenomenon, resulting in a severe shielding effect, which distorts the inversion results and makes it difficult to accurately reflect the true wave impedance characteristics of the strata, affecting the accuracy of reservoir prediction.

[0004] Among the methods of deterministic seismic inversion published in the literature, the two methods used in practice mainly include model-based inversion and constrained sparse pulse inversion. Due to the constraints of the current conventional inversion method implementation ideas and the limited bandwidth of seismic data, the geological characteristics of such wave impedance discontinuity are not considered, and it is difficult to achieve accurate prediction of reservoirs near strong reflection interfaces. Therefore, no one has paid attention to and proposed effective solutions for seismic inversion under such geological conditions.

[0005] Therefore, there is an urgent need for a seismic inversion method that can eliminate the strong reflection shielding effect to overcome the defects of the current seismic inversion method. Summary of the invention

[0006] In the face of the Gibbs effect problem caused by sudden changes in wave impedance, in order to further reduce the shielding effect of the strong reflection interface on the wave impedance on both sides in seismic inversion, it is necessary to further optimize the seismic inversion method and eliminate and weaken the errors caused by the Gibbs effect, so as to better maintain the wave impedance characteristics of the reservoir on both sides of the strong reflection interface and improve the accuracy of seismic inversion reservoir prediction.

[0007] In view of the above problems, the present invention provides a seismic inversion method for eliminating the strong reflection shielding effect.

[0008] The method comprises:

[0009] Obtain post-stack seismic data and well-log wave impedance curves, and perform well-seismic calibration;

[0010] Obtain de-shielded seismic data based on the seismic data;

[0011] Obtain a pseudo-wave impedance curve based on the well-log wave impedance curve, and make the synthetic seismic record of the pseudo-wave impedance curve match the de-shielded seismic data;

[0012] Obtain pseudo-wave impedance inversion data based on the de-shielded seismic data and the pseudo-wave impedance curve;

[0013] Carry out comprehensive reservoir interpretation based on the pseudo-wave impedance inversion data.

[0014] Furthermore, the obtaining of the de-shielded seismic data specifically is:

[0015] Perform post-stack de-shielding processing on the seismic data to obtain de-shielded seismic data;

[0016] The post-stack de-shielding processing of the seismic data is to use the reflection coefficient fitting method to achieve the de-shielding processing of strong reflections in the seismic data.

[0017] Furthermore, the obtaining of the pseudo-wave impedance curve specifically is:

[0018] Perform step-removing processing on the well-log wave impedance curve to obtain a pseudo-wave impedance curve, and make the synthetic seismic record of the pseudo-wave impedance curve match the de-shielded seismic data.

[0019] Furthermore, the obtaining of the pseudo-wave impedance inversion data includes:

[0020] Use the pseudo-wave impedance curve interpolation to establish an initial wave impedance model;

[0021] Based on the de-shielded seismic data and the pseudo-wave impedance curve, extract the wavelet, carry out post-stack seismic inversion, and obtain pseudo-wave impedance inversion data.

[0022] Furthermore, the carrying out of the comprehensive reservoir interpretation based on the pseudo-wave impedance inversion data includes:

[0023] Based on the histogram analysis of the pseudo-wave impedance curve, determine the value range of the pseudo-wave impedance of the reservoir;

[0024] According to the value range of the pseudo-wave impedance of the reservoir, perform reservoir identification on the pseudo-wave impedance inversion data.

[0025] The present invention also provides a seismic inversion system for eliminating the strong reflection shielding effect, and the system includes:

[0026] An acquisition unit, configured to acquire post-stack seismic data and well-log wave impedance curves, and perform well-seismic calibration;

[0027] Obtain de-shielded seismic data based on seismic data;

[0028] Obtain a pseudo-wave impedance curve based on the logging wave impedance curve, and make the synthetic seismic record of the pseudo-wave impedance curve match the de-shielded seismic data;

[0029] Based on the de-shielded seismic data and the pseudo-wave impedance curve, obtain pseudo-wave impedance inversion data;

[0030] An analysis and interpretation unit for analyzing and carrying out comprehensive reservoir interpretation based on the pseudo-wave impedance inversion data.

[0031] Further, the obtaining of the de-shielded seismic data is specifically as follows:

[0032] Perform post-stack de-shielding processing on the seismic data to obtain de-shielded seismic data;

[0033] The post-stack de-shielding processing of the seismic data is to use the reflection coefficient fitting method to achieve the de-strong reflection shielding processing of the seismic data.

[0034] Further, the obtaining of the pseudo-wave impedance curve is specifically as follows:

[0035] Perform step removal processing on the logging wave impedance curve to obtain a pseudo-wave impedance curve, and make the synthetic seismic record of the pseudo-wave impedance curve match the de-shielded seismic data.

[0036] Further, the obtaining of the pseudo-wave impedance inversion data includes:

[0037] Use the pseudo-wave impedance curve interpolation to establish an initial wave impedance model;

[0038] Based on the de-shielded seismic data and the pseudo-wave impedance curve, extract the wavelet, carry out post-stack seismic inversion, and obtain pseudo-wave impedance inversion data.

[0039] Further, the carrying out of the comprehensive reservoir interpretation based on the pseudo-wave impedance inversion data includes:

[0040] Based on the histogram analysis of the pseudo-wave impedance curve, determine the value range of the pseudo-wave impedance of the reservoir;

[0041] According to the value range of the pseudo-wave impedance of the reservoir, carry out reservoir identification on the pseudo-wave impedance inversion data.

[0042] The present invention has the following technical effects:

[0043] (1) The present invention addresses the problem of numerical distortion in seismic inversion near strong reflection interfaces, adopting a technical approach different from conventional seismic inversion techniques. By seismic processing, the influence of strong reflection energy shielding is eliminated, and weak reflection seismic signals of thin layers are restored and highlighted; the logging data is de-stepped to eliminate the Gibbs effect, enabling the seismic inversion results to better reflect the geophysical characteristics of thin layers and improving the accuracy of reservoir prediction.

[0044] (2) The technology of the present invention is relatively independent. Using the processed seismic data and pseudo-wave impedance curves, seismic inversion is achieved through existing inversion software. In the whole scheme, techniques such as seismic data well-seismic calibration, interpolation modeling, wavelet extraction, and seismic inversion are borrowed, and the technical feasibility is good.

[0045] (3) Compared with the current seismic attribute prediction method after de-shielding processing, the method proposed in this paper can achieve quantitative reservoir prediction results.

[0046] (4) Compared with traditional seismic inversion methods and processes, the method proposed in this paper specifically eliminates and weakens the influence of strong reflection energy shielding and the Gibbs effect, and can improve the resolution of seismic inversion and the accuracy of reservoir prediction.

[0047] Other features and advantages of the present invention will be described in the following specification, and part of them will be obvious from the specification or understood by implementing the present invention. The objectives and other advantages of the present invention can be realized and obtained through the structures pointed out in the specification, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for describing the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0049] Figure 1 Shows the flow chart of the seismic inversion method for eliminating strong reflection shielding effect according to an embodiment of the present invention;

[0050] Figure 2 Shows the result of well-seismic calibration of Well A and the measured wave impedance curve according to an embodiment of the present invention;

[0051] Figure 3 Shows the stacked seismic profile before removing strong reflection shielding according to an embodiment of the present invention;

[0052] Figure 4 Shows the stacked seismic profile after removing strong reflection shielding according to an embodiment of the present invention;

[0053] Figure 5 shows the pseudo-wave impedance curve of Well A and the result of seismic well-seismic calibration after de-shielding according to an embodiment of the present invention;

[0054] Figure 6 shows the pseudo-wave impedance inversion profile of Well A according to an embodiment of the present invention. Detailed implementation manners

[0055] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0056] The present invention provides a seismic inversion method for eliminating the strong reflection shielding effect, as Figure 1 shown, Figure 1 shows the flow chart of the seismic inversion method for eliminating the strong reflection shielding effect according to an embodiment of the present invention. The method includes: acquiring post-stack seismic data and well-log wave impedance curves, and performing well-seismic calibration; performing post-stack de-shielding processing on the seismic data to obtain de-shielded seismic data; performing de-stepping processing on the well-log curves to obtain pseudo-wave impedance curves, so that the synthetic seismic records of the pseudo-wave impedance curves match the de-shielded seismic data; using the pseudo-wave impedance curves to interpolate and establish an initial wave impedance model; based on the de-shielded seismic data and the pseudo-wave impedance curves, extracting wavelets and performing post-stack seismic inversion to obtain pseudo-wave impedance inversion data; based on the histogram analysis of the pseudo-wave impedance curves, determining the value range of the pseudo-wave impedance of the reservoir; and identifying the reservoir according to the value range of the pseudo-wave impedance of the reservoir.

[0057] Specifically, acquire post-stack seismic data and well-log wave impedance curves, and perform well-seismic calibration; Figure 2 is the result of well-seismic calibration for the post-stack seismic data of a certain oilfield and the well-log wave impedance curve of Well A. Figure 2 The position shown by the strong reflection interface in a is a strong energy seismic reflection event in this area, and the energy of this strong reflection is much higher than the reflection of the lower formation; Figure 2 b shows that the wave impedance curve near the strong reflection interface has a mutation, and the reservoir is within the time range of 20 ms below the strong reflection interface; Figure 2 c is the synthetic seismic record of the well-log. The weak wave peak seismic reflection corresponding to the reservoir is covered by the sidelobes of the wavelet of the strong reflection interface due to its weak energy (the position shown by the arrow in the figure), and it is difficult to truly reflect the lateral variation characteristics of the reservoir.

[0058] Perform post-stack de-screening processing on seismic data to obtain de-screened seismic data; specifically, in implementation, the reflection coefficient fitting method is used to achieve strong reflection shielding processing of seismic data. To meet the needs of inversion, two conditions need to be satisfied simultaneously: while removing the strong reflection energy generated by discontinuous interfaces, maintaining the seismic response characteristics of other formations.

[0059] Specifically, in implementation, according to the formation conditions near the strong reflection interface, the intensity of the strong reflection axis in seismic data, and the different qualities of seismic data, under the condition of removing strong reflection energy while maintaining the seismic response characteristics of other formations, the post-stack strong reflection removal processing method used is not limited to reflection coefficient fitting, and methods such as matching pursuit and lithology removal can also be used.

[0060] Figure 3 and Figure 4 are the seismic profiles before and after strong reflection shielding processing using the reflection coefficient fitting method respectively. Compared with before processing, the seismic reflection amplitude of the reservoir section below the strong reflection interface becomes stronger and the continuity becomes better, and the seismic reflection energy of the reservoir is effectively restored. Figure 4 as indicated by the arrow.

[0061] Perform step removal processing on well logging curves to obtain a pseudo-wave impedance curve that matches the de-screened post-stack seismic data;

[0062] After the seismic data is completed with strong reflection shielding processing, it is equivalent to eliminating the wave impedance difference between the formations on both sides of the strong reflection interface, and the energy changes greatly. In order to match the de-screened post-stack seismic data to carry out seismic inversion, it is necessary to eliminate the wave impedance difference equivalent to the strong reflection from well logging data to obtain a pseudo-wave impedance curve.

[0063] Specifically, in implementation, in order to obtain well logging data that matches the de-screened post-stack seismic data, the pseudo-wave impedance curve is obtained through the following steps.

[0064] (1) Determine the top depth t0 and bottom depth t1 of the discontinuous boundary corresponding to the strong reflection interface;

[0065] (2) Respectively calculate the average wave impedance of the formations on both sides of the strong reflection interface, and calculate the stepped wave impedance corresponding to the strong reflection interface according to the following formula;

[0066]

[0067] where, represents the stepped wave impedance; PI u represents the average wave impedance of the formation above the strong reflection interface; PI d represents the average wave impedance of the formation below the strong reflection interface; t i represents the i-th depth sampling point;

[0068] (3) To maintain the measured wave impedance characteristics of the target layer section, the pseudo-wave impedance is calculated according to the following formula;

[0069]

[0070] Where, represents the pseudo-wave impedance; represents the stepped wave impedance; PI i represents the initial wave impedance; PI u represents the average wave impedance of the formation above the strong reflection interface;

[0071] Figure 5 b is the pseudo-wave impedance curve of Well A obtained by the above steps. Figure 5 c is the synthetic seismogram corresponding to the pseudo-wave impedance curve. Compared with the de-masked seismic data in a, the two have good similarity, indicating that while the pseudo-wave impedance curve maintains the wave impedance characteristics of the reservoir, it matches well with the actual seismic data. Figure 5 a, the two have good similarity, indicating that while the pseudo-wave impedance curve maintains the wave impedance characteristics of the reservoir, it matches well with the actual seismic data.

[0072] An initial wave impedance model is established by interpolating the pseudo-wave impedance curve; based on the de-masked seismic data and the pseudo-wave impedance curve, a wavelet is extracted, and post-stack seismic inversion is carried out to obtain pseudo-wave impedance inversion data. Figure 6 is the pseudo-wave impedance inversion profile. In the figure, the darker gray color indicates a relatively low wave impedance value, indicating the development of the reservoir. In the figure, the pseudo-wave impedance inversion result is in good agreement with the low-value area of the wave impedance curve at Well Point A, that is, the favorable reservoir development section. Furthermore, the distribution characteristics of the pseudo-wave impedance of the reservoir are analyzed, and based on the pseudo-wave impedance inversion data, comprehensive reservoir interpretation is carried out.

[0073] The present invention also provides a seismic inversion system for eliminating the strong reflection shielding effect. The system includes: an acquisition unit for acquiring post-stack seismic data and well log wave impedance curves, and performing well-seismic calibration; obtaining de-masked seismic data based on the seismic data; obtaining a pseudo-wave impedance curve based on the well log wave impedance curve, so that the synthetic seismogram of the pseudo-wave impedance curve matches the de-masked seismic data; and obtaining pseudo-wave impedance inversion data based on the de-masked seismic data and the pseudo-wave impedance curve.

[0074] It also includes an analysis and interpretation unit for analyzing and carrying out comprehensive reservoir interpretation based on the pseudo-wave impedance inversion data.

[0075] Obtaining the de-masked seismic data specifically includes: performing post-stack de-masking processing on the seismic data to obtain the de-masked seismic data.

[0076] Obtaining the pseudo-wave impedance curve specifically includes: performing de-stepping processing on the well log wave impedance curve to obtain the pseudo-wave impedance curve, so that the synthetic seismogram of the pseudo-wave impedance curve matches the de-masked seismic data.

[0077] Obtaining pseudo-wave impedance inversion data includes: establishing an initial wave impedance model by interpolating the pseudo-wave impedance curve; extracting a wavelet based on the de-shielded seismic data and the pseudo-wave impedance curve, and performing post-stack seismic inversion to obtain pseudo-wave impedance inversion data. Conducting comprehensive reservoir interpretation based on the pseudo-wave impedance inversion data includes: determining the value range of the pseudo-wave impedance of the reservoir based on histogram analysis of the pseudo-wave impedance curve; and identifying the reservoir for the pseudo-wave impedance inversion data according to the value range of the pseudo-wave impedance of the reservoir.

[0078] Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A seismic inversion method for eliminating the shielding effect of strong reflections, characterized in that, the method includes: Obtain post-stack seismic data and logging wave impedance curves, and perform well-seismic calibration; Obtain de-shielded seismic data based on the seismic data; Perform step removal on the logging wave impedance curve to eliminate the wave impedance difference between the formations on both sides of the strong reflection interface, and obtain a pseudo-wave impedance curve that matches the de-shielded post-stack seismic data, so that the synthetic seismic record of the pseudo-wave impedance curve matches the de-shielded seismic data; The pseudo-wave impedance curve is obtained through the following steps: (1) Determine the top surface depth of the discontinuous boundary corresponding to the strong reflection interface and the bottom surface depth ; (2) Respectively obtain the average wave impedance of the formations on both sides of the strong reflection interface, and calculate the step wave impedance corresponding to the strong reflection interface according to the following formula; Among them, represents the stepped wave impedance; represents the average wave impedance of the formation above the strong reflection interface; represents the average wave impedance of the formation below the strong reflection interface; represents the depth of the i-th depth sampling point; (3) To maintain the measured wave impedance characteristics of the target interval, calculate the pseudo-wave impedance according to the following formula; Among them, represents the pseudo-wave impedance; represents the stepped wave impedance; represents the initial wave impedance; Based on the de-shielded seismic data and the pseudo-wave impedance curve, obtain pseudo-wave impedance inversion data; Based on the pseudo-wave impedance inversion data, carry out comprehensive reservoir interpretation.

2. The seismic inversion method for eliminating the shielding effect of strong reflections according to claim 1, characterized in that, the obtaining of the de-shielded seismic data is specifically: Perform post-stack de-shielding processing on the seismic data to obtain de-shielded seismic data; The post-stack de-shielding processing of the seismic data is realized by using the reflection coefficient fitting method to perform de-strong reflection shielding processing on the seismic data.

3. The seismic inversion method for eliminating the shielding effect of strong reflections according to claim 1 or 2, characterized in that, the obtaining of the pseudo-wave impedance inversion data includes: Use the pseudo-wave impedance curve interpolation to establish an initial wave impedance model; Based on the de-shielded seismic data and the pseudo-wave impedance curve, extract the wavelet, carry out post-stack seismic inversion, and obtain pseudo-wave impedance inversion data.

4. The seismic inversion method for eliminating the shielding effect of strong reflections according to claim 3, characterized in that, the carrying out of comprehensive reservoir interpretation based on the pseudo-wave impedance inversion data includes: Based on the histogram analysis of the pseudo-wave impedance curve, determine the value range of the pseudo-wave impedance of the reservoir; According to the value range of the pseudo-wave impedance of the reservoir, carry out reservoir identification on the pseudo-wave impedance inversion data.

5. A seismic inversion system for eliminating the shielding effect of strong reflections, characterized in that, the system includes: An acquisition unit for acquiring post-stack seismic data and logging wave impedance curves, and performing well-seismic calibration; Obtain de-shielded seismic data based on the seismic data; Perform step removal on the logging wave impedance curve to eliminate the wave impedance difference between the formations on both sides of the strong reflection interface, and obtain a pseudo-wave impedance curve that matches the de-shielded post-stack seismic data, so that the synthetic seismic record of the pseudo-wave impedance curve matches the de-shielded seismic data; The pseudo-wave impedance curve is obtained through the following steps: (1) Determine the top surface depth and bottom surface depth of the discontinuous boundary corresponding to the strong reflection interface and ; (2) Respectively obtain the average wave impedance of the formations on both sides of the strong reflection interface, and calculate the step wave impedance corresponding to the strong reflection interface according to the following formula; Among them, represents the stepped wave impedance; represents the average wave impedance of the formation above the strong reflection interface; represents the average wave impedance of the formation below the strong reflection interface; represents the depth of the i-th depth sampling point; (3) To maintain the measured wave impedance characteristics of the target interval, calculate the pseudo-wave impedance according to the following formula; Among them, represents the pseudo-wave impedance; represents the stepped wave impedance; represents the initial wave impedance; Based on the de-shielded seismic data and the pseudo-wave impedance curve, obtain pseudo-wave impedance inversion data; An analysis and interpretation unit for analyzing and carrying out comprehensive reservoir interpretation based on the pseudo-wave impedance inversion data.

6. The seismic inversion system for eliminating the shielding effect of strong reflections according to claim 5, characterized in that, The obtaining of the de-screened seismic data specifically is as follows: Performing post-stack de-screening processing on the seismic data to obtain the de-screened seismic data; The performing of post-stack de-screening processing on the seismic data realizes the de-screening processing of strong reflection shielding of the seismic data by using the reflection coefficient fitting method.

7. The seismic inversion system for eliminating the strong reflection shielding effect according to claim 5, characterized in that the obtaining of the pseudo-wave impedance inversion data includes: Establishing an initial wave impedance model by interpolating the pseudo-wave impedance curve; Based on the de-screened seismic data and the pseudo-wave impedance curve, extracting the wavelet, conducting post-stack seismic inversion, and obtaining the pseudo-wave impedance inversion data.

8. The seismic inversion system for eliminating the strong reflection shielding effect according to any one of claims 5-7, characterized in that the conducting of reservoir comprehensive interpretation based on the pseudo-wave impedance inversion data includes: Determining the value range of the pseudo-wave impedance of the reservoir based on the histogram analysis of the pseudo-wave impedance curve; Identifying the reservoir for the pseudo-wave impedance inversion data according to the value range of the pseudo-wave impedance of the reservoir.

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