A seismic imaging correction method to eliminate the influence of coal seams

Abstract

The present invention relates to a seismic imaging correction method for eliminating the influence of coal seams, and belongs to the technical field of integrated seismic data processing and interpretation. The present invention constructs a geological model of the target area through actual well logging data, performs forward simulation calculations on the geological model to obtain the corresponding relationship between two-way travel time and formation velocity, uses this relationship to correct the relationship between two-way travel time and formation velocity obtained from seismic reflection data, and then uses the corrected relationship between two-way travel time and formation velocity to adjust the seismic reflection data to achieve correction of the seismic imaging results. The present invention can use actual well logging data to achieve correction of seismic reflection data, eliminate interference caused by strong reflection signals from coal seams, and enable reflection imaging results to more accurately represent the actual stratigraphic structural morphology.

Description

Technical Field

[0001] The invention relates to a seismic imaging correction method for eliminating the influence of coal seams, and belongs to the technical field of integrated seismic data processing and interpretation. Background Art

[0002] The significant difference in wave impedance between coal-bearing and non-coal-bearing strata results in strong reflection signals in coal seams, which can interfere with the reflection signals from the underlying strata and affect the reflection imaging of the strata. For example, in the Ordos Basin, where coal-bearing strata are extensively developed, the differences in lateral thickness and number of low-velocity coal seams lead to inaccurate imaging of the underlying strata structure and wave group reflection structure beneath the coal seams. This poses significant challenges to exploration and development, increasing the risks of exploration and development. Currently, there is no clear method to address the distortion of the underlying strata structure and wave group reflection structure caused by coal seams in the Ordos Basin. Summary of the Invention

[0003] The purpose of the present invention is to provide a seismic imaging correction method for eliminating the influence of coal seams, so as to solve the problem that the strong reflection signal of the coal seams causes the seismic imaging results to fail to reflect the true stratum morphology.

[0004] In order to solve the above technical problems, the present invention provides a seismic imaging correction method for eliminating the influence of coal seams. The correction method comprises the following steps:

[0005] 1) Obtain multi-layer geological logging data and interpreted horizon data of the target area including coal seams, and construct the corresponding geological model;

[0006] 2) Perform forward modeling on the constructed geological model and determine the relationship between the corresponding two-way travel time and formation velocity based on the forward modeling results;

[0007] 3) obtaining seismic reflection data of the target area and determining the relationship between the corresponding two-way travel time and formation velocity from the seismic reflection data;

[0008] 4) using the relationship between the two-way travel time and the formation velocity obtained in step 2) to correct the relationship between the two-way travel time and the formation velocity obtained in step 3);

[0009] 5) The relationship between the corrected two-way travel time and the formation velocity is used to construct the stratigraphic structural morphology of the target area.

[0010] The present invention constructs a geological model of the target area using actual well logging data, performs forward modeling on the geological model to obtain the corresponding relationship between two-way travel time and formation velocity. This relationship is used to correct the relationship between two-way travel time and formation velocity obtained from seismic reflection data. The corrected relationship between two-way travel time and formation velocity is then used to adjust the seismic reflection data, thereby correcting the seismic imaging results. The present invention can use actual well logging data to correct seismic reflection data, eliminating interference caused by strong reflection signals from coal seams, and ensuring that the reflection imaging results can more accurately represent the actual stratigraphic structure.

[0011] Furthermore, the logging data acquired in step 1) includes acoustic logging data, density logging data and VSP logging data.

[0012] Furthermore, the geological model constructed in step 1) includes the stratum where the coal seam is located, the stratum above the coal seam and the stratum underlying the coal seam.

[0013] Furthermore, the step 2) is to perform forward simulation based on the layer velocity, density and thickness of each layer.

[0014] Furthermore, the correction in step 4) refers to correcting the relationship between the two-way travel time and the formation velocity obtained in step 3) to the relationship between the two-way travel time and the formation velocity obtained in step 2). BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a flow chart of the seismic imaging correction method for eliminating the influence of coal seams according to the present invention;

[0016] Figure 2 is a schematic diagram of a multi-layer geological model of a target area including coal seams in an embodiment of the present invention;

[0017] Figure 3-a is a t0-v relationship diagram obtained by forward simulation calculation of the target area in an embodiment of the present invention;

[0018] Figure 3-b is a t0-v relationship diagram obtained from seismic data in the target area in an embodiment of the present invention;

[0019] Figure 3-c is a t0-v relationship diagram after correction of the t0-v relationship obtained by forward simulation calculation in an embodiment of the present invention;

[0020] Figure 4-a is a geological structure morphology map obtained before correction in an embodiment of the present invention;

[0021] Figure 4-b This is a geological structure morphology map obtained after correction in the embodiment of the present invention. DETAILED DESCRIPTION

[0022] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0023] The present invention addresses the problem of structural illusions caused by low-velocity geological bodies (coal seams or oil shale) and proposes a method for constructing a low-velocity model of a low-velocity geological body (coal seam or oil shale) based on actual drilling information, and then using this velocity model to correct the two-way travel time of the underlying strata of the coal seam. This method is highly practical and can effectively eliminate the illusion of structural morphology and wave group reflection structure imaging caused by the coal seam, thereby improving the reliability of structural implementation and the fidelity of imaging. The process of this method is as follows: Figure 1 As shown, the implementation process of the present invention is described in detail below with reference to specific examples.

[0024] 1. Obtain multi-layer geological logging data containing coal seams in the target area and construct a corresponding geological model.

[0025] The well logging data and interpreted horizon data of the target area are obtained, wherein the well logging data include acoustic logging data, density logging data, and VSP logging data. The coal seam position is determined based on the interpreted horizon data, and the strata in the target area are divided according to the coal seam position. In this embodiment, the stratum above the coal seam is used as the first reflection layer, the stratum where the coal seam is located is used as the second reflection layer, and the layers underlying the coal seam are used as the third reflection layer, the fourth reflection layer, and so on. Figure 2 As shown, the thickness of each reflective layer is counted, and the interval velocity and density of each reflective layer are calculated according to the well logging data of each reflective layer, so as to obtain the geological model of the target area.

[0026] 2. Perform forward simulation on the geological model in step 1 to obtain the corresponding t0-v relationship.

[0027] In this embodiment, forward simulation is performed based on the density, velocity and thickness data of each reflector layer to obtain the corresponding forward model. The correlation between t0 and v is established from the forward simulation results, where t0 is the two-way travel time and v is the formation velocity. The correlation between t0 and v established in this embodiment is as follows: Figure 3-a shown.

[0028] 3. Obtain seismic reflection data of the target area and obtain the t0-v relationship from the seismic reflection data.

[0029] For this embodiment, the t0-v relationship obtained based on the seismic reflection data of the target area is as follows: Figure 3-b As shown, it can be seen that it is consistent with the t0-v relationship obtained by forward simulation (such as Figure 3-a ) is significantly different due to the presence of coal seams in the target area.

[0030] 4. The t0-v relationship obtained by forward simulation is used to correct the t0-v relationship obtained from seismic reflection data.

[0031] For this embodiment, the t0-v relationship obtained by forward simulation (such as Figure 3-a As shown in the figure, the t0-v relationship in the actual seismic data is corrected, and the correction results are shown in the figure. Figure 3-c As shown in the figure, the corrected t0-v relationship of the entire target area is obtained. Figure 3-a The t0-v relationship in Figure 3-b The t0-v relationship in is modified to Figure 3-b and Figure 3-a The places with big differences are Figure 3-a Make corrections.

[0032] 5. Use the corrected t0-v relationship to obtain the stratigraphic structural morphology of the target area.

[0033] For this embodiment, the target area stratum structure morphology obtained by the t0-v relationship before correction is as follows: Figure 4-a As shown in the figure, the target area stratigraphic structure morphology obtained by using the corrected t0-v relationship is as follows: Figure 4-b As shown, by comparison, Figure 4-b The stratigraphic structure is closer to the real stratigraphic structure.

[0034] Through the above process, it can be seen that the present invention can use actual logging data to correct seismic reflection data, eliminate the interference caused by strong reflection signals of coal seams, and make the reflection imaging results more accurately represent the actual stratigraphic structure.

Claims

1. A seismic imaging correction method for eliminating the influence of coal seams, characterized in that: The correction method includes the following steps: 1) Obtain multi-layer geological logging data and interpreted horizon data containing coal seams in the target area and construct a corresponding geological model; 2) Perform forward modeling on the constructed geological model and determine the relationship between the corresponding two-way travel time and formation velocity based on the forward modeling results; 3) obtaining seismic reflection data of the target area and determining the relationship between the corresponding two-way travel time and formation velocity from the seismic reflection data; 4) using the relationship between the two-way travel time and the formation velocity obtained in step 2) to correct the relationship between the two-way travel time and the formation velocity obtained in step 3); 5) The relationship between the corrected two-way travel time and the formation velocity is used to construct the stratigraphic structural morphology of the target area.

2. The seismic imaging correction method for eliminating coal seam influence according to claim 1, characterized in that: The logging data obtained in step 1) includes acoustic logging data, density logging data and VSP logging data.

3. The seismic imaging correction method for eliminating coal seam influence according to claim 1, characterized in that: The geological model constructed in step 1) includes the stratum where the coal seam is located, the stratum above the coal seam and the stratum underlying the coal seam.

4. The seismic imaging correction method for eliminating coal seam influence according to claim 3, characterized in that: The step 2) is to perform forward simulation based on the layer velocity, density and thickness of each layer.

5. The seismic imaging correction method for eliminating coal seam influence according to claim 1, characterized in that: The correction in step 4) refers to correcting the relationship between the two-way travel time and the formation velocity obtained in step 3) to the relationship between the two-way travel time and the formation velocity obtained in step 2).

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