A method for predicting oil and gas filling of a cavern

Abstract

The application discloses a kind of oil and gas filling cave prediction method, specifically comprising the following steps: S1, well seismic data extraction;S2, matrix calculation: apply well seismic data to calculate intra-class dispersion matrix and inter-class dispersion matrix;S3, matrix projection: two kinds of matrix are integrated and the integrated matrix is decomposed into features, and projection matrix is formed;S4, seismic data projection: the projection matrix calculated from the seismic data at the actual drilling well, the projection of all seismic data in the target area is calculated, i.e. the seismic waveform component after decomposition, and the seismic waveform component at the actual drilling well is extracted;S5, seismic waveform component screening reconstruction: the seismic waveform component is screened, and the screened seismic waveform component is reconstructed, and finally the optimized seismic waveform component model is obtained, i.e. the prediction of oil and gas filling cave can be completed.The application can quickly and accurately judge the category of carbonate cave, and is suitable for the prediction of oil and gas filling cave.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas exploration technology and relates to a method for predicting the type of carbonate caverns, specifically a method for predicting oil and gas filling caverns. Background Technology

[0002] In the process of oil and gas extraction, it is usually necessary to predict the oil and gas reserves in the target area in order to determine the drilling location, thereby improving extraction efficiency and reducing extraction costs.

[0003] In predicting oil and gas reservoirs, there is a special case: predicting the type of carbonate caverns. Carbonate caverns are divided into oil and gas-filled and unfilled types. Because both types of caverns exhibit impedance differences with their surrounding environment when predicted using conventional seismic data, it is impossible to distinguish the cavern type. Therefore, conventional seismic data cannot accurately predict the type of carbonate caverns.

[0004] Currently, the main method for predicting carbonate cavern categories is PCA-based waveform component analysis. However, since the decomposition and optimization reconstruction of waveform components in this method are based on unsupervised decomposition and manual selection, the decomposed waveform components cannot intuitively show whether the component is related to the oil and gas response. Manual selection and reconstruction of the decomposed waveform components are still required, which makes the use of this method for carbonate cavern category prediction very time-consuming and greatly limits its application in actual production. Summary of the Invention

[0005] To address the aforementioned shortcomings in existing technologies, this invention aims to provide a method for predicting oil and gas-filled karst caves, thereby enabling rapid and accurate prediction of such caves.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for predicting the filling of karst caves by oil and gas includes the following steps:

[0008] S1. Wellside seismic data extraction: Select multiple karst cave locations in the target area for drilling, classify the actual drilled wells into two categories: oil and gas filled wells and non-filled wells, and extract the wellside seismic data of the actual drilled wells;

[0009] S2, Matrix Calculation: Calculate the intra-class and inter-class scatter matrices using well-side seismic data;

[0010] S3. Matrix projection: Integrate the intra-class scatter matrix and the inter-class scatter matrix, and perform eigenvalue decomposition on the integrated matrix, that is, calculate the eigenvector corresponding to the largest eigenvalue, and form the projection matrix by the eigenvector corresponding to the largest eigenvalue.

[0011] S4. Seismic Data Projection: The projection of all seismic data in the target area is calculated using the projection matrix obtained from the seismic data at the actual drilling site. This is the decomposed seismic waveform components of all locations in the target area. The seismic waveform components at the actual drilling site are extracted. Since the cave type at the actual drilling site is known, the cave type represented by the seismic waveform components at the actual drilling site is also known.

[0012] S5. Seismic waveform component screening and reconstruction: First, the seismic waveform components related to the oil and gas response are screened out based on the seismic waveform components at the actual drilling site, and the screened seismic waveform components are reconstructed to obtain the optimized seismic waveform component model. The prediction of oil and gas filling caverns can be completed through the optimized seismic waveform component model.

[0013] As a limitation of this invention, the formula for calculating the intra-class scatter matrix in step S2 is as follows:

[0014]

[0015] The formula for calculating the inter-class scatter matrix is:

[0016] S b =(μ0-μ1)(μ0-μ1) T

[0017] Where S w Let S be the within-class scatter matrix. b Let X0 be the inter-class divergence matrix, X1 be the seismic data of the wellbore bypass of oil and gas filled wells, μ0 be the mean vector of the seismic data of the wellbore bypass of oil and gas filled wells, and μ1 be the mean vector of the seismic data of the wellbore bypass of non-filled wells.

[0018] As a further limitation of the present invention, the formula for integrating the intra-class scatter matrix and the inter-class scatter matrix in step S3 is as follows:

[0019]

[0020] As a further limitation of the present invention, the method for calculating the seismic waveform components in step S4 is as follows:

[0021] Y = W T X

[0022] Where W is the projection matrix and X is the seismic data of the target area.

[0023] As another limitation of the present invention, in step S5, a dynamic binary tree automatic component selection method is used to screen the decomposed seismic waveform components.

[0024] As a further limitation of the present invention, in step S5, the selected seismic waveform components are reconstructed by linear superposition.

[0025] By adopting the above-described technical solution, the beneficial effects achieved by this invention compared to the prior art are as follows:

[0026] (1) This invention calculates the intra-class divergence matrix and inter-class divergence matrix of the seismic data from the wellbore of actual drilling, and decomposes the seismic data of the target area according to the intra-class divergence matrix and inter-class divergence matrix to obtain the waveform diagram of the decomposed seismic data from the wellbore. By comparing the waveform diagram of the decomposed seismic data from the wellbore with the waveform diagram of the decomposed seismic data from the wellbore, the seismic data of the target area can be more intuitively reflected as to whether each component is related to the oil and gas response, which is convenient for subsequent automatic screening.

[0027] (2) The method for screening seismic waveform components in this invention is the dynamic binary tree automatic component selection method. This method can simultaneously and automatically screen the seismic waveform components of two types of karst caves, thus improving the screening efficiency.

[0028] In summary, this invention can quickly and accurately determine the type of karst caves and is applicable to the prediction of karst caves filled with oil and gas. Attached Figure Description

[0029] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0030] Figure 1 This is an operation flowchart of an embodiment of the present invention;

[0031] Figure 2 These are seismic data waveforms from two different types of actual drilled wells in an embodiment of the present invention;

[0032] Figure 2 (a) is a waveform diagram of seismic data from oil and gas filling wells;

[0033] Figure 2 (b) is a waveform diagram of seismic data from non-filled wells;

[0034] Figure 3 This is a waveform component decomposition effect diagram of seismic data from two different types of actual drilled wells in an embodiment of the present invention (only the first ten components are shown);

[0035] Figure 4 This is a waveform diagram of the original target area seismic data in an embodiment of the present invention;

[0036] Figure 5 This is a waveform diagram of the target area after the seismic data has been screened and reconstructed in an embodiment of the present invention. Detailed Implementation

[0037] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustrative and understanding purposes only and are not intended to limit the scope of the invention.

[0038] This embodiment discloses a method for predicting the filling of karst caves by oil and gas, such as... Figure 1 As shown, matrix calculations are performed by drilling in the target area and extracting seismic data from the wellbore. Then, matrix projection is applied to the calculated matrix, and the overall seismic data of the target area is decomposed into seismic waveform components based on the matrix projection. Finally, the seismic waveform components are filtered and reconstructed to predict oil and gas-filled caverns. The specific method is as follows:

[0039] S1, Seismic data extraction from the shaft side passage

[0040] First, multiple wells are drilled in the target area. The actual well locations should be at the locations of karst caves. Based on the oil and gas filling status of the karst caves at the drilled well locations, the drilled wells can be divided into two types: oil and gas filled wells and unfilled wells. Then, for each drilled well, 3x3, 5x5, or 7x7 well-side seismic data are extracted according to the size of the karst cave. The extracted well-side seismic data are then classified into two types: well-side seismic data for oil and gas filled wells and well-side seismic data for unfilled wells. Figure 2 As shown, the seismic data from wells with strong amplitude containing oil and gas are the seismic data from wells with oil and gas filling, while the seismic data from wells with mud filling (i.e., seismic data from wells without filling) are the seismic data from wells with mud filling.

[0041] S2, Matrix Calculation

[0042] The intra-class and inter-class scatter matrices are calculated using well-side seismic data. The formula for calculating the intra-class scatter matrix is ​​as follows:

[0043]

[0044] The formula for calculating the inter-class scatter matrix is:

[0045] S b =(μ0-μ1)(μ0-μ1) T

[0046] Where S w Let S be the within-class scatter matrix. b Let X0 be the inter-class divergence matrix, X1 be the seismic data of the wellbore bypass of oil and gas filled wells, μ0 be the mean vector of the seismic data of the wellbore bypass of oil and gas filled wells, and μ1 be the mean vector of the seismic data of the wellbore bypass of non-filled wells.

[0047] S3, Matrix Projection

[0048] The intra-class scatter matrix and the inter-class scatter matrix are integrated, and the resulting matrix is ​​subjected to eigenvalue decomposition. Eigenvalue decomposition is to calculate the eigenvector corresponding to the largest eigenvalue and then form the projection matrix using the eigenvectors corresponding to the largest eigenvalue.

[0049] The formula for integrating the intra-class scatter matrix and the inter-class scatter matrix is ​​as follows:

[0050]

[0051] S4, Seismic Data Projection

[0052] The projection of the seismic data in the target area is calculated using a projection matrix. This projection is the decomposed seismic waveform component. Subsequently, the seismic waveform components from known types of actual drilled wells are extracted, such as... Figure 3 As shown, the original seismic waveforms at the two types of actual drilling sites are decomposed into multiple waveform components.

[0053] The calculation method for seismic waveform components is as follows:

[0054] Y = W T X

[0055] S5, Seismic Waveform Component Screening and Reconstruction

[0056] The seismic waveform components of the target area are filtered using an algorithm, specifically a dynamic binary tree automatic component selection method. The filtered seismic waveform components, capable of distinguishing the karst cave filling information of the target area, are then reconstructed using linear superposition. The reconstructed seismic data is then output, displaying the karst cave filling status of the target area. Figure 4 and Figure 5 As shown, before screening and reconstruction, both types of karst caves exhibit beaded shadows. After screening and reconstruction, the beaded shadows in non-filled karst caves disappear, while the beaded shadows in oil and gas-filled karst caves remain. This allows for the prediction of oil and gas-filled karst caves.

[0057] It should be added here that when screening seismic waveform components, the seismic waveform components of the two known types of actual drilling locations extracted in step S4 should be used as a screening reference in order to select the seismic waveform components that can best distinguish the cave filling information of the target area.

[0058] It should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still modify the technical solutions described in the above embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for predicting the filling of karst caves by oil and gas, characterized in that, Specifically, the steps include the following: S1. Wellside seismic data extraction: Select multiple karst cave locations in the target area for drilling, classify the actual drilled wells into two categories: oil and gas filled wells and non-filled wells, and extract the wellside seismic data of the actual drilled wells; S2, Matrix Calculation: Calculate the intra-class and inter-class scatter matrices using well-side seismic data; S3. Matrix projection: Integrate the intra-class scatter matrix and the inter-class scatter matrix, and perform eigenvalue decomposition on the integrated matrix, that is, calculate the eigenvector corresponding to the largest eigenvalue, and form the projection matrix by the eigenvector corresponding to the largest eigenvalue. S4. Seismic Data Projection: The projection of all seismic data in the target area is calculated using the projection matrix obtained from the seismic data at the actual drilling site. This is the decomposed seismic waveform components of all locations in the target area. The seismic waveform components at the actual drilling site are extracted. Since the cave type at the actual drilling site is known, the cave type represented by the seismic waveform components at the actual drilling site is also known. S5. Seismic waveform component screening and reconstruction: First, the seismic waveform components related to the oil and gas response are screened out based on the seismic waveform components at the actual drilling site, and the screened seismic waveform components are reconstructed to obtain the optimized seismic waveform component model. The prediction of oil and gas filling caverns can be completed through the optimized seismic waveform component model.

2. The method for predicting oil and gas filling of karst caves according to claim 1, characterized in that, The formula for calculating the intra-class scatter matrix in step S2 is: The formula for calculating the inter-class scatter matrix is: S b =(μ0-μ1)(μ0-μ1) T Where S w Let S be the within-class scatter matrix. b Let X0 be the inter-class divergence matrix, X1 be the seismic data of the wellbore bypass of oil and gas filled wells, μ0 be the mean vector of the seismic data of the wellbore bypass of oil and gas filled wells, and μ1 be the mean vector of the seismic data of the wellbore bypass of non-filled wells.

3. The method for predicting oil and gas filling of karst caves according to claim 2, characterized in that: The formula for integrating the intra-class scatter matrix and the inter-class scatter matrix in step S3 is as follows:

4. The method for predicting oil and gas filling of karst caves according to claim 5, characterized in that: The calculation method for the seismic waveform components in step S4 is as follows: Y=W T X Where W is the projection matrix and X is the seismic data of the target area.

5. A method for predicting oil and gas filling of karst caves according to any one of claims 1-4, characterized in that: In step S5, the dynamic binary tree automatic component selection method is used to screen the decomposed seismic waveform components.

6. The method for predicting oil and gas filling of karst caves according to claim 5, characterized in that: In step S5, the selected seismic waveform components are reconstructed by linear superposition.

Images