A method for predicting earthquakes in a carbon dioxide sequestration area

Abstract

The application provides a carbon dioxide underground storage range earthquake prediction method, and the earthquake prediction method comprises the following steps: S1, obtaining an injection layer isobath structure map according to seismic data and injection well calibration data; S2, obtaining an amplitude variation curve of the injection layer according to prestack gather seismic data; S3, calculating a slope variation rate attribute according to the amplitude variation curve, and determining a threshold value of the slope variation rate attribute of a gas injection area; and S4, determining a final carbon dioxide gas injection area plane distribution range according to the prestack gather seismic data. The application provides a theoretical basis for predicting a carbon dioxide oil displacement range by using three-dimensional seismic data after gas injection, and the earthquake prediction method serves as a prerequisite for the above research method, so as to provide scientific guidance for safe implementation of carbon dioxide oil displacement in a research area.

Description

Technical Field

[0001] This invention relates to the fields of structural geology and petroleum geology, and in particular to a method for predicting the seismic extent of underground carbon dioxide storage. Background Technology

[0002] Currently, seismic monitoring for carbon dioxide flooding (CFD) typically employs time-shift seismic methods. These methods compare the differences between two sets of consistent seismic data before and after gas injection to study the extent of carbon dioxide spread in the formation. However, applying time-shift seismic methods to CFD monitoring still presents several unresolved issues, including: ① ensuring sufficient seismic monitoring time intervals for observing anomalies; and ② reducing the uncertainty of quantitative parameters such as pressure, temperature, saturation, salinity, and dissolved gas ratio during CFD displacement. Furthermore, in older oilfields where ideal time-shift seismic data is difficult to obtain, how to conduct CFD seismic monitoring remains a pressing issue. Summary of the Invention

[0003] In view of the above problems, the present invention is proposed to provide a method for earthquake prediction of underground carbon dioxide storage range that overcomes or at least partially solves the above problems.

[0004] According to one aspect of the present invention, a method for predicting the seismic extent of underground carbon dioxide storage is provided, the seismic prediction method comprising:

[0005] Step S1: Obtain the structural map of the injection layer based on seismic data and injection well calibration data;

[0006] Step S2: Obtain the amplitude variation curve of the injection layer based on the pre-stack gathering seismic data;

[0007] Step S3: Calculate the slope change rate attribute based on the amplitude change curve, and determine the threshold of the slope change rate attribute of the gas injection zone;

[0008] Step S4: Determine the final planar distribution range of the carbon dioxide injection zone based on the pre-stack seismic data.

[0009] Optionally, step S4: determining the final planar distribution range of the carbon dioxide injection zone based on the pre-stack gathering seismic data specifically includes:

[0010] Step S41: Calculate the three-dimensional data volume of the slope change rate attribute based on the pre-stack seismic data;

[0011] Step S42: Determine the distribution range of the gas injection zone based on the same depth structure diagram of the injection layer;

[0012] Step S43: Determine the final planar distribution range of the carbon dioxide injection zone.

[0013] Optionally, step S1: obtaining the injection layer contour map based on seismic data and injection well calibration data specifically includes:

[0014] Based on seismic data and injection well calibration data, structural interpretation of the injection layer was carried out to obtain the injection layer T0 map, and time-depth conversion was performed based on the velocity data of this area to obtain the injection layer depth map.

[0015] Optionally, step S2: obtaining the amplitude variation curve of the injection layer based on pre-stack gathering seismic data specifically includes:

[0016] Based on pre-stack gathering seismic data, we conducted an analysis of the amplitude variation characteristics of the injection layers in the gas injection zone and the non-gas injection zone with offset. We selected injection wells in the gas injection zone and pre-stack gathering data of the same non-gas injection zone to obtain the amplitude variation curves of the injection layers with offset.

[0017] Optionally, step S3: calculating the slope change rate attribute based on the amplitude change curve, and determining the threshold of the slope change rate attribute of the gas injection zone specifically includes:

[0018] The slope change rate attribute is calculated based on the amplitude change curve. The slope change rate attribute S of the steam injection zone and the non-steam injection zone is statistically analyzed to determine the threshold of the slope change rate attribute of the steam injection zone.

[0019] Optionally, the method for predicting the underground carbon dioxide storage range according to claim 2 is characterized in that step S41: calculating the three-dimensional data volume of the slope change rate attribute based on the pre-stack gather seismic data specifically includes: calculating the three-dimensional data volume of the slope change rate attribute according to the Shuey formula.

[0020] Optionally, the calculation of the slope change rate attribute three-dimensional data volume according to the Shuey formula specifically includes:

[0021] Based on pre-stack seismic data, the three-dimensional data volume of slope change rate attribute is calculated according to the Shuey formula, where the Shuey formula is r(θ)=r(0)+G sin2(θ / 2);

[0022] Where r(θ) represents the reflection coefficient, r(0) represents the reflection coefficient at zero angle of incidence, G represents the second derivative of the wave impedance, and θ represents the angle of incidence.

[0023] Optionally, step S42: determining the distribution range of the gas injection zone based on the injection layer iso-depth structural diagram specifically includes:

[0024] Based on the injection layer construction diagram, the planar map of the slope change rate attribute S is extracted, and the distribution range of the gas injection zone is determined according to the determined threshold.

[0025] Optionally, step S43: determining the final planar distribution range of the carbon dioxide injection zone specifically includes:

[0026] The production data of oil wells within the carbon dioxide injection zone are statistically analyzed, the cumulative carbon dioxide production is calculated, and the planar distribution range of the injection zone is calibrated to determine the final planar distribution range of the carbon dioxide injection zone.

[0027] This invention also provides an earthquake prediction system for the underground carbon dioxide storage area, which applies the above-described earthquake prediction method for the underground carbon dioxide storage area. The prediction system specifically includes:

[0028] The module for obtaining iso-depth structural maps of the injection layer is used to obtain iso-depth structural maps of the injection layer based on seismic data and injection well calibration data.

[0029] The amplitude variation curve acquisition module of the injection layer is used to acquire the amplitude variation curve of the injection layer based on pre-stack gathering seismic data.

[0030] The threshold determination module is used to calculate the slope change rate attribute based on the amplitude change curve and determine the threshold of the slope change rate attribute of the gas injection zone;

[0031] The planar distribution range determination module is used to determine the final planar distribution range of the carbon dioxide injection zone based on the pre-stack seismic data.

[0032] This invention provides a seismic prediction method for the underground carbon dioxide storage area. The seismic prediction method includes: Step S1: Obtaining a contour map of the injection layer based on seismic data and injection well calibration data; Step S2: Obtaining the amplitude variation curve of the injection layer based on pre-stack gathering seismic data; Step S3: Calculating the slope variation rate attribute based on the amplitude variation curve and determining the threshold of the slope variation rate attribute of the gas injection area; Step S4: Determining the final planar distribution range of the carbon dioxide gas injection area based on the pre-stack gathering seismic data. This provides a theoretical basis for predicting the sweep range of carbon dioxide flooding using post-injection 3D seismic data. By using the seismic prediction method as a prerequisite for the above research method, it aims to provide scientific guidance for the safe implementation of carbon dioxide flooding in the study area.

[0033] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 A flowchart illustrating a method for predicting the seismic extent of underground carbon dioxide storage, provided in an embodiment of the present invention;

[0036] Figure 2 This is a contour map of the target work area in one embodiment of the present invention;

[0037] Figure 3 This is a graph showing the amplitude variation of the gas injection section and the non-gas injection section with the offset distance in an example of the present invention.

[0038] Figure 4 This is the relationship between the S attribute and the carbon dioxide injection / production rate in an example of the present invention;

[0039] Figure 5 This is a predicted map of the underground storage range for carbon dioxide flooding in an example of the present invention. Detailed Implementation

[0040] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0041] The terms "comprising" and "having," and any variations thereof, in the specification, embodiments, claims, and drawings of this invention are intended to cover non-exclusive inclusion, such as including a series of steps or units.

[0042] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0043] The present invention provides a method for earthquake prediction of underground carbon dioxide storage range, comprising the following steps:

[0044] Based on seismic data and injection well calibration data, structural interpretation of the injection layer is carried out to obtain the injection layer T0 map, and time-depth conversion is carried out based on the velocity data of this area to obtain the injection layer depth-depth structural map.

[0045] Based on pre-stack seismic data, the amplitude variation characteristics of the injection layers in the gas injection zone and non-gas injection zone were analyzed with offset. Pre-stack gathers from injection wells in the gas injection zone and the same non-gas injection zone were selected to obtain amplitude variation curves of the injection layers with offset. The slope variation rate attribute was calculated based on the amplitude variation curves. The slope variation rate attribute S in the gas injection zone and non-gas injection zone was statistically analyzed to determine the threshold for the slope variation rate attribute in the gas injection zone. Based on the pre-stack seismic data, the three-dimensional data volume of the slope variation rate attribute was calculated using the Shuey formula. Based on the injection layer structure map, a planar map of the slope variation rate attribute S was extracted. The distribution range of the gas injection zone was determined based on the determined threshold. Production data from oil wells within the carbon dioxide gas injection zone were statistically analyzed to calculate the cumulative carbon dioxide production. This data was then calibrated against the planar distribution range of the gas injection zone to determine the final planar distribution range of the carbon dioxide gas injection zone.

[0046] The following are several specific embodiments of the application of the present invention.

[0047] Example 1

[0048] In a specific embodiment 1 of the present invention, the seismic prediction method for underground carbon dioxide storage range includes the following steps:

[0049] Step 1: Based on seismic data and injection well calibration data, perform structural interpretation of the injection layer, obtain the injection layer T0 map, and perform time-depth conversion based on the velocity data of this area to obtain the injection layer depth-structural map.

[0050] Step 2: Based on the pre-stack gathering seismic data, conduct an analysis of the amplitude variation characteristics of the injection layer system in the gas injection zone and the non-gas injection zone. Select the injection well in the gas injection zone and the pre-stack gathering data of the same non-gas injection zone to obtain the amplitude variation curve of the injection layer with the offset.

[0051] Step 3: Calculate the slope change rate attribute based on the amplitude change curve, statistically analyze the slope change rate attribute S between the steam injection zone and the non-steam injection zone, and determine the threshold of the slope change rate attribute in the steam injection zone.

[0052] Step 4: Based on the pre-stack seismic data, calculate the three-dimensional data volume of the slope change rate attribute according to the Shuey formula;

[0053] Step 5: Based on the injection layer construction diagram, extract the planar map of the slope change rate attribute S, and determine the distribution range of the gas injection zone according to the determined threshold.

[0054] Step 6: Collect production data of oil wells in the carbon dioxide injection zone, calculate the cumulative carbon dioxide production, and calibrate it with the planar distribution range of the injection zone to determine the final planar distribution range of the carbon dioxide injection zone.

[0055] Example 2

[0056] In a specific embodiment 2 of the present invention, such as Figure 1 As shown, Figure 1 This is a flowchart illustrating a method for predicting the seismic extent of underground carbon dioxide storage areas according to the present invention. The method for predicting the seismic extent of underground carbon dioxide storage areas includes:

[0057] In step 1, based on seismic data and injection well calibration data, the structural interpretation of the injection layer is carried out, the isochronous map of the injection layer is obtained, and the time-depth conversion is carried out based on the velocity data of this area to obtain the isodepth structural map of the injection layer.

[0058] In step 2, based on the pre-stack gathering seismic data, the amplitude variation characteristics of the injection layers in the gas injection zone and non-gas injection zone are analyzed with offset distance. The injection wells in the gas injection zone and the pre-stack gatherings of the same non-gas injection zone are selected to obtain the amplitude variation curves of the injection layers with offset distance.

[0059] In step 3, the slope change rate attribute is calculated based on the amplitude change curve, and the slope change rate attribute S of the steam injection area and the non-steam injection area is statistically analyzed to determine the threshold of the slope change rate attribute of the steam injection area.

[0060] In step 4, based on the pre-stack gathering seismic data, the three-dimensional data volume of the slope change rate attribute is calculated according to the Shuey formula, where the Shuey formula is r(θ)=r(0)+G sin2(θ / 2), where r(θ) represents the reflection coefficient, r(0) represents the reflection coefficient at zero angle of incidence, G represents the second derivative of the wave impedance, and θ represents the angle of incidence.

[0061] In step 5, based on the injection layer construction diagram, the planar map of the slope change rate attribute S is extracted, and the distribution range of the gas injection zone is determined according to the determined threshold.

[0062] In step 6, the production data of the oil wells in the carbon dioxide injection zone are statistically analyzed, the cumulative carbon dioxide production is calculated, and the planar distribution range of the injection zone is calibrated to determine the final planar distribution range of the carbon dioxide injection zone.

[0063] Example 3

[0064] In a specific embodiment 3 of the present invention, the invention is applied. Figure 2 In a specific embodiment of the present invention, based on seismic data and injection well calibration data, the structural interpretation of the injection layer is carried out to obtain the isochronous map of the injection layer, and based on the velocity data of the local area, time-depth conversion is carried out to obtain the isodepth structural map of the injection layer;

[0065] Figure 3In a specific embodiment of the present invention, based on pre-stack gather seismic data, the amplitude variation characteristics of the injected layers in the gas-injection zone and the non-gas-injection zone were analyzed with respect to offset. Pre-stack gathers from the injection wells in the gas-injection zone and the same non-gas-injection zone were selected to obtain amplitude variation curves of the injected layers with respect to offset. The gas-injection layers all exhibited obvious amplitude variation response characteristics with offset, i.e., the amplitude gradually decreased with increasing incident angle, and an amplitude reversal occurred with increasing offset. Wells located far from the injection wells within the block, although also showing carbon dioxide production, produced small amounts, and their seismic profiles did not exhibit obvious amplitude variation response characteristics with offset. This indicates that the gas injection volume has a direct impact on the amplitude variation response of the gas-injection layers with respect to offset.

[0066] Figure 4 In a specific embodiment of the present invention, the slope change rate attribute is calculated based on the amplitude change curve. The slope change rate attribute S of the steam injection zone and the non-steam injection zone is statistically analyzed to clarify the threshold of the slope change rate attribute of the steam injection zone. Specifically: when the injection volume / production volume is greater than 100t, the corresponding S attribute value is less than -50, indicating a major carbon dioxide flooding affected area; when the injection volume / production volume is 0-100t, the corresponding S attribute value is -50 to -18, indicating a minor carbon dioxide flooding affected area; when the injection volume / production volume is 0, the corresponding S attribute value is -18 to 50, indicating a non-carbon dioxide flooding affected area. See the table below:

[0067] Table 1. Carbon Dioxide Injection / Production Rate

[0068]

[0069] Figure 5 In a specific embodiment of the present invention, based on the injection layer structure diagram, a planar map of the slope change rate attribute S is extracted, and the distribution range of the gas injection zone is determined according to a defined threshold. Simultaneously, production data from oil wells within the carbon dioxide injection zone are statistically analyzed, cumulative carbon dioxide production is calculated, and this data is calibrated against the planar distribution range of the injection zone to determine the final planar distribution range of the carbon dioxide injection zone. The sweep surface exhibits a concentric radial ring shape, and the three sweep surfaces of the gas drive show a good correspondence with the three injection peaks in the injection history.

[0070] Beneficial effects: By conducting a quantitative study on the relationship between rock pore saturation and amplitude variation with offset, the study shows that carbon dioxide injection causes changes in pore pressure and saturation in reservoir pores, and these changes in turn cause changes in amplitude response characteristics with offset. This provides a theoretical basis for predicting the sweep range of carbon dioxide flooding using 3D seismic data after gas injection. By using seismic prediction methods as a prerequisite for the above research methods, the aim is to provide scientific guidance for the safe implementation of carbon dioxide flooding in the study area.

[0071] The above specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for predicting the seismic extent of underground carbon dioxide storage, characterized in that, The earthquake prediction method includes: Step S1: Obtain the structural map of the injection layer based on seismic data and injection well calibration data; Step S2: Obtain the amplitude variation curve of the injection layer based on the pre-stack gathering seismic data; Step S3: Calculate the slope change rate attribute based on the amplitude change curve, and determine the threshold of the slope change rate attribute of the gas injection zone; Step S4: Determine the final planar distribution range of the carbon dioxide injection zone based on the pre-stack seismic data.

2. The method for earthquake prediction of underground carbon dioxide storage area according to claim 1, characterized in that, Step S4: Determining the final planar distribution range of the carbon dioxide injection zone based on the pre-stack gathering seismic data specifically includes: Step S41: Calculate the three-dimensional data volume of the slope change rate attribute based on the pre-stack seismic data; Step S42: Determine the distribution range of the gas injection zone based on the same depth structure diagram of the injection layer; Step S43: Determine the final planar distribution range of the carbon dioxide injection zone.

3. The method for earthquake prediction of underground carbon dioxide storage area according to claim 1, characterized in that, Step S1: Obtaining the iso-depth structural map of the injection layer based on seismic data and injection well calibration data specifically includes: Based on seismic data and injection well calibration data, structural interpretation of the injection layer was carried out to obtain the injection layer T0 map, and time-depth conversion was performed based on the velocity data of this area to obtain the injection layer depth map.

4. The method for earthquake prediction of underground carbon dioxide storage area according to claim 1, characterized in that, Step S2: Obtaining the amplitude variation curve of the injection layer based on pre-stack gathering seismic data specifically includes: Based on pre-stack gathering seismic data, we conducted an analysis of the amplitude variation characteristics of the injection layers in the gas injection zone and the non-gas injection zone with offset. We selected injection wells in the gas injection zone and pre-stack gathering data of the same non-gas injection zone to obtain the amplitude variation curves of the injection layers with offset.

5. The method for earthquake prediction of underground carbon dioxide storage area according to claim 1, characterized in that, Step S3: Calculating the slope change rate attribute based on the amplitude change curve, and clarifying the threshold of the slope change rate attribute of the gas injection zone specifically includes: The slope change rate attribute is calculated based on the amplitude change curve. The slope change rate attribute S of the steam injection zone and the non-steam injection zone is statistically analyzed to determine the threshold of the slope change rate attribute of the steam injection zone.

6. The method for earthquake prediction of underground carbon dioxide storage area according to claim 1, characterized in that, The method for predicting the seismic range of underground carbon dioxide storage according to claim 2 is characterized in that step S41: calculating the three-dimensional data volume of the slope change rate attribute based on the pre-stack gather seismic data specifically includes: calculating the three-dimensional data volume of the slope change rate attribute according to the Shuey formula.

7. The method for predicting the seismic range of underground carbon dioxide storage according to claim 6, characterized in that, The calculation of the slope change rate attribute three-dimensional data volume according to the Shuey formula specifically includes: Based on pre-stack seismic data, the three-dimensional data volume of slope change rate attribute is calculated according to the Shuey formula, where the Shuey formula is r(θ)=r(0)+G sin2(θ / 2); Where r(θ) represents the reflection coefficient, r(0) represents the reflection coefficient at zero angle of incidence, G represents the second derivative of the wave impedance, and θ represents the angle of incidence.

8. The method for earthquake prediction of underground carbon dioxide storage area according to claim 1, characterized in that, Step S42: Determining the distribution range of the gas injection zone based on the iso-depth structural diagram of the injection layer specifically includes: Based on the injection layer construction diagram, the planar map of the slope change rate attribute S is extracted, and the distribution range of the gas injection zone is determined according to the determined threshold.

9. The method for predicting the seismic range of underground carbon dioxide storage according to claim 1, characterized in that, Step S43: Determining the final planar distribution range of the carbon dioxide injection zone specifically includes: The production data of oil wells within the carbon dioxide injection zone are statistically analyzed, the cumulative carbon dioxide production is calculated, and the planar distribution range of the injection zone is calibrated to determine the final planar distribution range of the carbon dioxide injection zone.

10. The seismic prediction system for underground carbon dioxide storage area according to claim 1, applying the seismic prediction method for underground carbon dioxide storage area according to any one of claims 1-9, is characterized in that, The prediction system specifically includes: The module for obtaining iso-depth structural maps of the injection layer is used to obtain iso-depth structural maps of the injection layer based on seismic data and injection well calibration data. The amplitude variation curve acquisition module of the injection layer is used to acquire the amplitude variation curve of the injection layer based on pre-stack gathering seismic data. The threshold determination module is used to calculate the slope change rate attribute based on the amplitude change curve and determine the threshold of the slope change rate attribute of the gas injection zone; The planar distribution range determination module is used to determine the final planar distribution range of the carbon dioxide injection zone based on the pre-stack seismic data.

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