A method of monitoring co2 storage using crosswell multi-component time-lapse seismic

Abstract

The application provides a method for monitoring CO2 storage by using interwell multi-component time-lapse seismic data, which comprises the following steps: performing seismic data conventional processing, wave field separation and time-lapse seismic data processing on the vertical component and the horizontal component of the time-lapse seismic data; obtaining the delay time through the maximum value of the time-lapse cross-correlation coefficient; calculating the relative velocity variation in each time window; obtaining the average velocity variation; performing channel-by-channel calculation on the upgoing wave field of the time-lapse vertical component and the time-lapse horizontal component; drawing the curve of the velocity variation with the depth variation; comprehensively comparing and constraining the multi-component results; determining the depth range of the velocity variation caused by CO2 injection; and pre-judging the potential leakage risk of CO2. The application can monitor the safety of CO2 storage by using interwell multi-component time-lapse seismic data, has high calculation efficiency and low cost investment, can determine the depth range of the velocity variation caused by CO2 injection, and can provide rapid detection for the potential CO2 leakage and timely warning for the leakage risk.

Description

Technical Field

[0001] This invention relates to the field of exploration geophysics, specifically a method for CO2 seismic monitoring and seismic storage between wells using multi-component time-lapse seismic monitoring. Background Technology

[0002] CO2 capture and storage (CFS) technology is considered one of the most effective methods for reducing CO2 emissions in recent years. It involves separating CO2 from industrial or related energy sources, liquefying and compressing it, and then injecting it underground for long-term storage, isolating it from the atmosphere. After CO2 storage, its migration and distribution need to be monitored to provide early warning of potential leaks. Time-lapse seismic monitoring in geophysics is considered the most effective method for monitoring the safety of CO2 storage.

[0003] For inter-well time-lapse seismic measurements, the application of monitoring CO2 seismic storage safety primarily utilizes travel-time tomography or full-waveform inversion methods to establish the time-lapse velocity field. Then, CO2 distribution and migration are determined through imaging and difference imaging. However, high-precision first-arrival acquisition is crucial input information, but it is labor-intensive and also affected by inversion errors and accuracy. For velocity changes caused by CO2 injection and potential leakage problems, an effective and rapid detection method is needed to obtain valuable monitoring results with lower computational costs. Summary of the Invention

[0004] The purpose of this invention is to provide a method for monitoring CO2 seismic storage between wells using multi-component time-lapse seismic monitoring, which provides rapid early warning of potential CO2 leakage problems and provides an effective and fast monitoring means for long-term CO2 storage monitoring.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for CO2 seismic monitoring between wells using multi-component time-lapse seismic monitoring includes the following steps:

[0007] 1) Seismic data obtained through conventional seismic data processing, including basic measurements and repeat measurements, are u b and u r The vertical and horizontal components of the basic measurement are respectively and The vertical and horizontal components of the repeated measurements are respectively and

[0008] 2) After wavefield separation and time-shifted seismic data processing, the vertical component of the ascending wave is obtained from the base measurements. and horizontal component upward wave The vertical component of the ascending wave is obtained from repeated measurements. and horizontal component upward wave

[0009] 3) Design a sliding time window, with a window size six times the period of the source wavelet;

[0010] 4) Extract the corresponding two seismic traces from the vertical component of the basic measurement and repeated measurement, calculate the time-shift cross-correlation coefficient through a sliding time window, and calculate the average velocity change caused by CO2 injection or leakage.

[0011] 5) Perform step 4) on all gathers in the vertical component of the upward wave of the basic and repeated measurements to obtain the curve of the average velocity change of the vertical component as a function of depth.

[0012] 6) Perform step 4) on all gathers in the horizontal component of the basic and repeated measurements to obtain the curve of the average velocity change of the horizontal component as a function of depth.

[0013] 7) By comprehensively comparing the obtained average velocity change curves, the depth range of velocity change caused by CO2 injection is determined, and the potential leakage risk of CO2 is predicted.

[0014] Based on the above technical solutions, the present invention also provides the following optional technical solutions:

[0015] In one alternative: In step 4), the formula for calculating the time-shift cross-correlation coefficient is:

[0016]

[0017] The time window length is 2t. w The center of the time window is located at time t, t s This represents the time shift of the repeated measurement wavefield relative to the fundamental measurement wavefield.

[0018] In one alternative approach: for fundamental measurements, the wave arrival time window t is given by the following formula:

[0019]

[0020] In one alternative approach: for monitoring measurements, assuming the velocity disturbance caused by CO2 injection is δv, then the relative velocity disturbance is... The perturbation travel is given by the following formula:

[0021]

[0022] In one alternative approach: the formula for calculating travel time variation is:

[0023]

[0024] In one alternative: the time-shifted cross-correlation coefficient R(t) s ) in t s =t max When the time reaches its maximum value, the average travel time disturbance equals the time shift, which is:

[0025]

[0026] In one alternative approach: the formula for calculating the relative velocity change for each time window is:

[0027]

[0028] In one alternative approach: the formula for calculating the average velocity change is:

[0029]

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] This invention provides a method for monitoring CO2 seismic storage across wells using multi-component time-lapse seismic data. This method boasts high computational efficiency and low cost, effectively detecting velocity changes caused by CO2 injection, indicating the depth of the CO2 injection layer, providing rapid early warning of potential CO2 leaks, and pinpointing the depth of any potential leaks. Due to its high efficiency and ease of implementation, this method offers a feasible technical means for real-time detection and long-term monitoring of CO2 storage safety. Attached Figure Description

[0032] Figure 1 This is a geological model for the basic measurements in the method of monitoring CO2 seismic seismic activity between wells using multiple components and time-lapse.

[0033] Figure 2 This is a geological model for repeated measurements after CO2 injection in a method for monitoring CO2 seismic activity across wells using multi-component time-lapse seismic monitoring.

[0034] Figure 3 This is a geological model for repeated measurements after CO2 leakage in a method for monitoring CO2 seismic leakage between wells using multi-component time-lapse seismic monitoring.

[0035] Figure 4 This refers to the vertical component seismic shot gather data used in the method of CO2 seismic monitoring for inter-well multi-component time-lapse seismic surveillance.

[0036] Figure 5 This refers to the vertical component seismic shot gather data repeatedly measured after CO2 injection in a method for CO2 seismic monitoring and CO2 seismic storage between wells using multi-component time-lapse seismic monitoring.

[0037] Figure 6This refers to the vertical component seismic shot gather data repeatedly measured after CO2 leakage in a method for monitoring CO2 seismic leakage between wells using multi-component time-lapse seismic monitoring.

[0038] Figure 7 This refers to the horizontal component seismic shot gather data used in the basic measurement of the method for CO2 seismic monitoring and storage between wells using multi-component time-lapse seismic monitoring.

[0039] Figure 8 This refers to the horizontal component seismic shot gather data repeatedly measured after CO2 injection in a method for CO2 seismic monitoring and CO2 seismic storage between wells using multi-component time-lapse seismic monitoring.

[0040] Figure 9 This refers to the horizontal component seismic shot gather data repeatedly measured after CO2 leakage in a method for monitoring CO2 seismic leakage between wells using multi-component time-lapse seismic monitoring.

[0041] Figure 10 The method for CO2 seismic seismic monitoring and CO2 seismic storage between wells is based on the up-wave wave field data obtained from the vertical component seismic shot gather data of the basic measurement through wave field separation.

[0042] Figure 11 The upflow wavefield data is obtained by wavefield separation from the vertical component seismic shot gather data repeatedly measured after CO2 injection in the method of CO2 seismic monitoring of inter-well multi-component time-lapse seismic ...

[0043] Figure 12 The upgoing wavefield data is obtained by wavefield separation from the vertical component seismic shot gather data repeatedly measured after CO2 leakage in the method of monitoring CO2 seismic storage by inter-well multi-component time-lapse seismic monitoring.

[0044] Figure 13 The up-wave field data is obtained from the horizontal component seismic shot gather data of the basic measurement through wavefield separation in the method of CO2 seismic monitoring of inter-well multi-component time-lapse seismic ...

[0045] Figure 14 The upgoing wavefield data is obtained by wavefield separation from the horizontal component seismic shot gather data repeatedly measured after CO2 injection in the method of CO2 seismic monitoring of inter-well multi-component time-lapse seismic ...

[0046] Figure 15 This refers to the upgoing wave field data obtained by wavefield separation from the horizontal component seismic shot gather data repeatedly measured after CO2 leakage in the method of monitoring CO2 seismic storage using multi-component time-lapse seismic monitoring between wells.

[0047] Figure 16 This is a curve showing the change in CO2 injection velocity with depth, calculated based on the vertical component, in a method for CO2 seismic monitoring of inter-well multi-component time-lapse seismic seismic monitoring.

[0048] Figure 17This is a curve showing the change in CO2 injection velocity with depth, calculated based on the horizontal component, in a method for CO2 seismic monitoring of inter-well multi-component time-lapse.

[0049] Figure 18 This is a curve showing the change in CO2 leakage velocity with depth, calculated based on the vertical component, in a method for monitoring CO2 seismic leakage using multi-component time-lapse seismic monitoring between wells.

[0050] Figure 19 This is a curve showing the change in CO2 leakage velocity with depth, calculated based on the horizontal component, in a method for monitoring CO2 seismic leakage using multi-component time-lapse seismic monitoring between wells. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0052] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0053] like Figure 1-19 As shown, a method for CO2 seismic monitoring and seismic storage between wells, provided in one embodiment of the present invention, includes the following steps:

[0054] 1) Seismic data obtained through conventional seismic data processing, including basic measurements and repeat measurements, are u b and u r The vertical and horizontal components of the basic measurement are respectively and The vertical and horizontal components of the repeated measurements are respectively and

[0055] 2) After wavefield separation and time-shifted seismic data processing, the vertical component of the ascending wave is obtained from the base measurements. and horizontal component upward wave The vertical component of the ascending wave is obtained from repeated measurements. and horizontal component upward wave

[0056] 3) Design a sliding time window, with a window size six times the period of the source wavelet;

[0057] 4) Extract two corresponding seismic traces from the vertical component of the ascending waves of the basic and repeated measurements, and calculate the time-shift cross-correlation coefficient using a sliding time window. The calculation formula is as follows:

[0058]

[0059] The time window length is 2t. w The center of the time window is located at time t, t s This represents the time shift of the repeated measurement wavefield relative to the fundamental measurement wavefield.

[0060] For basic measurements, the wave arrival time window t is given by the following formula:

[0061]

[0062] For monitoring and measurement, assuming the velocity disturbance caused by CO2 injection is δv, then the relative velocity disturbance is: The perturbation travel is given by the following formula:

[0063]

[0064] Further, the changes in travel time are obtained, and the calculation formula is as follows:

[0065]

[0066] That is:

[0067]

[0068] At that time, the cross-correlation coefficient R(t) s ) in t s =t max When the time reaches its maximum value, the average travel time disturbance equals the time shift, which is:

[0069]

[0070] Where τ is the average travel time disturbance of the wave arrival time window.

[0071] The formula for calculating the relative velocity change for each time window is as follows:

[0072]

[0073] The final average velocity change caused by CO2 injection or leakage is obtained by the following formula:

[0074]

[0075] 5) Perform step 4) on all gathers in the vertical component of the upward wave of the basic and repeated measurements to obtain the curve of the average velocity change of the vertical component as a function of depth.

[0076] 6) Perform step 4) on all gathers in the horizontal component of the basic and repeated measurements to obtain the curve of the average velocity change of the horizontal component as a function of depth.

[0077] 7) By comprehensively comparing the obtained average velocity change curves, the depth range of velocity change caused by CO2 injection is determined, and the potential leakage risk of CO2 is predicted.

[0078] The above embodiments of the present invention provide a method for CO2 seismic monitoring and seismic storage between wells using multi-component time-lapse seismic monitoring. Figure 1-9 Data obtained in one embodiment of the present invention, Figure 1-3 The geological models shown, depicting the time shifts before and after CO2 injection and CO2 leakage, are respectively geological models of basic measurements, repeated measurements after CO2 injection, and repeated measurements after CO2 leakage; the recorded... Figure 3-6 The data consists of vertical component seismic shot gathers, namely, the basic measurements, the repeated measurements after CO2 injection, and the repeated measurements after CO2 leakage. Figure 7-9 These are horizontal component seismic shot gather data from basic measurements, repeated measurements after CO2 injection, and repeated measurements after CO2 leakage; Figure 10-12 These are the ascending wavefield data obtained through wavefield separation from the vertical component seismic shot gather data of the basic measurements, repeated measurements after CO2 injection, and repeated measurements after CO2 leakage. Figure 13-15 These are the upgoing wavefield data obtained by wavefield separation from the horizontal component seismic shot gather data of the basic measurement, repeated measurement after CO2 injection, and repeated measurement after CO2 leakage; Figure 16 and Figure 17 It is designed for basic measurements and repeated measurements after CO2 injection. It calculates the velocity change versus depth curves based on the vertical and horizontal components, respectively. The global maximum value of the curve corresponds to the upper limit of the velocity change depth range caused by CO2 injection. By comparing and mutually constraining the results obtained from the two components, it determines the velocity change depth range caused by CO2 injection and whether there is a potential leakage risk. Figure 18 and Figure 19 This method addresses both basic measurements and repeated measurements after a CO2 leak. It calculates velocity variations as a function of depth based on both vertical and horizontal components. The global maximum value of the curve corresponds to the upper limit of the depth range of velocity variations caused by the CO2 leak. By comparing and constraining the results from the two components, the depth range of velocity variations after a CO2 leak is determined, providing an early warning of CO2 leak risks. Therefore, this invention's method for monitoring CO2 storage safety through inter-well multi-component time-lapse seismic monitoring can effectively monitor storage safety after CO2 injection and provide timely warnings of potential CO2 leak risks.

[0079] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A method of monitoring CO2 storage by cross-well multi-component time-lapse seismic, characterized in that, Includes the following steps: 1) obtaining basic measurement and repeated measurement seismic data through conventional seismic data processing, respectively and , wherein the vertical component and the horizontal component of the basic measurement are respectively and , and the vertical component and the horizontal component of the repeated measurement are respectively and ; 2) Field separation and time migration of seismic data to obtain upgoing P-wave on vertical component from base measurement and upgoing P-wave on horizontal component from base measurement upgoing P-wave on vertical component from repeat measurement and upgoing P-wave on horizontal component from repeat measurement ; 3) Design a sliding time window, with a window size six times the period of the source wavelet; 4) Extract the corresponding two seismic traces from the vertical component of the basic measurement and repeated measurement, calculate the time-shift cross-correlation coefficient through a sliding time window, and calculate the average velocity change caused by CO2 injection or leakage; 5) Perform step 4) on all gathers in the vertical component of the upward wave of the basic and repeated measurements to obtain the curve of the average velocity change of the vertical component as a function of depth. 6) Perform step 4) on all gathers in the horizontal component of the rising wave of the basic and repeated measurements to obtain the curve of the average velocity change of the horizontal component as a function of depth. 7) By comprehensively comparing the obtained average velocity change curves, determine the depth range of velocity change caused by CO2 injection, and make a prediction of the potential leakage risk of CO2.

2. The method of claim 1, wherein, In step 4), the formula for calculating the time-shift cross-correlation coefficient is: （1） where the time window length is , and the time window center is located at time , ' is the integral argument that varies within the time window, denotes the time shift of the repeated measurement wavefield relative to the base measurement wavefield.

3. The method for CO2 seismic monitoring and seismic storage between wells according to claim 2, characterized in that, For the base measurement, the time of the wave arrival time window is given by the equation: （2）。 4. The method for CO2 seismic monitoring and seismic storage between wells according to claim 3, characterized in that, For the monitoring measurements, assume that the velocity disturbance caused by the CO2 injection is The relative velocity disturbance is then The disturbance travel time is given by （3）。 5. The method of claim 4, wherein, The formula for calculating changes during travel is: （4）。 6. The method for CO2 seismic monitoring and seismic storage between wells according to claim 5, characterized in that, Time-shift cross-correlation coefficient In The maximum is reached at t = T, where the average travel-time perturbation equals the time-shift time, i.e. （5） wherein is the average travel time perturbation of the time window of wave arrival.

7. The method for CO2 seismic monitoring and seismic storage between wells according to claim 6, characterized in that, The formula for calculating the relative velocity change for each time window is as follows: （6）。 8. The method for CO2 seismic monitoring and seismic storage between wells according to claim 7, characterized in that, The formula for calculating the average velocity change is: （7）。

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