A method for monitoring carbon dioxide leakage in geological storage bodies

Abstract

The present invention discloses a method for monitoring carbon dioxide leakage in a geological storage body. The method comprises: setting a monitoring mechanism in the upper cover layer of the geological storage body, collecting carbon dioxide gas through the monitoring mechanism, and detecting the carbon dioxide gas in the gas. 13 C result, and compare the result value with the carbon dioxide injected into the injection well. 13 C detection results are compared. If the two are equal, it indicates that there is leakage; then the real-time observation data of carbon dioxide is monitored, and the disturbance data of the real-time observation data of carbon dioxide within a certain period of time is obtained by using the moving average method. The strength of carbon dioxide leakage is judged according to the peak value in the disturbance data. The larger the peak value, the greater the leakage intensity. The present invention can realize quantitative judgment of whether the carbon dioxide leakage event is continuous leakage or intermittent leakage based on the qualitative judgment of carbon dioxide leakage, combined with carbon dioxide disturbance data, and provide accurate guidance and favorable judgment for the safety of carbon dioxide geological storage.

Description

Technical Field

[0001] The present invention relates to the technical field of geological storage of carbon dioxide, and in particular to a method for monitoring leakage of carbon dioxide in a geological storage body. Background Art

[0002] The key issues in the safety evaluation and monitoring of carbon dioxide storage in geological bodies are how to identify the migration and enrichment status of carbon dioxide in the reservoir and how to monitor the leakage of carbon dioxide along potential fluid channels in the cap rock. These are issues that need to be solved urgently.

[0003] The current method in the field to determine whether carbon dioxide has leaked is to detect the carbon dioxide sample collected at the monitoring well. 13 The C isotope value is related to the carbon dioxide sample injected into the injection well. 13 The value of C isotope can be compared to determine whether there is a carbon dioxide leakage, but this method can only achieve qualitative analysis and cannot make a more specific quantitative judgment on the leakage situation.

[0004] It can be seen that the above existing methods for monitoring carbon dioxide leakage in geological storage bodies still have inconveniences and defects, and are in urgent need of further improvement. How to create a new method for monitoring carbon dioxide leakage in geological storage bodies, so that it can meet the quantitative judgment of carbon dioxide leakage in geological storage bodies based on qualitative analysis and combined with the disturbance data of real-time monitoring data of carbon dioxide at the monitoring well, and provide favorable support for the safety of carbon dioxide geological storage, has become a goal that the industry urgently needs to improve. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for monitoring the leakage of carbon dioxide in a geological storage body, so that on the basis of qualitative analysis, combined with the disturbance data of the real-time monitoring data of carbon dioxide at the monitoring well, it can meet the quantitative judgment of the leakage of carbon dioxide in the geological storage body, provide favorable support for the safety of carbon dioxide geological storage, thereby overcoming the shortcomings of the existing monitoring methods.

[0006] In order to solve the above technical problems, the present invention provides a method for monitoring carbon dioxide leakage in a geological storage body, the method comprising the following steps:

[0007] (1) A monitoring mechanism is set up in the cap layer above the geological storage body to collect carbon dioxide gas through the monitoring mechanism and detect the collected gas 13 The result of Cδ 13 C 监测孔 , and compare the result with the carbon dioxide injected into the injection well. 13 C test result value δ 13 C 注入井 For comparison, if δ 13 C 注入井 =δ13 C 监测孔 , indicating that there is a carbon dioxide leak, proceed to step (2);

[0008] (2) The real-time observation data of carbon dioxide is monitored by the monitoring agency, and the disturbance data of the real-time observation data of carbon dioxide within a certain period of time is obtained by using the moving average method. The strength of the carbon dioxide leakage is judged according to the peak value in the disturbance data. The larger the peak value, the greater the leakage intensity.

[0009] As a further improvement, step (2) also includes the step of performing fast Fourier transform processing on the obtained disturbance data to obtain carbon dioxide spectrum data in the corresponding time period, and intuitively judging the strength of the leakage according to the energy spectrum density in the spectrum data. The greater the energy spectrum density, the greater the leakage intensity, indicating the presence of continuous leakage events.

[0010] Further improvement, the method for obtaining the disturbance data in step (2) is:

[0011] First, the obtained carbon dioxide real-time observation data sequence is processed into a smooth data sequence using the moving average method. The mathematical expression of the moving average method is:

[0012]

[0013] Where Smoothed(i) is the value of the i-th point after smoothing, Original(j) is the value of the j-th point in the original data, and n is the size of the window, that is, the number of data points involved in the averaging operation;

[0014] Secondly, the smoothed data sequence is subtracted from the original data sequence to obtain the disturbance data in the corresponding time period.

[0015] Further improvement, the mathematical expression of the fast Fourier transform processing in step (2) is

[0016]

[0017] Where f(n) is the time domain signal, F(k) is the frequency domain representation, N is the signal length, is the rotation factor.

[0018] Further improvement, the monitoring mechanism includes an isolation sleeve, a one-way valve, a gas drying container and a thermal infrared carbon dioxide gas observation instrument connected in sequence, the isolation sleeve is inserted into the drill hole on the upper part of the geological burial body, and the one-way valve, gas drying container and thermal infrared carbon dioxide gas observation instrument are all connected by a ventilation hose.

[0019] As a further improvement, the lower end of the isolation casing is close to the geological fault on the upper part of the geological burial body.

[0020] As a further improvement, the gas drying container is a glass container containing a silicon dioxide desiccant.

[0021] As a further improvement, a three-way valve is also provided on the ventilation hose connecting the gas drying container and the thermal infrared carbon dioxide gas observation instrument, and the third port of the three-way valve is used to connect to the carbon dioxide collection bottle.

[0022] After adopting such a design, the present invention has at least the following advantages:

[0023] The method for monitoring the leakage of carbon dioxide in a geological storage body of the present invention firstly measures the carbon dioxide gas at the monitoring well. 13 C detection can qualitatively judge the leakage of carbon dioxide, and then combine the real-time monitoring data of carbon dioxide to quantitatively judge the strength of carbon dioxide leakage according to its disturbance data, providing favorable support for the quantitative judgment of carbon dioxide leakage in geological storage bodies. The carbon dioxide spectrum data obtained from the disturbance data can also more intuitively reflect the quantitative leakage of carbon dioxide, whether it is a continuous leakage event or an intermittent leakage event, and further provide accurate guidance and favorable judgment for the safety of carbon dioxide geological storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0025] Figure 1 It is a structural schematic diagram of the method for monitoring carbon dioxide leakage in a geological storage body according to the present invention.

[0026] Figure 2 : It is the real-time observation data, sliding average data and disturbance data curve of carbon dioxide in the corresponding period of the embodiment of the present invention. Among them, the blue line represents the original actual observation data (unit ppm), the red line represents the calculated sliding average data, and the black line represents the calculated real-time disturbance data.

[0027] Figure 3 It is the carbon dioxide disturbance data and its corresponding spectrum diagram for the corresponding period of time in the embodiment of the present invention. DETAILED DESCRIPTION

[0028] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to enable the scope of the present invention to be fully communicated to those skilled in the art.

[0029] In this embodiment, a monitoring mechanism is first set on the surface of the cap layer above the geological storage body to collect and monitor carbon dioxide gas. Figure 1 shown.

[0030] The monitoring mechanism described in this embodiment includes an isolation sleeve 1, a one-way valve 2, a gas drying container 3 and a thermal infrared carbon dioxide gas observation instrument 4 which are connected in sequence. The isolation sleeve 1 is inserted into the borehole at the upper part of the geological burial body 10, and the one-way valve 2, the gas drying container 3 and the thermal infrared carbon dioxide gas observation instrument 4 are all connected through a ventilation hose 5. A three-way valve 6 is also provided on the ventilation hose 5 connecting the gas drying container 3 and the thermal infrared carbon dioxide gas observation instrument 4, and the third port of the three-way valve 6 is used to connect a carbon dioxide collection bottle 7. In this way, through the isolation sleeve 1, the one-way valve 2, the gas drying container 3, the three-way valve 6 and the thermal infrared carbon dioxide gas observation instrument 4, real-time monitoring of carbon dioxide gas overflowing from the borehole can be achieved. And through the isolation sleeve 1, the one-way valve 2, the gas drying container 3, the three-way valve 6 and the carbon dioxide collection bottle 7, the collection of carbon dioxide gas overflowing from the borehole can be achieved, which is used to collect carbon dioxide gas. 13 C Determination of results.

[0031] In a preferred embodiment, the lower end of the isolation casing 1 is close to the geological fault 11 on the upper part of the geological storage body 10, so as to more accurately collect and monitor the carbon dioxide gas leaking from the carbon dioxide storage body 10. In addition, the isolation casing 1 can block the carbon dioxide gas in the shallow soil from entering the borehole, thereby avoiding errors in the monitoring results.

[0032] In this embodiment, the one-way valve 2 only allows carbon dioxide gas to be discharged from the borehole to the outside, and prevents carbon dioxide in the atmosphere outside the borehole from entering from the outside to the inside. The gas drying container 3 is a glass container containing a silica desiccant to dry the overflowed carbon dioxide gas and complete collection and real-time monitoring.

[0033] The method for monitoring carbon dioxide leakage in a geological storage body of the present invention comprises the following steps:

[0034] (1) Collect carbon dioxide gas through the above-mentioned monitoring mechanism and detect the collected gas 13 The result of Cδ 13 C 监测孔 The result is compared with the carbon dioxide injected into the injection well. 13 C test result value δ 13 C 注入井 For comparison, if δ 13 C 注入井 =δ 13 C 监测孔 , indicating that there is a carbon dioxide leak, and the qualitative analysis of carbon dioxide leakage is completed; if δ13 C 注入井 ≠δ 13 C 监测孔 , indicating that there is no carbon dioxide leakage, and the monitoring is completed;

[0035] (2) On the basis of the conclusion that there is a carbon dioxide leakage, the real-time observation data of carbon dioxide is detected by the thermal infrared carbon dioxide gas observation instrument 4 of the monitoring agency in real time, and the disturbance data of the real-time observation data of carbon dioxide within a certain period of time is obtained by using the moving average method. The strength of the carbon dioxide leakage is judged according to the peak value in the disturbance data. The larger the peak value, the greater the leakage intensity, thereby achieving a quantitative judgment of the carbon dioxide leakage.

[0036] The method for obtaining disturbance data is as follows:

[0037] First, the real-time observation data sequence of carbon dioxide is processed into a smooth data sequence using the moving average method. Specifically, a row of temperature data of the time series is taken out, and the mean of several consecutive points in the data sequence is calculated to reduce the noise in the data, smooth the curve and highlight the trend. The mathematical expression of the moving average method is:

[0038]

[0039] Among them, Smoothed(i) is the value of the i-th point after smoothing, Original(j) is the value of the j-th point in the original data, and n is the size of the window, that is, the number of data points involved in the averaging operation.

[0040] Secondly, the original data sequence is subtracted from the smoothed data sequence to obtain the disturbance data in the corresponding period, as shown in the attached figure. Figure 2 The specific calculation formula is:

[0041] f(i)=Original(i)-Smoothed(i) (2)

[0042] Figure 2 The blue line represents the original actual observation data (unit: ppm), the red line represents the calculated sliding average data, and the black line represents the calculated real-time disturbance data. Figure 2 It can be seen from the disturbance data curve that a large peak appeared when the monitoring time was late May 2018, indicating that the leakage intensity was large during this period and continuous leakage incidents occurred, which required attention and corresponding treatment.

[0043] A more preferred embodiment is that the above step (2) further includes the step of performing fast Fourier transform processing on the obtained disturbance data to obtain the carbon dioxide spectrum data in the corresponding time period, as shown in the attached Figure 3 As shown. The specific mathematical expression of fast Fourier transform processing is:

[0044]

[0045] Where f(n) is the time domain signal, F(k) is the frequency domain representation, N is the signal length, is the rotation factor.

[0046] The strength of the leakage can be intuitively judged based on the energy spectrum density in the obtained spectrum data. The larger the energy spectrum density, the greater the leakage intensity, indicating the existence of continuous leakage events.

[0047] Figure 3 The upper middle figure is the carbon dioxide disturbance data curve, and the lower figure is the spectrum image obtained from the carbon dioxide disturbance data. Figure 3 From the CO2 spectrum image in the monitoring period of late May 2018, the energy spectrum density was continuously high (all red) in the full frequency range (such as 0-250HZ), indicating that there were continuous leakage events, which is the same conclusion as the above disturbance data, but this judgment method is more intuitive and accurate. If the energy spectrum density is high and low in the CO2 spectrum image, it indicates that there is an intermittent leakage event, which needs to be paid attention to.

[0048] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Those skilled in the art may make some simple modifications, equivalent changes or modifications using the technical contents disclosed above, which all fall within the protection scope of the present invention.

Claims

1. A method for monitoring carbon dioxide leakage in a geological storage body, characterized in that: The method comprises the following steps: (1) A monitoring mechanism is set up in the cap layer above the geological storage body to collect carbon dioxide gas through the monitoring mechanism and detect the collected gas 13 The result of Cδ 13 C 监测孔 , and compare the result with the carbon dioxide injected into the injection well. 13 C test result value δ 13 C 注入井 For comparison, if δ 13 C 注入井 =δ 13 C 监测孔 , indicating that there is a carbon dioxide leak, proceed to step (2); (2) The real-time observation data of carbon dioxide is monitored by the monitoring agency, and the disturbance data of the real-time observation data of carbon dioxide within a certain period of time is obtained by using the moving average method. The strength of the carbon dioxide leakage is judged according to the peak value in the disturbance data. The larger the peak value, the greater the leakage intensity; The method also includes the step of performing fast Fourier transform processing on the obtained disturbance data to obtain the carbon dioxide spectrum data in the corresponding time period, and intuitively judging the strength of the leakage according to the energy spectrum density in the spectrum data. The greater the energy spectrum density, the greater the leakage intensity, indicating the existence of continuous leakage events. The method for obtaining disturbance data is as follows: First, the obtained carbon dioxide real-time observation data sequence is processed into a smooth data sequence using the moving average method. The mathematical expression of the moving average method is: Where Smoothed(i) is the value of the i-th point after smoothing, Original(j) is the value of the j-th point in the original data, and n is the size of the window, that is, the number of data points involved in the averaging operation; Secondly, the smoothed data sequence is subtracted from the original data sequence to obtain the disturbance data in the corresponding time period; The mathematical expression of fast Fourier transform processing is Where f(n) is the time domain signal, F(k) is the frequency domain representation, N is the signal length, is the rotation factor; The monitoring mechanism includes an isolation sleeve, a one-way valve, a gas drying container and a thermal infrared carbon dioxide gas observation instrument which are connected in sequence. The isolation sleeve is inserted into a borehole at the top of a geological burial body. The one-way valve, the gas drying container and the thermal infrared carbon dioxide gas observation instrument are all connected via a ventilation hose. The lower end of the isolation sleeve is close to a geological fault at the top of the geological burial body. The gas drying container is a glass container containing a silica desiccant.

2. The method for monitoring carbon dioxide leakage in a geological storage body according to claim 1, characterized in that: A three-way valve is also provided on the ventilation hose connecting the gas drying container and the thermal infrared carbon dioxide gas observation instrument, and the third port of the three-way valve is used to connect the carbon dioxide collection bottle.

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