Carbon dioxide plume monitoring-based carbon sequestration site safety assessment method

Abstract

The invention discloses a carbon dioxide plume monitoring-based carbon sequestration site safety assessment method. The method comprises the steps of obtaining monitoring data of each region in a carbon sequestration site in real time; monitoring data are stored in a monitoring database; when one kind of monitoring data obtained at the current monitoring moment is compared with the same kind of monitoring data at the previous monitoring moment, and the fluctuation amplitude exceeds a threshold value, the migration speed data are compared; if the migration speed data are the same, judging whether most of the other types of monitoring data do not fluctuate greatly, considering that the site is possibly abnormal when judging that most of the other types of monitoring data fluctuate greatly and the migration speed data obtained in the previous step is different, and entering the next step; acquiring permeability, porosity and bursting pressure data of the corresponding area at the current monitoring moment, judging whether the data are in a normal range or not, considering that potential safety hazards exist in the field when the data are not in the normal range, and giving an alarm. According to the invention, the site safety can be rapidly and timely evaluated accurately, the energy consumption is low, and the method is suitable for popularization.

Description

Technical Field

[0001] The present invention relates to a method for safety assessment of a carbon sequestration site based on carbon dioxide plume monitoring, belonging to the technical field of safety assessment of carbon sequestration sites. Background Art

[0002] Carbon dioxide sequestration is an important technology that captures CO2 emitted from industries and stores it in geological formations for a long time to reduce the concentration of atmospheric greenhouse gases and mitigate climate change. It can not only directly reduce carbon emissions from fossil energy and industrial processes, but also provide a carbon emission reduction path for high-emission industries (such as steel, cement, etc.) before renewable energy completely replaces them.

[0003] In actual implementation, after CO2 is injected and sequestered, it is necessary to conduct long-term assessment and monitoring of the safety of the carbon sequestration site to ensure the sequestration effect, prevent leakage risks, and estimate the impact on the environment. The existing safety assessment method is to deploy sensors for monitoring various geological parameters at the site. The geological parameters mainly involve pressure, microseismic waves, temperature and humidity, permeability, porosity, fracture pressure, and reservoir geochemical parameters (major ions, pH, alkalinity, stable isotopes, gas components, etc. of underground fluid samples), etc. Data is collected in real time through various types of sensors to achieve real-time monitoring of the site, so as to evaluate the safety of the site. It can be seen from the actual implementation that this method is simple and reliable, but there are the following defects: First, a large variety of sensors are required, with a large number. Each sensor needs to be monitored simultaneously, the data transmission frequency is high, and the energy consumption is large. Second, complex calculation and analysis of the monitoring data obtained by each sensor are required to make a safety assessment. The calculation and analysis process is cumbersome, and the assessment cannot be made quickly and timely. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for safety assessment of a carbon sequestration site based on carbon dioxide plume monitoring, which can quickly and timely make an accurate assessment of the safety of the carbon sequestration site, with low energy consumption, economic and environmental protection, and is suitable for popularization.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions: A method for safety assessment of a carbon sequestration site based on carbon dioxide plume monitoring, comprising the steps of: 1) Obtain the monitoring data of each area in the carbon sequestration site in real time. The monitoring data is the spatial distribution data and migration speed data of the carbon dioxide plume, as well as pressure data, microseismic wave data, humidity data, and temperature data. Among them, the carbon sequestration site is divided into several such areas; 2) Store the monitoring data obtained for each of the regions into a monitoring database according to the monitoring time. Among them, the monitoring data obtained at each monitoring time is recorded in units of the regions, and the monitoring data is arranged in the order of the monitoring time. 3) When the fluctuation amplitude of a certain type of monitoring data obtained at the current monitoring time exceeds the threshold compared with the same type of monitoring data obtained at the previous monitoring time, compare the migration speed data obtained at the current monitoring time with that at the previous monitoring time, where: if the migration speed data obtained at the current monitoring time is different from that at the previous monitoring time, it is considered that there may be an abnormality, and go to step 5); otherwise, go to step 4). 4) If the fluctuation of more than 80% of the monitoring data among other types of monitoring data obtained at the current monitoring time and the previous monitoring time is less than 10%, perform elimination processing on the monitoring data with a fluctuation amplitude exceeding the threshold in step 3), consider that the other monitoring data except the eliminated monitoring data at the current monitoring time are normal, store them in the monitoring database, and return to step 1); otherwise, it is considered that there may be an abnormality, and go to step 5). 5) Obtain the permeability, porosity, and fracture pressure data of the region corresponding to the monitoring data with a fluctuation amplitude exceeding the threshold at the current monitoring time. 6) If the permeability, porosity, and fracture pressure data are not within the normal range, it is considered that there is a safety hazard in the carbon sequestration site, and an alarm is issued; otherwise, it is considered that the carbon sequestration site is safe. 7) The evaluation is completed.

[0006] The advantages of the present invention are as follows: 1. The present invention introduces the monitoring of carbon dioxide plume information, which can timely detect abnormal migration of the geology of the carbon sequestration site, greatly reduces the types of sensors used, reduces the number of sensors, avoids high-frequency data transmission by a large number of sensors, greatly reduces energy consumption, improves feasibility and reduces costs.

[0007] 2. The present invention does not require complex calculations and analyses of the monitoring data obtained by each sensor, greatly simplifies the safety assessment process, and can quickly, timely, and accurately obtain the safety assessment results. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is the implementation flowchart of the safety assessment method for a carbon sequestration site based on carbon dioxide plume monitoring of the present invention.

[0009] Figure 2 is an example of the list of monitoring data stored in the monitoring database. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0010] Such as Figure 1, the present invention provides a method for safety assessment of a carbon sequestration site based on carbon dioxide plume monitoring, comprising the following steps: 1) Real-time obtain the monitoring data of each area within the carbon sequestration site. The monitoring data includes the spatial distribution data and migration velocity data of the carbon dioxide plume, as well as pressure data, microseismic wave data, humidity data, and temperature data. Among them, the carbon sequestration site is divided into several areas; 2) To improve the data processing efficiency and facilitate subsequent comparison, etc., according to the monitoring time (for example, monitoring once every 20 s), store the monitoring data obtained for each area into the monitoring database. Among them, record the monitoring data obtained at each monitoring time in units of areas, and the monitoring data is arranged in the order of the monitoring time; 3) When the fluctuation amplitude of a certain type of monitoring data obtained at the current monitoring time exceeds the threshold compared with the same type of monitoring data obtained at the previous monitoring time, compare the migration velocity data obtained at the current monitoring time with that obtained at the previous monitoring time. Among them: If the migration velocity data obtained at the current monitoring time is different from that obtained at the previous monitoring time, it is considered that there may be an abnormality, and go to step 5); Otherwise, if the migration velocity data obtained at the current monitoring time is the same as that obtained at the previous monitoring time, go to step 4); 4) If the fluctuation of more than 80% of the monitoring data among other types of monitoring data obtained at the current monitoring time and the previous monitoring time is less than 10%, then perform elimination processing on the monitoring data with a fluctuation amplitude exceeding the threshold in step 3), and consider that the other monitoring data except the eliminated monitoring data at the current monitoring time are all normal, store them in the monitoring database, and return to step 1); Otherwise, it is considered that there may be an abnormality, and go to step 5); 5) Obtain the permeability, porosity, and fracture pressure data of the area corresponding to the monitoring data with a fluctuation amplitude exceeding the threshold at the current monitoring time; 6) If the permeability, porosity, and fracture pressure data are not within the normal range, it is considered that there is a safety hazard in the carbon sequestration site, and an alarm is issued; otherwise, it is considered that the carbon sequestration site is safe; 7) The assessment ends.

[0011] In actual implementation, the present invention further includes completing the layout of various types of sensors in each area of the carbon sequestration site before step 1).

[0012] In step 1), the pressure data, microseismic wave data, humidity data, temperature data, spatial distribution data, and migration velocity data of the carbon dioxide plume are obtained through a pressure sensor, a microseismic wave detector, a humidity sensor, a temperature sensor, a distributed acoustic sensor, and a gas chromatograph respectively. Among them, the migration velocity data of the carbon dioxide plume is obtained by injecting a tracer into the carbon sequestration site before or during the injection of carbon dioxide, and then tracking the tracer by means of a gas chromatograph.

[0013] For step 2), the monitoring data in the monitoring database can be stored in the form of a list. As shown in the example Figure 2 below, the monitoring data for each region is stored independently, and the monitoring data for each region is arranged in sequence according to the monitoring time.

[0014] For the same type of sensor, at least one is deployed in each region. Among them: when multiple sensors of the same type are deployed in a region, the sensors are evenly distributed within the region, and the average value of the monitoring data obtained by each sensor is used as the monitoring data of this type in this region.

[0015] In the present invention, sensors of various types are deployed in each region of the carbon sequestration site to monitor the monitoring data of various types. When multiple sensors of the same type are deployed in a region, for example, if 3 pressure sensors are deployed in each region, then for any region, the 3 pressure sensors are evenly distributed, and the average value of the pressure data obtained by the 3 pressure sensors at the same monitoring time is used as the pressure data obtained by this region at this monitoring time.

[0016] In the present invention, the pressure data, microseismic wave data, humidity data, temperature data, spatial distribution data and migration speed data of the carbon dioxide plume are 6 different types of monitoring data.

[0017] In the present invention, the monitoring database is not only used to compare the monitoring data obtained before and after monitoring, which is conducive to quickly identifying abnormal data, but also can completely record the monitoring data of the carbon sequestration site. When carbon dioxide leaks, historical data can be traced quickly to find the cause quickly. In addition, it can also provide data support for the subsequent optimization of the construction of the carbon sequestration site.

[0018] In the actual design, the above threshold is designed to be 10%-20%.

[0019] In step 3), when judging the fluctuation range of the same type of monitoring data monitored at the current monitoring time and the previous monitoring time, it should be reasonably designed according to the type of monitoring data. For example, when judging the pressure data, the threshold can be set to 15%, that is, it should be judged whether the fluctuation of the pressure data obtained at the current monitoring time exceeds 15% of the pressure data obtained at the previous monitoring time. Another example is that when judging the temperature data, the threshold can be set to 20%, that is, it should be judged whether the fluctuation of the temperature data obtained at the current monitoring time exceeds 20% of the temperature data obtained at the previous monitoring time.

[0020] The prerequisite for implementing step 4) is that if the monitoring data of the same type obtained at the current monitoring moment and the previous monitoring moment has a fluctuation amplitude exceeding the threshold but the migration speed data remains unchanged, then step 4) needs to be further executed to judge the magnitude of the fluctuation amplitude of other monitoring data. In step 4), by comparing the current monitoring moment with the previous monitoring moment, it is necessary to judge whether 80% of the monitoring data among other types of monitoring data has fluctuated by less than 10%. If so, it is considered that the current monitoring is normal, and only the monitoring data with a fluctuation amplitude exceeding the threshold needs to be removed.

[0021] In actual implementation, when the monitoring data of a certain type changes significantly, if the geological conditions of the carbon sequestration site have really changed, it is very likely to affect the carbon dioxide sequestration, then it will inevitably cause synchronous changes in the monitoring data of other types. However, if only the monitoring data of this type changes significantly while the monitoring data of other types does not change synchronously, it is very likely that the sensor used to monitor the monitoring data of this type has a malfunction or error. Therefore, it is necessary to remove the abnormal data in this situation.

[0022] In the present invention, the key to judging whether the geological conditions of the carbon sequestration site have changed is the migration speed of the carbon dioxide plume. This is because once the geological conditions of the carbon sequestration site change in a way that affects carbon dioxide sequestration, the migration speed of the carbon dioxide plume will inevitably change, and the change is obvious and lasts for a long time. Therefore, it is primary to monitor whether the migration speed changes. By monitoring whether the migration speed data changes, it is possible to judge whether the geological conditions have changed more quickly and truly.

[0023] That is to say, in view of the fact that the plume phenomenon of carbon dioxide always exists during the sequestration process, the present invention innovatively introduces the monitoring of carbon dioxide plume information. By monitoring the stability of the plume phenomenon, the change of the site geological conditions is inferred. This approach not only greatly reduces the number of sensors but also ensures the accuracy and timeliness of safety assessment. Moreover, through long-term monitoring of carbon dioxide plume information, on the one hand, the stability during the operation of the carbon sequestration site can be accurately evaluated, and on the other hand, the pollution of the surrounding ecosystem and atmosphere caused by carbon dioxide leakage can be avoided.

[0024] Carbon dioxide plume monitoring is crucial in carbon sequestration technology. By tracking the migration distribution of underground CO2 in real time, it can ensure the safety and effectiveness of sequestration. The relevant data of carbon dioxide plume monitoring can be used to timely detect the risk of CO2 leakage, prevent it from polluting groundwater or escaping into the atmosphere, and ensure environmental safety.

[0025] In step 3), the elimination process for the monitoring data with a fluctuation amplitude exceeding the threshold is to use the same type of monitoring data at the previous monitoring moment for substitution, so as to achieve the elimination of abnormal data.

[0026] For step 5), in the carbon dioxide geological sequestration project, the real-time acquisition of geological parameters such as permeability, porosity, and fracture pressure is a key link to ensure the safety of carbon sequestration. Among them: permeability determines the migration ability of CO2 in the reservoir. A high permeability means a greater risk of carbon dioxide leakage; porosity is used to measure the carbon dioxide storage capacity in the rock. The larger the porosity, the greater the carbon sequestration volume, which also means a greater risk of carbon dioxide leakage; fracture pressure is used to reflect the maximum pressure that the caprock of the carbon sequestration site can withstand. If the fracture pressure exceeds the predetermined value, it indicates that there are fissures in the caprock, meaning there is a risk of carbon dioxide leakage.

[0027] In step 6), if the carbon sequestration site is considered to have potential safety hazards, the geological bodies that can be repaired within the investigation area are repaired (such as the fissures in the building layer caused by natural geological movement), otherwise no intervention is carried out. Among them, the area corresponding to the monitoring data with a fluctuation amplitude exceeding the threshold is used as the said investigation area.

[0028] In actual implementation, the repair can be carried out by means of remotely controlled robots. The repair materials are made outside the site and transported into the site, and then the robots are used to repair the inner wall fissures.

[0029] The advantages of the present invention are as follows: 1. The present invention introduces the monitoring of carbon dioxide plume information, which can timely detect abnormal migration of the geology of the carbon sequestration site, greatly reduces the types of sensors used, reduces the number of sensors, avoids high-frequency data transmission by a large number of sensors, greatly reduces energy consumption, improves feasibility and reduces costs.

[0030] 2. The present invention does not need to perform complex calculations and analyses on the monitoring data obtained by each sensor, greatly simplifies the safety assessment process, and can quickly, timely and accurately obtain the safety assessment results.

[0031] The above is the preferred embodiment of the present invention and the technical principles applied. For those skilled in the art, any obvious changes such as equivalent transformation and simple substitution based on the technical solution of the present invention without departing from the spirit and scope of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for safety assessment of a carbon sequestration site based on carbon dioxide plume monitoring, characterized in that, Including the steps: 1) Obtain in real time the monitoring data of each area within the carbon sequestration site. The monitoring data includes the spatial distribution data and migration speed data of the carbon dioxide plume, as well as pressure data, microseismic wave data, humidity data, and temperature data. Among them, the carbon sequestration site is divided into several such areas; 2) Store the monitoring data obtained for each area according to the monitoring time into the monitoring database. Among them, the monitoring data obtained at each monitoring time is recorded in units of the area, and the monitoring data is arranged in the order of the monitoring time; 3) When the fluctuation amplitude of a certain type of monitoring data obtained at the current monitoring time exceeds the threshold compared with the same type of monitoring data obtained at the previous monitoring time, compare the migration speed data obtained at the current monitoring time and the previous monitoring time. Among them: If the migration speed data obtained at the current monitoring time is different from that obtained at the previous monitoring time, it is considered that there may be an abnormality, and go to step 5); otherwise, go to step 4); 4) If the fluctuation of more than 80% of the monitoring data among the other types of monitoring data obtained at the current monitoring time and the previous monitoring time is less than 10%, perform elimination processing on the monitoring data with a fluctuation amplitude exceeding the threshold in step 3). It is considered that the other monitoring data except the eliminated monitoring data at the current monitoring time are normal, store them in the monitoring database, and return to step 1); otherwise, it is considered that there may be an abnormality, and go to step 5); 5) Obtain the permeability, porosity, and fracture pressure data of the area corresponding to the monitoring data with a fluctuation amplitude exceeding the threshold at the current monitoring time; 6) If the permeability, porosity, and fracture pressure data are not within the normal range, it is considered that there is a safety hazard in the carbon sequestration site, and an alarm is issued; otherwise, it is considered that the carbon sequestration site is safe; 7) The evaluation ends.

2. The method for safety assessment of a carbon sequestration site based on carbon dioxide plume monitoring according to claim 1, wherein, In step 1), the pressure data, the microseismic wave data, the humidity data, the temperature data, the spatial distribution data of the carbon dioxide plume, and the migration speed data are obtained through a pressure sensor, a microseismic wave detector, a humidity sensor, a temperature sensor, a distributed acoustic sensor, and a gas chromatograph respectively. Among them, the migration speed data of the carbon dioxide plume is obtained by injecting a tracer into the carbon sequestration site before or during the injection of carbon dioxide, and then tracking the tracer by the gas chromatograph.

3. The method for safety assessment of a carbon sequestration site based on carbon dioxide plume monitoring according to claim 2, wherein, For sensors of the same type, at least one is arranged in each area. Among them: When multiple sensors of the same type are arranged in an area, the sensors are evenly distributed in the area, and the average value of the monitoring data obtained by each sensor is used as the monitoring data of this type in the area.

4. The method for safety assessment of a carbon sequestration site based on carbon dioxide plume monitoring according to claim 1, wherein, The threshold is 10%-20%.

5. The safety assessment method for carbon sequestration sites based on carbon dioxide plume monitoring according to claim 1, wherein, In step 3), the elimination processing of the monitoring data with a fluctuation amplitude exceeding the threshold is to use the same type of monitoring data at the previous monitoring time to replace it.

6. The method for safety assessment of a carbon sequestration site based on carbon dioxide plume monitoring according to claim 1, wherein In step 6), if the carbon sequestration site is considered to have potential safety hazards, the geological bodies within the investigation area that can be repaired are repaired, otherwise no intervention is carried out. Among them, the area corresponding to the monitoring data with a fluctuation amplitude exceeding the threshold is used as the investigation area.

7. The method for safety assessment of a carbon sequestration site based on carbon dioxide plume monitoring according to claim 6, wherein The repair is carried out by means of a remotely operated robot. The repair materials are made outside the site and transported into the site, and then the robot is used to repair the inner wall cracks.

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