Joint monitoring of CO2-ECBM based on multiple geophysical methods: A case study of Shizhuang Town, Shanxi Province, China

Abstract

Among CCUS methods, carbon dioxide-enhanced coalbed methane (CO2-ECBM) is one of the most important applications. The CO2 migration range in the reservoir and impact on the fractures are the keys to safe storage. Multiple geophysical methods of time-lapse DAS-VSP, passive microseismic, and InSAR have been taken to monitor the CO2-ECBM project in Shizhuang Town, Shanxi Province, China. The time-lapse DAS-VSP technology captures the changes of seismic amplitude due to CO2 injection. Three phases of passive microseismic monitoring detected 217 microseismic events and 48 earthquakes. Based on the distribution of the microseismic events, the CO2 migration direction was inferred to be northeast of the injection well. A quantitative calculation method for the impact of natural earthquakes on the storage site was proposed. Studies on the relationship between microseismicity and earthquakes suggest that natural earthquakes do not significantly affect CO2 storage in the study area. InSAR combined unmanned aerial vehicle (UAV) photography measurement technology obtained the surface deformation results with a maximum displacement of 21 mm. The surface deformation also shows CO2 migration in a northeast direction, consistent with microseismic results. Finally, in order to verify the monitoring results of the above methods, the gas detection in the production well around the injection site was analyzed. The analysis results show that the primary direction of CO2 migration in the study area is the northeast direction, followed by the east direction. These geophysical techniques validate the accuracy of the monitoring results and provide new technical support for future CCUS projects.