Monitoring CO2 Injection at the CaMI Field Research Station Using Microseismic Noise Sources

Abstract

AbstractMonitoring subsurface velocity variations due to industrial activities using passive seismic imaging techniques has gained popularity in recent years. In this study, we examine the spatiotemporal variations of persistent, non‐ambient seismic noise during CO2 sequestration at the Containment and Monitoring Institute Field Research Station near Brooks, Alberta, Canada. Based on the temporal migration and power spectral density (PSD) analysis of continuous seismic records from both a dense geophone array and “X”‐shaped geophone lines operated from June to August 2019, we detect two non‐ambient local noise sources correlated with the local industrial activities during the two months: a dominant noise source (1–5 Hz) southeast of the study region and a slightly weaker noise source in the higher frequency range (5–15 Hz) around the injection well. The former noise source overlaps with the operations near a submersible disposal pump. The substantial diurnal variations in noise levels in PSD as a function of time of day, month and location are further evidence of these two noise sources. We propose that the persistent noise source around the injection well originated from the subsurface microtremors caused by the coupled interaction between the injected CO2 fluid and formation rocks. The proposed methods based on passive microseismic noise offer a potentially valuable strategy for long‐term evaluation of the safety of CO2 sequestration, which can be extended to future integrity monitoring of underground energy storage.