Time-Lapse Monitoring Using a Permanent Source ACROSS and Surface-Buried Geophones at the Aquistore CO2 Storage Site.

Abstract

Summary We demonstrate the effectiveness of reservoir monitoring using a permanent seismic source (accurately controlled, routinely operated signal system: ACROSS), and a sparse areal permanent array of buried geophones at the Aquistore CO₂ storage site. Since 2016, monitoring surveys have been conducted 4 times. Before real data analysis, a modeling study using a single source and a sparse array that matched the actual field geometry shows that our monitoring system can detect physical response changes despite the areal imaging distortion. By applying time-lapse processing and analysis to the field data, high NRMS amplitude anomalies are detected at the reservoir depth. The location and lateral growth pattern of the anomalies associated with CO₂ injection are consistent with the reported results of the 3D seismic data, even though the location is shifted to the northeast direction, which is outward from the source location. The anomalies may be a sign of seismic response changes associated with CO₂ injection, although it should be noted that they tend to be located outward from the source location as observed in the modeling study. Even though this monitoring system cannot bring comparable results to 3D seismic surveys, there is a way to use it for low-cost surveillance.