CCS reservoir monitoring using time-lapse seismic surveys

Abstract

　Japan CCS Co., Ltd. has been conducting a Carbon dioxide Capture and Storage (CCS) demonstration project in Tomakomai, Hokkaido, Japan, commissioned by the Ministry of Economy, Trade and Industry (METI) until FY2017 and by the New Energy and Industrial Technology Development Organization (NEDO) thereafter. In this project, a cumulative total of 300 kilotons of CO₂ was injected from April 2016 to November 2019, and monitoring of reservoir pressure and temperature, CO₂ behavior and distribution, seismic activity, and marine environment has been ongoing from prior to injection through to the present to confirm that the CO₂ remains stably stored underground. Time-lapse seismic surveys were conducted as part of the monitoring to understand the CO₂ behavior and distribution. The main target reservoir was a saline aquifer at a depth of approximately 1,000 m located several kilometers offshore, with the survey area having water depths ranging from less than 10 m to approximately 40 m. In data acquisition, data quality and survey geometry were critical factors, and both 2D and 3D seismic surveys were conducted to evaluate the effectiveness of each approach. In data processing, time-lapse processing was conducted using the pre-injection baseline survey and six repeat surveys acquired from the start of injection through FY2022. The surveys revealed two key findings. First, velocity decreases and amplitude changes near the reservoir were visualized due to CO₂ injection. Second, CO₂ behavior was tracked during the injection period and after completion of the 300-kiloton injection. These findings align with both reservoir simulation and synthetic wave simulation results, confirming that time-lapse seismic surveys are effective for monitoring CO₂ behavior and distribution.