Post-Injection Monitoring of Stored CO_2 at the Nagaoka Pilot Site: 5 Years Time-Lapse Well Logging Results

摘要

Monitoring is the major challenge in CO_2 geological sequestration. At the first Japanese pilot CO_2 injection site (Nagaoka), CO_2 was injected into a thin permeable zone at a depth of 1100 m and the total amount of injected CO_2 was 10,400 tons during the injection period from July 2003 to January 2005. After ceasing of CO_2 injection, well loggings which mainly consist of neutron logging, sonic logging and induction logging have been continued for 5 years. The Nagaoka site may provide the first field data set of post-injection monitoring and essential information on long-term CO_2 behaviour in a saline aquifer. In this paper reports the results of formation pressure, well logging and fluid sampling aiming to improve understanding of CO_2 long term behaviour in the reservoir. The results of time-laps well logging provide the evidences of the solubility trap and residual trap in progress at Nagaoka, suggesting CO_2 is stored safely in a complex sandstone reservoir.