Post-Injection monitoring of stored CO2 at the Nagaoka pilot site: 5 years time-lapse well logging results.

Abstract: Monitoring is the major challenge in CO₂ geological sequestration. At the first Japanese pilot CO₂ injection site (Nagaoka), CO₂ was injected into a thin permeable zone at a depth of 1100 m and the total amount of injected CO₂ was 10,400 tons during the injection period from July 2003 to January 2005. After ceasing of CO₂ 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 CO₂ behaviour in a saline aquifer. In this paper reports the results of formation pressure, well logging and fluid sampling aiming to improve understanding of CO₂ 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 CO₂ is stored safely in a complex sandstone reservoir. [Copyright &y& Elsevier]