Time‐lapse crosswell seismic tomography and well logging to monitor the injected CO 2 in an onshore aquifer, Nagaoka, Japan

Abstract

In comparison to the offshore location of the SACS (Saline Aquifer Storage) project, the Japanese Nagaoka project undertaken by RITE and ENAA looks at the geophysical monitoring of injection in an onshore saline aquifer. The was injected into a thin permeable zone of the reservoir at 20–40 tonnes per day. The injection started on July 2003 and ended on January 2005. The total amount of injected is about 10,400 tonnes. The pilot‐scale demonstration allowed an improved understanding of the movement in a porous sandstone reservoir. The results of time‐lapse crosswell seismic tomography indicate an area of P‐wave velocity decrease possibly due to saturation, and the zone near the injection well expanded clearly along the formation up dip direction during injection. The presence of was also identified by induction, sonic and neutron logging at the observation wells. The time‐lapse crosswell survey can provide valuable insight into the movement within porous sandstone reservoirs. There is no any leakage from the reservoir, even a huge earthquake (M6.8) hit the Mid‐Niigata area on October 23, 2004. Distance between the earthquake epicenter and the injection site is about 20 kms.