The first pilot injection test of CO2 for geological storage in Japan was carried out by Research Institute of Innovative Technology for the Earth (RITE) in cooperation with Engineering Advancement Association of Japan (ENAA) from 2000 to 2007, targeting at onshore saline aquifer with multiple monitoring work. The CO2 injection site is located at the Minami-Nagaoka gas field in Nagaoka city, 200 km north of Tokyo. At the test site, one injection well IW-1 and three observation wells OB-2, OB-3 and OB-4 of 40 m, 60 m and 120 m away from the injection well respectively, were drilled. The supercritical state CO2 of 99.9% pure was injected at the rate of 20-40 tons per day.
The injection interval at the injection well was restricted to a 12m thick permeable zone intercalated in a 60 m thick sandstone bed of early Pleistocene age, which lies about 1,100 m below the ground surface and more than 3,000 m above the gas reservoir. The injection started on 7 July 2003 and ended on 11 January 2005 with the total injected amount of 10,400 tons within eighteen months.
A series of monitoring consisted of time-lapse well logging of very frequent at every observation wells, seven times of crosswell seismic tomography between the observations wells of OB-2 and OB-3, continuous bottom-hole pressure/temperature measurement at the injection well and observation well OB-4, and fluid sampling at the injection well and observation well OB-2 was performed before, during and after the injection along with history-matching simulation study.
Through the integrated monitoring work until the end of 2007 at Nagaoka, we came to a gateway of the intimate understanding of CO2 behavior in the deep reservoir, that is, expansion and shrink, dissolution, and chemical reaction of CO2 during and after the injection and also of long-term fate of injected CO2.