Abstract
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Time Lapse Well Logging to Monitor the Injected CO2 at the Nagaoka Pilot Site
¹ÆfÞ, 124, 68-77, 2008.
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A pilot-scale sequestration of CO2 into an onshore aquifer has been conducted
by Research Institute of Innovative Technology for the Earth (RITE) in
cooperation with Engineering Advancement Association of Japan (ENAA) .
The CO2 injection site is located at Minami-Nagaoka gas field, Nagaoka
city, Niigata prefecture, Japan.
One injection well (IW-1) and three observation wells (OB-2, OB-3, 0E-4)
were drilled. CO2 was injected into a thin permeable zone of the reservoir
at 20-40 tonnes per day. The CO2 injection started on 7 July 2003, and
ended on 11 January 2005 with the total CO2 amount of 10,400 tonnes. The
pilot-scale demonstration allowed an improved understanding of the CO2
movement in a porous sandstone reservoir, by conducting time-lapse geophysical
well logs at the three observation wells. CO2 breakthrough was identified
by induction, sonic, and neutron logs. The sonic P-wave velocity decreased
up to 28% at OB-2, and 13% at OB-4. Small effects of CO2 saturation on
resistivity resulted in small changes in induction logs when the reservoir
was partially saturated.
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