Microseismic Monitoring at the CCS and CO_2-EOR Fields: Lessons from the Nagaoka Pilot CO_2 Injection Site

摘要

Injection of CO_2 will increase the formation pressure in the target reservoir. This will decrease therneffective pressure and may also lead to geomechanical deformation of the rocks. To guarantee safetyrnof storage, the CO_2 injection must be controlled not to damage the caprock. In hydrocarbon andrngeothermal reservoirs, it is well known that the injection or production of fluids can inducernmicroseismic events. Because of their small size, induced microseismicities usually are monitoredrnusing borehole instruments. The technology has been applied successfully to the CO_2 injection sites.rnAs part of the monitoring component of the Weyburn CO_2 injection project, geophones were installedrnin a disused borehole to record the microseismic events in relation to changes in injection andrnproduction in nearby wells. The event magnitudes detected by the geophones ranged between -3 to -1rnand the largest events recorded have magnitudes less than -1.0, and many are smaller than -2.0. Thisrnpresentation will give a simple review on microseismic monitoring results observed at the onshorernCO_2 injection sites such as Weyburn (Canada) and Lacq (France), and will introduce the case studyrnresults from the Nagaoka pilot site (Japan), including the field survey results after the earthquakes hitrnthe area in 2004 and 2007.