CHARACTERIZATION OF A FRACTURED RESERVOIR USING MICROEARTHQUAKES INDUCED BY HYDRAULIC INJECTIONS

Microseismic activity is induced by a number of engineering activities which involve fluid injection or extraction in naturally fractured ro ck masses. Evidence collected during the last 15 years of Hot Dry Rock (HDR) geothermal energy research has clearly indicated the very stron g positive correlation between induced microearthquake locations and f luid flow paths within the fractured rock mass. Microseismic monitorin g is now used regularly in HDR research as the only effective means of mapping hydraulic stimulations and monitoring hydromechanical process es during operation of the fractured reservoir. Many of the techniques that have been developed through HDR research are directly applicable to the hydrocarbon industry for the monitoring of hydraulic fracturin g treatments, waterflood operations and reservoir depletion. This pape r provides a brief introduction to the hydromechanical interactions th at result in induced microseismicity and presents case studies from th ree European HDR sites, where the monitoring of microseismic activity has proved vital in targeting production wells, mapping the progress o f stimulation and waterfloods, and understanding the hydromechanical b ehaviour of the fractured system. (C) 1996 Elsevier Science Ltd.