HISTORICAL REVIEW OF GEOPHYSICAL MONITORING AT WAIRAKEI-TAUHARA : WHAT HAVE WE LEARNT?

Abstract

A review of the history of geophysical monitoring at Wairakei-Tauhara has been undertaken to extract the essential knowledge about reservoir processes and environmental effects from the collection and analysis of geophysical monitoring data. The studies reviewed include changes in: ground deformation (subsidence), micro-gravity, groundwater level, heat-loss from surface thermal features, and micro-seismicity. Each of these data-sets provides a glimpse into the subsurface physical processes that accompany large scale reservoir fluid extraction and reinjection. When interpreted together with downhole data on pressures, temperatures and 2-phase saturation conditions, and modelled together as an integrated package, these geophysical monitoring datasets provide a valuable source of reservoir change information that can assist in the calibration of reservoir simulations, and improve forward projections (scenarios) of reservoir behavior under a variety of extraction-injection strategies.