Applicability of Zero-offset and Offset VSP for Time-lapse monitoring - CO2CRC Otway Project Case Study

Abstract

Time-lapse seismic technology is proven to be a powerful tool for monitoring of reservoir depletion or fluid (such as gas, water or steam) injection into subsurface formations. While being almost standard technique for offshore reservoirs, time lapse surveys are still relatively rare used onshore due to poor repeatability of land seismic data. Borehole time-lapse seismic surveys could be a good alternative because of very stable receiver, and, in certain cases, source conditions, acquisition and processing of zero-offset and offset VSP is reasonably fast. In this paper we analyse repeated zero-offset and offset VSP acquired in within CO2CRC Otway pilot project scientific program in year 2007 (pre-injection) and year 2010 (postinjection). We address repeatability of the data and possibility to use simple VSP techniques for monitoring purposes.