Offset VSP for monitoring of the injection of small quantities of CO2 - CO2CRC otway case study

Abstract

Time-lapse seismic methods have become an essential part of monitoring and verification operations for carbon capture and storage (CCS) projects. Within the range of seismic methods, lapse borehole seismic methods have a potential to become the leading technology in on-shore CO2 monitoring due to quiet and stable sensor conditions, and minimal land access issues. In this paper we demonstrate the results of 4D offset vertical seismic profiling (VSP) surveys for detection of small amount of injected carbon dioxide. VSP datasets were acquired as a part of the monitoring program of Stage 2C of the CO2CRC Otway Geosequestration Project (Victoria, Australia). Borehole seismic program included recording data from four VSP offsets before commencement of injection and after injection of 5kt, 10 kt and 15 kt of CO2. The time-lapse analysis of the results shows capabilities of the VSP methodology to detect a small CO2 plume and track its evolution within a geological formation. The results demonstrate the potential of borehole seismic for permanent reservoir monitoring.