Subsurface characterisation for future CCS applications using uncommon 3D surface and borehole seismic survey geometries at Harvey, Western Australia

Summary

Within the South West Hub Project we conducted a comprehensive integrated study to map the fault and fracture network surrounding the Harvey 3 well to obtain an understanding of their propensity to act as conduits for the injected CO2. Here we report only on the seismic investigations that had two objectives: The first one was to provide precise structural model for subsequent geomechanical studies. The second objective was design more environmentally friendly acquisition and overcome the land access issues. This is of a crucial importance at Harvey where farmers are opposed to any land disturbance that can affect their activities. We thus designed a comprehensive survey that addressed both objectives. The survey included a conventional component consisting of simultaneous recorded 3D surface and 3D VSP data sets and an alternative component that recorded multi-offset VSP survey along the public roads. 3D imaging results using diverse VSP geometries were compared to 3D surface data. Both products, borehole and surface 3D images, were used for the structural analysis. Multi-offset VSP survey on the other had was reanalysed using different decimation strategies for the purpose of optimising CO2 sequestration monitoring strategy. The main outcome of this analysis was the imaging concept that is limited only to public roads which bypasses access restriction and improves chance for better public acceptance in the future.

• 3D seismic surveys
• MOVSP
• CO₂ geosequestration