The available seismic data for the South West Hub clearly indicates that multiscale faults affect the target CO2 storage reservoir of the Lesueur Formations,and the potential top seal Eneabba Formation.
Based on the integration of existing and new (2010 vintage) 2D seismic dataset and Harvey-1 well data, this project primarily targets the evaluation of the faults hydraulic behaviour, i.e. the faults sealing potential for across-fault and up-fault flows. A secondary objective is to investigate the distribution of sub-seismic fractures and their impact on the trap integrity and reservoir compartmentalisation.
A new geological model, consistent with the integration of the latest 2D seismic reflection survey and available geophysical data, has been built. It integrates five stratigraphic horizons tied to formation tops in the new Harvey-1 data well (Neocomian UC, top basal Eneabba Shale, top Yalgorup, top Wonnerup and top Sabina Sandstone) and 13 main faults that can be correlated between at least two 2D-seismic lines that show constancy in dip, strike orientation and offset. This represents a first-order geological model, and the acquisition of additional seismic and well data is critical to reduce remaining geological uncertainty and further constrain the structural framework.
Key findings from the study:
- The likelihood of lateral migration of CO2 across faults between the Wonnerup Member and any interbedded sandstone (i.e. thief zones) in the Yalgorup Member can be locally high to the south of the SW Hub.
- The likelihood of lateral migration of CO2 across faults within the Wonnerup Member can also be locally high to the south of the SW Hub, with potential of westward migration beyond F1 if the CO2 column exceeds the local offset.
- Shale Gouge Ratio (SGR) values on the fault plane suggest an average to low likelihood of across-fault migration.
- The slip tendency magnitude for the SSE-NNW-oriented faults in the SW Hub are low (typically between 0.15 and 0.3) suggesting a low risk of fault failure under the present-day stress.
- The smallest critical pore pressure perturbations required to reach failure stress are located to the north of the SW Hub.
- The study provides a useful input into dynamic models to test compartmentalisation and containment.