Improving Geomechanical Characterisation using Distributed Fibre Optics Strain Sensing and Coupled Modelling

The Shallow Fault Project, conducted at CO2CRC’s Otway International Test Centre (OITC), aims to enhance understanding of CO2 behaviour in faults by injecting CO2 adjacent to a shallow fault and observing its movement. This field experiment addresses the challenge of predicting CO2 plume migration in faults, which is crucial for the long-term integrity of geological CO2 storage sites. The project focuses on Brumbys Fault, a small volume of CO2 will be injected and monitored using technologies, including fibre optics for sensing strain changes. While the primary focus is to monitor the migratory behaviour of the plume, the acquisition of strain change data presents an opportunity to interrogate the poorly constrained in-situ stress state of the shallow subsurface at the OITC. Coupled geomechanical models are produced exploring the different stress model scenarios - normal fault, strike-slip, and reverse fault regimes. The unique deformation profiles of each scenario can be validated against actual strain data thereby constraining the stress model. This study not only aims to provide insights into CO2 deformation and fluid migration within shallow faults but also serves as a basis for assessing deeper fault systems, thereby supporting the development of effective CO2 geological storage solutions.