Could faults provide conduits for fluid escape? New field data near the Otway International Test Centre

It is well known that faults affect fluid movement within the subsurface and this can have a host of implications for the measurement, monitoring, and verification of subsurface technologies (e.g., carbon capture and storage (CCS), energy storage, geothermal energy, and radioactive waste disposal). Faults are an important control on the escape of fluids from depth (e.g., Dockrill and Shipton, 2010). It is therefore important to consider the potential effect of faults in the shallow overburden to any future CCS sites. However, there is very little data on fault architecture in shallow sediments, and consequently their effect on fluid flow is far less well understood than flow through faults at hydrocarbon reservoir depths.

In early 2024, a novel field trial injection will be conducted at the CO2CRC Otway International Test Centre (OITC), located in southern Victoria, Australia (Figure 1). The injection will involve a small volume of CO2 (∼10 t) being injected into the Brumbys Fault, which will be monitored using various surface and downhole monitoring techniques (Tenthorey et al., 2022), to provide data on the transport of CO2 through shallow faults.