The CO2CRC Otway Project in southwestern Victoria, Australia has injected over 17 months 65 445 tonnes of a mixed carbon dioxide-methane fluid into the water leg of a depleted natural gas reservoir at a depth of approximately 2km. Pressurized sub-surface fluids were collected from the Naylor-1 observation well using a tri-level U-tube sampling system located near the crest of the fault-bounded anticline trap, 300 metres up-dip of the CRC-1 gas injection well. Relative to the pre-injection gas-water contact (GWC), only the shallowest U-tube initially accessed the residual methane gas cap. The pre-injection gas cap at Naylor-1 contains CO2 at 1.5 mol% compared to 75.4 mol% for the injected gas from the Buttress-1 supply well and its CO2 is depleted in 13C by 4.5%0 VPDB compared to the injected supercritical CO2. Additional assurance of the arrival of injected gas at the observation well is provided by the use of the added tracer compounds, CD4, Kr and SF6 in the injected gas stream.
Lessons learnt from the CO2CRC Otway Project have enabled us to better anticipate the challenges for rapid deployment of carbon dioxide in a commercial environment at much larger scales.