CO2 geosequestration potential in the Northern Perth Basin, Western Australia

Abstract

The proposed Coolimba Power Plant will generate 400 megawatts of baseload power from coal resources near Eneabba in Western Australia and will require geological storage of CO2. Potential storage sites have been assessed for capacity and containment security in depleted oil and gas fields, deep saline aquifers, and the coal seams based on existing openfile data. A combination of some of these options in a hybrid solution will likely be sufficient to store the >80 megatonnes (Mt) of CO2 emissions expected from the proposed power plant. The Dongara Field has the largest individual contingent storage capacity of all the onshore depleted hydrocarbon fields in the study area (13 to 30 Mt). Additional prospective storage capacity in deep saline aquifers adjacent to the field is between 12 and 46 Mt. Deep saline aquifers offer many CO2 storage options with an estimated combined prospective storage capacity of 167 to 512 Mt of CO2. These include stacked reservoirs below the existing hydrocarbon fields. The highest uncertainty in containment security for the saline aquifer storage sites is ‘up fault leakage’ owing to a lack of high-quality seismic data needed to adequately characterise the architecture of faults and traps. Additional containment risk is related to uncertainty in the CO2 migration direction after injection owing to poorly constrained structural geometry of the base-seal derived from seismic data with poorly constrained depth conversion. The highest uncertainty in containment security related to the depleted gas field storage is fault reactivation and well leakage.