Mineral Sequestration of Naturally Occurring CO2 in Rankin Trend Gases, Carnarvon Basin, Australia

High-CO2 gas fields serve as important analogues for understanding various processes related to CO2 injection and storage, including assessing the relative importance of mineral precipitation and/or solution trapping efficiency. In this paper, we present a high resolution study focused on the Gorgon gas field and associated Rankin Trend gases on Australia’s North West Shelf. The gas data we present here display clear trends for CO2 abundance (mole %) CO2 and d13C CO2 both areally and vertically. Generally, CO2 mol % decreases and becomes depleted in d13C with decreasing depth and towards the north; a pattern which also holds true for the greater Rankin trend gases in general. We propose that these variations were driven by the precipitation of a carbonate phase, namely siderite, which is observed as a common late stage mineral. The results from this study have important implications for carbon storage operations and suggest that significant volumes of CO2 may be sequestered from a gas plume over short migration distances.