The Petrel Sub-basin: a world-class CO

Abstract

In 2021, the Australian Government announced a round of offshore greenhouse gas acreage release, including an area where research by Shell/CSIRO in 2016/2017 indicated close to 1 Gt carbon dioxide storage potential within the Mesozoic sediments of the Sandpiper, Elang and Plover Formations of the Petrel Sub-basin. The joint Shell/CSIRO study assessed key containment issues (legacy wells, potentially conductive faults, top seal extent) and storage formation connectivity. To study containment risk, CSIRO assessed a single injection well scenario and concluded that injection of up to 20 MTPA would not create geomechanical failure. Based on these findings, a ~5000 km2 area of interest southeast of the Petrel Field was proposed as suitable for injection in the Plover/Elang formations. The Shell team constructed topographical dynamic models at five potential locations. Three further models were built to simulate a base case and two end-member scenarios: (1) high permeability (leak point risk) and (2) low-pressure dissipation (top seal risk). The study showed that the development of two injector wells at one of the locations could safely and conservatively store 149 Mt, injected over a period of 30 years. Similar capacity is expected at four out of the five locations identified within the investigated area. Expansion to >2 injection wells per location, additional injection into the Sandpiper Formation and expansion to the west of the initially mapped focus area all point to achievable gigatonne storage potential. The joint study significantly expanded the understanding of the storage capacity, with recommendations for further data acquisition in both greenhouse gas (GHG) permits (GHG21-1 and GHG21-2).