The Role of Tectonics, Sedimentology and Provenance in Architecturally Complex Deepwater Gravity Reservoirs – A Case Study from the Angel Formation, Dampier Sub-Basin, North West Shelf, Australia

Kerrie Deller, Australian School of Petroleum, University of Adelaide, Australia, [email protected]

The northern Dampier Sub-basin located on the North West Shelf, Australia has been a mature hydrocarbon province for over twenty years. It contains several major hydrocarbon fields including the Angel gas field, the Legendre oil field and the Exeter/Mutineer oil field complex. The main reservoir interval in these fields comprises deepwater mass gravity sands which are Tithonian to Berriasian in age. These sands were deposited during a time of active east-west orientated rifting and continental break-up along the western margin of Australia. 

Complete understanding of the geological environment in which deepwater sands were deposited is critical to the successful exploration and development of the deepwater fields. Intricate knowledge of the relationship between regional tectonics, sediment supply, sediment type and their variation over time is imperative for the accurate determination of architectural reservoir style.

Geological interpretations are challenging in the Dampier sub-basin due to the complicated relationship between tectonics and sedimentation events combined with poor seismic resolution below the Muderong Shale. A combined dataset of 2D/3D seismic integrated with core and wireline interpretations will better constrain the regional tectonic setting, facies/sediment variation and provenance for this geologically complex region. Appropriate analogues are being investigated, a task deemed complicated as outcrop analogues deposited in extensional rift settings are rarely found to exist.