New insights into the offshore Canning Basin using a seamless onshore/offshore stratigraphic model

SummaryThe Canning Basin in Western Australia is classified as a frontier basin. Of the 345 wells drilled onshore, only eight have intercepted small commercial hydrocarbon deposits. The offshore Canning Basin is one of the world’s most underexplored Paleozoic basins with six wells in a 75,000 km2 area with no commercial oil deposits discovered. To overcome the limited stratigraphic data from offshore wells, the well-constrained onshore stratigraphy has been mapped offshore through the development of a seamless onshore/offshore stratigraphic model.The model is an amalgamation of over 5000 km of 2D seismic data, 25 petroleum wells and potential field data. Large-scale structures that cross the coastline were mapped and allowed for the transfer of stratigraphy from onshore to offshore. Key Paleozoic stratigraphic units were continuously mapped across the onshore/offshore transition and were identified to thin towards the Roebuck Basin as Mesozoic and Cenozoic sediments increase in thickness. Thick Ordovician and Devonian units that host commercial hydrocarbon deposits onshore could not be confidently identified in the offshore Oobagooma Sub-Basin due to the attenuation of the seismic signal by inferred overlying volcanic units. Ordovician sedimentary units, however, can be mapped offshore across the adjacent Broome Platform but are comparatively thin (~2 km). Geochemical data acquired from mafic volcanic units indicate that they share a similar source and are more extensive than previously reported.This model has produced a more accurate stratigraphic model of the offshore Canning Basin. A multifaceted approach of mapping stratigraphy and structures across the onshore/offshore transition and gathering new geochemical data has provided new insights into the offshore Canning Basin that can inform future petroleum exploration activities.