Officer Basin

[3][2] This basin's extensive depositional history, with sedimentary thicknesses exceeding 6 km and spanning roughly 350 Ma during the Neoproterozoic, make it an ideal candidate for hydrocarbon production.

Australia is characterized by ancient cratons that detail the complex tectonic and geologic history that has occurred over the course of Earth's evolution.

[5] The breakup of Gondwana resulted in the creation of large onshore and offshore sedimentary basins between the western and eastern Australian cratons.

[1] The sediments that constitute the Officer Basin were first deposited upon an unconformable surface over variably metamorphosed basement rocks.

[1] After this depositional sequence, the basin experienced significant folding and erosion from the Areyonga movement, which was followed by subsidence during the Marinoan glacial period.

[1] The main sedimentary sequence that holds the largest potential for hydrocarbon production and storage is the Buldya Group, which includes coarse siliciclastics overlain by mixed siltstone, shale, carbonate and evaporite succession.

[6] Regional tectonism during the Neoproterozoic resulted in the formation of several distinct structural zones that intersect the deepest part of the basin.

The Browne formation constitutes the most identifiable and thickest basal unit of the Officer, and shows remarkable lateral continuity, with limited change in facies across the basin.

[7] Several progradational sequences have been identified within the Hussar, suggesting that its depositional environment was a transitional one, ranging from shelf and shoreline to tidal flat and fluvial.

[3] This drastic difference in source rock maturity is attributable to the complex tectonic history the Officer Basin has experienced.

The seven major tectonic events that the Officer Basin experienced extended the maturation window to up to 1 km in some areas, allowing for production to occur much later in time in younger units compared to older ones.

[1] These beds can show excellent hydrocarbon-generating potential and despite their disperse nature, the diverse trapping mechanisms present within Supersequence 1 may allow for significant accumulations of hydrocarbons.

[3] The salt tectonics present within the Browne could allow for a wide range of trapping mechanisms, from anticlinal to fault-bound, due to deformation of overlying strata, making more local hydrocarbon accumulations likely in the deeper, central portion of the basin.

[3] However, the subsequent deposition of the Hussar, Kanpa and Steptoe formations were not as deep as the Browne, allowing for hydrocarbon generation from these units to extend into the Phanerozoic.