Publication Name: The Sedimentary Basins of WA
Authors: K. A. R. Ghori
Publication Volume: 2
Date Published: December 1998
Number of Pages: 25
Reference Type: Book Section
Abstract:
Geochemical analyses confirm the presence of good quality but thin oil source rocks within the Neoproterozoic succession of the western Officer Basin. The available geochemical dataset, however, is insufficient to positively identify the source of oil and bitumen shows observed in petroleum and mineral wells.Excellent oil source-beds are present in finely laminated shale and siltstone facies within an evaporitic succession penetrated in mineral corehole NJD 1 located on the Kingston Shelf, and are marginally mature for oil generation.
Within the Yowalga Sub-basin fair to good oil source-beds are identified in thin organic-rich shales of the Browne, Hussar and Kanpa formations at Kanpa 1A, Yowalga 3 and Empress 1A respectively. In this sub-basin the Neoproterozoic succession is very thick and its maturity varies from immature to overmature for different formations, depending on the maximum depth of burial.
Fair source-beds have also been identified in mineral corehole LDDH 1located in the northwestern Gibson Sub-basin. The highest measured maturity in the northeastern part of this sub-basin is from Dragoon 1 where over 2500 m of section has been removed during compressional and halokinitic uplift. Along the southern margin of the Gibson Sub-basin the Neoproterozoic is partly within the oil window, whereas in the northwestern part of the sub-basin it is mature to overmature (in LDDH 1).
Modelling indicate that the main phases of oil generation within the Neoproterozoic succession occurred during the latest Neoproterozoic, Cambrian and Permo-Triassic. These phases vary both stratigraphically and geographically across the basin, depending on the depositional and structural history of the area.