Structural Styles and Hydrocarbon Prospectivity of the Ceduna Sub-Basin, Australia: Part Two

Abstract

The objective of this study is to build on the findings from the first part of the research and assess the prospectivity of the Ceduna sub-basin. Two potential hydrocarbon plays were described in the area of interest (AOI) within the Ceduna sub-basin. The first potential play comprises of tilted fault blocks at the base the Tiger – White Pointer Supersequence level sourced by the White Pointer – Blue whale Supersequences and sealed by intraformational seals. The second potential hydrocarbon play can be described as rollover anticlines at the Hammerhead – Top Tiger Supersequences level that are sourced by the underlying Tiger Supersequence black shales and sealed by overlying Dugong Supersequence and intraformational seals. Multiple 2D basin models were created in the area of interest to test four different scenarios that aim to provide a detailed risk analysis of major controlling variables on the petroleum system. These variables were identified from a comprehensive literature review and after a thorough seismic interpretation of a 3D seismic survey in the AOI. The four examined scenarios are open faults, closed faults, open and closed faults, and lateral facies changes with open and closed faults. These models aim to further the understanding on migration pathways, trap-fault dependency and source-reservoir distribution in the AOI. The 2D modeling exercise indicated that faults and the timing of fault opening and reactivation play a major role on trap formation, migration and accumulation within the identified hydrocarbon plays. However, for the rollover anticline play, the models showed that the anticlines can still retain a significant amount of hydrocarbons regardless of where faults were open or closed. On the other hand, the models highlighted the vital role that facies distribution and lateral heterogeneity play on determining source, reservoir and seal locations, which impacts the amount and location of hydrocarbon accumulations. With the aid of the 2D models that were produced the major risk with lowest probability of success are the traps and the seal integrity while the highest probability of success are the reservoir and source rocks for both plays. Overall the best play is considered as the rollover anticlines which is part of the identified prospect. Rollover anticlines show a high potential since they are not fault dependent and have a low chance of being reactivated.

AAPG Datapages/Search and Discovery Article #90332 © 2018 AAPG International Conference and Exhibition, Cape Town, South Africa, November 4-11, 2018