Seismic Interpretation of the Pegasus Basin, New Zealand, to Assess its Evolution and Hydrocarbon Potential
Daniel Stuart Renshaw - 2014
Honours Degree of Bachelor of Science (Petroleum Geology & Geophysics)
Australian School of Petroleum
The University of Adelaide
The Pegasus Basin lies to the east of Cook Strait, New Zealand and is an active, deep water passive margin basin within the greater East Coast Province. The basin is still widely considered a frontier basin with exploration in the early stages. The first high quality 2D seismic survey was shot in 2009 and forms the basis of this project. No wells have been drilled and as a result, much of the geology remains speculative. A structural and stratigraphic framework of the Pegasus Basin was generated by interpreting a number of key stratigraphic successions and bounding faults on seismic data create a series of stratigraphic surfaces and time structure and thickness maps. Using this framework, in conjunction with previous research, an evolution timeline was developed for the basin. Following this, it was possible to assess the hydrocarbon potential of the gas hydrate layer across the basin, along with numerous other play types previously documented in literature. Finally, this led to an overall appraisal of the petroleum system and hydrocarbon potential of the Pegasus Basin.
It was determined that the Pegasus Basin developed in three stages; along the ancient Gondwana subduction margin (140-85 Ma), as a northward prograding passive margin basin (85-23 Ma) and in conjunction with the modern subduction margin (23 Ma – present). The gas hydrate layer was found to be semi continuous across the entire basin and potentially interacts with five documented play types; thrust anticlines along the Hikurangi deformation front, blind thrusts in Neogene turbidites south of the deformation front, stratigraphic pinchouts of Neogene turbidites, traps beneath the gas hydrate layer and compound stratigraphic/base hydrate surface traps. Further work is required to refine the petroleum systems and identify prospective areas for further exploration in the Pegasus Basin.