The Great South Basin - Antrim International's Exploration Strategy

摘要

The Great South Basin is a tensional basin formed by the middle Cretaceous separation of New Zealand from the Australian-Antarctic landmass. Through time deposition within this basin has ranged from fluvial-lacustrine to distal marine facies type at a specific location being dependent upon elevation within the basin and the temporal variations in sealevel high- and low-stands. Integration of well data and seismic has identified a number of facies, the mapping of which provides one component of the petroleum systems analysis of the basin and permits the identification of areas having the highest petroleum potential on the block. As in other basins in southeast Australasia, the abundant coals and carbonaceous shales of Cretaceous and Tertiary age offer both oil and gas generation potential, particularly within and on the flanks of the Central Graben, an attractive sub-basin with respect to hydrocarbon prospectivity in which Antrim International is concentrating its exploration activity. Source rock kinetics and basin modeling from a number of points within the basin, provide good constraints on the anticipated hydrocarbon type, timing of generation and migration and potential volumes of hydrocarbon available for trapping. Structural mapping utilising seismic data is ongoing and is designed to identify leads and prospects and define the structural and isopachal configuration of critical units which, together, will provide quantitative input into petroleum system definition and also reserves determination for the identified leads and prospects. The reservoir component of this petroleum system is provided by the basinwide sands found in the Cretaceous and Palaeocene. The best developed sands are in the Cretaceous and are of proven reservoir quality. However, there are significant and mapable, spacial variations in reservoir quality due to facies type and differences in sand provenance. Transgressive marine shales within the Cretaceous and Palaeocene sections provide ideal top and crossfault seals for potential reservoirs of the same age. Mapping of the proximal, basin edge limits of these shales is ongoing.