New Insights into the North Taranaki Basin from New Zealand's First Broadband 3D Survey

Abstract

For decades, the Taranaki basin has been New Zealand's only producing basin whilst exploration for large new hydrocarbon discoveries has moved to more frontier basins. Statistically speaking, the Taranaki basin should still hold numerous large fields; however, the information currently available is not sufficient to solve the challenges in understanding the petroleum system. The North Taranaki basin has widespread 2D seismic coverage and numerous wells that have not encountered commercial accumulations. This is attributed to the structural complexity in the basin and the absence of necessary information to help understand the basin evolution. An oilfield services company identified the North Taranaki graben as one area that has huge potential yet to be understood. A modern broadband, long-offset 3D survey was modelled and expected to provide the necessary information to finally understand the petroleum system and provide evidence for material hydrocarbon accumulations. In this investigation we assess the hydrocarbon potential of the basin using the newly acquired data. Advanced acquisition techniques were implemented for increased coverage and bandwith, including continuous line acquisition, sliding-notch broadband acquisition and imaging techniques, and delta source, resulting in a full broadband acquisition. Raypath distortions and depth uncertainty are significantly reduced processing through vertical transverse isotropy (VTI) anisotropic Kirchhoff prestack depth migration with a geologically constrained velocity model. Resolution of the deepest sections in the central graben have identified structures never before seen, as well as fault definition critical to understand charge. Here, we demonstrate the potential of the basin that has been unlocked thanks to the technology advances in acquisition and processing. 3D seismic interpretation and amplitude-versus-offset (AVO) analysis support the renewed potential of the basin.