2D seismic data and gas chimney interpretation in the South Taranaki Graben, New Zealand.

摘要

The Taranaki Basin is one of the major oil and gas producing basins offshore New Zealand. The study area covers an area of 10,000 km² in the basin, and includes 171 2D seismic lines and six wells, which are provided by the New Zealand Petroleum & Minerals. Some previous studies refer to the study area as the South Taranaki Graben.;This thesis provides detailed mapping and interpreted subsurface stratigraphy and structure of five horizons, i.e. basement top, Pakawau Group top, Kapuni Group top, Wai-iti Group top, and seafloor. It undertakes studies of the relation between the basin evolution, faults, and depositional patterns. In addition, the gas chimneys were investigated along with hydrocarbon migration pathways to surrounding oil and gas fields.;The horizons were identified based on observed discontinuities and seismic attributes. The seismic reflection characters of the horizons and their associated sequences are described in this study. The horizons have been mapped as time structural, isochron, and isopach maps. Seismic attributes were used in horizon interpretation and gas chimney detection.;The mapping of these horizons combined with seismic facies character provides detailed overview of the structural evolution and depositional history in the study area. A map of the gas chimneys along with the late normal faults distribution shows that the gas chimneys are mostly common above the Cretaceous source rocks. Fault provide migration pathways for the gases through the seal rocks. Petrophysical analysis shows that the Kapuni Group contains a sizable amount of hydrocarbons, high porosities, and permeability. In combination with the structure of the Kapuni Group, the hydrocarbons within the group migrate to two producing fields through two migration pathways.