Integrated 3D petroleum generation, migration and charge modelling in the Kupe-Kapuni region, south-eastern Taranaki Basin

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Kroeger KF, Funnell RH, Fohrmann M, Hill MG. 2019. Integrated 3D petroleum generation, migration and charge modelling in the Kupe-Kapuni region, south-eastern Taranaki Basin. Lower Hutt (NZ): GNS Science. 67 p. (GNS Science report; 2019/73). doi:10.21420/VHDN-9755.

Abstract

This report presents workflows and results of integrated petroleum systems modelling of the Kupe region in the south-eastern Taranaki Basin. A series of PetroMod™ 3D models have been built for numerical forward modelling of the complex tectonic and sedimentological evolution of the area. The models use a detailed structural and stratigraphic model based on high-resolution grids (100 x 100 m) developed from new reflection seismic data interpretation carried out as part of the GNS 4D Taranaki project. Results give new insights into the workings of the petroleum system along the Manaia Anticline, a major petroleum fairway in the Taranaki Basin, and the so-far undrilled area west of the Manaia Anticline. Modelling has resulted in revision of the temperature and source rock maturation histories that now explain high source rock maturities encountered in the area despite low present-day temperature gradients. Early maturation is interpreted to have been driven by burial to a depth of 5 km during the Paleogene, a hotter-than-present-day thermal regime, and additional heat conservation due to warm climates. The re-interpretation of the Cretaceous–Recent thermal history suggests that the deepest of the three source rock intervals present, the Cretaceous Rakopi Formation, is over-mature in a large part of the Manaia Fairway and that charge of the petroleum-producing Kupe Field occurred from the overlying Paleocene Farewell Formation instead. This is consistent with geochemical fingerprinting of Kupe Field fluids. The revised maturation history also indicates that the Eocene Mangahewa Formation may have expelled significant amounts of petroleum, which is considered to be important for the charge of Oligocene and Miocene sandstone reservoirs. Models indicate that charge of reservoirs in the Miocene succession is possible, but migration pathways are very sensitive to carrier bed configuration and fault properties. Leakage has been previously identified to be a major risk along the Manaia Anticline. Reconstruction of Late Miocene and Pleistocene uplift has enabled us to reproduce the impact of structural development on charge and leakage of reservoirs. Nevertheless, the basin-wide petroleum plumbing system and the quantitative impact of fault leakage need further investigation and will be the focus of additional modelling in the Taranaki Basin. (auth)