Petroleum Prospectivity Analysis of Acreage Blocks W13-19 & W13-20 in the offshore North Perth Basin: Overburden Aspect Andi Alamsyah (1) (2), Mark Bunch (2), Wahidah (1)
1. Geophysics Department, Universitas Mulawarman
2. Australian School of Petroleum, University of Adelaide
Abstract
Overburden rock is the sum of all layers above the source rock, reservoir rock and seal. It is one of an essential element in petroleum system due to it affecting the performance of every other element and process of the petroleum system. In this study, the combination of literature, well completion reports and the generation of a map and analysis charts have been used to investigate the performance of overburden rock in assessing the petroleum Prospectivity Analysis of Acreage Blocks W13-19 & W13-20 in the offshore North Perth Basin. At first, a thickness map of overburden was generated from seismic data to see its distribution in the acreage W13-19 and W13-20. A porosity chart over time was analyzed to see how overburden rock affects these properties, particularly in the reservoirs (Dongara Sequences and Cattamarra Coal Measures Sequences) and the regional seal (Kockatea Shale and Cadda Sequences). Eventually, a vitrinite reflectance over time plot was analyzed to understand the relationship between the thickness of overburden and maturity level of the source rock as well as the effect on the time of generation. From this investigation, we understood that both central and southern Houtman Sub-basin have a relatively same quantity of overburden accumulation and sufficient enough to hydrocarbon to be generated from potential source rock while Wittecarra Terrace that is part of Abrolhos Sub-basin has smaller accommodation space due its position in footwall block which is higher than Houtman Sub-basin. As consequence, it accumulates a thinner amount of sediment. On the other hand, having known that there are three subsidences that influence the thickness of overburden and sedimentation rate, the most influencial subsidence is in early Permian to early Jurassic.
Keywords: Overburden rock, petroleum prospectivity, northern perth basin
