Stratal architecture and structural evolution of the Orange Basin, offshore Namibia : implications on hydrocarbon prospectivity

• Main Author: Mohammed, Muneef Mahjoob
• Published: University of Leeds 2013
• Subjects: 551.4096881
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.616299

Despite a significant increasing interest in the hydrocarbon system in deep water continental margins, the controls on the development of hydrocarbon system in these areas remain poorly constrained. The integration between the tectonostratigraphic evolution and hydrocarbon system modelling of the Namibian continental margin has provided new insights into the understanding of the main controls on the hydrocarbon system in deep water margins. The tectono-stratigraphic evolution of the Namibian margin has been divided into four main phases (pre-rift, syn-rift, transition and post-rift) which are separated by regional unconformities. The late syn-rift phase shows a significant thickness variation that is not controlled by faulting. This is considered to be depth dependent stretching. Towards the west, this thickness is covered by the seaward dipping reflectors (SDRs) which represent the initial phase of sea floor spreading. The transition from the rift to the post-rift phase is characterised by development the anoxic conditions that result in deposition of the organic rich Aptian source rock which represent the main source rock interval of the Kudu gas field. The high resolution of the seismic data has enabled more details on the development of the overburden (post-rift phase) of the margin to be obtained. The post-rift overburden has been subdivided into a number of second order and third order depositional sequences that are bounded by type-1 sequence boundaries. The tectono-stratigraphic evolution revealed that the margin has undergone two main tectonic uplift events at the end of Late Cretaceous and Late Tertiary resulting in a rapid switch in the location of sediment accumulations towards the middle and outer margin. The switch in the location of deposition has resulted in an increase of the burial and temperature in the deep water margin, and consequently an increase of the maturation of source rock intervals in this area as is documented in the results of the hydrocarbon system modelling. This is likely to have implications for other mature passive margin basins .