Insights into the Petroleum System Evolution of the southern Orange Basin, South Africa

Abstract

An integrated approach to investigate the petroleum system of the southern Orange Basin, South Africa reveals that the principal controls on hydrocarbon generation and leakage are spatial and temporal variations in post-rift overburden deposition. The model predicts present day gas seepage at the sea floor and this is calibrated against observed seepage events. D basin modelling of an east-west trending transect across the Orange Basin passive margin was undertaken accounting for variations in stratigraphy, structural deformation, source rock distribution and characteristics and heat flow variations associated with continental break-up. Petroleum generation and migration modelling was performed using compositional kinetic schemes, and migration and leakage routes calibrated to signs of current-day active leakage collected during seismic interpretation. The use of seismic indicators of hydrocarbon leakage as calibration data for constraining migration predictions is essential for the reconstruction of hydrocarbon generation and migration scenarios, as they provide the validation of the model with respect both to the physical properties and distribution of the sedimentary sequences as well as the dynamics of oil and gas migration. Modelling results indicate that the main period of hydrocarbon generation occurred in the Late Cretaceous, the time of maximum burial on the shelf. Following an erosion event at the end of the Cretaceous, deposition shifted over the shelf break and significant sediment volumes prograded into the deep basin. This led to a second pronounced maturation event focussed specifically under the prograding Tertiary wedges. The model predicts that the kitchen area is active today and is also the source of hydrocarbons that are observed to be seeping at the present day sea floor.

Tectonic variation and structural evolution of the West Greenland continental margin

“…A petroleum system modelling approach has been applied in various research studies (e.g. Burrus et al, 1991;Johannesen et al, 2002;Kubala et al, 2003;Paton et al 2007). Where sufficient data are available, thermal and petroleum systems models are useful in predicting the hydrocarbon potential of a basin.…”

Influence of mechanical stratigraphy on multi-layer gravity collapse structures: insights from the Orange Basin, South Africa

“…(Light et al, 1993, 84 Muntingh & Brown, 1993, Paton et al, 2007, 2008, Hirsch et al, 2010. basin is extensive, though limited to the shelf margin, and has been used by previous studies (e.g.…”

Backward modelling of the subsidence evolution of the Colorado Basin, offshore Argentina and its relation to the evolution of the conjugate Orange Basin, offshore SW Africa

“…However, while a change in sediment supply could have surely played a role in shaping the overall subsidence history of the two basins, it is also possible that other processes might have come into play as well. In this regard, seismic profiles across the Orange Basin show several unconformities that are partially interpreted as erosional truncation horizons (Brown et al 1995;Hirsch et al, 2010;Kuhlmann, et al 2010;Paton et al, 2007). In addition, Hirsch et al (2010) evaluated that the best fit between modeled and observed vitrinite reflectance data can be achieved only by considering an erosion of about 1,000 m. Furthermore, erosional events are also in agreement with investigations onshore South Africa by Braun et al (2014).…”