New Insights Into the Exploration Prospects of the Central and Northern Karoo Basin, South Africa

Abstract

Until recently the ~700,000 km² Karoo Basin, South Africa was considered largely unproductive for hydrocarbons, resulting in very limited onshore exploration. However, with continued advances in hydrocarbon resource assessment, development and production, particularly in regards to more unconventional play types, the Karoo Basin has recently become a viable target for exploration. Modern-day hydrocarbon exploration has focused on the southern part of the basin, considered to be the most prospective area for shale gas due to the deeply buried, thermally mature black shales of the Permian Whitehall Formation. The northern and central portions of the basin have been largely overlooked, due in part to a lesser maximum basin down-warping and associated sediment accumulation.

Perhaps the largest hurdle in the understanding of exploration prospects in the Karoo Basin centers on the effects of dolerite dikes and sills. These intrusives, referred to under the umbrella term of the Karoo Dolerites are not only spatially extensive across the basin, but also intrude varying stratigraphic levels in the Karoo sedimentary sequence. The presence of the Karoo Dolerites has led to several, potentially opposing effects of the intrusions on the viability of exploration prospects. As a positive consequence dolerite sills and ring dike complexes potentially create traps. However, due to the intrusion of sills and dikes at temperatures greater than 1000 degrees Celsius modified surrounding sediments. The extent of the intrusive heating zone is likely dependent on a number of factors, including the thickness of the intrusive, composition of the associated sediment packages.

We present new evidence and subsequent interpretation of potential exploration prospects within the central and northern areas of the Karoo Basin based on integrated mapping, satellite imagery, gravity, and magnetic datasets. These interpretations include the evaluation of viable play types, sediment packages, and the effects of the Karoo Dolerites.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018