Understanding the Potential of the Unconventional Karoo Basin Play, S. Africa: Progress and Problems
Bada, Gábor 1; Law, Ben 2; Hughes, Daniel 2;
Wallis, Roderick J.2
(1)TXM Oil and Gas Ltd., Budapest, Hungary. (2) Falcon Oil and Gas Ltd., Denver, CO.
The Karoo basin, where Falcon/TXM is well positioned in its
deepest, southern part off the areas with extensive doleritic volcanics, hosts
South Africa’s main coal deposits that supply most of the country’s energy
supply. As South Africa is seeking to diversify its energy portfolio from coal
to natural gas, unconventional hydrocarbons are a potential game changer in
South Africa's energy landscape.
The Karoo basin is an underexplored area where initial exploration
confirmed the presence of hydrocarbons at several stratigraphic levels. It is a
proven effective petroleum system also through the existence of pyrobitumen
filled fractures and outcrops ("pseudocoal"). Main source and
reservoir rocks are within the Permian Ecca Supergroup. Black shales (e.g.,
Prince Albert, Whitehill Fms.) and overlying turbiditic and deltaic sands
(e.g., Laingsburg, Fort Brown Fms.) are the main elements in the Karoo hydrocarbon
system representing an unconventional fractured shale gas and tight sand play,
respectively. Source rocks are originally liquid-prone with type I/II kerogen
and with TOC values up to 15%. Of key importance in the play assessment appears
to be the high level of thermal maturity (up to 5.0 Ro %) due to deep burial
(5-7 km), and subsequent uplift and erosion in major parts of the Karoo basin.
Associated uncertainties, such as the gas retention potential of shales and
reservoir integrity of tight sands, represent fundamental challenges. A
systematic exploration program is now focusing on these topics to unlock the
potential of the Karoo basin resources.
This contribution reviews i) the progress made in the understanding of the geology and hydrocarbon system of the Karoo basin, ii) the identified critical issues and iii) the efforts made to characterize and validate the real value of this unconventional play.
AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.