Play by Play: Whitehill Formation
In any list of top unconventional plays for oil and gas, one and only one play stands out in the whole of sub-Saharan Africa: South Africa’s Karoo Basin. This is not without reason. A 2013 study by the United States Energy Information Administration (EIA) places recoverable shale gas and coal-bed methane (CBM) reserves at 390 tcf, with potential for increase. This positions South Africa as the eighth biggest shale gas reserve holder in the world. The most promising plays for unconventional oil and gas prospects in the Karoo are the Whitehill, the Prince Albert and the Collingham formations. These plays are part of the Ecca Group, within the Karoo Supergroup, and compose what is known as the Lower Ecca Shales. Whitehill is located between the lower Prince Albert and the more recent Collingham formations and all are located in the Central and South Eastern areas of the Karoo Basin.
The Whitehill Formation
Within the Karoo, the play with the greatest potential for shale gas production is Whitehill. This lower Permian formation ranges between depths of 5,500 and 10,000 feet and is much thinner than the Prince Albert formation, with gross organic thickness between 100 and 300 feet.
The total organic content count in the most prospective areas for shale gas ranges between 3 and 14 percent, giving very good indications for the formation of dry gas. Just like Prince Albert, Whitehill has a thermal maturity ranging between 2 and 4 percent, placing it right in the dry gas interval. With Whitehill being about one million years younger than the Prince Albert shale, problems with excessive maturity are not as visible, but it is likely that some of the areas exposed to solidified volcanic matter may be over-matured and converted to graphite.
Hydraulic fracturing is a likely candidate for gas extraction, due to the formation’s mineral composition. Civil society opposition to the use of this technique in South Africa, along with political delays and policy reviews have, however, prevented fracking in the area so far.
The 60,180 square miles of exploration area covering the Whitehill formation presents the highest concentration of dry gas resources of all the shale formations in the Karoo, at 59 bcf per square mile. The EIA estimates that risked shale gas in-place could be as high as 845 tcf, although data is limited. Risked technically recoverable shale gas resources are placed at 211 tcf, taking into account complex geology but good reservoir mineral composition.