Play by Play: Prince Albert Formation
The most promising plays for unconventional oil and gas prospects in South Africa’s Karoo Basin are the Prince Albert, the Whitehill 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. They all date from the Permian period, though Prince Albert belongs to the Lower Permian period, and is therefore overlain by the more recent Whitehill and Collingham formations. The formations are located in the central and south-eastern areas of the Karoo Basin.
The Prince Albert Formation
The Prince Albert formation ranges greatly in depth, between 6,000 and 10,000 feet; the deepest areas are located in the south of the formation. Prince Albert averages a thickness of 400 feet, with ranges between 200-and 800-feet intervals. Net organic thickness, where hydrocarbon potential is likely to develop, averages 120 feet.
Information on the true potential of the Prince Albert is limited. In this area only one appraisal well has yet been drilled: Cranemere CR1. This test well, which pierced a higher shale formation named Fort Brown, was drilled in 1968 over a 158-feet interval and flowed at more than 8 mcf per day of natural gas. The well gave good indications of lower formations with high total organic content. In fact, Bundu Gas and Oil Exploration, a subsidiary of Australian company Challenger Energy and a mover in the South African shale scene, based the application for its current license in the area on this well.
As the oldest of the lower Permian shale formations in the Karoo, having formed between 275 and 280 million years ago, the Prince Albert formation might suffer from over-maturity. While total organic content is particularly high in the area, it is understood that the pressured reservoir might have partially converted carbon content to graphite and carbon dioxide. This will be less problematic in younger plays, such as Whitehill and Collingham.
A 2013 study by the Energy Information Administration gives very positive indications for the Prince Albert shale’s potential, as thermal maturity figures place it perfectly in the dry gas interval. Prince Albert has an area of 60,180 square miles of dry gas potential, showing a concentration of 43 bcf of dry gas per square mile. This points to potential gas in-place estimates of close to 385 tcf. Risked technically recoverable shale gas resources in the Prince Albert formation are estimated at 77 tcf.