Play by Play: Collingham 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. Collingham is the most recent of these formations, lying above Whitehill and the lower Prince Albert formations. The plays are located in the central and south-eastern areas of the Karoo Basin.
The Collingham Formation
The youngest of the Karoo’s lower Permian shale formations, the Collingham shale is usually paired with its older counterpart, Whitehill. In fact, estimates for the total organic carbon content and reservoir properties of both formations are nearly identical.
The Collingham Shale is at an average depth of 7,800 feet in the region designated as most advantageous for gas concentration. Organic content registers at a gross thickness of 200 feet, which translates into a net thickness of 80 feet of organic content with potential for hydrocarbons formation. As the youngest of the Ecca formations, Collingham is least likely to suffer from over-maturity. This differentiates the play from the older Prince Albert Shale.
Thermal maturity is higher in Collingham than in its older counterparts, registering at 3 percent, but it is still well within the dry gas interval. In all, this translates into an estimated average ratio of 36 billion cubic feet of gas per square mile over the play’s 60,180 square miles. Risked gas in-place estimates put forward by the EIA are 328 trillion cubic feet, with technically recoverable shale gas estimated at 82 tcf. This makes Collingham the second largest accumulation of reserves among the three formations, after Whitehill, and a likely first choice for gas exploration and production activity in the Karoo basin.