Shale Gas Strategic Project
The Department of Mineral Resources and Energy established the Shale Gas Strategic Project (“the Project”), and in October 2019, mandated the Petroleum Agency SA (PASA) and the Council for Geoscience (CGS) to undertake a regional programme of shale gas resource evaluation and geo-environmental baseline investigations in the south-central Karoo Basin.
The shale gas project seeks to respond to concerns regarding the actual extent of South Africa’s shale gas resource as well as the potentially negative environmental and social effects of shale gas exploration and production. The regional programme of shale gas evaluation and geo-environmental baseline monitoring studies for the south-central Karoo Basin is to provide a scientific response to the concerns raised. The programme comprises 5 work packages, namely, Karoo Deep Drilling; Petroleum Resource Evaluation; Baseline Groundwater Monitoring Network; Risk Assessment of Abandoned Wells and Baseline Seismicity Monitoring Network.
The South African Karoo Basin potentially hosts large shale gas resources estimated at 370 trillion cubic feet (Tcf) by the US.EIA. Subsequent resource evaluation by the Agency, using all available data, has resulted in a recoverable
resource estimate of 209 Tcf. The exploitation of such a large amount of indigenous gas could hold many benefits for South Africa in terms of energy security, economic growth and job creation.
The Karoo basins of southern Africa record 100 million years of sedimentation in the heartland of the supercontinent Gondwana, in a range of depositional environments. The erosional remants of the Main Karoo Basin cover approximately 700 000 km of southern Africa today, and together with sediments in subsidiary Karoo-aged basins, these rocks play host to led South Africa’s onshore fossil fuel reserves.
Following initial petroleum exploration in the Karoo Basin during the 1960s and 1970s, the focus of exploration activities eventually shifted offshore, due to the perceived low potential for large conventional oil plays onshore. However, the global success of recent technological developments (particularly reservoir fracturing and horizontal drilling) in recovering petroleum from low permeability reservoirs, combined with the emergence of natural gas as an economically viable fossil fuel, has led to renewed interest in the petroleum potential of Karoo sediments, and the emergence of the Karoo Basin as an important exploration target in South Africa.
Current petroleum exploration activities in the Karoo are focused on three unconventional play types: shale gas, coalbed methane and biogenic gas, although the potential for conventional hydrocarbon plays also exists.
The Permian-aged lower Ecca Group in the southern Main Karoo Basin is comprised of a number of fine-grained formations of variable prospectivity. Of these, the Whitehill Formation is considered to be the most prospective for shale gas.
The Whitehill Formation is characterised by high total organic carbon content (up to 14 %; average 4.5 %), high thermal maturity (Ro = 1-4 %), high quartz content (50 % average with carbonate-rich intervals) and sufficient thickness for commercial development
(35 m average). Legacy exploration data demonstrates that it is regionally continuous over some 200,000 km and buried to depths of up to 4 km in the extreme south of the basin.
Additional positive indicators include numerous gas shows in the lower Ecca Group and underlying Dwyka Group in the southern Karoo Basin and the occurrence of pyrobitumen (pseudo-coal) in fissures, indicating the existence of an originally oil-prone source rock.
Intrusions of the Karoo dolerite suite outcrop across much of the Main Karoo Basin, with the exception the deep southern marginal zone. While their subsurface geometry and distribution is not well understood at present, it is possible that intrusion of the dolerite magma may have resulted in the fracturing, contact metamorphism and degassing of shales in places, resulting in reservoir compartmentalization. However, Karoo dolerites have also been reported to serve as cap rocks for conventional traps.
High maturities along the basin’s southern margin (the Cape Fold Belt) indicate graphite-facies metamorphism of the Whitehill Formation (e.g. Branch et al. 2007), with maturities decreasing northwards. The effect of high maturity on the gas content of the Whitehill remains to be determined, with Karoo Deep Drilling gas content measurements of fresh deep core currently available.
Comparisons with analogue shale plays suggests that the Whitehill Formation may be the most prospective in areas of distal deposition, where stratigraphic thicknesses greater than 30 m are buried to depths greater than 1.5 km but not subjected to maturities greater than 3.5 % Ro, and where sub-surface dolerite intrusions are minor or absent. However, the location of any potential sweetspot must be considered speculative at present, due to the sparse distribution of legacy exploration data.
Government Notice – Proposed investigation in terms of Section 50 of the Act: Mineral and Petroleum Resources Development Act… read more
Gazetted Regulations:
1. Proposed-Regulations-pertaining-to-the-Exploration-and-Production-of-Onshore-Oil-and-Gas-Requiring-Hydraulic-Fracturing.pdf (cer.org.za)…
read more
2. Unconventional Gas Regulations For Water Use Version 07-05-2021.pdf (dws.gov.za)…
read more
Shale Gas Development in the Central Karoo: A Scientific Assessment of the Opportunities and Risks… read more
South Africa’s Technical Readiness to Support the Shale Gas Industry (2017)… read more
Science Action Plan for Shale Gas in the Karoo Basin… read more
Executive Summary Shale Gas Report – 18 Sept 2012… read more
Mining, Minerals & Energy Policy Development/Operating Mines/Shale Gas… read more
