y2017m09b12
20170928070400
assa
nadine@assaf.org.za
assa
South African Journal of Science
S. Afr. J. Sci
1996-7489
09282017
113
9/10
Deflating the shale gas potential of South Africa’s Main Karoo basin
Michiel
de Kock
DST-NRF CIMERA, Department of Geology, University of Johannesburg, Johannesburg, South Africa
http://orcid.org/0000-0002-5036-3438
Nicolas
Beukes
DST-NRF CIMERA, Department of Geology, University of Johannesburg, Johannesburg, South Africa
Elijah
Adeniyi
DST-NRF CIMERA, Department of Geology, University of Johannesburg, Johannesburg, South Africa
Doug
Cole
Council for Geoscience, Pretoria, South Africa
Annette
Götz
School of Earth and Environmental Sciences, University of Portsmouth, Portsmouth, United Kingdom
http://orcid.org/0000-0002-7467-3617
Claire
Geel
Department of Geological Sciences, University of Cape Town, Cape Town, South Africa
Frantz-Gerard
Ossa
DST-NRF CIMERA, Department of Geology, University of Johannesburg, Johannesburg, South Africa
The Main Karoo basin has been identified as a potential source of shale gas (i.e. natural gas that can be extracted via the process of hydraulic stimulation or ‘fracking’). Current resource estimates of 0.4–11x109 m3 (13–390 Tcf) are speculatively based on carbonaceous shale thickness, area, depth, thermal maturity and, most of all, the total organic carbon content of specifically the Ecca Group’s Whitehill Formation with a thickness of more than 30 m. These estimates were made without any measurements on the actual available gas content of the shale. Such measurements were recently conducted on samples from two boreholes and are reported here. These measurements indicate that there is little to no desorbed and residual gas, despite high total organic carbon values. In addition, vitrinite reflectance and illite crystallinity of unweathered shale material reveal the Ecca Group to be metamorphosed and overmature. Organic carbon in the shale is largely unbound to hydrogen, and little hydrocarbon generation potential remains. These findings led to the conclusion that the lowest of the existing resource estimates, namely 0.4x109 m3 (13 Tcf), may be the most realistic. However, such low estimates still represent a large resource with developmental potential for the South African petroleum industry. To be economically viable, the resource would be required to be confined to a small, well-delineated ‘sweet spot’ area in the vast southern area of the basin. It is acknowledged that the drill cores we investigated fall outside of currently identified sweet spots and these areas should be targets for further scientific drilling projects.
09282017
1
10.17159/sajs.2016/crossmark
sajs.co.za
false
2016-11-08
2017-06-10
2017-09-28
https://creativecommons.org/licenses/by/4.0/
https://creativecommons.org/licenses/by/4.0/
10.17159/sajs.2017/20160331
20170928070400
http://www.sajs.co.za/deflating-shale-gas-potential-south-africa%E2%80%99s-main-karoo-basin/michiel-o-de-kock-nicolas-j-beukes-elijah-o-adeniyi-doug-i-cole-annette-e-g%C3%B6tz-claire-geel-frantz
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http://www.sajs.co.za/sites/default/files/publications/pdf/SAJS-113-9-10_DeKock_ResearchArticle.pdf
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http://www.sajs.co.za/sites/default/files/publications/pdf/SAJS-113-9-10_DeKock_ResearchArticle.pdf
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http://www.sajs.co.za/sites/default/files/publications/pdf/SAJS-113-9-10_DeKock_ResearchArticle.pdf
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http://www.sajs.co.za/sites/default/files/publications/pdf/SAJS-113-9-10_DeKock_ResearchArticle.pdf
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http://www.sajs.co.za/sites/default/files/publications/pdf/SAJS-113-9-10_DeKock_ResearchArticle.pdf
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http://www.sajs.co.za/sites/default/files/publications/pdf/SAJS-113-9-10_DeKock_ResearchArticle.pdf
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http://www.sajs.co.za/sites/default/files/publications/pdf/SAJS-113-9-10_DeKock_ResearchArticle.pdf