Shale-gas potential from Cretaceous succession in South Africa’s Orange Basin: Insights from integrated geochemical evaluations

Abstract

Shale sediments were collected from four Cretaceous stratigraphic units across four explorations well locations in South Africa’s Orange Basin and analysed to determine organic-matter characteristics, such as amount, quality, thermal maturity, and their viability as gas resources. The geochemical results show that the Cretaceous shales contain moderate organic quantities, as shown by TOC averagely up to 1.29%. The organic facies consist primarily of Type III kerogen, as proven alongside low hydrogen indexes between 40 and 133 mg HC/g TOC. As seen under a reflected light microscope, the dominance of such land plant-rich organic matter is in harmony with the significant amount of Vitrinite macerals. These organic sediments can produce primarily gas when they mature. The geological and geochemical properties of the organic sediments, chiefly Type III kerogen, generate both wet and dry gas, particularly when adequate thermal maturity is enhanced at deeper locations. Thus, the Orange Basin is considered promising for shale gas exploration and production.

Keywords:

• Shale gas
• source rocks
• Orange Basin
• organic matter
• kerogen

Acknowledgements

The authors gratefully acknowledge the University of Malaya research grant (IF064-2019) and the study support provided by Usmanu Danfodiyo University Sokoto via TeTFUND intervention. Furthermore, special appreciation goes to Mr Zamri, Aliff, and Madam Zaleha for their analytical assistance. Finally, we would like to express our gratitude to Integrated Geochemical Interpretation (IGI) Ltd for providing an academic license for the p: IGI geochemical software.

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could appear to have influenced the work described in this article.

Additional information

Funding

This work was supported by Institut Pengurusan dan Pemantauan Penyelidikan; Universiti Malaya; TETFund National Research Fund.