The Coalbed Methane Resource Potential of the Ermelo Coalfield, South Africa

Abstract

The evaluation of the coalbed methane (CBM) potential of the Ermelo Coalfield in the Mpumalanga Province of South Africa forms part of an on-going hydrocarbon evaluation programme by the Agency. The primary objective of this study is to identify play fairways and assess the petroleum geology and hydrocarbon potential in the Permian coal-bearing Karoo-aged basin. Evaluating the CBM resource potential of the Ermelo coalfield was a three stage process that involved gathering and evaluating the quality of existing borehole data. Generally exploration borehole locations, lithology descriptions and coal composition (proximate analysis) data are available for the Ermelo coalfield. Because direct gas content data is lacking for the Ermelo coalfield, the gas storage capacity (gas content) was estimated by the indirect method of Kim (1977) which calculates dry, ash-free gas storage capacity of bituminous coal from proximate analysis using temperature, pressure and depth data. The gas-in-place (GIP) was therefore calculated based on the volumetric method of Mavor and Nelson (1997), whereby the volumes of gas is deterministically estimated. The key geological parameters (i.e. reservoir area, coal interval thickness, depth to top of the coal interval, and gas storage capacity) were assessed in an effort to evaluate the potential gas distribution within the Ermelo coal zone. Our results shows that the coals vary in rank from high volatile bituminous to medium bituminous. It is considered favourable for the occurrence of CBM due to the presence of extensive coal deposits and depths adequate for CBM development and preservation. References: Mavor, M. and Nelson, C.R. (1997). Coalbed Reservoir Gas-In-Place Analysis, Gas Research Institute, Report No. GR1-97/0263 Kim, A.G. (1977) Estimating methane content in bituminous coals from adsorption data. US Bureau of Mines Report of Investigations, 8245, pp.22

AAPG Datapages/Search and Discovery Article #90332 © 2018 AAPG International Conference and Exhibition, Cape Town, South Africa, November 4-11, 2018