Evaluation of the Coalbed Methane Prospectivity of the Ermelo Coalfield (Amersfoort Project Area), Main Karoo Basin, South Africa

The evaluation of the coalbed methane (CBM) potential of the Ermelo Coalfield in the Mpumalanga Province of South Africa. Previous studies done by the Agency revealed that the coals vary in rank from high volatile bituminous to medium bituminous and considered favourable for the occurrence of CBM due to the presence of extensive coal deposits and adequate depths for CBM development and preservation. 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. The Ermelo Coalfield is located in the extensive Permian age coals of South Africa’s Main Karoo Basin with the most significant coal seams contained within the Ecca Group. The coalfield is considered highly prospective for coalbed methane and also gassy sandstone overlying the coal horizons. Gas contents have been reported in studies associated with previous mining attempts but no actual measured gas contents are available. The Agency adopted a three-stage process that involved gathering and evaluating the quality of existing borehole data for evaluating the CBM resource potential of the basin. 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.