Proceedings, 7th African Rift Geothermal Conference
Kigali, Rwanda 31st October – 2nd November 2018
Zambia: Exploration of the Non-volcanic, Fault Hosted Bwengwa River Geothermal Resource Area
Peter Vivian-Neal1, Maxwell Wilmart2, Jill Haizlip2, Nicholas Hinz2, Peter Harrison3 and Sendoi Sikokwa1
1 Kalahari GeoEnergy Ltd, 40 Jesmondine, Lusaka, Zambia,
2 Geologica Geothermal Group Inc, 5 Third Street, Suite 420, San Francisco, CA 94103, USA
3 Pretoria, South Africa
Zambia, Bwengwa River, fault hosted, resource assessment
The Bwengwa River Geothermal Resource Area is associated with a Karoo basin bounding regional extensional normal fault, with prolific near-boiling hot springs and terrace deposits that is constrained by embayments. Temperature gradient holes have encountered a >100°C reservoir at the contact between the base of the Karoo sediments and the Proterozoic basement. Fluid geochemistry and cation geothermometry are consistent between the well fluids and the hot springs and indicate a deeper reservoir of ~150°C. Geophysics surveys indicate a buried zone of sub-parallel subsidiary basement splay faults basinward of the main basin bounding fault zone.
The conceptual model of the reservoir has a ~150°C up-flow ascending along the buried splays beneath the Karoo sediments that act as a cap rock, and outflow both basinward and up-dip within the fault zone coming to surface at hot springs that extend over 9 km. Recharge is along subsidiary faults and the elevated topography. This model has been refined with the benefit of ongoing exploration and has been used for an initial resource capacity estimate and for slim well targeting.
A probabilistic power density estimate of a discovered 150°C resource yields an expected power capacity of 2-93 MWe (P90-P10) with a most likely value of 15 MWe (P50). Ongoing exploration in 2018 2019 may increase this capacity estimate and confidence level prior to a planned feasibility study that will include the concept of cascaded energy being supplied to a community agro-processing hub.
The full report in PDF file format is available here. (16 pages, 1.75Mb)