BWEENGWA RIVER PROJECT LOCATION
The Bweengwa River Geothermal Resource Area covers the southern part of Lochinvar National Park and traditional lands sparsely occupied by the pastoralist Tonga ethnic group to the south of the Park. The area is accessed via the Livingstone – Lusaka truck road from Monze, which is some 45km by tarred and gravel roads.
The Park was established in 1972 having previously been a cattle ranch. It is noted for its wetlands around the Chunga Lagoon which are part of a RAMSAR site with significant diversity of wetland birds. Too small at 410km² to contain the ranges of most large mammals, it hosts the much-diminished endemic Kafue Lechwe (>250,000 in 1971 – <28,660 in 2015) and Buffalo (>800 in 2011, apparently <100 in 2015). The last sighting of Giraffe was in the 1960s and of Leopard in the 1970’s.
Human encroachment, domestic/wild animal conflict, and poaching have seen the degradation of the southern part of the Park, now dominated by cattle herds being grazed and watered. Wildlife is now concentrated north of the Gypsum mine and in the environs of Chunga Lagoon.
Figure 1:
Map showing Bweengwa River Geothermal Resource area in relation to Lochinvar National Park, the concentrations of Wildlife and the active Gypsum mine
BWEENGWA RIVER GEOTHERMAL RESOURCE
Exploration work undertaken:
- Geological mapping
- Hydrochemistry sampling
- Geophysics (including ground magnetics, AMT resistivity, radiometric, gravity, combined 3D modelling, and LiDAR/Thermal IR)
- Shallow soil temperature measurements
- Engineering, drilling and logging of fourteen (14) temperature gradient holes, designated Wells LOCH 01-14.
- Commencement of deep (1100 m) slim well drilling.
Current results confirm a geologic setting conducive for geothermal hydrothermal systems
Initial Indicated Resource: Greater than 10MW of usable power
The surface manifestations of the Bweengwa River Geothermal Resource Area include geothermal springs that extend over 9km and lie on the southern basin bounding regional fault of the Kafue Trough. Ongoing exploration has to-date included the drilling of fourteen temperature gradient/slim wells totalling 3,500m.
Results confirm a geologic setting conducive for geothermal hydrothermal systems and give a strong probability of a medium-low enthalpy geothermal resource that can support a power generation project of at least 10MW. Heat-in-place, power density and heat flow methods were used, providing a consistent estimated usable resource capacity in the range of 10-20MW.
The Bweengwa River Geothermal Resource Area contains compelling evidence of the three key elements required for hosting a hydrothermal system: temperature, permeability and water. Evidence for minimum reservoir temperature from 130C to more than 150C is provided by both fluid chemistry and temperature gradient holes. Permeability is confirmed by the discharge of the hot springs along the regional bounding fault and the associated geologic structures. The reservoir is in fractured basement rocks at a shallow to medium depth adjacent to the bounding fault. The source of water is local meteoric water that is plentiful.
The resource capacity is being verified by the 2019 drill programme, if successful, will lead to a feasibility study by the end of the year.
Geologica Geothermal Group
Update: Bweengwa River Preliminary Geothermal Resource Assessment – April 2016
Bweengwa River Geothermal Resource Area is within Kalahari GeoEnergy’s defined exploration area covering the Kafue Trough, which included five other identified targets.
CONCEPTUAL CROSS-SECTION
Geological Setting
Bweengwa River is situated in the Kafue Trough, a sedimentary basin filled by the Permian-aged Karoo sequence, overlying metamorphic Basement rocks (Figure 2); it is located to the west of Lusaka and extends westward into the Barotse Basin.
Figure 2:
Conceptual cross section across basin margin and fault zone Abbreviations:
EGF = Escarpment Grit Formation
MMF = Madumabisa Mudstone Formation
GCF = Gwembe Coal Formation
Loch 2,4,5,7 = drilled wells
STEPS TO DEVELOP AND PRODUCE POWER AT BWEENGWA RIVER
Development:
For development of each 10MW to consist of:
- Wells: Produce and inject ~1,000 m²/h of ~130-160˚C geothermal fluid: 3-4 production and 2-3 injection wells; Wells either vertical or directionally drilled to maximise penetration of reservoir
- Well-head Equipment: Fluid collection and reinjection piping systems, pumps, wellhead and pipeline valves and monitoring equipment
- Power Plant: Water-cooled binary unit capable of generating 10MW net including heat exchangers, turbines and auxiliary equipment
- A generator step-up transformer and switch yard to export power to the transmission line. Access/meter/sync point to energized 33kV line <6 km from location of wells
Concurrent Exploration to increase resource:
- Geophysics suggests likely extensions and systems at Bweengwa River Resource Area
- Company has identified and is conducting surface exploration including geophysics at additionally identified targets within the Kafue Trough exploration area
- Assessment is that license area may contain 50-80MW. KGE’s objective is to have 50MW either in production or as defined resources by 2022
Kalahari GeoEnergy Ltd is a member of the International Geothermal Association. For further information on Geothermal Energy and power production please see