Campbell, Stuart Alexander (2018) Energy potential of the Ecca Group from the southern Main Karoo Basin, South Africa. Doctoral thesis, Keele University.

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Abstract

Energy shortages and sporadic, controlled blackouts have been a defining feature of South Africa’s aging national energy grid for more than a decade. To investigate local energy sources from shale gas, two boreholes were drilled in the southern Main Karoo Basin into the Permian-aged Ecca Group by the Karoo Research Initiative. Borehole KZF-1 (Western Cape) intersected thick shale successions of the lower Ecca Group and revealed the stratigraphic duplication of the Whitehill (shale gas target) and Prince Albert Formations. This structural deformation was most likely as a result of the organic-rich formations, acting as a decollement for thrust faults related to the north-south directed compression of the Cape Orogeny. Reservoir compartmentalisation and gas escape along porous fault zones hinder hydrocarbon exploration in the area. Borehole KWV-1 (Eastern Cape) revealed thick successions of turbiditic sandstones and a moderately elevated geothermal gradient. The clastic rocks have low permeabilities and high thermal conductivities. Analysis of the petro- and thermophysical data from the Ripon Formation sandstones, from both the core and nearby Ecca Pass outcrop location, show the potential of the formation as an Enhanced Geothermal Reservoir, with temperatures exceeding 100°C being suitable for energy production from a binary geothermal power plant. The comparison of combined gamma-ray logs, geothermal potential of samples (specific heat capacity, thermal diffusivity, and thermal conductivity) and lithological logs show a correlation between lithological composition and geothermal reservoir potential that can be identified in gamma-ray log patterns. These correlations can be extrapolated for purposes of geothermal exploration in non-cored nearby boreholes. The numerous pre-existing faults, decreasing from the basin’s southern margin towards the basin interior, elevate the risk of inducing seismic events from the use of reservoir stimulation techniques associated with energy exploration, as well as wastewater management associated with future extraction activities.

Item Type: Thesis (Doctoral)
Subjects: G Geography. Anthropology. Recreation > G Geography (General)
Divisions: Faculty of Natural Sciences > School of Geography, Geology and the Environment
Depositing User: Lisa Bailey
Date Deposited: 12 Dec 2018 16:53
Last Modified: 12 Dec 2018 16:54
URI: http://eprints.keele.ac.uk/id/eprint/5586

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