On the Structure and Geothermal Energy Potential of the Sedimentary Basins of Africa

Abstract

The increase in the African population size and the corresponding increase in energy demand is one of the most relevant challenges facing continental Africa to date. This problem, coupled with the need for the reduction of greenhouse gases in the context of climate change, exacerbates the demand for more sustainable renewable energy sources. Harnessing geothermal energy (the energy/heat stored in the earth) might provide a solution in meeting these energy demands.

In this research, we provide constrains on some of the key parameters that are important for determining preliminary geothermal energy resources potential estimates of Africans sedimentary basins. Here we provide estimates and comparisons on the porosity-depth relationships of the sedimentary basins of Africa to determine if these are similar enough to be assumed identical for modelling purposes. We also provide a 25km resolution sediment thickness map for continental Africa.

Given the scale of the continent and the heterogeneous nature of the quality of the available data, few studies have attempted to model the geothermal energy resource potential of Africa. The ones that did, have made assumptions due to the scarcity and poor quality of the available data that largely ignore the differences between basins and their potential reservoirs. Additionally, we find that the current highest resolution public sediment thickness map for Africa, is insufficient for performing more detailed numerical modelling of the resource potential.

We compile publicly available Porosity-depth data and construct basins specific porosity-depth relationships based on standard burial compaction equations. These curves are subsequently analysed to determine potential burial anomalies and their discrepancies with standard clastic sediment curves. The new sediment thickness map is created via the Basin3D inversion modelling software of TNO, using satellite gravity data and geological constrains obtained from the literature.

This research provides critical sidenotes on the assumptions made in previous geothermal energy potential modelling work and provides new sediment thickness maps that can be used as either a starting point or as validation for local basin modelling. These results as part of the work done by Geothermal Atlas for Africa project, aim to provide a starting for future geothermal energy exploration studies to be performed in the countries of Africa.