Predicting Temperature Patterns and Flow Behaviour of Poorly Constrained Geothermal fields: The Case of Songwe Extensional Basin (Tanzania)

Abstract

Energy plays a fundamental role in societies impacting everything from basic human needs like lighting, cooling and heating to complex industrial processes that significantly influence social development, economic growth, and national security particularly in terms of access and affordability for all citizens. The world’s electricity demand grew by 2.2% in 2023 and is expected to rise at a faster rate by an average of 3.4% in 2026 (IEA, 2024). With the global climate warming, it is important to reduce our societal impact on Earth by using clean energy sources. One of the clean sources is geothermal energy which has a great potential to reduce dependency on the fossil fuels. Geothermal energy sources can deliver both, heat and electricity. Tanzania has a huge geothermal potential that has not yet been used and has only been explored to a limited extent. This thesis attempts to identify the geothermal potential of southwest Tanzania with appropriate drilling zones by assessing the main components of a geothermal system reservoir which are temperature, permeability and fluid flow at Songwe Tanzania. It is one of the identified potential development areas with very little information available.
The work flow begins with chapter 2 where a geological and thermal numerical model is set up to simulate the temperature at depth. The thermal model considers pure conductive heat flow to achieve a first idea of the temperature distribution in the different geological layers.
Chapter 3 describes the conducted field study at the thermal spring areas as well as the laboratory analysis of the samples in order to understand the geothermal fluid source by using geochemical modelling, obtain the reservoir temperature through geothermometer calculation and locate the up-flow and the outflow zones of the geothermal field.
In chapter 4 numerical simulations of fluid and convective heat flow are performed to allow understanding the heat transport by fluids and the hydrogeological behaviour of the geothermal reservoir by varying thermal and physical parameters.
Chapter 5 shows possible drilling locations for a first geothermal well in the study area, whereby areas of different productivity are distinguished.