Evaluation of the Existing State of Geothermal Exploration and Development in Nigeria

Relatively little expenditure for hydroelectricity and fossil fuels have had a restraining influence on levels of exploration and development for geothermal energy resources in Nigeria for the past several years. The focus of development has been in the areas of low temperature geothermal energy involving the exploration and assessment of hot spring resources primarily for recreational applications ? although possibly for other direct uses depending on local infrastructure and access to appropriate energy markets. The geological structure of Nigeria influences geothermal exploration extent within each geological province. Sedimentary basins in Nigeria have been explored for hydrocarbons for several decades, thus the oil companies collected large subsurface temperature data basis. But not much is known about geothermal conditions within Nigerian Precambrian crystalline province. On the basis of BHT data from oil wells it has been found that geothermal gradient in Niger Delta ranges from 1.5 to 4.9°C/100m and in Anambra Basin (directly to the north) it can reach 5.7°C/100m. Exploration for geothermal energy in northern Nigeria based on shallow water wells (down to 600 m deep) was carried out over 20 years ago. The other aspect of geothermal exploration in Nigeria is investigating of the thermal springs and seepages, which occur mainly within sediments of the Middle and Upper Benue Trough. The water of the warmest springs in that area: Akiri and Ruwan Zafi have the temperature about 56°C and it suggests the occurrence of some geothermal anomalies. So far, there are probably only three (direct) geothermal energy utilisation sites in Nigeria. The Ikogosi warm spring (37°C) located in south-western part of the country, in Ekiti state, the Wikki warm spring (39°C) located in Bauchi (North-eastern) part of Nigeria and the Rafin Rewa spring (42°C) located in Plateau (North-central) state of Nigeria. Hence this paper reviews the current status of the geothermal industry (both high and low temperature) in Nigeria.