Geothermal Potential in Bangladesh - Results from Investigations of Abandoned Deep Wells

Abstract

Temperature data for a large number of abandoned deep wells, once drilled for oil and gas exploration, have been collected, together with results from other sources for geothermal conditions. These depend on the ongoing tectonic activity in parts of Bangladesh. Rapidly filling deep sedimentary basins represent volumes with low thermal gradients (ca 20 K km-1), while rising regions with shallow crystalline rocks represent volumes with considerably higher thermal gradients. Several deep drill holes in the SE slope of the Rangpur Saddle have gradients of ca 35 K km-1. This region is currently under further investigation with respect to the hydraulic conductivity of their deep stratigraphic formations. In the central part of the Rangpur Saddle local high groundwater temperatures are observed, especially in connection with graben structures in the crystalline basement where Gondwana age coal containing sedimentary units make up the graben fill. At the base of the coal beds the groundwater temperature is in excess of 50 oC. Further studies are planned in order to determine the thermal gradient, the stress and the fracture status of the rising crystalline basement. A third geothermal target region is the fold belt in the SE part of Bangladesh, where locally warm springs occur. A geothermal map of Bangladesh is presented here for the first time.
The geothermal investigations are a joint project between the Royal Institute of Technology, Sweden and the Department of Geology at the Dhaka University in Bangladesh. The project is sponsored by the Futura Foundation in Stockholm.