Assessment of Geothermal Gradient in Bogala Area, Sri Lanka

Geothermal gradient gives important assessment to geothermal potential in an area. This study aimed to study geothermal potential in Sri Lankan crust using measurement from available deep mines. Bogala Graphite mines is one of accessible deep mine available and located 124 km away from the well demarcated tectonic boundary in Sri Lanka. In this research, 476 m deep Bogala Graphite mines was selected to study the geothermal gradient in Sri Lankan crust. Drill holes made in the bed rock horizontally, temperature sensors placed approximately in the same direction and kept continuously around 72 hours period. All the places selected to install sensors were far ends of long run abandoned tunnels/ adits in the mine. The average values of temperatures in those levels were computed, and then geothermal gradient was calculated as 28.046 0C/km. This method gave some reliable information about, how temperature gradient varies at different levels of Sri Lankan crust.