The First Deep Geothermal Exploratory Slimhole at Admiralty Lane, Singapore

Singapore has at least two known hot springs with surface water temperatures of 50–90 °C. Together with its estimated high heat flow, Singapore is thought to have a geothermal potential. To assess the potential, we focus our study on the northern part of Singapore, where elevated shallow subsurface temperatures have been identified. Two deep exploratory slimhole sites are selected within this region. One slimhole has been successfully drilled to a record-breaking depth of 1.1 km within Singapore’s granite bedrock at Admiralty Lane. Subsurface temperatures are measured, and rock core samples are collected from this slimhole. Data analysis reveals a high geothermal gradient at depths beyond 800 m, surpassing the global average continental geothermal gradient. If this temperature gradient remains constant beyond 1.1 km deep, the rock temperature at 4–5 km deep can be estimated to reach 200 °C. The temperatures are found to be hotter than many other non-volcanic regions around the world. Additionally, laboratory measurements on the rock core samples found that the granite at the Admiralty Lane site, also known as the Simpang granite, has an above-average radiogenic heat production, that if consistent to over 10 km deep, can contribute significantly to Singapore’s anomalously high heat flow. The study to date finds that Singapore’s Simpang granite has high geothermal gradient, heat production, and heat flow. These findings underscore Singapore’s promising geothermal potential, warranting further exploration to deeper depths, such as 5 km. This journey could unlock opportunities for sustainable energy initiatives.