Geothermal Resources in Southern Thailand : Integrated Geoscientific Investigations and Assessments

Abstract

Utilization of geothermal energy resources has increased over the last decades due to climate change concerns. Southern Thailand is hosts 30 hot major springs with the surface discharge temperatures varying between 40 and 80 °C. From all, seven were selected in the first stage using a 60 °C surface discharge temperature and 100°C reservoir temperature of silica geothermometer cutoff value. In a second stage a quantitative potential assessment applying positive attitude factors technique was applied using numerical scores. A final ranking shows that two hot springs sites, in RN1 hot spring of Ranong geothermal system and PG1 hot spring of PhangNga Province, have a good potential for further developed. For the PG1 site was possibility of the origin of the hot spring is derived from deep circulation and which is controlled by faults that are associated either with the igneous bodies. A regional forced convective-circulation model for geothermal area is suggested, reflecting deep structural controls of the fluid pathways in the area, which has limited the degree of mixing. On the other hand, Saline Hot Spring Khlong Thom (KB4) of Krabi geothermal system is an active hot spring site, making it a real saline hot spring, in comparison to hyper saline hot spring water, which can be found worldwide often. It was found that the salinity of the hot spring water is from saline groundwater intrusion into the shallow to intermediate deep aquifers. Hot water is coming from the depth via open faults and fractures and geochemical data suggest a possible recharge of the geothermal system by meteoric water. Mixing of the hot water and the brackish water is considered in the shallow subsurface, acting also as a geothermal reservoir. Shallow, mainly vertical faults separating this reservoir in small compartments thus making groundwater flow very localized.