Document Type
Conference Proceeding
Publication Date
2016
Abstract
In 2015, a 1-km core hole was drilled into granitic rock at the Muang Rae geothermal area. Previous drilling in 1993 to 200 m was unsuccessful in obtaining flows, but one of the “dry” wells began flowing in August, 2013 at 9.75 L/s of 96.9°C water from a fracture zone 80 m deep. In the sandy bed of the Pai River, 150 m south of that well is a 600-m long line of hot seeps, oriented NE, with highest temperature measured at 94.5°C. Geology is foliated Triassic (?) granitic rock cut by a NE-SW-trending normal fault zone (dip 65° NW) with extensive fluorite mineralization. Mineral equilibrium geothermometer analysis predicts a reservoir temperature of 132°C. The core hole was sited NW of the seep zone to drill into the fault zone at 600 m. MT indicated a low-resistivity anomaly 150-500 m deep at the site. The well did not flow, but was pumped at 6.4 L/s of 86°C water with 2.5 m of drawdown. Temperature logs indicate the well intersects a fracture with flowing hot water of 91.5°C at 600 m. The log shows a temperature inversion related to the transient effect of conductive heating of the surrounding rock by hot-water flow in the fracture. The bottom 150 m of the well shows a 23°C/km temperature gradient, which reflects the regional crustal conductive gradient.
Copyright Statement
This document was originally published in Geothermal Resources Council Transactions by Geothermal Resources Council. Copyright restrictions may apply.
Publication Information
Wood, Spencer H.; Pirarai, Kriangsak; Fuangswasdi, Aranya; Kaentao, Wiboon; Waibel, Albert; and Singharajwarapan, Fongsaward S.. (2016). "Muang Rae Geothermal System: Drilling and Borehole Geophysics, 1000-m Core Hole into Granitic Rock, Amphoe Pai, Mae Hong Son Province, Northern Thailand". Geothermal Resources Council Transactions, 40659-670.