11:45 〜 12:00
[S27-1-06] Magnetotelluric surveys to delineate shallow reservoir of low-enthalpy geothermal systems in Thailand
invited
Most of Thailand geothermal fields are classified as the low-enthalpy system which can be efficiently utilized with the current technology for power production. The geothermal exploration assessment program was then initiated. The deep geophysical survey is one of the major parts of the program.
Since 2014, Mahidol University incorporation with a joint venture leading by Thailand Department of Groundwater Resources has been conducting magnetotelluric surveys on the selected geothermal fields in northern and southern Thailand. The 3-D resistivity distribution of those fields, up to a depth of 2 km, were carried out by a 3-D magnetotelluric inversion, WSINV3DMT, using impedance tensor and tipper data.
The obtained resistivity models support the conceptual model of the previously proposed hydrothermal system in most of the fields. The heat source is the deep resistive granitic rocks. The derived model also reveals the geological and fault structures acted as the fluid pathway to the surface where the hot spring manifestation occurred. The shallow conductive structures are mapped and can be referred as the geothermal reservoir in the formed of fluid-filled fractures in weathered granitic rocks or a clay cap formed in the sedimentary layers. The deep 1 km drilled well was then conducted in one of the fields. The core log data coincides with the resistivity model derived from the magnetotelluric survey. The methodology developed during the past surveys can be applied to other low-enthalpy geothermal fields and could help accelerating the geothermal energy utilization in Thailand.
Since 2014, Mahidol University incorporation with a joint venture leading by Thailand Department of Groundwater Resources has been conducting magnetotelluric surveys on the selected geothermal fields in northern and southern Thailand. The 3-D resistivity distribution of those fields, up to a depth of 2 km, were carried out by a 3-D magnetotelluric inversion, WSINV3DMT, using impedance tensor and tipper data.
The obtained resistivity models support the conceptual model of the previously proposed hydrothermal system in most of the fields. The heat source is the deep resistive granitic rocks. The derived model also reveals the geological and fault structures acted as the fluid pathway to the surface where the hot spring manifestation occurred. The shallow conductive structures are mapped and can be referred as the geothermal reservoir in the formed of fluid-filled fractures in weathered granitic rocks or a clay cap formed in the sedimentary layers. The deep 1 km drilled well was then conducted in one of the fields. The core log data coincides with the resistivity model derived from the magnetotelluric survey. The methodology developed during the past surveys can be applied to other low-enthalpy geothermal fields and could help accelerating the geothermal energy utilization in Thailand.