GEOTHERMAL CHARACTERISTICS OF SEDIMENTARY RESERVOIR IN THE FOLD-AND-THRUST BELT: INSIGHT FROM WESTERN TAIWAN
In the outcrop analysis, we combined previously available data with new measurements in the field, mapping significant thrust faults, synclines and anticlines. Through lineament interpretation and fracture investigation at the surface and by comparing the spatial locations with the major geological structures in the region, the correlation between tectonics and fracture distribution can be revealed. Moreover, this approach enables us to evaluate how the fracture characteristics of the stratigraphic layers in the study area might impact the hydrogeology.
In three drillings data, critical fault-generated fractures with fluid veins indicate possible fault surfaces accompanied by fracture zones. The downhole dip meter has provided dipping changes, strongly suggesting the presence of detachment faults, which are possibly related to overpressure zones once causing mud loss and blowout while drilling. Porosity estimations derived from logging data have provided the characteristics of potential reservoirs within the sandstones, and the geothermal gradient reaches 40-45 ℃/km.
Two essential cross-section profiles have been established. The sedimentary reservoir with fault-related fractures plays a potential role in determining the geothermal resource in western Taiwan.