Deep geothermal well in Yuanshan, Taiwan, indicates upwelling heat source at 4000m
A conceptual diagram of the geothermal geological model of Yuanshan Mountain in Yilan City was drawn by Researcher Chien-Chieh Lee of the Institute of Earth Sciences, Academia Sinica. (source: Academia Sinica)
Carlo Cariaga
10 Dec 2025
A deep geothermal well drilled in Yuanshan, Taiwan indicates an upwelling heat source that warrants further investigation and exploration drilling.
The deep geothermal well drilled in the township of Yuanshan in Yilan County, Taiwan indicates an upwelling of a high-temperature geothermal heat source at depth, with the potential of a nearby exploitable high-temperature heat source. Thus, Academia Sinica recommends the drilling of more test wells to successfully explore and develop the resource.
Drilling of a deep geothermal well in Yuanshan, which was first announced in October 2024, was done by CPC Taiwan with Academia Sinica. A release from a few weeks ago indicated that the bottomhole temperature was below expectations, although the well was still useful for providing insights on the subsurface and the geothermal resource. The latest publication from Academia Sinica provides more details on the technical findings from the deep geothermal well.
A rapid temperature increase at depth
Lee Chien-cheng, a researcher at the Institute of Earth Sciences, Academia Sinica and the chief principal investigator of the “Taiwan Geothermal Research and Technology Development Project,” recalled that the well temperature was still below 100 °C at a depth of 3000 meters. This was concerning for the team, but the temperature rose rapidly upon reaching 3500 meters depth. Finally, a temperature of 150 °C was reached at the target depth of 4000 meters.
The rapid temperature increase at depth is indicative that there is indeed a heat source, and that the center of the heat source is probably already close to the drilled well. The goal of the team is to reach exploitable temperatures at a depth of only 300 meters.
Moreover, analysis of the drilling data revealed that the lower Xicun and Zhongling formations have favorable geological conditions for water fracturing that is less likely to trigger earthquakes. This technology can help create permeable channels, thus creating more favorable conditions for geothermal development
More test wells recommended
The results of the first deep geothermal well in Yuanshan have confirmed that there is a geothermal resource in the area. To fully map the geothermal upwelling pattern, the team has recommended the drilling of more test wells. Chen Yu-kao, Executive Secretary of the Sustainable Science Center at Academia Sinica, stated that an average of 3 to 5 test wells will be needed to successfully develop a geothermal project based on international experience.
The Yuansan well has now been temporarily converted into a monitoring well and has been outfitted with fiber optic temperature and vibration sensors. The team hopes to continue collecting exploration data to accurately locate and better characterize the high-temperature strata. This data will then be the basis for deciding whether a conventional geothermal or enhanced geothermal systems will be more appropriate for the project site.
Source: Academia Sinica
