Chena Hot Springs is located in the east-central part of the Alaska within the Yukon-Tanana Plateau, about 75 km east of Fairbanks. It is a moderate temperature deep circulation system typical of interior Alaska. The main shallow upflow zone is about 2000 ft long and 300 ft wide. The system is located at the edge of a granitic body where deep circulating geothermal waters reach the surface by way of fractures along the contact with surrounding host rocks. The hot springs discharge at temperatures around 165 ?F (74 ?C); nevertheless, the geochemical data suggest the source temperatures to be around 250 ?F (121 ?C). With current drilling activities to 1020 ft (311 m), temperatures of up to 176 ?F (80 ?C) have been measured.

The temperature and pressure data from the current wells show that the geothermal system is similar to the Basin-and-Range type geothermal systems. This similarity allowed application of most of the exploration methods that are used in other fault/fracture related systems. These include a detailed geological study of the area, AMT, an airborne gamma ray spectroscopy, EM and magnetic survey, and drilling with reservoir analysis. The small size of the system has enabled us to apply the conventional exploration methods with better control. The system is attractive as it is smaller in scale compared to most of the Basin-and-Range systems, but still showing a similar complex hydrologic character.

So far, 11 exploration wells have been drilled as part of a DOE-GRED contract and 7 wells by the resort with depths 300ft-1000 ft. The highest temperatures in the 700-1000 ft depth range are found about 1000 ft west of the main hot springs vent area and the geothermal waters here show highest concentration of helium and dissolved solids. The location and size of the deeper high temperature system are not clearly understood with current drilling data because of the high permeability zone at shallow depth. The wells at both ends of the shallow convective zone have gradients two or three times the regional background which suggests the deep source is spread in a much wider area relative to the shallow zone. Currently, one 700 ft deep well with flow rate of 500 gpm has been used for running a 250 kWh power unit. Further deeper drilling has been proposed in order to understand the deep thermal regime. If the high target temperatures are reached at exploitable depths with sufficient flow rates, the production capacity could be 1-10 MW. The electricity production is possible in this low enthalpy system as a result of low surface temperatures relative to the moderate subsurface temperatures.
ubsurface temperatures.

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