Well Simulation of Heat Transfer in a Deep Geothermal Single Well

This paper presents a novel geothermal well design concept that utilizes the low permeability interlayer in a reservoir with a single (tubing-in-casing) well to form an open-loop geothermal heat extraction system. In this new system, cold water is injected through the annulus between tubing and casing (above the packer) into the upper layer while hot water is produced from the lower layer and then transported to the wellhead through the insulated tubing. The low permeability interlayer acts as a barrier to avoid early thermal breakthrough often occurring in a normal single well system. We have developed a couple wellbore-reservoir model using T2Well to numerically simulate the performance of the new single well system with various sizes of the low permeability interlayer. The simulation results suggest that the radial distance of the low permeability interlayer should be greater than 206 m, so that the injected cold water can extract heat from the formation during the migration along this radial distance and will not affect the produced water temperature. Therefore, this novel geothermal well design is suitable for areas with low permeability interlayer, thus the heat output of the deep geothermal single well can be increased.