Analysis of Wellbore Heat Transfer in Enhanced Geothermal System using CFD Modeling

Wellbores in Enhanced Geothermal System extends several kilometers from the ground surface, providing large heat transfer areas between the flowing fluid and the surrounding formations. Various techniques and approximations to model wellbore heat transfer have been presented in the literature. Most of the wellbore simulators assume steady one-dimensional flowing without considering heat transfer with the surroundings. Unsteady fluid flowing within a vertical injection and production well, together with wellbore heat transfer was modeled using Computational Fluid Dynamics (CFD) simulator Fluent in this paper. The time-evolving results show that almost the entire pipe is in the hydro-fully developed condition, but not thermal-fully developed in the initial phase. Heat transfer direction in the upper section is opposite to that in the lower section due to the opposite gradient vector. In addition, the temperature variation along each wellbore due to the Joule-Thomson effect is significant.