Parametric Sensitivity Study of Operating and Design Variables in Wellbore Heat Exchangers

Abstract

A numerical study was conducted to evaluate the
potential for using a Wellbore Heat Exchanger
model for power generation. Variables studied
included operational parameters such as
circulation rates, wellbore geometries and
working fluid properties, and regional properties
including basal heat flux and formation rock
type. Energy extraction is strongly affected by
fluid residence time and heat transfer contact
area, and by formation thermal properties. Water
appears to be the most appropriate working fluid.
Aside from minimal tubing insulation, tubing
properties are second order effects.
On the basis of the sensitivity study, a Best Case
model was simulated, and results compared
against existing, low-temperature power
generation plants. Even assuming ideal work
conversion to electric power, a wellbore heat
exchange model cannot generate 200 kW at the
onset of pseudo-steady state. Using realistic
conversion efficiency, the method is unlikely
able to generate 50 kW.