Parametric Sensivity Study of Operating and Design Variables in Wellbore Heat Exchangers [report]

G. Michael Shook, Gopi Nalla, Gregory L. Mines, K. Kit Bloomfield
2004 unpublished
This report documents the results of an extensive sensitivity study conducted by the Idaho National Engineering and Environmental Laboratory. This study investigated the effects of various operating and design parameters on wellbore heat exchanger performance to determine conditions for optimal thermal energy extraction and evaluate the potential for using a wellbore heat exchanger model for power generation. Variables studied included operational parameters such as circulation rates, wellbore
more » ... on 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, heat transfer contact area, and 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 the 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 (682.4e+3 BTU/h) at the onset of pseudosteady state. Using realistic conversion efficiency, the method is unlikely to generate 50 kW (170.6e+3 BTU/h). iv v ACKNOWLEDGMENTS The authors wish to thank DOE for funding this project; Raymond LaSala, whose interest in evaluating the feasibility of wellbore heat exchangers motivated this critical study; John Finger from Sandia National Laboratories for his valuable contributions; and our program manager, Joel Renner, for providing support and suggestions for this project.
doi:10.2172/910645 fatcat:tgly2z7vvfg47naomqpcf5mfyi