Analysis of the Results from the Downhole Coaxial Heat Exchanger (DCHE) Experiment in Hawaii

Abstract

Analysis of the experimental results from the DCHE experiment (Morita et al, 1992), was carried out to investigate the insulation performance of the inner pipe used in the DCHE and the heat transfer characteristics in the formation. The equivalent thermal conductivity of the pipe was estimated to be 0.06 W/mK. This indicates that the performance of the insulated pipes used as the inner pipe is sufficiently high for DCHE application. Analysis also indicated that the heat transfer mechanism during the experiment was almost pure conduction and that the thermal conductivity of the formation was 1.6 W/mK. This value is concordant with the thermal conductivity of water saturated Hawaiian Basalt (Horai, 1991). Also the fact that the observed heat transfer mechanism in the formation was pure conduction indicates that heat was extracted mainly from a low permeability conduction zone of the HGP-A reservoir.