Thermal Stimulation of Geothermal Wells: A Review of Field Data

Abstract

Thermal stimulation is the process of permeability change caused by temperature change. Data from New Zealand, and published data from elsewhere, is reviewed to determine the pattern of such changes. The record of injection wells shows that, in the absence of deposition, permeability increases roughly in proportion to time to the power of 0.4-0.7. Comparison between injection and production data shows that permeability increases with cold injection, sometimes more than two orders of magnitude. The increase depends strongly on the temperature contrast between reservoir and injectate, perhaps in proportion to the cube of the temperature contrast. Thermal stimulation is widespread and often unrecognised, being present for example in every well drilled or tested with cold fluid.