In-situ determination of heat flow in unconsolidated sediments

Subsurface thermal measurements are the most effective, least ambiguous tools for locating geothermal resources. Measurements of thermal gradient in the upper few tens of meters can delineate the major anomalies, but it is also desirable to combine these gradients with reliable estimates of thermal conductivity, to provide data on the energy flux and to constrain models of the heat sources responsible for the anomalies. Problems associated with such heat flow measurements include the economics of casing or grouting holes, the long waits and repeated visits necessary to obtain equilibrium temperature values, the possible legal liability arising from disturbance of aquifers, the hazards presented by pipes protruding from the ground, and the security problems associated with leaving cased holes open for periods of weeks to months.