Heat-flow measurement in non-homogeneous terrains. Its application to geothermal areas

Abstract

Taking into account the great importance of thermal prospections in geothermal research, it was decided to give an experimental answer to some questions concerning the measurement in non-homogeneous terrains such as flysch. With this aim, the testing ground was located on flysch having high limestone content in marly clays, in a thermally anomalous area (heat flow = 16.39 · 10 −6 cal/cm 2 sec). Geological and thermal characteristics of the field, thickness and nature of the whole impervious layer, contact temperature of the latter and the underlying pervious layer were already known, as several deep wells had already been drilled in this area. Three geothermal wells were bored at 80 m depth with a 20 m spacing; they differed in diameter and filling-up system. Lithology of drilled rocks was also different. Data are reported on the following items: • - relationship of actual structural features to heat flow and gradient measurements close to the surface; • - influence of the specific siting of a well within the chosen area; • - value of heat flow at different depths in the shallow wells drilled into flysch with calcareous, shaly and marly layers; • - influence of wells' diameter and filling-up system on measurements taken; • - approximation of obtained heat flow value in the flysch, carried out by means of gradient and heat conductivity measurements.