Thermal Conductivity Measurement Techniques for Geothermal Exploration Heat Flow Surveys

Abstract

Although most thermal conductivity measurements for terrestrial heat flow surveys are made using variations of the divided bar apparatus, the technique presents a number of constraints to the timely completion of thermal exploration for geothermal resources. The apparatus is a laboratory device and is both tedious and time consuming for routine processing of samples. Using the needle probe method, consistent, reliable results can be obtained for saturated unconsolidated materials when proper corrections are made for volume of liquid. Thermal conductivities were obtained on solid cores of several rock types as well as numerous suites of drill cuttings. Divided bar determinations were made on the solid cores which were crushed to powders and measured using the divided bar cell and needle probe techniques. Measurements corrected for water saturation have shown excellent agreement among the three techniques with an average difference of less than a few percent. Utilizing a recently developed field portable needle probe apparatus, on site thermal conductivity values can be obtained from drill cutting in less than ten minutes.