Downhole Measurements of Thermal Conductivity in Geothermal Reservoirs

The line source method of determining thermal conductivity is extended to include the transient effect associated with the fluid in flowing geothermal wells. The general equations describing transient heat flow are utilized. Approximate solutions are derived and compared to the exact solution of the general equations. The proposed method is operationally simple since the heater, and the associated problems of obtaining adequate thermal contact between the heater and the sides of the borehole are eliminated. Using this method downhole measurements were obtained and favorably compared with laboratory measurements on characterized core specimens taken from wells in a hot dry rock geothermal reservoir.