Statistical methods for estimates of heat flow in Australia

Abstract

Normally, special purpose drill holes are required to provide direct determinations of surface heat flow. These provide core samples for thermal conductivity measurements and allow access for measurements of a reliable geothermal gradient after long periods of equilibration. Different, indirect procedures are now required to provide estimates of heat flow for offshore basins. Bottom hole temperatures can be used with suitable corrections to provide an indication of the regional geothermal gradient. However, the corresponding thermal conductivities are more difficult to determine. Geophysical logs can be used to detect the major lithologies but detailed statistical analysis is required for numerical estimates. Complex mixing models are now suggested for geothermal surveys linking physical properties to variations in the mineralogy of each well.