Determination of Matrix Thermal Conductivity from Dry Drill Cuttings

Abstract

This paper reports experimental data relating the observed dry-bulk thermal conductivities of powdered minerals to the porosities of the powdered aggregates. The mineral samples were obtained by crushing quartz, calcite, and feldspar crystals. Experiments also were conducted on clays from various sources. The experimental data suggest an exponential relationship between the dry-bulk thermal conductivity and the aggregate porosity. The thermal conductivities of the original quartz, calcite, and feldspar crystals were determined in a dry state to estimate their matrix thermal conductivities. An empirical relationship was determined among dry-bulk thermal conductivity, aggregate porosity, and matrix thermal conductivity. This empirical relationship provided estimates of matrix thermal conductivity that were consistent with theoretical mix formulae for 50:50 mixtures of combinations of the minerals quartz, calcite, and feldspar, and also a sample of Flag Sandstone from the North West Shelf, Australia. The method was used to estimate heat flows at the sites of two Australian North West Shelf wells: Dampier 1 and Tryal Rocks 1, which are 47.4 mW/m2 and 79.7 mW/m2, respectively. These values are less than sea floor estimates of heat flow in the same region, and suggest nonconductive heat-transfer processes within the North West Shelf sedimentary section.