THERMAL-CONDUCTIVITY OF WILCOX AND FRIO SANDSTONES IN SOUTH TEXAS (GULF-OF-MEXICO BASIN)

Thermal conductivity and petrographic data are presented for verifying mechanistic models of sandstone thermal conductivity. We measured the thermal conductivity of 83 Wilcox and Frio sandstones from south Texa s in the Gulf of Mexico sedimentary basin, and correlated conductivity to petrographic variables. Thermal conductivities of water-saturated sandstones at 20 degrees C (68 degrees F) and 3 MPa (435 psi) were mea sured on core plugs using a divided-bar apparatus. Thermal conductivit y ranges from 2.06 to 5.73 W/m/K over a porosity range of 2.4 to 29.6% . Because of a higher quartz content, Wilcox sandstones at a given por osity are more conductive than Frio sandstones. A grain-matrix conduct ivity of 5.9 W/m/K is estimated for Wilcox sandstones; matrix conducti vity is adequately described with an arithmetic mixing model. Thermal conductivities of clean (<25% clay) sandstones can be described by a m ultilinear function of decreasing thermal conductivity with increasing porosity and increasing thermal conductivity with quartz content. For clean, quartzose (>35% of the solids) sandstones, the dependence on q uartz content can be dropped and thermal conductivities can be predict ed with a linear decrease in conductivity with increasing porosity. Th ese sandstones appear isotropic with respect to thermal conductivity.