NMR Determination of Porosity and Permeability of Western Tight Gas Sands

摘要

Samples of fine-grained sandstone from the Colorado Interstate Gas Exploration (CIGE), Natural Buttes No. 21 core, Uinta Basin, Utah were studied using pulsed nuclear magnetic resonance (NMR) and standard mineralogical techniques. Brine-saturated rock porosities varied from 1 to 13% and were found deducible from the magnitude of the proton NMR. The complex pore geometry and presence of authigenic carbonate and clay minerals in these samples precluded the use of standard flow models for predicting brine permeabilities from T sub 1 decays. A network model of the pore system is proposed and shown capable of accurately reproducing measured rock permeabilities, which varied from 10 exp -4 to 1 millidarcy. (ERA citation 06:018047)