From optics to upscaled thermal conductivity: Green River oil shale

A novel approach for high-resolution (∼1 cm) spatial mapping of thermal conductivity from optical photographs of oil shale is developed and applied to the Mahogany Zone of the Green River Formation. A theoretically consistent constitutive equation for conductivity, parallel/perpendicular to the geologic bedding, as a function of organic content and temperature is proposed for unretorted Green River oil shale and shown to be in agreement with all published experimental measurements to date. Conductivity maps of a core spanning the full thickness of the Mahogany Zone are numerically upscaled, for intervals 10–80 cm long, and analytical equations capable of approximating the upscaled values to within ±5% error are presented. These obviate computationally costly numerical upscaling in the future. Upper bounds for upscaled anisotropy ratios (=parallel/perpendicular conductivity) were found to lie within 1.5 (typical case) and 2 (extreme case); with highest anisotropies occurring in the least conductive regions. The results of this work should benefit numerical models of in-situ retorting of oil shale resources at the core and field scales.