Oil shale has been a source of oil for many decades in several countries. Globally the resurgence of oil shale is a result from: rising oil prices, which has made oil production from oil shale economic; countries securing their domestic energy supply, which reduces their reliance on oil imports from politically unstable states; and increasing demand for conventional oil, which is not being met by new conventional oil discoveries. Production of oil from oil shale requires the organic material in oil shale to be retorted. This usually takes place through contacting dried oil shale with hot recycled shale ash. This paper presents a detailed model of heat transfer in granular material and combines this with oil shale thermodynamics to estimate the rate of oil production from oil shale. A range of scenarios are presented including changing oil shale composition, adjusting the particle size, changing the initial temperature of the oil shale and adjusting the extent of mixing between the two materials. It is shown that chemical reactions of oil shale have a significant influence on the final equilibrium temperature and the time taken to reach this temperature. This equilibrium temperature also depended on the initial temperature of the materials and the ratio between those materials but was not influenced by the particle size nor the extent of mixing of the mixture. However, the time taken to reach this equilibrium temperature was affected by all variables.