"A mathematical model has been developed for simulating the processes involved in the in-situ retorting of rubblized beds of oil shale. The model is a transient, one-dimensional treatment of a packed-bed reactor. It is based on the thermodynamics and kinetics of the numerous chemical reactions and physical processes that are most important for hot inert-gas retorting and for combustion retorting. The validity of the model is tested by comparison with experimental retort data. The predicted retorting results for conditions of interest to commercial, modified, in-situ retorting are discussed in detail. The initial shale properties, such as grade, carbonate content, and bed porosity, are shown to have an important bearing on the maximum retort temperature, the rate of retorting, and the oil yield. The input-gas properties, such as composition, flow rate, and temperature, are likewise shown to strongly influence the retorting results. The latter properties, particularly the input-gas composition and flow rate, can readily be changed during the course of the retorting operations and thereby offer a sensitive means of retort control."