The proposed TS-4 project in the Upper Rimrock formation in Uintah County, Utah, has been evaluated using INTERCOMP’s in-situ combustion model. The project involves both in-situ reverse combustion and steam flooding. The combustion preheats the formation before the steam flooding. It is limited and contained in a middle 10-foot interval with a correlatable high permeability streak within the 65 foot pay zone. A high communication path was created between the air injector and the producers in order to obtain adequate injectivity and sustain a stable reverse combustion. The effect is tantamount to initiating a fracture in this zone, parallel to the bedding plane. The process performance was optimized under different pattern sizes and injection rates. Under the conditions of this study, the following conclusions are drawn: 1. The proposal for the TS-4 project is considered feasible. 2. Combustion can be propagated in a 10 foot interval within a 65 foot pay. The heterogeneity of the formation helps to confine the combustion within the interval. The combustion spreads out more into the adjacent layers in a homogeneous formation. 3. A high communication path between the injector and the producer is necessary to achieve a stable reverse combustion. Instability of the front and combustion ‘echoes’ develop as the formation pressure increases. 4. Oil recovery by steam flooding is accelerated in a formation pre-heated by combustion; although the overall process time and cost may not justify pre-heating for this purpose only. Ultimate recovery remains essentially the same with or without the pre-heat reverse combustion. 5. High steam injection rate improves the recovery performance. A rate of 10.0 B/D/acre-ft was found adequate. The best performance is obtained when the injection is concentrated in the bottom zone. 6. A recovery of nearly 40% 00IP is possible from the Upper Rimrock formation in Northwest Asphalt Ridge with the TS-4 design. Under “optimum” conditions, the ultimate recovery is about the same for the 0.25, 0.5, 1.0 and 2.0 acre patterns. The true optimum pattern size and air injection rate will be determined by the economics. 7. Gravity segregation was evident during the steam flooding and possibly enhanced the steam flood performance. The pressure was low and the vertical spread of the combustion front was too poor for any significant gravity segregation during the reverse combustion.