Electrical heating of oil sand formations involves high temperatures, which can lead to in-situ gas generation as a result of aquathermolysis and thermal cracking of bitumen. The thermal cracking of bitumen can also lead to formation of coke at higher temperatures. Prediction of the volume of the produced gas and coke is very important in design and implementation of thermal processes dealing with high temperatures such as electrical heating and steam assisted gravity drainage with addition of oxygen. In this work a reaction kinetics model has been developed based on the experimental data of in-situ gas generation from an Athabasca bitumen sample. The kinetic parameters were estimated using the experimental data in the temperature range 360-420 degrees C. The results show that coke formation can be significant at higher temperatures. An important observation was that a plateau to H2S production is not expected at higher temperatures. In addition, the results show that operation at 370 degrees C produces a gaseous composition that minimizes the volume of the produced gas at the surface. A simple scaling analysis is presented that allows clarification of the scatter that has been observed in the reported produced hydrogen sulfide versus the operation temperature. The developed model provides a useful tool for the estimation of produced gas composition during thermal recovery processes.