An experimental study was carried out to investigate the role of various clay and non-clay minerals present in reservoir formations on steam distillation process. Dead oil samples (100 g) of two heavy oil reservoirs with 30 g of water and 10 g of crushed rock mixed with different clay minerals were kept under steam pressure with 150, 200, and 250 degrees C in a batch autoclave reactor for a period of 40 hours, and the results were compared with respect to the changes in the density, viscosity and chemical composition of remaining heavy oil. Three different clay minerals (bentonite, kaolinite, and sepiolite) were added to the crushed rock to observe their effects. Among these clay minerals, kaolinite had the greatest effect on steam distillation. Kaolinite has an inert surface compared to other clay minerals which can be considered as an catalytic effect to make easier the evaporation of the volatile components of heavy oil during steam distillation. On the other hand, bentonite which has a swelling property in the presence of water may not allow the entrance of oil molecules because of its low permeability has retard/decrease the evaporation of volatile components. In case of kaolinite addition, density and viscosity of remaining oil are the greatest comparing with the two other minerals added. In addition, the asphaltene content of the remaining oil after distillation increased compared to original oil sample for all added clay minerals.