Investigation of initial water mobility and its effects on SAGD performance in bitumen reservoirs and oil sands

Steam assisted gravity drainage (SAGD) has become a preferred in-situ recovery technology for oil sands and bitumen deposits in Canada. In some production history matching studies, the initial water was found to be mobile in SGAD projects, which could cause high steam loss, difficult pressure control, high steam oil ratio (SOR), etc. It is crucial to determine the initial water mobility in order to optimize SAGD performance. In this paper, a novel method is presented to effectively determine the mobility of initial water existing as the continuous wetting phase in the bitumen reservoirs. More specifically, wax was used as the oil phase, for the first time, to simulate the immobile oil phase in bitumen reservoirs and oil sands. Experimental results indicated that the interstitial water could still flow when the water saturation was as low as 5% in the simulated bitumen-water system. A triangular tube bundle model was constructed and tuned to match the experimental results. The model was used to simulate the water relative permeability curves at different initial water saturations. A correlation of the initial water mobility with the initial water saturations was developed through data analysis. The impact of initial water movement on SAGD operations was illustrated using an analytical approach, and the associated energy loss was calculated. The results showed that the initial water mobility can lead to severe energy loss.