Investigation of SAGD Recovery Process in Complex Reservoir

Abstract

AbstractAlberta's oil sands deposits, with an estimated 1.7 trillion barrels of bitumen in place, account for approximately 40% of the world's bitumen resource. And steam-assisted gravity drainage (SAGD) has opened the door to produce a large number of bitumen reservoirs in Canada. The success of SAGD has been mostly demonstrated by numerical simulation with homogeneous reservoir models. But, this process is very sensitive to reservoir heterogeneities; therefore, it is urgent and necessary to have a comprehensive understanding of the effects of reservoir heterogeneities on SAGD performance for wider and more successful implementation.This study presented a numerical investigation for evaluating the potential applicability of SAGD recovery process under complex reservoir conditions such as shale barriers, thief zones with bottom and/or top water layers, overlying gas cap and fracture systems in McMurray formation. In order to achieve the general vision and overcome some limitations in literature, these are of factors were evaluated in both individual and simultaneous case studies. Bitumen recovery, average oil production rate, and cumulative steam-oil ratio obtained from thermal simulation were the three main parameters used for evaluation of the attractiveness of bitumen recovery operations. The simulation results indicated that the near well regions are very sensitivity with shale layers and only long, continuous shale barriers (larger than 50m or 25%) can effect to SAGD performance at the above well regions. Besides that, the thief zones have a strongly detrimental effect on SAGD. The results also proved that SAGD recovery process enhanced in the presence of vertical fractures but horizontal fractures were harmful on the recovery. Fracture spacing was not a very important parameter in the performance of steam process in fractured models and the increasing of horizontal fractures extension will reduce ultimate oil recovery in SAGD process. This paper is a worthy guideline for SAGD operations in complex geological reservoirs.