Enhancing SAGD performance using additional steam Injector into oilsand Reservoir with lateral shale stringers

The SAGD involves a dual horizontal wells drilled through the reservoir, one to inject steam and one to produce the gravity drop of the bitumen and condensate. The Steam-Assisted Gravity Drainage (SAGD) process using two horizontal wells (hereinafter Dual SAGD process) has proven to be economical and successful for recovery of bitumen from oil sands reservoirs, however its performance is particularly sensitive to the effect of abrupt changes in vertical permeability by presences of lateral shale layer or stringers, since the SAGD process is operated by buoyant rise of steam. In addition, the shale with extremely high viscosity immobile oil limits the degree of lateral communication and grows of the steam chamber.
In this study, experiments and numerical simulations using the CMG’s STARSTM were carried out in order to represent fluids flow characteristics in a steam chamber and production fluids of the SAGD process observed by the experiments. The numerical model was constructed based on two-components (water and heavy oil) black oil, three-phase (water, heavy oil and steam) and the Intermediate3-Stone1 wettability model.
Based on the extended numerical model for a field scale size, oil productions from oil sands reservoir were predicted. The lateral shale layer or stringers were assumed as the impermeable lateral layers to cease vertical growth of steam chamber. Furthermore, a modified SAGD process by adding the second steam injector located over the shale layer is presented and compared with the usual Dual SAGD process. By using the modified process, the production rate is enhanced after switching steam injection from the lower injector to the second injector by setting longer vertical spacing and larger injection pressure.