Coupling a Thermal Reservoir Simulator with a Dynamic, Multiphase Wellbore Flow Simulator to Rigorously Model Complex SAGD Well Geometries and Completions

In this paper, we propose a methodology to iteratively couple a wellbore simulator and a reservoir simulator in order to model the complex flow regimes that exist in a producing SAGD well while still taking into consideration the fluid movement and distribution within the reservoir. The process was successfully tested and implemented in two SAGD pads and the results were compared with those obtained using a commercial, fully-coupled reservoir-wellbore model. This method addresses the modeling limitations encountered in typical thermal reservoir simulators that use source/sink or discretized formulations to describe wellbore flow. SAGD producers exhibit overly complex flow regimes caused by the presence of a steam phase that can condense within the wellbore and promote significant variations in temperatures and pressures along the tubulars. Therefore, standalone wellbore simulators are necessary to predict performance as accurately as possible; however, using a wellbore simulator alone will neglect the effects caused by varying inflow conditions from the reservoir. With these variations occurring both in time and in space (along the wellbore), it is necessary to include the dynamic input of a reservoir simulator, hence the rationale for coupling both models. The algorithm devised to integrate the wellbore and reservoir simulators was coded into a standalone GUI-driven computer program called a coupler. The coupler was used to evaluate the performance of new SAGD pairs and new infill producers featuring flow devices and slanted trajectories. In this work, we will present the results of field case studies with the proposed coupling approach to evaluate the effect on ultimate recovery of drilling new SAGD pairs and SAGD infills using toe-up or toe-down trajectories as well as fitting these wells with inflow control devices. When applying the coupling workflow to the case studies, we determined that despite challenging conditions, it is possible to have inclined SAGD wells properly transition from preheating to production as well as allowing access to previously untapped parts of the reservoir resources, which increased ultimate recovery.