An Expanded Well Model for Accurate Simulation of Reservoir-well Interactions

We present a new framework for modeling wells in reservoir simulation. This approach is based on an “expanded well model” in which the well region is expanded geometrically to include portions of the reservoir. The well region is then represented as an “equivalent” multi-segmented well defined by a list of connections for all completed segments. This generalizes and simplifies well-reservoir flow modeling by shifting the interface between the well region and the reservoir region. As is the case with standard well models, the well region is linked to the reservoir region through use of well indices. In the case of the expanded well model, these well indices, along with the connections between segments in the equivalent multi-segmented well, are computed by upscaling an underlying fine-scale description of the reservoir and well. The method is applied to model a hydraulically-fractured well and production in a tight-gas reservoir. In both cases, direct application of standard approaches is shown to lead to inaccurate coarse-scale predictions. Use of the expanded well model, by contrast, provides high degrees of accuracy in both cases.