Efficient modeling of nonconventional wells with downhole inflow control devices

Abstract

Complex well configurations coupled with downhole inflow control devices offer great potential for the efficient production of oil reservoirs. With systems of this type, chokes can be set to isolate a zone or to provide a more uniform inflow profile, which acts to delay the breakthrough of water and gas. While it is possible to apply existing finite difference reservoir simulators, such models can be time consuming to build and the accuracy of the results depends on the grid and the well model. To obtain the correct well model (well index) for the finite difference simulator, a reference solution (analytical or numerical) is needed. In this work, semianalytical solution methods (based on Green's functions), appropriate for modeling the performance of nonconventional wells operating under single phase flow conditions, are developed and applied to model these complex well configurations. The approach entails a fully coupled nonlinear formulation that accounts approximately for reservoir heterogeneity as well as for pressure drops in the annulus, tubing and downhole chokes. Numerical results for a variety of cases are presented, including examples involving nonconventional wells operating with downhole chokes in a highly heterogeneous fluvial reservoir. Comparisons with finite difference results are presented where appropriate and demonstrate the general level of accuracy of the semianalytical procedure. The use of the method for the determination of optimal choke settings is demonstrated. The semianalytical model developed here can also be used for the calculation of well index.