Modeling of Multilateral and Maximum Reservoir-Contact Wells in Heterogeneous Porous Media

摘要

Maximum reservoir contact and multilateral wells offer more efficient production capabilities for certain classes of oil and gas reservoirs. These wells can be configured to have maximum contact with reservoir production zones. This is particularly important for highly compartmentalized, heavy oil, and off-shore reservoirs. In computer modeling of reservoir production, traditional well models can only represent wells in directions that are parallel to the simulation grid which is usually not the case for maximum reservoir contact wells. An accurate well model that can effectively represent maximum reservoir contact and multilateral wells is necessary. Current state of the art numerical well model for complex wells uses Green's function to compute the production index for each finite-difference block. The advantage of this approach is that the calculated production index fits naturally into the current finite-difference method used. The disadvantages of this method are such that it only partially accounts for heterogeneity, it is based on slightly- compressible single-phase flow and it sometimes generates negative production indices. A novel line-well model for complex wells is proposed and studied. The line-well model places wells on the edges of computational blocks instead of centers as in traditional well models. This approach offers a physically meaningful yet simple way to compute production index for each individual segments of a complex well. This configuration also insures the proper handling of heterogeneity around wells. The line- well approach also allows easy implementation in both finite- difference and finite-element methods. Verification of this well model for a traditional well arrangement with a commercial finite-difference simulator shows excellent agreement. Case studies show the efficiency and effectiveness of this well model in modeling reservoirs with multilateral wells.