A New Generation EOS Compositional Reservoir Simulator: Part I - Formulation and Discretization

This paper was selected for presentation by an SPE Program Committee following review of information contained in an abstract submitted by the author(s). Contents of the paper, as presented, have not been revparashar iewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material, as presented, does not necessarily reflect any position of the Society of Petroleum Engineers, its officers, or members. Papers presented at SPE meetings are subject to publication review by Editorial Committees of the Society of Petroleum Engineers. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of the Society of Petroleum Engineers is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of where and by whom the paper was presented. Abstract A fully implicit equation-of-state (EOS) compositional simulator for large scale reservoir simulation is presented. The simulator uses a multiblock, domain decomposition approach; that is, the reservoir is divided into non-overlapping subdomains that are solved locally in parallel (inner iteration). The subdomain grids are defined independently of each other and their connections are attained through a global interface problem (outer iteration) formulated in terms of appropriate equations that guarantee continuity of total component fluxes. Parallel, iterative techniques are employed to solve the resulting nonlinear equations. The model formulation has been successfully tested for a dry gas cycling process on a single fault block. The numerical results show that the simulator and fluid-related calculations can be conducted efficiently and robustly. Promising results have been obtained using the proposed multiblock approach for nonmatching grids between fault blocks for two-phase flow problems. This work is presented in two parts. In Part I we outline the mathematical formulation and discuss numerical solution techniques, while in Part II we address framework and multiprocessing issues. Introduction The overall objective of this research is the development of a new-generation framework and simulator suitable for massively parallel processors. The next generation of reservoir simulators may need, at least, to be able to run high-resolution reservoir studies on the order of a million gridblocks; to model complex physical processes in a realistic manner; to perform conditional simulation efficiently, and to integrate field