Sequential Implicit Approach for Compositional Reservoir Simulation in Conjunction with Unstructured Grids
Bruno Ramon Batista Fernandes1; francisco Marcondes2; Kamy Sepehrnoori3
1 Center for Petroleum and Geosystems Engineering; 2 Metallurgical Engineering and Material Science Department, Federal University of Ceará; 3 Petroleum and Geosystems Engineering Department, The University of Texas at Austin
doi:10.20906/CPS/COB-2015-2688
Resumo
Various formulations are used to solve complex systems of partial differential equations that describe important physical phenomena. The approach for solving the resulting equations from the modeling of the fluid flow has a great effect on the simulator's performance making its use prohibitive or not in practice from computational point of view. In compositional reservoir simulation, the numerical formulations are usually divided into two broad classes: volume balance and mass balance. The former formulation uses a volume balance equation to determine the pressure of each gridblock. In this work, a semi-implicit volume balance formulation was implemented into The University of Texas Compositional Simulator (UTCOMP) for unstructured grids in conjunction with the finite-volume method. The semi-implicit formulation implemented is implicit in pressure and phase saturations and explicit in moles (IMPSAT). This formulation is compared with the original IMPEC (implicit pressure, explicit compositions) formulation of UTCOMP, which was previously validated with analytical solutions and commercial simulators. The results obtained suggest that for coarse grids the IMPES formulation presents the lowest computational time; however as the grids are refined the semi-implicit improves its performance in terms of computational time when compared to the IMPES formulation.
Palavras-chave: Compositional reservoir simulation; Segregated formulation; IMPEC; IMPSAT; Finite-volume method