Simulação composicional de reservatórios de petróleo utilizando o método implícito

Abstract

Implicit and explicit formulations are applied in numeric analyses to obtain approximate solutions for differential equations. The first solves the dependent variable directly in terms of known variables in a previous time step. In the second, a dependent variable is solved by a system of equations and a iterative method is required to obtain the solution. A positive aspect of the implicit method is the increase of the time steps in the solutions, as a result, the systems solution becomes faster and more precise. However, adding more variables to the solution matrix will increase the computational effort. In most cases, alternative resolution techniques will be needed as parallel processing. Nonetheless, there are others formulations for solving partial differential equations modeling fluid flow for compositional simulations in porous media that combine these two formulations. The IMPEC and IMSAT are the most known. The purpose of these adaptations are to optimize the simulator development. At the present work the IMPEC method was adapted with the addition of the pressure from injectors well in the solution matrix (implicit method). Implementations were made for serial and parallel, cartesian and non-structured meshes in the compositional simulator, UTCOMP from the University of Texas at Austin. Moreover, other equations well were added based on posterior works. The results are presented in terms of well pressure variation and reservoir oil production. In addition, a comparative studied between the implicit and explicit formulation for the well pressure is presented.