SPECIFIED ADAPTIVE IMPLICIT METHOD FOR UNSTRUCTURED GRIDS IN COMPOSTIONAL RESERVOIR SIMULATION

Edilson Pimentel Drumond Filho¹; Bruno Ramon Batista Fernandes¹; Francisco Marcondes¹; Kamy Sepehrnoori²

¹ Federal University of Ceará; ² The University of Texas at Austin

doi:10.20906/CPS/COB-2015-2231

Resumo

Compositional reservoir simulation is an important tool for predicting oil reservoir production and it has been large used in the last decades. Since compositional reservoir simulation, in general, involves a large number of components the numerical implementation of this physical model is a key step. Different numerical approaches have been proposed in literature to optimize the CPU time of this formulation. These formulations present many similarities; therefore they were organized in major groups which shared some basic features. Two of these groups are of interest in this work: IMPEC (Implicit Pressure/Explicit Composition) and FI (Fully Implicit). In the IMPEC formulation the pressure is evaluated implicitly, and the remaining variables explicitly. Fully Implicit (FI) methods, in the other side, compute all the primary variables implicitly. Both techniques present advantages and disadvantages. A new formulation is proposed in this work that combine features of both IMPEC and FI approaches. We called the new formulation of Specified Adaptive Implicit Method (SAIM), since the grid blocks are treated as FI are fixed during the whole simulation. Herein the well grid blocks are always treated as FI; the neighbors of these grid blocks can also be treated as FI, and also the neighbors of last grid blocks. The performance of SAIM is compared with the FI and IMPEC approaches in terms of average time step and total CPU time required for each simulation. The results obtained indicate the SAIM formulation is able to outperform the IMPEC in many situations.

Palavras-chave: SAIM; Compositional Reservoir Simulation; EbFVM