On a Methed of Automatic Generation of Pseudofunctions for Realistic Application of Multi-phase Reservoir Simulation

(1) Directional Pseudofunctions based on Frontal Advance Profile

Abstract

Spatial and time discretisations cause truncation errors that are always serious and long-standing hazards for the simulation of multiphase reservoir problems. Especially in field-scale applications, reliability of the simulated results greatly depends on how those errors are controlled within reasonable degee througth so-called “pseudofunctions”. For the purpose of preparing proper pseudofunctions to minimise spatial truncation error, then making the simulated results insensitive to how reservoir is discretised or gridded, the author incorporated a comprehensive process of generating pseudofunctions into the general-purpose black oil reservoir simulator. The method presented here generates dynamic pseudofunctions automatically during the iterative step of the calculation. It is based on the frontal advance theory, and has a dynamic feature in which, in deriving pseudofunctions of certain grid, the zonal segregation of phases, gravity-capillary equilibrium, variation of phase representative depth, and directionality of pseudofunctions are simultaneouly considered. Using 1-dimensional models with different gridding, several validation runs were made. The results showed that the proposed method could give almost identical performances for different vertical griddings.