Avaliação dos parâmetros de archie por meio de simulação numérica em modelos digitais de rochas sedimentares.

Abstract

The Archie equation is the most important model used for the calculation of fluid saturations in hydrocarbon reservoirs, which directly affects the evaluation of in situ reserves. This model depends on parameters that are difficult to measure. In this work, a method is proposed based on the numerical simulation of the propagation of the electric field on digital models of carbonate and sandstone rocks, for the calibration of the Archie equation's parameters. X-ray microtomography images of the samples weresegmented into four domains: internal pores, external pores, intermediate phase and matrix. The analysis of digital models allowed to quantify topological properties of rocks such as macropore tortuosity factor and connectivity, through Euler's number, of the four domains that constitute the digital models of rocks. Three-dimensional models of the rocks were generated and represented by numerical meshes on which four alternative scenarios of fluid saturation were simulated. For each scenario, the calibrated parameters of the Archie equation were determined and the factors that affect these parameters were analyzed. It is observed that the connectivity of the conductive domains controls the values of these parameters. Finally, an analysis of the impact of calibrated parameters on the evaluation of hydrocarbon reserves for two real reservoirs, one carbonate and the other arenitic, was carried out. For the carbonate reservoir, numerically calibrated parameters resulted in reserves similar to that of reference models, while for the siliciclastic reservoir the reserves estimated by the method proposed in this work were substantially lower than those estimated by the Archie equation using commonly adopted generic parameters.