Applicability of fractal capillary pressure models to sandstones

Abstract

The microscopic fractal theory plays an important role in the prediction of macro petrophysical parameters. However, the significant fractal dimension changes with the fractal regime or the capillary pressure model. We adopt three traditional capillary pressure models and a modified capillary pressure model to characterize the fractal behavior of six sandstones from the Songliao Basin. The various models indicated an overall nonfractal behavior for the sandstones in a pore-throat size regime; however, they showed a fractal behavior in the small pore-throat regime and a nonfractal behavior in the large pore-throat regime. The modified model was identified as the most appropriate capillary-pressure model to characterize the fractal behavior of sandstones, since it avoids the oversimplifications of pore morphologies and the unreasonable omissions typical of traditional models. This scope of this study was to promote a correct understanding of the fractal behavior of sandstones by using capillary pressure models.