Molecular Insights into Crude Oil Imbibition in Calcite Nanopores

Ejaz Ahmed, Huajie Zhang, Mert Aybar, Hongwei Zhang, and Rui Qiao

Abstract

The imbibition of fluids into porous media with nanoscale pores plays a key role in applications such as oil recovery from unconventional reservoirs and nanomaterial processing. While the imbibition of pure fluids has been extensively studied, the imbibition of fluid mixture is little explored. Here we report the molecular dynamics study of the spontaneous imbibition of model crude oil into nanometer-wide mineral pores, both when pore walls are dry and prewetted by a residual water layer. Results show the fastest imbibition and quickest propagation of single-layer oil molecules in the dry pore and single-component apolar oil system. The presence of a residual water layer slows down but still allows the imbibition of single-component oil. Introducing polar components into the oil further slows down the imbibition into dry nanopores, due partly to the clogging of the pore entrance. Strong selectivity toward apolar oil is observed. The slowdown and apolar oil selectivity are somewhat alleviated by the presence of a residual water layer on pore walls, largely due to the reduced pore clogging by polar oil. The detailed macroscopic and microscopic analyses of these imbibition behaviors offer insights to help optimize enhanced oil recovery and nanomaterial processing.