Generalized Modeling of Spontaneous Imbibition Based on Hagen–Poiseuille Flow in Tortuous Capillaries with Variably Shaped Apertures

TLDR

Spontaneous imbibition of wetting liquids in porous media is a ubiquitous natural phenomenon that has attracted extensive study, yet many capillary‑driven flow models based on Hagen–Poiseuille flow in cylindrical capillaries face limitations that motivate geometrical modifications. The study develops a generalized spontaneous imbibition model that accounts for pore size and shape, tortuosity, and initial wetting‑phase saturation. The authors analytically derive relationships among imbibition weight, rate, gas recovery, and material/liquid properties, and validate the model against published data from diverse porous media such as rocks, fibers, and silica glass. The model generalizes existing theories and, when tested against data, accurately describes imbibition in various porous media, revealing that pore shape need not be assumed cylindrical.

Abstract

Spontaneous imbibition of wetting liquids in porous media is a ubiquitous natural phenomenon which has received much attention in a wide variety of fields over several decades. Many traditional and recently presented capillary-driven flow models are derived based on Hagen–Poiseuille (H–P) flow in cylindrical capillaries. However, some limitations of these models have motivated modifications by taking into account different geometrical factors. In this work, a more generalized spontaneous imbibition model is developed by considering the different sizes and shapes of pores, the tortuosity of imbibition streamlines in random porous media, and the initial wetting-phase saturation. The interrelationships of accumulated imbibition weight, imbibition rate and gas recovery and the properties of the porous media, wetting liquids, and their interactions are derived analytically. A theoretical analysis and comparison denote that the presented equations can generalize several traditional and newly developed models from the literature. The proposed model was evaluated using previously published data for spontaneous imbibition measured in various natural and engineered materials including different rock types, fibrous materials, and silica glass. The test results show that the generalized model can be used to characterize the spontaneous imbibition behavior of many different porous media and that pore shape cannot always be assumed to be cylindrical.