Assessment of extended DLVO-based water film on multiphase transport
behavior in shale microfractures
Abstract
This study presents a novel model to predict gas-water two-phase
transport behaviors in shale microfractures by incorporating a mobile
water film with varying thickness according to the extended
Derjaguin-Landau-Verwey-Overbeek (DLVO) theory as well as multiple fluid
transport mechanisms (i.e., real gas transport controlled by the Knudsen
number and water slippage). This model is implemented in real shale
microfractures via digital-core imaging. A gas-water displacement
process is modelled by the invasion percolation theory, while a local
multiphase distribution is determined by combining disjoining pressure
with capillary force. Key findings reveal that gas relative permeability
(RP) decreases by 17% and water RP enhances by 33.5%, when the mean
aperture decreases from 1.67 to 0.0418μm. Neglecting water film brings a
decrease in water RP and an overestimation of gas transport ability.
Moreover, two critical microfracture apertures are determined, which
enhances an understanding of the water film impact on gas-water
transport properties in application.