Assessment of extended Derjaguin–Landau–Verwey–Overbeek‐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 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 modeled 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 decreases by 17% and water RP enhances by 33.5%, when the mean aperture decreases from 1.67 to 0.0418 μm. 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.

Heterogeneous Effect of Organic Matter on Accumulation Behaviors of Shale Gas in Water

“…When the gas is confined in the pores, it will exhibit different occurrence behaviors, which cause flow mechanisms of unconventional oil and gas to be quite different from conventional oil and gas. − Because of the characteristics of low permeability in shale, hydraulic fracturing has become an important technology for effective exploitation of the shale gas resource. , The use of hydraulic fracturing means that water will accompany the whole process of production. Although the flow mechanism, the occurrence behavior, and the phase state of fluids in nanopores have attracted extensive attention and have become the research hotspot, − it is still limited in oil and gas development. − Especially when the water in the reservoir is considered, − as a result of the limitation of research means and methods, it is still unable to give a detailed occurrence and migration mechanism for the shale gas.…”