Nanoscale Phase Measurement for the Shale Challenge: Multicomponent Fluids in Multiscale Volumes

Abstract

Hydrocarbon recovery from shale reservoirs provides an increasing share of world energy. These resources are multicomponent fluid mixtures within multiscale geometries, and understanding their associated phase-change thermodynamics presents an array of challenges for experimentalists, theorists, operators, and policy makers. Here, we quantify hydrocarbon mixture phase behavior via direct imaging of connected channels spanning 4 orders of magnitude (10 nm to 10 μm) with supporting density functional theory. The methane/propane mixture dew point shifts, with early condensation of heavy components in nanopores because of a combination of capillarity and competitive surface adsorption. The bubble point in nanoconfinement is found to be deeply suppressed (∼3-fold), to below the bulk dew point of the original mixture, because of the exchange of mixture components with larger connected volumes. The trapping of the heaviest components of hydrocarbon mixtures within the smallest connected pores has implications for shale operations, reserve estimation, and ultimately energy security.

Confinement-Mediated Phase Behavior of Hydrocarbon Fluids: Insights from Monte Carlo Simulations

“…21 The predictions from engineering DFT were also compared against experiments conducted in a nanofluidic channel and showed an underestimation of capillary pressure. 22 Monte Carlo (MC) molecular simulations have been widely used to support experiments and validate theoretical models for the investigation of fluid phase behavior under confinement. 21,23−28 The inhomogeneous molecular distribution and the fluid−pore interactions of different absorbents and hydrocarbons are more accurately described at the molecular level by MC methods in contrast to theoretical models.…”

“…By comparing these results to grand-canonical Monte Carlo (GCMC) simulations, engineering DFT was proven to be able to predict the vapor–liquid equilibrium reliably . The predictions from engineering DFT were also compared against experiments conducted in a nanofluidic channel and showed an underestimation of capillary pressure …”

Experimental Study on the Criticality of a Methane/Ethane Mixture Confined in Nanoporous Media

“…For example, it has been experimentally proven that phase transition in confined space occurs isothermally at a lower pressure, or isobarically at a higher temperature, than that in the bulk phase. − Recently, the critical point of pure fluids in confined space has also been unambiguously demonstrated to locate at a lower temperature and pressure than that in bulk by us using an isochoric cooling method . Experimental studies on the phase behavior of confined mixtures, on the other hand, are relatively scarce in the literature, − not to mention the fact that their phase behavior in the critical region has never been experimentally explored, which, in turn, results in disagreement and conflicting conclusions about the pore critical point (PCP) of mixtures in confinement; PCP is defined as a point beyond which the condensation of confined fluids can no longer occur. Therefore, the purpose of this work is to verify its existence and demonstrate its shift from the bulk critical point.…”

Studying key processes related to CO2 underground storage at the pore scale using high pressure micromodels

“…However, further opportunity remains to design micro and nano-models that can capture molecular-scale information. This may include the development of nanofluidics devices [253][254][255] , which have proven to be excellent tools for accessing critical phenomena at the molecular level, including non-conventional phase behaviors. However, challenges still need to be addressed in term of experimentation (clogging, nonvalidity of conventional fluid mechanics equations, etc.).…”