Compressibility of Supercritical Methane in Nanopores: A Molecular Simulation Study

Document Type

Article

Publication Date

2-20-2020

Abstract

Unmineable coalbeds are a promising source of natural gas and can act as a receptacle for CO2 sequestration. This is because they are composed of extensive nanoporous systems, which allow for significant amounts of methane or CO2 to be trapped in the adsorbed state. The amount of the fluid confined in the coal seams can be determined from seismic wave propagation using the Gassmann equation. However, to accurately apply the Gassmann theory to coalbed methane, the effects of confinement on methane in these nanoporous systems must be taken into account. In this work, we investigate these effects of confinement on supercritical methane in model carbon nanopores. Using Monte Carlo and molecular dynamics simulations, we calculated the isothermal elastic modulus of confined methane. We showed that the effects of confinement on the elastic modulus of supercritical methane are similar to the effects on subcritical fluids: (1) the elastic modulus of the confined fluid is higher than in bulk; (2) for a given pore size, the modulus monotonically increases with pressure; and (3) at a given pressure, the modulus monotonically increases with the reciprocal pore size. However, these effects appeared much more pronounced than for subcritical fluids, showing up to seven-fold increases of the modulus in 2 nm pores. Such a significant increase should be taken into account when predicting wave propagation in methane-saturated porous media.

Identifier

85080902287 (Scopus)

Publication Title

Energy and Fuels

External Full Text Location

https://doi.org/10.1021/acs.energyfuels.9b03592

e-ISSN

15205029

ISSN

08870624

First Page

1506

Last Page

1513

Issue

2

Volume

34

Fund Ref

Nanjing Institute of Technology

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