Molecular simulation of natural gas transport and storage in shale rocks with heterogeneous nano-pore structures

Abstract

Although natural gas is widely produced from shale, the mechanisms of natural gas transport in shale matrices remain poorly understood due to the complex chemical compounds of the matrices and the nanoscale pore size distribution. Using molecular simulations, we investigate natural gas transport and storage in nanopore networks. Carbonbased 3-D pore networks are generated from 2-D scanning electron microscopy (SEM) images of a shale rock using the Markov Chain Monte Carlo simulation method. We employ a grand canonical Monte Carlo (GCMC) simulation to calculate adsorption isotherms of natural gas in carbon-based 3-D pore networks, which can be fit by a Langmuir isotherm model. To investigate gas transport in the same structures, we insert an external driving force into non-equilibrium molecular dynamics (NEMD) simulations and find that Knudsen diffusion is the dominant transport mechanism in the pore networks. Although porosity and pore connectivity affect the natural gas diffusion in the pore networks, we typically observe a linear relationship between average molar flow rate through a cross-sectional area and the external driving force.

Numerical analysis of the hydrofracturing behaviour of heterogeneous glutenite considering hydro‐mechanical coupling effects based on bonded particle models

“…Some factors play critical roles in the optimisation and evaluation of hydraulic fracturing stimulation, namely, crack types (tensile or shear), the reasons for crack nucleation, propagation, and coalescence in deep reservoirs, the effects of heterogeneous gravels, and in‐situ stresses . It is known that the initiation and growth behaviours of hydrofracturing cracks are strongly influenced by the heterogeneity of reservoir rocks such as glutenite that is found extensively in tight gas reservoirs . Therefore, if the influencing mechanisms and factors are not clearly understood and resolved, it is not possible to predict, control, and optimise the hydraulic fracturing efficiency, which would ultimately impact oil and gas production.…”

A non-equilibrium molecular dynamics study of methane transport in clay nano-pores

“…One of the distinctive characteristics of shale rock formations is that typically more than 60 % of their porosity can be attributed to small nano-pores less than 30 nm in diameter [1][2][3][4][5][6][7][8][9][10]. As a result, these formations have extremely low permeability, typically of the order of magnitude of one hundred nanodarcies [11].…”

Visual representation and characterization of three-dimensional hydrofracturing cracks within heterogeneous rock through 3D printing and transparent models

“…Unconventional natural gas reservoirs usually are composed of different minerals and have a composite or heterogeneous microstructure (Fouche et al 2004;He et al 2015). As a result, the initiation and propagation of hydrofracturing cracks are usually influenced by the contrast between Young's modulus and Poisson's ratio of different components (Garcia et al 2013;Sarmadivaleh and Rasouli 2015;Stanchits et al 2014).…”