A Mercury Intrusion Porosimetry Method for Methane Diffusivity and Permeability Evaluation in Coals: A Comparative Analysis

Abstract

Mercury intrusion porosimetry (MIP) has been utilized for decades to obtain the pore size, pore volume and pore structure of variable porous media including inorganic rocks and organic rock (e.g., shales and coals). Diffusivity and permeability are the two crucial parameters that control gas transport in coals. The main purpose of this work is to derive the CH 4 effective gas diffusivity and permeability in different rank coals with vitrinite reflectance of 0.46-2.79% R o,m by MIP. Furthermore, regular CH 4 diffusivity and permeability measurements are conducted to compare with the results of the derived CH 4 diffusivity and permeability with MIP data. In this work, CH 4 diffusivity and permeability of different rank coals are acquired with established equations, which are basically in accordance with the experimental values. However, the coal rank (maximum vitrinitere flectance, R o,m) exhibits no significant relation to the effective diffusion coefficient (De) and gas diffusivity (D). The cementation factor (m values) varies from 2.03 to 2.46, which tends to exhibit a semi-consolidated structure for coals compared with other rocks (e.g., dolomite, limestone, sandstone and red brick). The results show that the cementation factor could be an important factor for gas flow in coals. The correlation of CH 4 diffusivity to porosity and permeability of 12 coal samples were explored, and it appears that CH 4 diffusivity exhibits an increasing trend with an increase of permeability, and two different exponential relationships respectively exist in diffusivity versus porosity and permeability versus porosity. Therefore, this study could be conducive to gas sequestration or gas production during enhanced coalbed methane (CBM) recovery.

Spectral Induced Polarization of Biochar in Variably Saturated Soil

“…The cementation exponent was also set to the value of 2. This is the lower limit for m found by Fang et al (2018) for coal using gas diffusion measurements. The model showed a reasonable fit to the measured s 0 for the 2% sand-biochar mixtures (Fig.…”

Pore Structure of Coals by Mercury Intrusion, N2 Adsorption and NMR: A Comparative Study

“…Coals with higher microporosity at high coal rank are commonly less permeable for fluid [4], and such a relationship is apparent for coals with high carbon content due to the larger amount of super micropores, micropores and mesopores. The establishment of the pore structure model can further help to understand the microscopic pore development characteristics of reservoir heterogeneity more simply and systematically, which can effectively reflect the mechanism of fluid diffusion and seepage [17], evaluate the fluid permeability of reservoir, and prevent the occurrence of gas burst accidents in "suffocating" coal seam.…”

Fractal Characteristics of Porosity of Electrospun Nanofiber Membranes

“…Porosity Measurement. Current methods for measuring material porosity include nitrogen adsorption (see [14]), mercury intrusion (see [4]), impregnation (see [15]), and mass density (see [16]). e pore size of materials with pore size less than 50 nm can be measured by this nitrogen adsorption method, but it is only suitable for ultrafine powder materials.…”

“…ese pores will directly affect the properties of the electrospun nanofiber membrane. At present, the methods of measuring the porosity of the electrospun nanofiber membrane include density method, image method, and mercury intrusion method (see [2][3][4]). However, these methods are timeconsuming and costly.…”