Evaluation of Matrix Swelling Behavior in Shale Induced by Methane Sorption under Triaxial Stress and Strain Conditions

Abstract

Gas sorption can lead to the volumetric swelling of the shale matrix and reduction of the effective pore volume, which further impacts the gas transportation in micro-and nanopores in shale. At present, it is very challenging to directly measure the pore volume shrinkage (i.e., pore volumetric strain) in the laboratory. In this study, an innovative method is proposed to quantify the pore volumetric strain resulting from the sorption-induced matrix swelling in shale. More specifically, Gibbs methane sorption capacities of the Barnett and Eagle Ford shale core samples were determined via volumetric and gravimetric methods, respectively. Meanwhile, the bulk volume swelling of the shale core sample was also measured during the gas sorption process. Correlations between the sorption-induced bulk and pore volumetric strains were developed to calculate the pore volume shrinkage ascribed to the gas sorption, which was further validated with the measured gas sorption capacities. It is found that the pore volume shrinkage is 3.7−4.8 times greater than the bulk volume swelling during the gas sorption process for the Barnett shale, while such a ratio reaches as high as 59.8−67.1 times for the Eagle Ford shale. In addition, the sorptioninduced bulk and pore volumetric strains follow a power law relationship for both Barnett and Eagle Ford shales, which yields a nearly identical absolute gas sorption isotherm with the ones determined using volumetric and gravimetric methods. The results of this study give insight into the feasibility of characterizing the sorption-induced pore volume shrinkage in shales and illustrate the benefits of applying both gravimetric and volumetric methods to evaluate the gas sorption behaviors.

Declining High-Pressure Sorption Isotherms on Shale and Coal: Systematic Comparison of the Contributing Factors

“…Thus, although the difference between helium- and CH 4 /CO 2 -based void volumes (or skeleton volumes of the sample) can be considered constant, this effect of the error in V void (or V sample 0 ) will be gradually magnified with increasing test pressure (increasing ρ gas ) during the sorption measurement, consequently giving rise to declining isotherms at high pressures. Second, when conducting the sorption measurement, the sorbent sample is exposed to a high-pressure CH 4 /CO 2 environment, and the swelling and shrinkage effects of the sorbent sample as a result of CH 4 /CO 2 sorption and compression at a high pressure occur unavoidably, with the dominant former having been discussed frequently in previous studies. ,,,− The swollen sample would occupy a greater bulk space, and it would therefore be expected that this would affect V void in eq (or V sample 0 in eq ) and, hence, the measured sorption . If not considering this effect, an “overestimated” V void (or “underestimated” V sample 0 ) for CH 4 /CO 2 sorption is also used in eq or as well as leading to the underestimation of the true adsorbed amount.…”

Experimental setup for CO2 injection for Enhance Shale Gas Recovery (ESGR) - A Review

“…Shale swelling is an important prospect to understand CO2 injection for methane gas recovery. Gas sorption capacity affects gas storage, matrix swelling and gas flow mechanisms in nanoporous organic rich shale gas reservoirs (Pang, Chen, Soliman, Morse, & Hu, 2019). In published literature, three kinds of shrinkage available such as transient shrinkage, slow swelling, and stable strain.…”

Deformation of Nanoporous Materials in the Process of Binary Adsorption: Methane Displacement by Carbon Dioxide from Coal

“…This process offers higher yields of natural gas, reduced pollution by eliminating wastewater, and sequestration of CO 2 , a known greenhouse gas. ,, Geosorbents such as coals and shales are composed of poroelastic nanoporous matrices that deform significantly upon gas adsorption and desorption. − For example, organic fractions of shale have been shown to swell in excess of 20% upon the adsorption of hydrocarbons . Nanoporous matrix swelling causes shrinkage of the free gas pore volume and fracture aperture spacings and significant reduction of the reservoir permeability. , …”

“…12 Nanoporous matrix swelling causes shrinkage of the free gas pore volume and fracture aperture spacings and significant reduction of the reservoir permeability. 13,14 Although the effects of adsorption-induced deformation and their practical importance are well documented for geosorbents and other nanoporous solids, most theoretical and experimental efforts are limited to single component adsorption. There are various approaches for modeling multicomponent adsorption on carbons, zeolites, and MOFs that do not take into account the adsorbent deformation.…”