Swelling of Australian coals in supercritical CO2

Day, Stuart; Fry, Robyn; Sakurovs, Richard

doi:10.1016/j.coal.2007.09.006

Cited by 319 publications

(282 citation statements)

References 19 publications

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“…Despite the fact that superposition of adsorptioninduced and poroelastic strains works well for high pressure data, the model is unsuccessful at very low concentrations, i.e. below ~0.2 mmol·g coal -1 in the data of Day et al (2008). To date, no explanations exist for the "remaining strain offset".…”

mentioning

confidence: 96%

“…Fig. 11a presents an example of volumetric strain data, experimentally obtained by Day et al (2008) on unconfined samples at increasing gas pressure, plotted against sorbed CO 2 concentration.…”

Section: Mechanism 1: Changes In Surface Roughness At Cleat Interfacementioning

confidence: 99%

“…This effect is recognized by other authors, and is attributed to superposition of adsorption-induced and poroelastic strains (Hol and Spiers, 2012;Pan and Connell, 2007;Vandamme et al, 2010), where at higher CO 2 pressure (here: above ~4 MPa) poroelastic compression of the matrix significantly affects the measured swelling strains. Correcting the data of Day et al (2008) for poroelastic effects (following Hol and Spiers, 2012), yields a roughly linear trend that extends down to ~0.2 mmol·g coal -1 (Fig. 11a).…”

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confidence: 99%

“…a) Volumetric strain, experimentally obtained by Day et al (2008) (Day et al, 2008) and the Prosper Haniel coal tested here. The measured strains plotted in Fig.…”

mentioning

confidence: 99%

“…To date, no explanations exist for the "remaining strain offset". We then took multiple swelling strain data sets for different samples reported in the literature (Astashov et al, 2008;Battistutta et al, 2010;Czaplinski, 1991, 1993;Cui et al, 2007;Day et al, 2008;Hol and Spiers, 2012), and quantified the magnitude of the "remaining strain offset". Only high pressure data (P f >6 MPa) by Hol and Spiers (2012), and Day et al (2008) were corrected for linear poroelastic effects.…”

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confidence: 99%

See 4 more Smart Citations

Sorption and changes in bulk modulus of coal — experimental evidence and governing mechanisms for CBM and ECBM applications

Hol

Gensterblum

Massarotto

2014

International Journal of Coal Geology

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Recent studies report that the stiffness of coal changes, when exposed to sorbing gases such as CH 4 and CO 2 . Although this effect might be potentially important for predicting the in situ mechanical behavior of coal seams during CH 4 production or CO 2 sequestration, very little understanding exists on the underlying mechanisms. In this paper, we report a single, long-duration mechanical test on a large, cube-shaped coal sample (Ruhr Basin, Germany). The sample was subjected to isostatic loading and unloading; first in the evacuated state (as received), and then each time after exposing it to pressurized, non-adsorbing He, or sorbing N 2 , CH 4 , and CO 2 . We find that exposure to sorbing gases led to swelling, which introduced a hysteresis in the stress-strain trajectory followed during mechanical loading. This hysteresis was almost absent in the evacuated state, and its magnitude depended strongly on the amount of adsorption-induced swelling exhibited by the sample. The apparent bulk modulus determined here for the CO 2 -equilibrated state was approximately 25% lower compared to the evacuated state. We qualitatively consider mechanisms that affect the elastic behavior of coal at the matrix and bulk scale, and argue that the observed effects are a combined effect of 1) changes in surface roughness at cleat interfaces and microfractures, and 2) a thermodynamic coupling between stress state, sorption capacity and swelling strain. The changes in stiffness relate to fluid-rock interaction effects, as well as to the presence of fractures, and hence not to the inherent elastic properties of the solid phase itself. We discuss the characteristics of each mechanism and the connection of the proposed mechanisms with formation-scale geomechanical effects of coal layers under conditions relevant to CBM/ECBM.

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mentioning

confidence: 96%

Section: Mechanism 1: Changes In Surface Roughness At Cleat Interfacementioning

confidence: 99%

mentioning

confidence: 99%

“…a) Volumetric strain, experimentally obtained by Day et al (2008) (Day et al, 2008) and the Prosper Haniel coal tested here. The measured strains plotted in Fig.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

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Sorption and changes in bulk modulus of coal — experimental evidence and governing mechanisms for CBM and ECBM applications

Hol

Gensterblum

Massarotto

2014

International Journal of Coal Geology

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A transverse isotropic model for microporous solids: Application to coal matrix adsorption and swelling

et al. 2013

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[1] Understanding the adsorption-induced swelling in coal is critical for predictable and enhanced coal bed methane production. The coal matrix is a natural anisotropic disordered microporous solid. We develop an elastic transverse isotropic poromechanical model for microporous solids which couples adsorption and strain through adsorption stress functions and expresses the adsorption isotherm as a multivariate function depending on fluid pressure and solid strains. Experimental data from the literature help invert the anisotropic adsorptive-mechanical properties of Brzeszcze coal samples exposed to CO 2 . The main findings include the following: (1) adsorption-induced swelling can be modeled by including fluid-specific and pressure-dependent adsorption stress functions into equilibrium equations, (2) modeling results suggest that swelling anisotropy is mostly caused by anisotropy of the solid mechanical properties, and (3) the total amount of adsorbed gas measured by immersing coal in the adsorbate overestimates adsorption amount compared to in situ conditions up to 20%. The developed fully coupled model can be upscaled to determine the coal seam permeability through permeability-stress relationships.

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Poromechanics of Saturated Isotropic Nanoporous Materials

Vermorel¹,

Pijaudier‐Cabot²,

Miqueu³

et al. 2012

Damage Mechanics of Cementitious Materials and Structures

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Poromechanics offers a consistent theoretical framework for describing the mechanical response of porous solids. When dealing with fully saturated nanoporous materials, which exhibit pores of the nanometer size, additional effects due to adsorption and confinement of the fluid molecules in the smallest pores must be accounted for. From the mechanical point of view, these phenomena result into volumetric deformations of the porous solid, the so-called "swelling" phenomenon, and into a change of the apparent permeability. The present work investigates how poromechanics may be refined in order to capture adsorption and molecular packing induced effects in nanoporous solids. The revisited formulation introduces an effective pore pressure, defined as a thermodynamic variable at the representative volume element scale (mesoscale), which is related to the mechanical work of the fluid at the pore scale (nanoscale). Accounting for the thermodynamic equilibrium of the system, this effective pore pressure is obtained as a function of the bulk fluid pressure, the temperature and the total and excess adsorbed masses of fluid. We derive the analytical swelling strains due to sorption and molecular packing. A good agreement in the comparison with experimental data dealing with the swelling of coal due to methane and carbon dioxyde sorption is observed, as a preliminary stage towards modelling partially saturated solids and applications to cement paste.

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Swelling of Australian coals in supercritical CO2

Cited by 319 publications

References 19 publications

Sorption and changes in bulk modulus of coal — experimental evidence and governing mechanisms for CBM and ECBM applications

Sorption and changes in bulk modulus of coal — experimental evidence and governing mechanisms for CBM and ECBM applications

A transverse isotropic model for microporous solids: Application to coal matrix adsorption and swelling

Poromechanics of Saturated Isotropic Nanoporous Materials

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