Effect of 3-D stress state on adsorption of CO2 by coal

Hol, Sander; Peach, C. J.; Spiers, Christopher J.

doi:10.1016/j.coal.2012.01.001

Cited by 52 publications

(58 citation statements)

References 54 publications

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“…Because static moduli are calculated on the basis of external stress-strain data, and dynamic moduli on the basis of ultrasonic wave propagation through the solid phase, these observations clearly point in the direction of multiple scaledependent processes operating in coal-adsorbate systems. The reduction in stiffness observed in static tests has been explained by "adsorptive weakening" or plasticization processes activated by the presence of CH 4 /CO 2 in the coal skeleton (De Silva and Ranjith, 2012;Viete and Ranjith, 2007), or alternatively by a direct coupling between stress state, sorbed concentration and swelling strain (Hol et al, 2011(Hol et al, , 2012a.…”

Section: Accepted M Manuscriptmentioning

confidence: 99%

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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Section: Accepted M Manuscriptmentioning

confidence: 99%

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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“…However, most sites investigated to date have shown reduced CO 2 injectivity with time due to permeability reduction in the coal seam [3,4,6]. These effects are generally recognized to be caused by sorption-induced swelling of the coal as a result of CO 2 injection and sorption, while CH 4 is desorbed [7][8][9][10][11][12][13]. This exchange, or preferential adsorption effect, is considered to be due to either the reduction of CH 4 partial pressure as CO 2 penetrates the system or to truly selective adsorption of CO 2 over CH 4 [2].…”

Section: Introductionmentioning

confidence: 95%

“…These represent highly restrictive assumptions. An alternative, more general approach lies in extending the thermodynamic model developed by Hol et al [9] for the equilibrium concentration of a pure gas/fluid (CO 2 ) adsorbed by unconfined coal matrix material (or indeed any material exhibiting monolayer adsorption, i.e. any Langmuir type sorbent).…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic models for swelling of unconfined coal due to adsorption of mixed gases

Liu

Peach

Zhou

et al. 2015

Fuel

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“…CO2 adsorption-induced volume strain has been studied by many researchers under unconfined conditions or uniaxial strain conditions [28,38,42]. In this section, we consider the adsorption-induced strain from the perspective of unconfined conditions.…”

Section: Adsorption-induced Swelling Strainmentioning

confidence: 99%

“…In connection with swelling strain, Hol et al [38] and Liu et al [39] considered thermodynamic models of gas adsorption and studied the effect of stress on the adsorption concentration of gas as well as sorption behavior. Their starting point is different from this paper based on directly volumetric changes.…”

Section: Swelling Strain and Swelling Stressmentioning

confidence: 99%

Strength Reduction of Coal Pillar after CO2 Sequestration in Abandoned Coal Mines

Liu

Wang

et al. 2017

Minerals

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CO 2 geosequestration is currently considered to be the most effective and economical method to dispose of artificial greenhouse gases. There are a large number of coal mines that will be scrapped, and some of them are located in deep formations in China. CO 2 storage in abandoned coal mines will be a potential option for greenhouse gas disposal. However, CO 2 trapping in deep coal pillars would induce swelling effects of coal matrix. Adsorption-induced swelling not only modifies the volume and permeability of coal mass, but also causes the basic physical and mechanical properties changing, such as elastic modulus and Poisson ratio. It eventually results in some reduction in pillar strength. Based on the fractional swelling as a function of time and different loading pressure steps, the relationship between volumetric stress and adsorption pressure increment is acquired. Eventually, this paper presents a theory model to analyze the pillar strength reduction after CO 2 adsorption. The model provides a method to quantitatively describe the interrelation of volumetric strain, swelling stress, and mechanical strength reduction after gas adsorption under the condition of step-by-step pressure loading and the non-Langmuir isothermal model. The model might have a significantly important implication for predicting the swelling stress and mechanical behaviors of coal pillars during CO 2 sequestration in abandoned coal mines.

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Effect of 3-D stress state on adsorption of CO2 by coal

Cited by 52 publications

References 54 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

Thermodynamic models for swelling of unconfined coal due to adsorption of mixed gases

Strength Reduction of Coal Pillar after CO2 Sequestration in Abandoned Coal Mines

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