Experimental investigations on the effect of CO2 on mechanics of coal

Masoudian, Mohsen S.; Airey, David; El-Zein, Abbas

doi:10.1016/j.coal.2014.04.001

Cited by 109 publications

(49 citation statements)

References 27 publications

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“…9) in tests performed during adsorption at constant confining stress was a non-expected result. This reduction, observed in other experiments as well, may be due to coal softening (reduction of elastic moduli), as observed previously in the literature (Czaplinski and Holda, 1982;Masoudian et al, 2014) or CO 2 -enhanced coal creep as documented by Hagin and Zoback (2010) while adsorption-induced swelling is still taking place.…”

Section: Experimental Results: Uncertainties Unexpected Phenomena Amentioning

confidence: 51%

“…Salient observations from selected experimental studies include the following (Chikatamarla et al, 2004;Czaplinski and Holda, 1982;Day et al, 2008;Hagin and Zoback, 2010;Levine, 1996;Masoudian et al, 2013;Masoudian et al, 2014;Mazumder et al, 2006;Pan et al, 2010;Pini, 2009;Pone et al, 2009;Viete and Ranjith, 2006): (1) CO 2 equilibration times increase as the specimen size increases and vary from about 1 h to more than 20 days, (2) swelling along the direction perpendicular to the bedding plane is generally higher -up to 60% -than along the direction parallel to the bedding plane, (3) absolute permeability decreases with Terzaghi's effective stress at a given fluid pressure, however, the variation of permeability as a function of pressure of the adsorbate fluid at constant Terzaghi's effective stress is not clear, and (4) CO 2 sorption in coal lowers -up to 25% -the coal Young's modulus and shear strength and enhances creep, compared to dry coal or coal saturated with helium.…”

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confidence: 98%

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Measurement and modeling of adsorptive–poromechanical properties of bituminous coal cores exposed to CO2: Adsorption, swelling strains, swelling stresses and impact on fracture permeability

Espinoza

Vandamme

Pereira

et al. 2014

International Journal of Coal Geology

102

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International audienceThe reservoir response of unmineable coal seams to primary and enhanced natural gas recovery is strongly affected by gas sorption and the swelling properties of the coal reservoir rock. In-depth understanding of the process of gas sorption/desorption in the coal matrix, induced deformation and measurement of relevant physical parameters are critical for predictive reservoir management. Models used in industry practice are based on swelling strains measured in “free” swelling coal or on empirical correlations between strain and adsorption, and predict permeability changes based on changes of porosity or stress calculated assuming an analogy with thermoelasticity. However, not only coal seams are subjected to in-situ stresses and geometrical boundary conditions but also sorption and strain are strongly coupled. Representative experiments and a truly coupled model for coal seams are needed in challenging applications. We present a set of triaxial testing measurements on 38 mm diameter fractured sub-bituminous/bituminous coal cores exposed to CO2. Testing includes the measurement of fluid uptake, adsorption-induced strains and stresses, and the impact on simultaneously measured permeability. Noteworthy, we measured increases in effective stress of up to 29 MPa when injecting CO2 at 5 MPa and preventing the coal core to swell. The results are analyzed with a poromechanical model in which coal matrix microporosity and adsorption-induced phenomena are embedded into a fractured reservoir rock with transverse isotropic properties. The adsorptive–mechanical coupling in the coal matrix is integrated through an adsorption stress function and fractured coal permeability is estimated as a function of Terzaghi's effective stresses (parallel and perpendicular to the bedding plane). The experimental results and model predictions help identify the characteristic response of coal microporosity and cleat macroporosity on the poromechanical response of coal cores, and suggest that order of magnitude changes of reservoir permeability observed in the field are linked to sorption-induced change on Terzaghi's effective horizontal stress under laterally constrained displacement condition. Together, the modeling and experimental characterization offer unprecedented insights into the mechanics of coal

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Section: Experimental Results: Uncertainties Unexpected Phenomena Amentioning

confidence: 51%

mentioning

confidence: 98%

Measurement and modeling of adsorptive–poromechanical properties of bituminous coal cores exposed to CO2: Adsorption, swelling strains, swelling stresses and impact on fracture permeability

Espinoza

Vandamme

Pereira

et al. 2014

International Journal of Coal Geology

102

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“…Th e reservoir behavior of coal seams can infl uence the adsorption process since it determines the pressure distribution of gas within the reservoir, and since the amount of adsorbed gas is related to the pressure and temperature. [9][10][11] Th e need for coupled modeling of geological sequestration of CO 2 has been addressed and investigated in many studies. In addition, the mechanical behavior can aff ect the other two aspects.…”

Section: Introductionmentioning

confidence: 99%

The role of coal seam properties on coupled processes during CO₂sequestration: A parametric study

2015

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It has been proposed that a considerable amount of CO2 can be safely sequestered from the atmosphere in geological formations such as coalbeds. In spite of promising evidence of the economic and technical viability of CO2 sequestration in coal seams, many of its hydro‐geomechanical aspects are not fully understood. This paper presents a coupled hydro‐mechanical model that is used to assess the reservoir performance of a coalbed and the induced surface and subsurface deformations. A series of numerical simulations has been performed to study the effects of different parameters on the reservoir and geomechanical behaviors associated with CO2 injection. A single‐phase dual‐porosity model is coupled to a one‐dimensional poroelastic model and an analytical model for the ground surface movements. Through these simulations, the role of three sets of parameters at different scales is investigated: fracture characteristics, matrix characteristics, and geomechanical/geometrical characteristics. The comparative impacts of these parameters on reservoir permeability, volume of the stored CO2, and deformations of the coalbed and the ground surface, are quantitatively assessed, in order to identify the most important parameters influencing the hydro‐mechanical response of the ground.

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“…To date, the effects of adsorbates on coal strength changes have received considerable attention in the research literature [3][4][5][11][12][13]. Coal mass mechanical properties can be weakened by the adsorption of a more chemically reactive adsorbate.…”

Section: Introductionmentioning

confidence: 99%

“…A number of studies to date have concerned coal mechanical property changes as the effect of sorption, however, most studies focus on CO 2 , CH 4 and N 2 sorption-induced coal strength property alteration [3][4][5]11,17]. However, unlike conventional gas reservoirs which generally have little moisture content, coal seams are usually saturated with ground water in situ, especially for the more hydrophilic low-rank coals such as Victorian brown coal which can hold up to 70% of water by weight [18].…”

Section: Introductionmentioning

confidence: 99%

Effects of Water and Brine Saturation on Mechanical Property Alterations of Brown Coal

et al. 2018

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Abstract:The adsorption of moisture or brine into coal causes the coal mass mechanical properties to be significantly altered, which can greatly affect the coal mining and coal seam gas extraction process. A study was therefore initiated to investigate the influence of moisture and brine saturations (5-25%) on brown coals' strength through a series of unconfined compressive strength tests, with the aid of acoustic emission, optical 3-D deformation analysis and scanning electron microscopy. According to the results, the coal mass is weakened by up to 26% upon the adsorption of moisture and water saturated samples show no crack propagation, whereas brine saturation enhances coal strength by up to 21% and delays crack propagation due to the crystallization of sodium chloride. Besides, a high brine concentration (25%) greatly improves coal mass strength but impairs the increase of Young's modulus due to its corrosive nature, which is consistent with the values of maximum strain at failure of the tested samples (3.9%, 3.1% and 3.6% for 5%, 15% and 25% brine saturated samples, respectively). In addition, because of the precipitation of sodium chloride in coal and the increase of conductivity of pore fluid, more acoustic emission signals are detected for brine saturated samples, while water saturated samples exhibit mush less acoustic release compared to the unsaturated samples.

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Experimental investigations on the effect of CO2 on mechanics of coal

Cited by 109 publications

References 27 publications

Measurement and modeling of adsorptive–poromechanical properties of bituminous coal cores exposed to CO2: Adsorption, swelling strains, swelling stresses and impact on fracture permeability

Measurement and modeling of adsorptive–poromechanical properties of bituminous coal cores exposed to CO2: Adsorption, swelling strains, swelling stresses and impact on fracture permeability

The role of coal seam properties on coupled processes during CO₂sequestration: A parametric study

Effects of Water and Brine Saturation on Mechanical Property Alterations of Brown Coal

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Experimental investigations on the effect of CO2 on mechanics of coal

Cited by 109 publications

References 27 publications

Measurement and modeling of adsorptive–poromechanical properties of bituminous coal cores exposed to CO2: Adsorption, swelling strains, swelling stresses and impact on fracture permeability

Measurement and modeling of adsorptive–poromechanical properties of bituminous coal cores exposed to CO2: Adsorption, swelling strains, swelling stresses and impact on fracture permeability

The role of coal seam properties on coupled processes during CO2sequestration: A parametric study

Effects of Water and Brine Saturation on Mechanical Property Alterations of Brown Coal

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The role of coal seam properties on coupled processes during CO₂sequestration: A parametric study