Influence of the effective stress coefficient and sorption-induced strain on the evolution of coal permeability: Model development and analysis

Chen, Zhongwei; Liu, Jishan; Pan, Zhejun; Connell, Luke D.; Elsworth, Derek

doi:10.1016/j.ijggc.2012.01.015

Cited by 140 publications

(62 citation statements)

References 43 publications

(60 reference statements)

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“…Second, the diffusion coefficient was assumed to be constant, which is not consistent with other studies (Bird et al 1960;Lama and Nguyen 1987;Kranz et al 1990). Moreover, although the importance of the effect of desorption time on CBM extraction has been widely investigated, many researchers have not taken the geomechanical process into consideration (Reeves and Pekot 2001;Shi and Durucan 2004;Palmer 2009), or have primarily assumed the absolute permeability to be a constant during both gas/water production and dry-gas production (Clarkson et al 2007;Ziarani et al 2011), as a consequence of which they missed an important phenomenon of coalbed reservoirs (Cui and Bustin 2005;Gu and Chalaturnyk 2005;Chen et al 2009Chen et al , 2012Connell 2009;Liu and Rutqvist 2010;Wang et al 2011Wang et al , 2012.…”

Section: Introductionmentioning

confidence: 99%

Impact of Various Parameters on the Production of Coalbed Methane

Chen¹,

Liu²,

Kabir³

et al. 2013

SPE Journal

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Coalbed-methane (CBM) reservoirs are naturally fractured formations, comprising both permeable fractures and matrix blocks. The interaction between fractures and matrix presents a great challenge for the forecast of CBM reservoir performance. In this work, a dual-permeability model was applied to study the parameter sensitivity on the CBM production, because the dual-permeability model incorporates not only the influence from matrix and fractures but also that between adjacent matrix blocks. The mass exchange between two systems is defined as a function of desorption time constant at the standard condition, coal matrix porosity, and the difference of gas pressure between two systems. Correspondingly, gas diffusivity in matrix is considered as a variable and represented by a function of shape factor, gas desorption time, and reservoir pressure. These relations are integrated into a fully coupled numerical model of coal geomechanical deformation and gas desorption/gas flow in both systems. This numerical approach demonstrates the important nonlinear effects of the complex interaction between matrix and fractures on CBM production behaviors that cannot be recovered without rigorously incorporating geomechanical influences. This model was then used to investigate the sensitivity of CBM extraction behavior to different controlling factors, including gas desorption time constant, initial fracture permeability, fracture spacing, swelling capacity, desorption capacity, production pressure, and fracture and matrix porosities. Modeling results show that the peak magnitudes of gasproduction rate increase with initial fracture permeability, sorption and swelling capacities, and matrix porosity, and decrease with gas desorption time constant and production pressure. These results also show dramatic increase in gas-production efficiency with decreasing magnitudes of fracture spacing. The comparison of the transient contributions of the desorbed gas and the free phase gas from the matrix system to gas production shows that the free phase gas plays the dominant role at the early stage, but diminishes when the adsorption phase gas takes over the dominant role, indicating the necessity of incorporating free phase gas impact in simulation models. The numerical model was also applied to match the history data from a gas-production well. A better matching result than that for the single-permeability model demonstrates the potential capability of the dual-permeability model for the forecast of CBM production. IntroductionCoal seams are naturally fractured reservoirs, comprising both permeable fractures and matrix blocks. The micropores within coal matrix are the main gas-storage site, whereas the microfractures, fissures, fractures, and faults comprise the main conduits for gas seepage and migration. Coal permeability changes with CBM reservoir-pressure depletion during production, whereas the desorption of gas from the coal matrix tends to increase fracture openings and increase coal permeability. These two processes are competitive ...

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Section: Introductionmentioning

confidence: 99%

Impact of Various Parameters on the Production of Coalbed Methane

Chen¹,

Liu²,

Kabir³

et al. 2013

SPE Journal

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“…It is obvious that the increases in ScCO 2 injection pressure will reduce the effective pressure of the coal seam. The permeability of deep coal seam increases with the effective pressure decrease . Therefore, the deep coal seam with low permeability is one of the geological media to potentially store huge amounts of ScCO 2 .…”

Section: Discussionmentioning

confidence: 99%

An experimental study on the permeability changes of anthracite reservoirs in different depths of Qinshui Basin induced by supercritical CO₂ injection

Jia

Cao

2019

Energy Science & Engineering

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Geological sequestration of supercritical CO2 (ScCO2) in deep coal seam has been considered as one of the most promising options for reducing greenhouse gas emission. The permeability of a coal seam, a key parameter estimating the CO2 injectivity, determines the success of ScCO2 storage in the deep coal seam. The deep coal seam has a low initial permeability and a further permeability loss induced by the adsorption‐swelling effects of coal during ScCO2 injection. This paper presents a set of measurements on the permeability changes of anthracite reservoirs in different depths of Qinshui Basin induced by ScCO2 injection. The results indicate that the change in anthracite permeability presents a negative exponential decrease with the buried depth increase. The depth of anthracite reservoir increases from 800 to 1400 m, and its permeability will decrease from 4.59 × 10−2 to 8.04 × 10−4 mD. The permeability change induced by ScCO2 injection is the combining effects of temperature, pressure, and adsorption‐swelling, and the permeability change can be described by a negative exponential model during ScCO2 injection to anthracite reservoir in different depths. The loss coefficient of permeability is up to three magnitudes induced by ScCO2 injection to the anthracite reservoir in the depth of 800 m, 2‐3 magnitudes in 1000‐1200 m, and 1‐2 magnitudes in 1400 m. Although the initial permeability of anthracite reservoirs in the same depth exists differences, the permeability loss coefficient almost has the same magnitudes induced by ScCO2 injection. Comparing with the permeability loss coefficient of the anthracite reservoir in different depths, the permeability variation of the shallow coal seam is more sensitive than the deep induced by ScCO2 injection. However, the deep coal seam has a relatively large fracture pressure, so the allowable ScCO2 injection pressure in the deep coal seam is greater than the shallow.

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“…Pini et al (2009) reported that gas species-dependent coefficient for swelling was required to match their permeability data for CO 2 (0.62) and N 2 (2.4); however they contributed this difference mainly to the potential weakening impact of CO 2 on the coal sample (reduced Young's Modulus). Chen et al (2012) used a partition ratio that varies linearly with the cleat porosity to match the permeability of CH 4 /CO 2 for three different coals.…”

Section: Discussionmentioning

confidence: 99%

“…This is mainly due to the fact that, unlike under uniaxial strain conditions, only a portion of the free matrix swelling strain (as opposed to matrix shrinkage strain in CBM production) contributes to the cleat permeability changes measured in the laboratory under a constant confining pressure. Several studies have shown that an improved/good match to the laboratory data for CH 4 and CO 2 can indeed be obtained by using a correction factor (or a partition ratio) to the free swelling strain in the field permeability models (Robertson and Christiansen, 2007;Pini et al, 2009;Liu and Rutqvist, 2010;Connell et al, 2010;Chen et al, 2012). However, the previous studies tend to focus on matching the permeability data for individual tests, and a more holistic view of how swelling strain affects the cleat permeability/porosity of a core under a fixed confining pressure is still largely lacking.…”

Section: Introductionmentioning

confidence: 99%

How gas adsorption and swelling affects permeability of coal: A new modelling approach for analysing laboratory test data

Shi¹,

Durucan²,

Shimada³

2014

International Journal of Coal Geology

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Influence of the effective stress coefficient and sorption-induced strain on the evolution of coal permeability: Model development and analysis

Cited by 140 publications

References 43 publications

Impact of Various Parameters on the Production of Coalbed Methane

Impact of Various Parameters on the Production of Coalbed Methane

An experimental study on the permeability changes of anthracite reservoirs in different depths of Qinshui Basin induced by supercritical CO₂ injection

How gas adsorption and swelling affects permeability of coal: A new modelling approach for analysing laboratory test data

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Influence of the effective stress coefficient and sorption-induced strain on the evolution of coal permeability: Model development and analysis

Cited by 140 publications

References 43 publications

Impact of Various Parameters on the Production of Coalbed Methane

Impact of Various Parameters on the Production of Coalbed Methane

An experimental study on the permeability changes of anthracite reservoirs in different depths of Qinshui Basin induced by supercritical CO2 injection

How gas adsorption and swelling affects permeability of coal: A new modelling approach for analysing laboratory test data

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An experimental study on the permeability changes of anthracite reservoirs in different depths of Qinshui Basin induced by supercritical CO₂ injection