Complex evolution of coal permeability during CO2 injection under variable temperatures

Qu, Hao; Liu, Jishan; Chen, Zhongwei; Wang, Jingguo; Pan, Zhejun; Connell, Luke D.; Elsworth, Derek

doi:10.1016/j.ijggc.2012.04.003

Cited by 88 publications

(35 citation statements)

References 61 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The adsorption, desorption, and seepage of ternary gases in coal seams have thermal effects, which are nonisothermal processes. We assume that the solid and fluid are always in thermal equilibrium and the governing equation for heat transfer is expressed as:

\begin{matrix} \frac{\partial [{()(, ρ C_{p})}_{normalc} T]}{\partial t} + η_{normalc} \nabla T + q_{st1} \frac{ρ_{normals} ρ_{ga1}}{M_{g1}} \frac{\partial V_{sg1}}{\partial t} + q_{st2} \frac{ρ_{normals} ρ_{ga2}}{M_{g2}} \frac{\partial V_{sg2}}{\partial t} + \\ q_{st3} \frac{ρ_{normals} ρ_{ga3}}{M_{g3}} \frac{\partial V_{sg3}}{\partial t} + K α_{T} T \frac{\partial (ε_{s1} + ε_{s2} + ε_{s3})}{\partial t} - \nabla \cdot (λ_{normalc} \nabla T) = 0 \end{matrix}

In which, \{\begin{matrix} {()(, ρ C_{p})}_{c} = (1 - φ) ρ_{s} C_{s} + φ (M_{g1} C_{1} C_{v1} + M_{g2} C_{2} C_{v2} + M_{g3} C_{3} C_{v3}) \\ η_{c} = - k normal∇ C_{1} R T ρ_{g1} C_{v1} false/ μ_{1} - k normal∇ C_{2} R T ρ_{g2} C_{v2} false/ μ_{2<...>} \end{matrix}

…”

Section: Fully Coupled Equations Of the Thm Fields For Gas Mixture Ecmentioning

confidence: 99%

Numerical study on enhancing coalbed methane recovery by injecting N₂/CO₂ mixtures and its geological significance

Fan

Wang

Deng

et al. 2019

Energy Science & Engineering

View full text Add to dashboard Cite

As an effective carbon utilization technology, the injection of N2/CO2 mixtures into coal seams has significant potential for improving coalbed methane recovery. Considering the technical barrier that injection of pure CO2 decreases the well injectivity index and pure N2 injection leads to the rapid methane recovery, a method of injecting N2‐enriched gas mixtures with a constant component is proposed. In this study, a thermo‐hydro‐mechanical (THM) coupling numerical model for enhanced coalbed methane (CBM) recovery by injecting N2/CO2 mixtures is established. This model includes complex interactions of coal deformation, competitive adsorption, ternary gas seepage, and heat transfer. The THM coupling model is first validated, and then applied to investigate the evolution of mixed gas concentrations, reservoir permeability, reservoir temperature, CH4 production, and N2/CO2 storage during N2/CO2 enhanced CBM recovery. The results show that the displacement radius and concentration of the mixed gas in the coal seam increased with gas injection pressure increase. The concentration of CH4 gradually decreased with time, and the early decline is faster than the later stage. The sweep of the N2 flow accelerates CH4 desorption and migration, promoting a reduction in reservoir temperature near the production well. Reservoir permeability evolution results from the combined effects of ternary gases (CH4, CO2, N2) competitive adsorption, gas pressure, and geostress on the coal seam within the THM fields. At the methane natural depletion stage (within 250 days), the permeability of coal reservoir first decreases and then increases. With the arrival of the N2/CO2 mixture, the permeability decreases dramatically. From the perspective of cumulative CH4 production, the optimal composition is dominated by the synergistic effect of maximizing breakthrough time and minimizing coal matrix swelling. For 30% CO2‐70% N2, the CH4 recovery ratio reached 71.76%, representing an increase of 16.67% compared to natural depletion.

show abstract

\begin{matrix} \frac{\partial [{()(, ρ C_{p})}_{normalc} T]}{\partial t} + η_{normalc} \nabla T + q_{st1} \frac{ρ_{normals} ρ_{ga1}}{M_{g1}} \frac{\partial V_{sg1}}{\partial t} + q_{st2} \frac{ρ_{normals} ρ_{ga2}}{M_{g2}} \frac{\partial V_{sg2}}{\partial t} + \\ q_{st3} \frac{ρ_{normals} ρ_{ga3}}{M_{g3}} \frac{\partial V_{sg3}}{\partial t} + K α_{T} T \frac{\partial (ε_{s1} + ε_{s2} + ε_{s3})}{\partial t} - \nabla \cdot (λ_{normalc} \nabla T) = 0 \end{matrix}

In which, \{\begin{matrix} {()(, ρ C_{p})}_{c} = (1 - φ) ρ_{s} C_{s} + φ (M_{g1} C_{1} C_{v1} + M_{g2} C_{2} C_{v2} + M_{g3} C_{3} C_{v3}) \\ η_{c} = - k normal∇ C_{1} R T ρ_{g1} C_{v1} false/ μ_{1} - k normal∇ C_{2} R T ρ_{g2} C_{v2} false/ μ_{2<...>} \end{matrix}

…”

Section: Fully Coupled Equations Of the Thm Fields For Gas Mixture Ecmentioning

confidence: 99%

Numerical study on enhancing coalbed methane recovery by injecting N₂/CO₂ mixtures and its geological significance

Fan

Wang

Deng

et al. 2019

Energy Science & Engineering

View full text Add to dashboard Cite

show abstract

“…[11][12][13] Scholars have made great achievements on the factors that affect the coal permeability, including stress, temperature, and adsorption-induced coal swelling, and they have developed models to describe coal permeability variation account to these factors. [14][15][16][17] Coal permeability is highly sensitive to the effective stress. Some tests are conducted to study the effects of effective stress changes in coal permeability.…”

Section: Introductionmentioning

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

View full text Add to dashboard Cite

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.

show abstract

“…There are several works which tested coal samples under lower temperatures (e.g. Long et al, 2009;Perera et al, 2012;Qu et al, 2012;Wang et al, 2013;Xu et al, 2014;Yin et al, 2013) that are not included in this study.…”

Section: Introductionmentioning

confidence: 99%

Structural changes in coal at elevated temperature pertinent to underground coal gasification: A review

Akbarzadeh

Chalaturnyk

2014

International Journal of Coal Geology

View full text Add to dashboard Cite

Complex evolution of coal permeability during CO2 injection under variable temperatures

Cited by 88 publications

References 61 publications

Numerical study on enhancing coalbed methane recovery by injecting N₂/CO₂ mixtures and its geological significance

Numerical study on enhancing coalbed methane recovery by injecting N₂/CO₂ mixtures and its geological significance

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

Structural changes in coal at elevated temperature pertinent to underground coal gasification: A review

Contact Info

Product

Resources

About

Complex evolution of coal permeability during CO2 injection under variable temperatures

Cited by 88 publications

References 61 publications

Numerical study on enhancing coalbed methane recovery by injecting N2/CO2 mixtures and its geological significance

Numerical study on enhancing coalbed methane recovery by injecting N2/CO2 mixtures and its geological significance

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

Structural changes in coal at elevated temperature pertinent to underground coal gasification: A review

Contact Info

Product

Resources

About

Numerical study on enhancing coalbed methane recovery by injecting N₂/CO₂ mixtures and its geological significance

Numerical study on enhancing coalbed methane recovery by injecting N₂/CO₂ mixtures and its geological significance

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