Stress distribution and permeability modelling in coalbed methane reservoirs by considering desorption radius expansion

Reisabadi, Mohammadreza Zare; Haghighi, Manouchehr; Sayyafzadeh, Mohammad; Khaksar, Abbas

doi:10.1016/j.fuel.2020.119951

Cited by 10 publications

(4 citation statements)

References 26 publications

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“…In the natural coal reservoir environment, stress, moisture, and adsorption are important factors that affect coal permeability. , Wu et al and Sam et al explained the formation mechanisms resulting in stress in the coal reservoir. In early research, many scholars confirmed the dynamic relationship between stress and permeability , and the effect of stress on coal pores and fractures .…”

Section: Discussionmentioning

confidence: 99%

A Study of the Dynamic Changes in Wet Coal’s Water Film and Permeability under Stressed Conditions

Cheng

et al. 2022

Energy Fuels

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Coal permeability is an important influential factor in the efficient development and utilization of coalbed methane (CBM); however, coal is in an environment of combined gas and water and is exposed to continuous reservoir pressure for considerable periods, which makes permeability changes in its natural state extremely complicated and those changes difficult to evaluate. In this study, we established a dual-porosity permeability model suitable for wet coal that considered the influence of stress and gas adsorption. In the process of modeling, the shapes of the matrix pores and fractures were simplified into regular cylindrical and slit; based on the generalized Hooke’s law, the effective stress–strain relationship of the coal matrix and fracture was represented; meanwhile, the adsorption capacity decay coefficient λ was introduced to describe the influence of moisture on gas adsorption; and then changes in the pore radius and fracture width under the action of stress and gas adsorption were quantified. Moreover, the interaction between the water film and the pore wall and the influence of stress and gas adsorption in the natural reservoir environment were considered, relating to the dynamic water film calculation formula in matrix pores and fractures under the influence of stress and gas adsorption that was derived, revealing the dynamic evolution law of water film thickness under the action of stress and gas adsorption. By combining the above influential factors and based on the relationship between permeability–porosity–pore radius (fracture width), a dual-porosity permeability model that considered the effects of stress, gas adsorption, and dynamic water film combinations was established. Further, we compared the predicted results of this model with published experimental data and discuss the influence of stress and gas adsorption on water film thickness and the contribution of matrix permeability and fracture permeability to resultant permeability under different water saturations. The complex variation of wet coal permeability under stress and gas adsorption is revealed.

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Section: Discussionmentioning

confidence: 99%

A Study of the Dynamic Changes in Wet Coal’s Water Film and Permeability under Stressed Conditions

Cheng

et al. 2022

Energy Fuels

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“…In situ stress. The in situ stress significantly influences the stability of the wellbore surface and fracture propagation, but its implication for DCBM depressurization should not be ignored [20,24,25]. For example, the analysis results indicate that the minimum horizontal principal stress in the No.…”

Section: In Situ Stress and Reservoir Pressure Of Deep Coal Seamsmentioning

confidence: 99%

Characteristics of In Situ Stress and Reservoir Pressure in Deep Coal Seams and Their Influences on Reservoir Depletion: A Field Case Study

Xia

et al. 2023

Geofluids

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The production of coalbed methane resources is greatly dependent on the reservoir depletion process. To improve the depressurization efficiency of deep coalbed methane (DCBM) reservoirs, the fluid production characteristics and implications of in situ stress and reservoir pressure for reservoir depletion in the eastern margin of the Ordos Basin are analyzed. The results indicate that the duration of the single-phase water production stage is overall long, with the gas declining stage occurring too early. The daily gas production volume of DCBM wells is only a few hundred m3. For DCBM reservoirs, it is considered that in situ stress, initial reservoir pressure, and critical desorption pressure significantly affect the fluid production and depressurization process. A high in situ stress in deep coal seams is likely to damage the flow conductivity of fracture systems due to the increase in effective stress during reservoir depletion. Based on the in situ stress characteristics of deep coal seams and their implications for reservoir depletion, we propose that the depressurization of DCBM reservoirs during gas production can be promoted via a new method of stress release. Slots or cavities created in coal seams by high-pressure hydraulic jet can provide space for stress release. This novel depressurization method could help improve the gas production efficiency of DCBM reservoirs.

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“…Based on the stress environment in which the coal seam is located, it is easy to know that the force generated by gas adsorption/desorption is much smaller than the overlying rock pressure, , so for some specific structures of coal, the force of gas on the matrix of coal mainly causes changes in pore volume. Therefore, considering the effect of gas desorption during coal seam mining, , the calculation equation of coal body porosity can be expressed in formula . φ k = V k V 0 = V k 0 + normalΔ V k V 0 = φ 0 + normalΔ V k V 0 = φ 0 + ε m ′ where V k 0 is the initial volume of the double porosity system of coal in m 3 and Δ V k is the volume change of the double porosity system in m 3 .…”

Section: Model Constructionmentioning

confidence: 99%

“…Based on the stress environment in which the coal seam is located, it is easy to know that the force generated by gas adsorption/desorption is much smaller than the overlying rock pressure, , so for some specific structures of coal, the force of gas on the matrix of coal mainly causes changes in pore volume. Therefore, considering the effect of gas desorption during coal seam mining, , the calculation equation of coal body porosity can be expressed in formula . where V k 0 is the initial volume of the double porosity system of coal in m 3 and Δ V k is the volume change of the double porosity system in m 3 .…”

Section: Model Constructionmentioning

confidence: 99%

Evolutionary Model and Experimental Validation of Gas-Bearing Coal Permeability under Negative Pressure Conditions

Shi

Zeng

et al. 2023

ACS Omega

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Coal bed methane drainage is the main approach to lower risks of coal seam while raising the efficiency in natural resource utilization. The negative pressure used for extraction in coal mines is largely determined empirically due to a lack of experimental research on how coal permeability changes under the combined influence of effective stress and negative pressure. This results in low gas extraction efficiency and concentration. In this paper, to study the effect law of complex stress and extraction on coal permeability during coal and gas co-mining, a test system was specially designed to determine the gas flow and coal permeability of coal samples under different stress paths and negative pressure conditions in the lab. The study analyzed the correlation between coal permeability, effective stress, and negative pressure and subsequently developed a permeability evolution model for gas-bearing coal under negative pressure conditions. The results showed that the permeability of coal increases with the increase in negative pressure and decreases with the increase in effective stress; the permeability of coal can be abruptly changed by changes in stress loading patterns; the established model of permeability evolution of gas-bearing coal can better reflect the correlation between permeability, effective stress, and negative pressure. The research outcomes offer a valuable theoretical foundation for the efficient extraction and utilization of methane in coal mines.

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Stress distribution and permeability modelling in coalbed methane reservoirs by considering desorption radius expansion

Cited by 10 publications

References 26 publications

A Study of the Dynamic Changes in Wet Coal’s Water Film and Permeability under Stressed Conditions

A Study of the Dynamic Changes in Wet Coal’s Water Film and Permeability under Stressed Conditions

Characteristics of In Situ Stress and Reservoir Pressure in Deep Coal Seams and Their Influences on Reservoir Depletion: A Field Case Study

Evolutionary Model and Experimental Validation of Gas-Bearing Coal Permeability under Negative Pressure Conditions

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