Apparent Permeability Coupling of Adsorbed and Free Gases for Deep Shale: Theoretical Model and Measurements

Mu, Zhongqi; Ning, Zhengfu; Gu, Keming; Lyu, Fangtao

doi:10.1021/acs.energyfuels.2c01998

Cited by 2 publications

(1 citation statement)

References 40 publications

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“…The effect of gas slippage can be incorporated into permeability models through two different methods. In the first method, the slip boundary condition of the continuity model is modified through multiplying a slippage factor to the continuity equation. ,− In the second method, various flow regimes are captured by permeability models through superposition of each flow regime using the contribution weight coefficients. ,− However, all permeability models in this stage assume intrinsic permeability as a constant, which is unrealistic during gas injection/extraction processes. In the second stage, the combined effects of effective stress and gas slippage are considered.…”

Section: Introductionmentioning

confidence: 99%

A Review of Swelling Effect on Shale Permeability: Assessments and Perspectives

et al. 2023

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The significant effect of gas sorption induced swelling on shale permeability has been observed through laboratory measurements and explained through permeability models over the past decades. However, there are lab observations that cannot be explained by these models. This knowledge gap prompts this review. Our goal is to form perspectives on how to resolve this gap through assessing the role of swelling on shale permeability. This goal is achieved through the following three steps: (1) collection of experimental shale permeability data measured under both constant effective stress and constant confining pressure conditions; (2) collection and classification of shale permeability models under the influence of gas sorption induced swelling strains; (3) assessments of co-relations between shale permeability data and permeability models. On the basis of all assessments, we conclude that the discrepancies between model predictions and laboratory measurements depend on the relation between bulk and pore swelling strains, pore size scales, and consistencies of strain treatments in the experiments and models. Models assuming that bulk swelling strain is different from pore swelling strain can better explain lab observations than those assuming that they are the same. When the pore size transitions from the micron-scale to the nano-scale, the effect of swelling on shale permeability gradually diminishes. The inconsistencies between how swelling strains are measured in the lab and treated in the models are common in the literatures and affect the discrepancies between model predictions and lab observations. On the basis of these assessments, we form our perspectives: (1) transformation between bulk and pore swelling strains should be characterized and incorporated both for experiments and in permeability models; (2) shale multiscale pore structural characteristics should be characterized when assessing the swelling effect on shale permeability; (3) the time-dependent nature of swelling strain and permeability evolution should be incorporated into future experiments and permeability models.

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Section: Introductionmentioning

confidence: 99%

A Review of Swelling Effect on Shale Permeability: Assessments and Perspectives

et al. 2023

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End-Member Mixing Model for Methane Carbon Isotope Fractionation During Shale Gas Desorption and Its Application

Zhai,

Tao,

Zou

et al. 2024

ACS Omega

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Unlike conventional natural gas reservoirs, shale gas development involves systematic changes in methane carbon isotopes that cannot be effectively described by existing isotope fractionation models and mechanisms. Therefore, based on fundamental theories such as Rayleigh fractionation, mass transfer flow, and mass conservation, this study established isotopic fractionation equations for methane in adsorbed and free gas. By considering adsorbed and free gases as two end-members and using an isotope mixing model, a fractionation model for methane carbon isotopes during shale gas desorption was constructed. This model quantifies the isotopic fractionation effects during shale gas desorption and elucidates the mechanism of methane carbon isotope fractionation. Using on-site desorbed gas content and isotope data, parameter fitting and model calculations were conducted to characterize methane carbon isotope variations throughout the process of shale core field desorption. The results show a pattern of "initially negative and then turning positive," consistent with those of physical simulation experiments. It was clarified that differences in mixing the two endmembers and isotopic fractionation play key roles in the variation of methane carbon isotopic composition in shale gas. By applying the methane carbon isotope fractionation model, the contribution of adsorbed gas during shale gas production was explored. It was found that in the early stage of development, the adsorbed gas in Well JY 1 was negligible. After nearly seven years of development, the contribution of adsorbed gas in the later stage has only reached nearly 15%, indicating that the production contribution of adsorbed gas is still less than 0.3 million cubic feet per day. The open flow of Well JY 6−2 is more conducive to the production of adsorbed gas, but the production capacity is still mainly contributed by free gas, indicating that the shale gas production capacity in the later stage in the Jiaoshiba gas field is still primarily dominated by free gas.

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Apparent Permeability Coupling of Adsorbed and Free Gases for Deep Shale: Theoretical Model and Measurements

Cited by 2 publications

References 40 publications

A Review of Swelling Effect on Shale Permeability: Assessments and Perspectives

A Review of Swelling Effect on Shale Permeability: Assessments and Perspectives

End-Member Mixing Model for Methane Carbon Isotope Fractionation During Shale Gas Desorption and Its Application

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