A model for <scp>stress‐dependence</scp> of apparent permeability in nanopores of shale gas reservoirs

Hatami, Mohammad; Bayless, David J.; Sarvestani, Alireza S.

doi:10.1002/aic.16541

Cited by 12 publications

(15 citation statements)

References 54 publications

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“…In the second stage, the combined effects of effective stress and gas slippage are considered. These permeability models ,, are able to capture the deformation of shale and alteration of pore size as a result of effective stress change under variable boundary conditions spanning from displacement-controlled to stress-controlled ones. In the third stage, the combined effects of effective stress, gas sorption, 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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“…The gas production process included desorption, diffusion, and seepage . The gas average molecular free path was comparable with its pore size; consequently, the interaction between fluid and wall in shale nanopores would be enhanced . There would be some deviation when Darcy’s law was taken into account, and gas flow mechanisms were extremely complicated.…”

Section: Introductionmentioning

confidence: 99%

“…Yu et al derived an analytical model of gas transport in a single pore based on the results of molecular simulations, coupled with continuum theory and diffusion effects, and extended it to the whole pore network. In addition, stress sensitivity, induced by gas exploration, would reduce porosity and permeability and has been widely studied. , Fluid velocity distribution was considered crucial to model shale nanopore transport . Li et al used the Langmuir-slip model to describe the bulk gas transport velocity and modeled the apparent permeability considering the dynamic changes in pore size.…”

Section: Introductionmentioning

confidence: 99%

An Apparent Permeability Model in Organic Shales: Coupling Multiple Flow Mechanisms and Factors

Song

et al. 2023

Langmuir

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It is of great significance to study shale apparent permeability under the action of multiple flow mechanisms and factors because shale reservoirs possess complex pore structures and flow mechanisms. In this study, the confinement effect was considered, with the thermodynamic properties of gas being modified, and the law relating to the conservation of energy adopted to characterize bulk gas transport velocity. On this basis, the dynamic change of pore size was assessed, from which shale apparent permeability model was derived. The new model was verified by three steps: experimental and molecular simulation results of rarefied gas transport, shale laboratory data, and comparison with different models. The results revealed that, under the conditions of low pressure and small pore size, the microscale effects became obvious, which significantly improved gas permeability. Through comparisons, the effects of surface diffusion and matrix shrinkage, including the real gas effect, were obvious in the smaller pore sizes; nevertheless, the stress sensitivity effect was stronger in larger pore sizes. In addition, shale apparent permeability and pore size decreased with an increase in permeability material constant and increased with increasing porosity material constant, including internal swelling coefficient. The permeability material constant had the greatest effect on gas transport behavior in nanopores, followed by the porosity material constant; however, the internal swelling coefficient had the least effect. The results of this paper will be important for the prediction and numerical simulation of apparent permeability relating to shale reservoirs.

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“…Over the past few decades, many countries have succeeded in developing shale gas commercially owing to the continuous improvement of hydraulic fracturing and horizontal drilling technologies, with shale gas receiving considerable attention in the energy field. − Shale is an extremely dense, fine-grained sedimentary rock composed of clastic, clay minerals, and organic matter. Shale gas refers to a natural gas that occurs in organic shale.…”

Section: Introductionmentioning

confidence: 99%

Characterization of the Knudsen Number and Gas Transport in Shale Reservoirs: Coupling the Microfracture Network and Capillary Network

Song

et al. 2023

Ind. Eng. Chem. Res.

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An accurate understanding of gas seepage mechanisms in shale reservoirs would have a positive impact on promoting shale gas development. Shale is a complex dual-porosity medium composed of a microfracture network and capillary network. However, most shale dual-porosity permeability models have usually ignored the influence of key mechanisms, such as effective stress and gas adsorption. In addition, the depiction and analysis of the Knudsen number has not been fully discussed in previous studies. In this study, the inner relationship between intrinsic permeability and porosity has been taken to be a bridge, with the fracture width including the pore radius being quantified, leading to a modification of the Knudsen number in the microfracture network and capillary network. Based on the modified Knudsen number, a dual-porosity permeability model has been developed for typical shale reservoirs that considered real gas effect, flow regimes, effective stress, and gas adsorption. The reliability of the new model has been validated by published experimental data under different conditions and through comparisons with the existing theoretical models. Finally, the evolution law relating to gas apparent permeability and the Knudsen number in the microfracture network and capillary network has been discussed, and the effects of different factors concerning apparent permeability and the Knudsen number have been quantified. Based on the results, the relationships between the coupled effects relating to the rock deformation field, the microfracture network seepage field, the capillary network seepage field, and the Knudsen number have been proposed. Moreover, the mechanisms relating to the internal swelling coefficient and gas rarefaction coefficient, including different pore network occupancies on total gas transport capacity, have been presented. The research results will provide a basis for the accurate numerical simulation for shale gas and will be of great significance to the economic development of shale gas in the future.

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A model for stress‐dependence of apparent permeability in nanopores of shale gas reservoirs

Cited by 12 publications

References 54 publications

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

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

An Apparent Permeability Model in Organic Shales: Coupling Multiple Flow Mechanisms and Factors

Characterization of the Knudsen Number and Gas Transport in Shale Reservoirs: Coupling the Microfracture Network and Capillary Network

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