Why shale permeability changes under variable effective stresses: New insights

Cui, Guanglei; Liu, Jishan; Wei, Mingyao; Shi, Rui; Elsworth, Derek

doi:10.1016/j.fuel.2017.10.068

Cited by 90 publications

(48 citation statements)

References 73 publications

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“…The research ideas in this article can also be applied to other unconventional gas, such as shale gas. The widely application of horizontal well and hydraulic fracturing make the economic exploration of low porosity and permeability shale gas possible [24]. Different from hydraulic fracturing in coal reservoir, a large amount of proppant is usually injected keep the fractures open in shale reservoir [25].…”

Section: Of 16mentioning

confidence: 99%

“…(2) The main fracture network formed by hydraulic fracturing is treated as a rectangular area for equivalence. In fact, the field monitoring equipment such as micro-seismic and acoustic emission shows that the stimulated zone formed by hydraulic fracturing is ellipsoidal, However, the rectangular approach is still widely applied with good results [24,29]. (3) The gas pre-extraction in coal seam by ultra-long boreholes is studied in this work under the assumption that the coal seams in the extraction area are not mined and the mining in the adjacent seam has little impact.…”

Section: Of 16mentioning

confidence: 99%

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The Influence of the Injected Water on the Underground Coalbed Methane Extraction

et al. 2020

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The increasing demand on coal production has led to the gradually increase of mining depth and more high methane mines, which bring difficulties in terms of coalbed methane (CBM) extraction. Hydraulic fracturing is widely applied to improve the production of CBM, control mine gas, and prevent gas outbursts. It improves coal bed permeability and accelerate desorption and migration of CBM. Even though the impacts of hydraulic fracturing treatment on the coal reservoirs are rare, negative effects could not be totally ignored. To defend this defect, the presented work aims to study the influence of water filtration on coal body deformation and permeability evolution. For this purpose, a simulation based finite element method was developed to build a solid-fluid coupled two-phase flow model using commercial software (COMSOL Multiphysics 5.4). The model was verified using production data from a long strike borehole from Wangpo coal mine in Shanxi Province, China. Several simulation scenarios were designed to investigate the adverse impacts of hydraulic fracturing on gas flow behaviors. The mechanisms of both relative and intrinsic permeability evolutions were analyzed, and simulation results were presented. Results show that the intrinsic permeability of the fracture system increases in the water injection process. The impacts of water imitation were addressed that a critical time was observed beyond which water cannot go further and also a critical pressure exists above which the hydraulic pressure would impair the gas flow. Sensitivity analysis also showed that a suitable time and pressure combination could be observed to maximize gas extraction. This work provides an efficient approach to guide the coal bed methane exploitation and other unconventional gas reservoirs.

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Section: Of 16mentioning

confidence: 99%

Section: Of 16mentioning

confidence: 99%

The Influence of the Injected Water on the Underground Coalbed Methane Extraction

et al. 2020

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“…The effective stress regulates the permeability of shale and production rate of gas reservoirs. 4,5 Permeability measurements in laboratory scales are generally conducted under two conditions: constant effective stress (CES), where the difference between confining pressure and gas pressure is kept constant, and constant confining pressure (CCP), where the gas pressure is changed with a constant volumetric stress applied at the boundaries. 6 CES tests are particularly suitable for studying the sorptioninduced effects on gas permeability, independent from rock poroelastic response.…”

Section: Introductionmentioning

confidence: 99%

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

2020

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Predicting long‐term production from gas shale reservoirs is a challenging task due to changes in effective stress and permeability during gas production. Unlike coal, the variation of sorbing gas permeability with pore pressure in shale does not always feature a biphasic trend under a constant confining pressure. The present contribution demonstrates that the biphasic dependence of permeability on pore pressure depends on a number of physical and geometrical factors, each with a distinct impact on gas permeability. This includes pore size, adsorption isotherm, and the variation of gas viscosity with pore pressure. A single‐capillary model is proposed for the apparent permeability of real gas in shale. Results indicate that the biphasic relation between apparent permeability and pore pressure is prevalent when the sorbing gas flows in sufficiently small pores. In addition, the effects of sorption isotherm and internal resistance of nonideal gas to flow cannot be ignored.

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“…The unpropped fracture conductivity of shale is also affected by vertical stress . Studies have shown that loading effective stresses on the fractures can significantly change the fracture width and the fluid velocity and pressure distribution within the fracture . A rough‐walled fracture can be deformed by vertical stress, thereby reducing the fluid flow ability of the fracture .…”

Section: Introductionmentioning

confidence: 99%

Influence factors of unpropped fracture conductivity of shale

Gou

et al. 2020

Energy Science & Engineering

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Hydraulic fracture is widely performed to enhance oil and gas production in the development of unconventional reservoirs. This paper proposes a numerical model for the calculation of the unpropped fracture conductivity of shale. This numerical model consists of three basic models, namely, the numerical reconstruction model of fracture morphology, fracture deformation model under closed stress, and fluid flow model. The numerical model can be used to analyze the influencing factors of the unpropped fracture conductivity of shale quantitatively. The results demonstratethat the fracture misalignment of shale is a prerequisite for unpropped fractures with conductivity at high closed stress. Furthermore, the unpropped fracture conductivity of shale decreases exponentially with the increase in closed stress. Moreover, closed stress is the factor having the most significant influence on the unpropped fracture conductivity of shale, followed by roughness and fracture morphology. The negative effect of closed stress can be reduced by increasing the fracture morphology during the fracturing operation. K E Y W O R D Sclosed stress, conductivity, fracture morphology, shale, unpropped fracture | 2025 LU et aL.

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Why shale permeability changes under variable effective stresses: New insights

Cited by 90 publications

References 73 publications

The Influence of the Injected Water on the Underground Coalbed Methane Extraction

The Influence of the Injected Water on the Underground Coalbed Methane Extraction

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

Influence factors of unpropped fracture conductivity of shale

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