Quantitative characterization of single-phase flow through rough-walled fractures with variable apertures

Dong, Jiabin; Ju, Yang

doi:10.1007/s40948-020-00166-w

Cited by 14 publications

(8 citation statements)

References 54 publications

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“…It is now understood that proppant degradation mechanisms may occur in fracture deposits under extreme reservoir conditions, and of these mechanisms, crushing and embedment of proppants require close attention [2,21,44]. The simultaneous processes of mechanical instability of proppants which occur upon resisting high fracture closure stress and proppant grain indentation into the fracture surface can lead to a drastic increase in fracture tortuosity and fracture aperture reductions, lowering the fracture permeability [14]. Although many macro-scale experimental and numerical studies have been conducted to understand the ultimate impact of crushing and embedment, the realistic proppant and rock response upon undergoing crushing and embedment is yet to be fully studied.…”

Section: Introductionmentioning

confidence: 99%

Grain-scale analysis of proppant crushing and embedment using calibrated discrete element models

et al. 2022

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Proppant crushing and embedment in hydraulically-induced fractures is a major drawback to the recovery of unconventional oil/gas and geothermal energy production. This study provides a grain-scale analysis of the fracture evolution mechanisms of proppant crushing, rock fracture damage during proppant embedment, the influence of realistic reservoir/fracture fluid on proppant embedment, and the behaviour of proppant packs subjected to in-situ stresses using a discrete element modelling (DEM) approach. The results of this study reveal that the selection of an appropriate proppant type based on the nature of the reservoir formation plays a vital part in quantifying the degree of proppant crushing and embedment within fractures. The utilisation of frac-sand proppants instead of ceramic proppants in shallow soft sedimentary-based siltstone formations reduces proppant embedment up to 88%. However, whatever the depth of the fracture, the injection of ceramic proppants into granite-based geothermal formations is preferred to that of frac-sand proppants due to their lower proppant embedment and greater crush resistance. DEM analysis detected rock-spalling during the proppant embedment process, which ultimately led to the initiation of tensile-dominant secondary fractures in rocks. Fracture initiation, propagation, and coalescence during proppant crushing are analysed using calibrated DEM proppant-rock assemblies. Importantly, this study reveals that the saturation of formation rocks with fracturing/reservoir fluids may cause a significant increase in proppant embedment. Furthermore, proppant crushing, embedment, and re-arrangement mechanisms in proppant packs with different proppant distributions are analysed in this comprehensive numerical study.

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Section: Introductionmentioning

confidence: 99%

Grain-scale analysis of proppant crushing and embedment using calibrated discrete element models

et al. 2022

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“…Compared with the relatively flat surface of concrete, the surface of fractures in concrete is rough, and the geometric characteristics are complicated [16,17]. The roughness and complicated geometric characteristics affect the hydraulic characteristic of fractures (hydraulic aperture) [18][19][20][21]; the hydraulic characteristic controls the flow state of water in fractures [22] and the flow state, in turn, affects the leaching characteristics [7]. Leaching also alters the fracture geometric characteristics [23,24], and the evolution of fracture geometric characteristics then affect the characteristics of fracture space [25]; this determines the hydraulic characteristics of fractures [26], and the evolution of hydraulic characteristics will further affect the leaching characteristics on the surface of concrete fractures [13].…”

Section: Introductionmentioning

confidence: 99%

Effect of Leaching Behavior on the Geometric and Hydraulic Characteristics of Concrete Fracture

et al. 2022

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The leaching of material from concrete fracture surfaces has an impact on the structural concrete in service, but the number of studies that consider the effect of the coupling of the leaching, fracture geometry and hydraulic processes on concrete fractures is insufficient. In this study, a series of experiments was conducted, and a leaching model proposed, to investigate the mechanism of leaching behavior on the geometric and hydraulic characteristics of concrete fractures. Following the leaching experiment, the evolution of fracture geometric characteristics was observed by a three-dimensional (3D) laser scanning technique, finding that the fracture produces residual leached depth and local uneven leaching, which results in a decrease in roughness. The hydraulic characteristics were then investigated by permeability tests, and it was found that the fracture hydraulic aperture and permeability increase monotonically with leaching time. A simulation of fluid flow in a numerical fracture revealed the effect of residual leached depth and a decrease in roughness on the hydraulic characteristics. Finally, based on the analysis of the chemical composition of the leaching solution, a leaching model of concrete rough fracture surface is proposed and the mechanism of leaching behavior is discussed. These new findings are useful for the understanding of the development of leaching, local to concrete fracture surfaces.

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“…Focusing on flow behaviors in single rough fractures, researchers have devoted substantial efforts to permeability in rock fractures by separating intact rock blocks with negligible matrix permeability [13][14][15][16][17]. The results indicate that the flow behaviors, flow capacity, and permeability evolution through single fractures are influenced by many factors such as fracture opening, roughness coefficient, and inlet water pressure [6,[18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Numerical Modeling of Fluid Flowing Properties through Porous Media with Single Rough Fractures

et al. 2021

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Due to the existence of pores in the fracture surface, the permeability of pore-fracture media is more complicated, and its permeability law and mechanism are worthy of an in-depth study. The rough fracture surface of this paper is obtained by 3D laser scanning technology, taken a small part of the middle area to carry out the finite element simulation of single fracture seepage, and studied the distribution of flow velocity fields and the nonlinear characteristics by changing the inlet flow rate, fracture thickness, and size of fracture surface. Given that for the same fracture opening, the flow velocity decreases from the middle position to both sides. When the roughness increases locally, the flow velocity suddenly increases. The nonlinear coefficient decreases as the fracture thickness increases. A dual-media model which consists of porous matrix and a single rough surface was established to study the seepage characteristics through two media. Given that it takes less time to reach a steady state when the permeability coefficient of the matrix is greater than that of the fracture. After reaching the steady state, the flow direction of the fluid in the matrix is consistent with the fluid direction in the fracture, and both are perpendicular to the isosurface of pore water pressure.

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Quantitative characterization of single-phase flow through rough-walled fractures with variable apertures

Cited by 14 publications

References 54 publications

Grain-scale analysis of proppant crushing and embedment using calibrated discrete element models

Grain-scale analysis of proppant crushing and embedment using calibrated discrete element models

Effect of Leaching Behavior on the Geometric and Hydraulic Characteristics of Concrete Fracture

Numerical Modeling of Fluid Flowing Properties through Porous Media with Single Rough Fractures

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