Fracture permeability under normal stress: a fully computational approach

Lavrov, Alexandre

doi:10.1007/s13202-016-0254-6

Cited by 22 publications

(14 citation statements)

References 29 publications

(49 reference statements)

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“…This implies that fault permeability is usually noticeably different during unloading from the loading phase even when they are stressed equally (Gutierrez et al 2000). The hysteretic property of the fault permeability under normal loading simply connotes a manifestation of the general irreversibility of rock deformation (Lavrov 2017). However, concerning the simple relationship between fractures, stress and strain during injection, contributions from many studies have presented theories, numerical approach and analysis of injection-induced fault reactivation and seismic slip (e.g.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of the influence of discontinuity orientations on fault permeability evolution and slip displacement

Eyinla

Gan

Oladunjoye

et al. 2021

Geomech. Geophys. Geo-energ. Geo-resour.

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A pre-existing plane of weakness along the fault is comprised of a particular pattern of joints dipping at different orientations. The fault stress state, partially defined by the orientation of fault, determines the potential of slip failure and hence the evolution of fault permeability. Here the influence of fault orientation on permeability evolution was investigated by direct fluid injection inside fault with three different sets of fault orientations (45°, 60° and 110°), through the coupled hydromechanical (H-M) model TOUGHREACT-FLAC3D. The influence of joints pattern on slip tendency and magnitude of potential induced seismicity was also evaluated by comparing the resulted slip distance and timing. The simulation results revealed that decreasing the dip angle of the fault increases the corresponding slip tendency in the normal fault circumstance. Also, with changing joints dip angle associated with the fault, the tendency of the fault slip changes concurrently with the permeability evolution in a noticeable manner. Permeability enhancement after the onset of fault slip was observed with the three sets of fault angles, while the condition of 60° dipping angle resulted in highest enhancement. Joints pattern with a dip angle of 145° (very high dip) and 30° (very low dip) did not trigger a shear slip with seismic permeability enhancement. However, high dip and intermediate dip angles (135°, 50° and 70°) yielded high permeability in varying orders of magnitude. The large stress excitation and increasing permeability during shear deformation was noticeably high in intermediate joint dip angles but decreases as the angle increases. Article highlights The magnitude of injection-induced permeability enhancement is largely influenced by the fault and joint spatial orientations. With a slight change in the joint direction, there is an increasing possibility for fault to approach a different critical state of failure. Stress elevation at the point of failure is controlled by the orientations of fault/joint planes with respect to the direction of maximum principal stress.

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Section: Introductionmentioning

confidence: 99%

Numerical investigation of the influence of discontinuity orientations on fault permeability evolution and slip displacement

Eyinla

Gan

Oladunjoye

et al. 2021

Geomech. Geophys. Geo-energ. Geo-resour.

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“…Thus, various analytical equations, experimental tests and numerical methods have been proposed to quantify the aperture distribution and flow behavior in the fracture under normal and shear stresses. [8][9][10][11] Single fracture has been approximately modeled by using two smooth parallel plates that are separated by a constant distance, with the fluid flowing through it that follows the cubic law. 12,13 However, in the nature, the surfaces of most rock fractures are rough, which results in nonuniformly distributed aperture fields in fractures.…”

Section: Introductionmentioning

confidence: 99%

Size Effect on the Permeability and Shear Induced Flow Anisotropy of Fractal Rock Fractures

et al. 2018

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The effect of model size on fluid flow through fractal rough fractures under shearing is investigated using a numerical simulation method. The shear behavior of rough fractures with selfaffine properties was described using the analytical model, and the aperture fields with sizes ¶ Corresponding author. This is an Open Access article published by World Scientific Publishing Company. It is distributed under the terms of the Creative Commons Attribution 4.0 (CC-BY) License. Further distribution of this work is permitted, provided the original work is properly cited. varying from 25 to 200 mm were extracted under shear displacements up to 20 mm. Fluid flow through fractures in the directions both parallel and perpendicular to the shear directions was simulated by solving the Reynolds equation using a finite element code. The results show that fluid flow tends to converge into a few main flow channels as shear displacement increases, while the shapes of flow channels change significantly as the fracture size increases. As the model size increases, the permeability in the directions both parallel and perpendicular to the shear direction changes significantly first and then tends to move to a stable state. The size effects on the permeability in the direction parallel to the shear direction are more obvious than that in the direction perpendicular to the shear direction, due to the formation of contact ridges and connected channels perpendicular to the shear direction. The variances of the ratio between permeability in both directions become smaller as the model size increases and then this ratio tends to maintain constant after a certain size, with the value mainly ranging from 1.0 to 3.0. 1840001-1

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“…Computational approach provides an insight into the mechanics of deformational sequence in fault under stress, and thus impacts on the permeability (Lavrov 2017). Operationally, fluid injection is a process adopted for optimizing recovery in tight reservoir, especially in enhanced geothermal systems, and it has improved drastically in the past decades.…”

Section: Introductionmentioning

confidence: 99%

Analysis of the influence of joint direction on production optimization in enhanced geothermal systems

Eyinla

2021

J Petrol Explor Prod Technol

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Heat extraction from geothermal reservoir by circulating cold water into a hot rock requires an amount of fluid pressure, which is capable of inducing fault opening. Although stress change promotes the potential of fault failure and reactivation, the rate at which fluid pressurization within the fault zone generates variations in pore pressure as fault geometry changes during geothermal energy production have not been thoroughly addressed to include the effects of joint orientation. This study examines how different fault/joint models result in different tendency of injection-induced shear failure, and how this could influence the production rate. Here, a numerical simulation method is adopted to investigate the thermo-hydro-mechanical (THM) response of the various fault/joint models during production in a geothermal reservoir. The results indicate that pore pressure evolution has a direct relationship with the evolution of production rate for the three joint models examined, and the stress sensitivity of the individual fault/joint model also produced an effect on the production rate. Changing the position of the injection well revealed that the magnitude of shear failure on the fault plane could be controlled by the hydraulic diffusivity of fluid pressure, and the production rate is also influenced by the magnitude of stress change at the injection and production wells. Overall, the location of the injection well along with the fault damage zone significantly influenced the resulting production rate, but a more dominating factor is the joint orientation with respect to the maximum principal stress direction. Thus, the rate of thermal drawdown is affected by pore pressure elevation and stress change while the fault permeability and the production rate are enhanced when the joint’s frictional resistance is low.

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Fracture permeability under normal stress: a fully computational approach

Cited by 22 publications

References 29 publications

Numerical investigation of the influence of discontinuity orientations on fault permeability evolution and slip displacement

Numerical investigation of the influence of discontinuity orientations on fault permeability evolution and slip displacement

Size Effect on the Permeability and Shear Induced Flow Anisotropy of Fractal Rock Fractures

Analysis of the influence of joint direction on production optimization in enhanced geothermal systems

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