Fluid flow through rock joints: The effect of surface roughness

Brown, Stephen R.

doi:10.1029/jb092ib02p01337

Cited by 870 publications

(628 citation statements)

References 23 publications

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“…The results of our investigation demonstrate that bulk permeability at great depth in the brittle crust (3 -7 km depth) appears to be controlled by critically-stressed fractures and faults as previously reported by Barton et al [1995] at much shallower depths.…”

Section: Discussionsupporting

confidence: 82%

Fracture permeability and in situ stress to 7 km depth in the KTB scientific drillhole

Ito¹,

Zoback²

2000

Geophysical Research Letters

151

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Abstract.To better understand the mechanisms that control fluid flow and hydraulic conductivity at significant depth in the brittle crust, we have examined the relationship between fracture permeability and in situ stress in the German continental deep drillhole (the KTB main hole) through analysis of high resolution temperature profiles. Our analysis shows that over the entire 3 -7 km depth range studied, permeable fractures and faults (i.e., those associated with distinct thermal anomalies) lie close to the Coulomb failure line for a coefficient of friction of about 0.6.This indicates that critically-stressed faults in the crust are also the most permeable faults. This includes a major Mesozoic thrust fault at 7.1 km that is being reactivated as a strike-slip fault in the current stress field. Conversely, non-critically stressed fractures and faults do not appear to be permeable as they are not associated with identifiable thermal anomalies. IntroductionIt is ProcedureThe KTB site is located in the Oberpfalz region in 1045

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Section: Discussionsupporting

confidence: 82%

Fracture permeability and in situ stress to 7 km depth in the KTB scientific drillhole

Ito¹,

Zoback²

2000

Geophysical Research Letters

151

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“…The transition length between mated and unmated behavior is -1/X/-N of the lattice size, so that the complete surface contains a large number of No mechanical model of deformation is assumed; wherever the surfaces "interpenetrate," a contact (i.e., aperture zero) is shown [Brown, 1987]. This approximation is justified because we remain at relatively small contact areas; Walsh et al [1997] verified that the effect of using the interpenetrating model (versus a fracture wall deformation model [see, e.g., Unger and Mase [1993]) on predicted flow properties is negligible for the contact areas even as large as 30%.…”

Section: Three Dimensions: Importance Of Contacts and Non-lcl Regionsmentioning

confidence: 99%

Flow in rock fractures: The local cubic law assumption reexamined

Oron¹,

Berkowitz²

1998

Water Resources Research

314

187

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Abstract. We investigate the validity of applying the "local cubic law" (LCL) to flow in a fracture bounded by impermeable rock surfaces. A two-dimensional order-of-magnitude analysis of the Navier-Stokes equations yields three conditions for the applicability of LCL flow, as a leading-order approximation in a local fracture segment with parallel or nonparallel walls. These conditions demonstrate that the "cubic law" aperture should not be measured on a point-by-point basis but rather as an average over a certain length. Extending to the third dimension, in addition to defining apertures over segment lengths, we find that the geometry of the contact regions influences flow paths more significantly than might be expected from consideration of only the nominal area fraction of these contacts. Moreover, this latter effect is enhanced by the presence of non-LCL regions around these contacts. While contact ratios of 0.1-0.2 are usually assumed to have a negligible effect, our calculations suggest that contact ratios as low as 0.03-0.05 can be significant. Analysis of computer-generated fractures with self-affine walls demonstrates a nonlinear increase in contact area and a faster-than-cubic decrease in the overall hydraulic conductivity, with decreasing fracture aperture; these results are in accordance with existing experimental data on flow in fractures. Finally, our analysis of fractures with selfaffine walls indicates that the aperture distribution is not lognormal or gamma as is frequently assumed but rather truncated-normal initially and increasingly skewed with fracture closure.

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“…Under these assumption, the NavierStokes equation reduces to the Reynolds equation [Pinkus and Sternlicht, 1961;Brown, 1987]:…”

Section: Solving Under Lubrication Approximationsmentioning

confidence: 99%

Influence of asperities on fluid and thermal flow in a fracture: A coupled lattice Boltzmann study

2013

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[1] The characteristics of the hydro-thermal flow which occurs when a cold fluid is injected into a hot fractured bedrock depend on the morphology of the fracture. We consider a sharp triangular asperity, invariant in one direction, perturbing an otherwise flat fracture. We investigate its influence on the macroscopic hydraulic transmissivity and heat transfer efficiency, at fixed low Reynolds number. In this study, numerical simulations are done with a coupled lattice Boltzmann method that solves both the complete Navier-Stokes and advection-diffusion equations in three dimensions. The results are compared with those obtained under lubrication approximations which rely on many hypotheses and neglect the three-dimensional (3-D) effects. The lubrication results are obtained by analytically solving the Stokes equation and a two-dimensional (integrated over the thickness) advection-diffusion equation. We use a lattice Boltzmann method with a double distribution (for mass and energy transport) on hypercubic and cubic lattices. Beyond some critical slope for the boundaries, the velocity profile is observed to be far from a quadratic profile in the vicinity of the sharp asperity: the fluid within the triangular asperity is quasi-static. We find that taking account of both the 3-D effects and the cooling of the rock, are important for the thermal exchange. Neglecting these effects with lubrication approximations results in overestimating the heat exchange efficiency. The evolution of the temperature over time, toward steady state, also shows complex behavior: some sites alternately reheat and cool down several times, making it difficult to forecast the extracted heat.Citation: Neuville, A., E. G. Flekkøy, and R. Toussaint (2013), Influence of asperities on fluid and thermal flow in a fracture: A coupled lattice Boltzmann study,

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Fluid flow through rock joints: The effect of surface roughness

Cited by 870 publications

References 23 publications

Fracture permeability and in situ stress to 7 km depth in the KTB scientific drillhole

Fracture permeability and in situ stress to 7 km depth in the KTB scientific drillhole

Flow in rock fractures: The local cubic law assumption reexamined

Influence of asperities on fluid and thermal flow in a fracture: A coupled lattice Boltzmann study

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