Laboratory assessment of the equivalent apertures of a rock fracture

Piggott, Andrew R.; Elsworth, Derek

doi:10.1029/93gl01384

Cited by 51 publications

(25 citation statements)

References 6 publications

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“…However, careful positioning and orientation of the two surfaces is required before the subtraction since the profiles are initially unmated}the upper and lower rough surfaces are measured in an open-book format. To limit skewing of the aperture data, the mean planes of both surfaces are calculated and are made parallel to each other [18]. Figure 1 shows the parallel digitized rough surfaces of a natural fracture in novaculite.…”

Section: Fe Meshmentioning

confidence: 99%

“…However, as a first-order estimation, the arithmetic mean aperture of the initial differenced surface is used for model prediction. This is calibrated by adjusting the separation between the two virtual parallel surfaces, and setting the initial hydraulic aperture to that obtained from the experiment [13]}mechanical and hydraulic apertures are assumed approximately equivalent [18].…”

Section: Fe Meshmentioning

confidence: 99%

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A numerical model simulating reactive transport and evolution of fracture permeability

Yasuhara

Elsworth

2006

Int. J. Numer. Anal. Meth. Geomech.

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SUMMARYA numerical model is presented to describe the evolution of fracture aperture (and related permeability) mediated by the competing chemical processes of pressure solution and free-face dissolution/precipitation; pressure (dis)solution and precipitation effect net-reduction in aperture and free-face dissolution effects netincrease. These processes are incorporated to examine coupled thermo-hydro-mechano-chemo responses during a flow-through experiment, and applied to reckon the effect of forced fluid injection within rock fractures at geothermal and petroleum sites. The model accommodates advection-dominant transport systems by employing the Lagrangian-Eulerian method. This enables changes in aperture and solute concentration within a fracture to be followed with time for arbitrary driving effective stresses, fluid and rock temperatures, and fluid flow rates. This allows a systematic evaluation of evolving linked mechanical and chemical processes. Changes in fracture aperture and solute concentration tracked within a wellconstrained flow-through test completed on a natural fracture in novaculite (Earth Planet. Sci. Lett. 2006, in press) are compared with the distributed parameter model. These results show relatively good agreement, excepting an enigmatic abrupt reduction in fracture aperture in the early experimental period, suggesting that other mechanisms such as mechanical creep and clogging induced by unanticipated local precipitation need to be quantified and incorporated. The model is applied to examine the evolution in fracture permeability for different inlet conditions, including localized (rather than distributed) injection. Predictions show the evolution of preferential flow paths driven by dissolution, and also define the sense of permeability evolution at field scale.

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Section: Fe Meshmentioning

confidence: 99%

Section: Fe Meshmentioning

confidence: 99%

A numerical model simulating reactive transport and evolution of fracture permeability

Yasuhara

Elsworth

2006

Int. J. Numer. Anal. Meth. Geomech.

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“…The figure shows that with the parallel plates, the time needed for the injected fluid to reach the exit is constant, while there is a delay in the time needed for the fluid flowing through the void created by the fracture to reach the exit, depending on which path is taken. As pointed out by Piggott and Elsworth (1993), the complex pore structure triggered local migration of the substance inside the fracture. In other words, selective flows are occurring.…”

Section: Results In the Tracer Testsmentioning

confidence: 92%

Mechanical and hydraulic behavior of a rock fracture under shear deformation

et al. 2014

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With regard to crystalline rock that constitutes deep geology, attempts have been made to explore its hydraulic characteristics by focusing on the network of numerous fractures within. As the hydraulic characteristics of a rock are the accumulation of hydraulic characteristics of each fracture, it is necessary to develop the hydraulic model of a single fracture to predict the large-scale hydraulic behavior. To this end, a simultaneous permeability and shear test device is developed, and shear-flow coupling tests are conducted on specimens having fractures with varied levels of surface roughness in the constant normal stiffness conditions. The results show that the permeability characteristics in the relation between shear displacement and transmissivity change greatly at the point where the stress path reaches the Mohr-Coulomb failure curve. It is also found that there exists a range in which transmissivity is not proportional to the cube of mechanical aperture width, which seems to be because of the occurrence of channeling phenomenon at small mechanical aperture widths. This channeling flow disappears with increasing shear and is transformed into a uniform flow. We develop a simulation technique to evaluate the macroscopic permeability characteristics by the lattice gas cellular automaton method, considering the microstructure of fracture, namely the fracture surface roughness. With this technique, it is shown that the formation of the Hagen-Poiseuille flow is affected by the fracture microstructure under shear, which as a result determines the relationship between the mechanical aperture width and transmissivity.

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“…Effective stresses are retained within a narrow range by controlling the upstream back pressure. This measurement records permeability, and through this defines change in average aperture within the system (PIGGOTT and ELSWORTH, 1993). Second, the net efflux of dissolved mineral mass is measured periodically to provide a record of net mass removal, and to correlate this with observed changes in aperture, defined by the flow tests.…”

Section: Experimental Observationsmentioning

confidence: 99%

Short-Timescale Chemo-Mechanical Effects and their Influence on the Transport Properties of Fractured Rock

Elsworth¹,

Yusuhara²

Pageoph Topical Volumes

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Abstract-Anomalous changes in permeability are reported in fractures circulated by fluids undersaturated with respect to the mineral host. Under net dissolution and net removal of mineral mass, fractures may alternately gape or seal, depending on the prevailing mechanical and chemical conditions. The influence on transport properties is observed to be large, rapid, and irreversible: Permeabilities may change by two orders of magnitude in a month, and the direction of permeability change may switch spontaneously, for no apparent change in environmental forcing. These behaviors are apparent in continuous circulation experiments conducted on fractures in novaculite and limestone, intermittently imaged by X-ray CT. In novaculite, permeability reduces by two orders of magnitude as silica is net removed from the sample. Surprisingly, these changes can occur at modest temperatures ($80°C) and stresses ($3.5 MPa), where compaction progresses as temperatures are incremented. Isothermal ($20°C) circulation tests in limestone show similar compaction driven by pressure solution. Where circulation remains undersaturated in Ca, the change in permeability spontaneously switches from net reduction to net increase as a wormhole forms. The surprising magnitude and rapidity of these changes are investigated in the context of the competition between stress-and chemistry-mediated effects.

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Laboratory assessment of the equivalent apertures of a rock fracture

Cited by 51 publications

References 6 publications

A numerical model simulating reactive transport and evolution of fracture permeability

A numerical model simulating reactive transport and evolution of fracture permeability

Mechanical and hydraulic behavior of a rock fracture under shear deformation

Short-Timescale Chemo-Mechanical Effects and their Influence on the Transport Properties of Fractured Rock

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