Fluid Flow through Rough Rock Fractures: Parametric Study
01 Jun 2016-International Journal of Geomechanics (American Society of Civil Engineers)-Vol. 16, Iss: 3, pp 04015067
TL;DR: In this paper, two-dimensional fractures with different surface roughness were simulated in a finite-element modeling (FEM) program, and the fluid-flow parameters were evaluated, including fracture inflow pressure, aperture of the fracture, and shearing displacement during flow.
Abstract: The knowledge of fluid flow through rock fractures is directly related to hydrocarbon migration, waste disposal, and carbon dioxide sequestration. The hydraulic nature and response of the fractures are directly controlled by the roughness of the fracture surfaces. However, this parameter is hard to understand because it can behave differently under different ambient conditions. The prevalent controlling parameters are the fracture inflow pressure, aperture of the fracture, and shearing displacement during flow. To understand the influence of these parameters, a systematic study was carried out numerically on different fracture geometries. In this paper, two-dimensional fractures with different surface roughness were simulated in a finite-element modeling (FEM) program, and the fluid-flow parameters were evaluated. The Navier–Stokes (NS) equation was used to model the fluid flow through the roughness profiles generated using Barton’s joint roughness coefficient. By simulating the laminar fluid flow...
Citations
More filters
11 Jun 2010
Abstract: The validity of the cubic law for laminar flow of fluids through open fractures consisting of parallel planar plates has been established by others over a wide range of conditions with apertures ranging down to a minimum of 0.2 µm. The law may be given in simplified form by Q/Δh = C(2b)3, where Q is the flow rate, Δh is the difference in hydraulic head, C is a constant that depends on the flow geometry and fluid properties, and 2b is the fracture aperture. The validity of this law for flow in a closed fracture where the surfaces are in contact and the aperture is being decreased under stress has been investigated at room temperature by using homogeneous samples of granite, basalt, and marble. Tension fractures were artificially induced, and the laboratory setup used radial as well as straight flow geometries. Apertures ranged from 250 down to 4µm, which was the minimum size that could be attained under a normal stress of 20 MPa. The cubic law was found to be valid whether the fracture surfaces were held open or were being closed under stress, and the results are not dependent on rock type. Permeability was uniquely defined by fracture aperture and was independent of the stress history used in these investigations. The effects of deviations from the ideal parallel plate concept only cause an apparent reduction in flow and may be incorporated into the cubic law by replacing C by C/ƒ. The factor ƒ varied from 1.04 to 1.65 in these investigations. The model of a fracture that is being closed under normal stress is visualized as being controlled by the strength of the asperities that are in contact. These contact areas are able to withstand significant stresses while maintaining space for fluids to continue to flow as the fracture aperture decreases. The controlling factor is the magnitude of the aperture, and since flow depends on (2b)3, a slight change in aperture evidently can easily dominate any other change in the geometry of the flow field. Thus one does not see any noticeable shift in the correlations of our experimental results in passing from a condition where the fracture surfaces were held open to one where the surfaces were being closed under stress.
1,557 citations
TL;DR: A review of previous works that have focused on the estimation of equivalent permeability of two-dimensional (2D) discrete fracture networks (DFNs) considering the influences of geometric properties of fractured rock masses is provided in this article.
Abstract: Fracture networks play a more significant role in conducting fluid flow and solute transport in fractured rock masses, comparing with that of the rock matrix. Accurate estimation of the permeability of fracture networks would help researchers and engineers better assess the performance of projects associated with fluid flow in fractured rock masses. This study provides a review of previous works that have focused on the estimation of equivalent permeability of two-dimensional (2-D) discrete fracture networks (DFNs) considering the influences of geometric properties of fractured rock masses. Mathematical expressions for the effects of nine important parameters that significantly impact on the equivalent permeability of DFNs are summarized, including (1) fracture-length distribution, (2) aperture distribution, (3) fracture surface roughness, (4) fracture dead-end, (5) number of intersections, (6) hydraulic gradient, (7) boundary stress, (8) anisotropy, and (9) scale. Recent developments of 3-D fracture networks are briefly reviewed to underline the importance of utilizing 3-D models in future research.
116 citations
07 Apr 2009
TL;DR: In this paper, a model representing pressure-dissolution-like behavior is adapted to define the threshold and resulting response in terms of fundamental thermodynamic properties of a contacting fracture.
Abstract: A model is presented to represent changes in the mechanical and transport characteristics of fractured rock that result from coupled mechanical and chemical effects. The specific influence is the elevation of dissolution rates on contacting asperities, which results in a stress- and temperature-dependent permanent closure. A model representing this pressure-dissolution-like behavior is adapted to define the threshold and resulting response in terms of fundamental thermodynamic properties of a contacting fracture. These relations are incorporated in a stress-stiffening model of fracture closure to define the stress- and temperature-dependency of aperture loss and behavior during stress and temperature cycling. These models compare well with laboratory and field experiments, representing both decoupled isobaric and isothermal responses. The model was applied to explore the impact of these responses on heated structures in rock. The result showed a reduction in ultimate induced stresses over the case where chemical effects were not incorporated, with permanent reduction in final stresses after cooling to ambient conditions. Similarly, permeabilities may be lower than they were in the case where chemical effects were not considered, with a net reduction apparent even after cooling to ambient temperature. These heretofore-neglected effects may have a correspondingly significant impact on the performance of heated structures in rock, such as repositories for the containment of radioactive wastes.
61 citations
TL;DR: In this paper, the joint roughness coefficient (JRC) is an important indicator that characterizes the physical and mechanical behaviors of a jointed rock mass, and the effects of sampling interval on JRC were assessed during the JRC calculation process.
39 citations
25 Jun 2017
TL;DR: Wei et al. as mentioned in this paper reviewed and summarized the geometrical, fractal and hydraulic properties of fracture networks and fracture networks in fracture porous media, including fracture length distribution, aperture distribution, boundary stress and anisotropy.
Abstract: Fractures and fracture networks play an important role in fluid flow and transport properties of oil and gas reservoirs. Accurate estimation of geometrical characteristics of fracture networks and their hydraulic properties are two key research directions in the fields of fluids flow in fractured porous media. Recent works focusing on the geometrical, fractal and hydraulic properties of fractured reservoirs are reviewed and summarized in this mini-review. The effects of several important parameters that significantly influences hydraulic properties are specifically discussed and analyzed, including fracture length distribution, aperture distribution, boundary stress and anisotropy. The methods for predicting fractal dimension of fractures and models for fracture networks and fractured porous media based on fractal-based approaches are addressed. Some comments and suggestions are also given on the future research directions and fractal fracture networks as well as fractured porous media. Cited as : Wei, W., Xia, Y. Geometrical, fractal and hydraulic properties of fractured reservoirs: A mini-review. Advances in Geo-Energy Research, 2017, 1(1): 31-38, doi: 10.26804/ager.2017.01.03
37 citations
Cites background from "Fluid Flow through Rough Rock Fract..."
...…is significantly related with fracture surface roughness (Olsson and Barton, 2001), Reynolds number (Zimmerman and Main, 2004; Xiong et al., 2011), contact (Zimmerman and Bodvarsson, 1996; Li et al., 2008), shear process (Javadi et al., 2014), hydraulic gradient (Guha Roy and Singh, 2015), etc....
[...]
References
More filters
TL;DR: In this paper, a polynomial expression, like Forchheimer law, was used to describe the dependence of pressure drop on flow rate for non-linear fluid flow through rough fractures.
118 citations
TL;DR: In this article, it was shown that the onset of turbulence is delayed from 2100 to about 4000 Reynolds number for flow in porous tubes with suction when compared to flow in non-porous tubes.
114 citations
TL;DR: In this article, a naturally fractured coal specimen was chosen and the subcritical CO 2 flow was maintained by monitoring the injection pressures and ambient temperature; the variations in permeability under various scenarios were also investigated.
99 citations
TL;DR: In this article, the results of fluid flow experiments carried out for air flow through a fractured granite sample under various pressures of confinement are presented, showing that the cubic law appears to be applicable for flow cases that return a Forcheimer number for non-Darcian flow cases where inertial effects were modest.
95 citations
TL;DR: In this article, the authors used a mobile-immobile (MIM) model to simulate the measured breakthrough curves and found that the MIM model was doing a better job than the Fickian type advection-dispersion equation (ADE).
88 citations