Abstract
Abstract The influences of contact shape and contact area on nonlinear fluid flow properties through fractures are investigated by solving Navier-Stokes equations. The evolutions of nonlinear relationships between flow rate and hydraulic pressure drop, Forchheimer coefficients, nonlinear factor, critical hydraulic gradient, distributions of flow streamlines, and tracer flow paths at different times are systematically estimated. The results show that the nonlinear relationships between flow rate and hydraulic pressure drop can be well described by Forchheimer’s law, in which the nonlinear term coefficient b is approximately three orders of magnitude larger than the linear term coefficient a. The smaller contact area corresponds to smaller variations in many aspects such as flow rate, critical hydraulic gradient, flow streamlines, and tracer flow paths. The critical hydraulic gradient decreases with the increasing degree of contact shape variations while the contacts have the same mean area. The increase in hydraulic pressure drop can induce significant eddies and decrease the permeability and/or conductivity of fractures. However, the distributions of streamlines and tracer flow paths are not dramatically disturbed under a large hydraulic pressure drop.
Highlights
Accurate estimations of hydraulic properties of rock fractures are of very importance in many fields such as geothermal energy development [1, 2] and enhanced oil recovery [3,4,5]
The present work studied the effects of the contact shape and contact area on nonlinear flow properties of fluids through fractures by numerically solving Navier-Stokes equations
The results show that with the increment of hydraulic pressure drop from 0.01 Pa to 0.5 Pa, the flow rate increases nonlinearly, following Forchheimer’s law
Summary
Accurate estimations of hydraulic properties of rock fractures are of very importance in many fields such as geothermal energy development [1, 2] and enhanced oil recovery [3,4,5]. The effects of contact shape and contact area on nonlinear flow properties of fluids through fractures induced by high hydraulic pressure drop by solving Navier-Stokes equations have not yet been systematically investigated. With boundary stiffness and is in the range of 0.01~0.16 when boundary stiffness = 0 ~ 2 GPa/m, joint compression strength = 100 ~ 150 MPa, and initial normal stress = 0:5 ~ 2:0 MPa. the contact area and locations are dependent on shear displacement and fracture surface morphologies [12], and the effect of the contact area ratio on nonlinear fluid flow properties is not estimated. The effects of joint surface roughness (JRC), Reynolds number (Re), and shear displacement on nonlinear properties of fluid flow have been systematically investigated [23,24,25,26], the influences of the contact shape and contact area have not been studied in an in-depth way. The streamlines of fluid flow under different shapes and areas of contacts and different hydraulic pressure drops are estimated, and the distributions of tracer flow paths at different times are discussed
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