Abstract
Predicting equivalent permeability in fractured reservoirs requires an understanding of the fracture network geometry and apertures. There are different methods for defining aperture, based on outcrop observations (power law scaling), fundamental mechanics (sublinear lengthaperture scaling), and experiments (BartonBandis conductive shearing). Each method predicts heterogeneous apertures, even along single fractures (i.e., intrafracture variations), but most fractured reservoir models imply constant apertures for single fractures. We compare the relative differences in aperture and permeability predicted by three aperture methods, where permeability is modeled in explicit fracture networks with coupled fracturematrix flow. Aperture varies along single fractures, and geomechanical relations are used to identify which fractures are critically stressed. The aperture models are applied to realworld largescale fracture networks. (Sub)linear length scaling predicts the largest average aperture and equivalent permeability. BartonBandis aperture is smaller, predicting on average a sixfold increase compared to matrix permeability. Application of critical stress criteria results in a decrease in the fraction of open fractures. For the applied stress conditions, Coulomb predicts that 50% of the network is critically stressed, compared to 80% for BartonBandis peak shear. The impact of the fracture network on equivalent permeability depends on the matrix hydraulic properties, as in a lowpermeable matrix, intrafracture connectivity, i.e., the opening along a single fracture, controls equivalent permeability, whereas for a more permeable matrix, absolute apertures have a larger impact. Quantification of fracture flow regimes using only the ratio of fracture versus matrix permeability is insufficient, as these regimes also depend on aperture variations within fractures.
Original language  English 

Pages (fromto)  40454063 
Number of pages  19 
Journal  JGR Solid Earth 
Volume  121 
Issue number  5 
DOIs  
Publication status  Published  1 May 2016 
Keywords
 equivalent permeability
 fracture aperture
 fracture permeability
 hydraulic aperture
 naturally fractured reservoirs
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Datasets

Deterministic fracture network models from the Potiguar basin, Brazil
Bisdom, K. (Creator), Bertotti, G. (Creator), Bezerra, F. H. R. (Creator), van Eijk, M. (Creator), Van der Voet, E. (Creator) & Reijmer, J. (Creator), TU Delft  4TU.Centre for Research Data, 2017
DOI: 10.4121/UUID:988152DA3AC344CB9D87C7365E3707B6
Dataset