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A new approach to upscaling fracture network models while preserving geostatistical and geomechanical characteristics

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Title: A new approach to upscaling fracture network models while preserving geostatistical and geomechanical characteristics
Authors: Lei, Q
Latham, J-P
Tsang, C-F
Xiang, J
Lang, P
Item Type: Journal Article
Abstract: A new approach to upscaling two-dimensional fracture network models is proposed for preserving geostatistical and geomechanical characteristics of a smaller-scale “source” fracture pattern. First, the scaling properties of an outcrop system are examined in terms of spatial organization, lengths, connectivity, and normal/shear displacements using fractal geometry and power law relations. The fracture pattern is observed to be nonfractal with the fractal dimension D ≈ 2, while its length distribution tends to follow a power law with the exponent 2 < a < 3. To introduce a realistic distribution of fracture aperture and shear displacement, a geomechanical model using the combined finite-discrete element method captures the response of a fractured rock sample with a domain size L = 2 m under in situ stresses. Next, a novel scheme accommodating discrete-time random walks in recursive self-referencing lattices is developed to nucleate and propagate fractures together with their stress- and scale-dependent attributes into larger domains of up to 54 m × 54 m. The advantages of this approach include preserving the nonplanarity of natural cracks, capturing the existence of long fractures, retaining the realism of variable apertures, and respecting the stress dependency of displacement-length correlations. Hydraulic behavior of multiscale growth realizations is modeled by single-phase flow simulation, where distinct permeability scaling trends are observed for different geomechanical scenarios. A transition zone is identified where flow structure shifts from extremely channeled to distributed as the network scale increases. The results of this paper have implications for upscaling network characteristics for reservoir simulation.
Issue Date: 1-Jul-2015
Date of Acceptance: 4-Jun-2015
URI: http://hdl.handle.net/10044/1/24580
DOI: 10.1002/2014JB011736
ISSN: 2169-9356
Publisher: American Geophysical Union
Start Page: 4784
End Page: 4807
Journal / Book Title: Journal of Geophysical Research. Solid Earth
Volume: 120
Issue: 7
Copyright Statement: © 2015 American Geophysical Union. All rights reserved.
Sponsor/Funder: Exxon Mobil Upstream Research Company
Natural Environment Research Council (NERC)
Engineering & Physical Science Research Council (E
Artelia Eau Environnment
Engineering & Physical Science Research Council (EPSRC)
Concrete Layer Innovations
W.F. Baird & Associates Coastal Engineers Ltd
Technological Resources PTY Ltd
Engineering & Physical Science Research Council (EPSRC)
Funder's Grant Number: itf-ISF-3
NE/L000660/1
EP/M012794/1
N/A
GR/S42699/01
CLI/AKA/587
N/A
N/A
EP/H030123/1
Keywords: Science & Technology
Physical Sciences
Geochemistry & Geophysics
Scaling
Fractures
Random walk
Geomechanical constraints
Permeability
Flow structure
STRESS-DEPENDENT PERMEABILITY
SCALING RELATIONS
DEFORMATION BANDS
POROUS-MEDIA
LENGTH
DISPLACEMENT
FAULTS
CONNECTIVITY
CRYSTALLINE
GROWTH
0402 Geochemistry
0403 Geology
0404 Geophysics
Publication Status: Published
Online Publication Date: 2015-06-06
Appears in Collections:Earth Science and Engineering
Faculty of Engineering