A new approach to upscaling fracture network models while preserving geostatistical and geomechanical characteristicsShow others and affiliations
2015 (English)In: Journal of Geophysical Research - Solid Earth, ISSN 2169-9313, E-ISSN 2169-9356, Vol. 120, no 7, p. 4784-4807Article in journal (Refereed) Published
Abstract [en]
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 = 2munder 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 54m× 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.
Place, publisher, year, edition, pages
American Geophysical Union (AGU), 2015. Vol. 120, no 7, p. 4784-4807
National Category
Geosciences, Multidisciplinary
Identifiers
URN: urn:nbn:se:uu:diva-293688DOI: 10.1002/2014JB011736ISI: 000359746700008OAI: oai:DiVA.org:uu-293688DiVA, id: diva2:928150
2016-05-142016-05-142023-08-01Bibliographically approved