Are open fractures necessarily aligned with maximum horizontal stress?

Laubach, Stephen E.; Olson, Jon E.; Gale, Julia

doi:10.1016/j.epsl.2004.02.019

Cited by 235 publications

(101 citation statements)

References 9 publications

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“…Partially mineralized fractures and fractures sub-parallel to the recent major stress direction are both reported to provide larger apertures (e.g. Heffer and Lean 1993;Laubach et al 2004;Marrett et al 2007;Singhal and Gupta 2010;Teufel et al 1991, Figs. 8, 13).…”

Section: Fracture System Parameters and Permeabilitymentioning

confidence: 99%

Predictability of properties of a fractured geothermal reservoir: the opportunities and limitations of an outcrop analogue study

et al. 2017

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Section: Fracture System Parameters and Permeabilitymentioning

confidence: 99%

Predictability of properties of a fractured geothermal reservoir: the opportunities and limitations of an outcrop analogue study

et al. 2017

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“…We only consider the relation between stress and hydraulically open fractures; i.e., we do not consider the role of cement bridges in keeping fractures open [Laubach et al, 2004;Philip et al, 2005;Hooker et al, 2012].…”

Section: Models For Critically Stressed Fracturesmentioning

confidence: 99%

The impact of different aperture distribution models and critical stress criteria on equivalent permeability in fractured rocks

2016

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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 length‐aperture scaling), and experiments (Barton‐Bandis 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 fracture‐matrix flow. Aperture varies along single fractures, and geomechanical relations are used to identify which fractures are critically stressed. The aperture models are applied to real‐world large‐scale fracture networks. (Sub)linear length scaling predicts the largest average aperture and equivalent permeability. Barton‐Bandis 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 Barton‐Bandis peak shear. The impact of the fracture network on equivalent permeability depends on the matrix hydraulic properties, as in a low‐permeable 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.

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“…The association of localized crack-seal texture (in dolomite cement bridges) and fracture porosity is also present in some dolomites (Gale et al, 2004).…”

Section: Mineral Bridgesmentioning

confidence: 99%

Advanced technology for predicting the fluid flow attributes of naturally fractured reservoirs from quantitative geological data and modeling

Olson¹,

Lake²,

Laubach³

2004

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Abstract:This report summarizes the work carried out during the period of September 29, 2000 to January 15, 2004. High temperatures and reactive fluids in sedimentary basins dictate that interplay and feedback between mechanical and geochemical processes significantly influence evolving rock and fracture properties. Not only does diagenetic mineralization fill in once open fractures either partially or completely, it modifies the rock mechanics properties that can control the mechanical aperture of natural fractures. In this study, we have evolved an integrated methodology of fractured reservoir characterization and we have demonstrated how it can be incorporated into fluid flow simulation. The research encompassed a wide range of work from geological characterization methods to rock mechanics analysis to reservoir simulation. With regard to the characterization of mineral infilling of natural fractures, the strong interplay between diagenetic and mechanical processes is documented and shown to be of vital importance to the behavior of many types of fractured reservoirs. Although most recent literature emphasizes Earth stress orientation, cementation in fractures is likely a critically important control on porosity, fluid flow attributes, and even sensitivity to effective stress changes. The diagenetic processes of dissolution and partial cementation are key controls on the creation and distribution of open natural fractures within hydrocarbon reservoirs.The continuity of fracture-porosity is fundamental to how fractures conduct fluids. In this study, we have made a number of important discoveries regarding fundamental properties of fractures, in particular related to the prevalence of kinematically significant structures (crack-seal texture) within otherwise porous, opening-mode fractures, and the presence of an aperture size threshold below which fractures are completely filled and above which porosity is preserved. These observations can be linked to models of quartz cementation. Significant progress has been made as well in theoretical fracture mechanics and geomechanical modeling, allowing prediction of spatial distributions of fractures that mimic patterns observed in nature. Geomechanical modeling shows the spatial arrangement of opening mode fractures (joints and veins) is controlled by the subcritical fracture index of the material. In particular, we have been able to identify mechanisms that control the clustering of fractures in slightly deformed rocks. Fracture mechanics testing of a wide range of clastic rocks shows that the subcritical index is sensitive to diagenetic factors. We show geomechanical simulations of fracture aperture development can be linked to diagenetic models, modifying fracture porosity as fractures grow, and affect the dynamics of fracture propagation. Fluid flow simulation of representative fracture pattern realizations shows how integrated modeling can give new insight into permeability assessment in the subsurface. Using realistic, geomechanically generated fracture patterns...

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Are open fractures necessarily aligned with maximum horizontal stress?

Cited by 235 publications

References 9 publications

Predictability of properties of a fractured geothermal reservoir: the opportunities and limitations of an outcrop analogue study

Predictability of properties of a fractured geothermal reservoir: the opportunities and limitations of an outcrop analogue study

The impact of different aperture distribution models and critical stress criteria on equivalent permeability in fractured rocks

Advanced technology for predicting the fluid flow attributes of naturally fractured reservoirs from quantitative geological data and modeling

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