Role of fluid pressure in jointing

Secor, Donald T.

doi:10.2475/ajs.263.8.633

Cited by 545 publications

(245 citation statements)

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“…Natural hydraulic fractures (NHF) are fractures induced by the presence of elevated fluid pressure with respect to hydrostatic pressure. The importance and existence of NHFs in the Earth's crust has been debated for over 30 years [Secor, 1965], yet the conditions under which they form remain controversial. Flekkøy et al [2002] present the development of a numerical model that couples a discrete spring network representation and Darcy's law to model fluid pressure induced øfractures (hydrofractures).…”

Section: Application Of Lbdem To Natural Hydraulic Fracturingmentioning

confidence: 99%

Direct simulation of fluid‐solid mechanics in porous media using the discrete element and lattice‐Boltzmann methods

Boutt¹,

Cook²,

McPherson³

et al. 2007

J. Geophys. Res.

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[1] A detailed understanding of the coupling between fluid and solid mechanics is important for understanding many processes in Earth sciences. Numerical models are a popular means for exploring these processes, but most models do not adequately handle all aspects of this coupling. This paper presents the application of a micromechanically based fluid-solid coupling scheme, lattice-Boltzmann discrete element method (LBDEM), for porous media simulation. The LBDEM approach couples the lattice-Boltzmann method for fluid mechanics and a discrete element method for solid mechanics. At the heart of this coupling is a previously developed boundary condition that has never been applied to coupled fluid-solid mechanics in porous media. Quantitative comparisons of model results to a one-dimensional analytical solution for fluid flow in a slightly deformable medium indicate a good match to the predicted continuum-scale fluid diffusion-like profile. Coupling of the numerical formulation is demonstrated through simulation of porous medium consolidation with the model capturing poroelastic behavior, such as the coupling between applied stress and fluid pressure rise. Finally, the LBDEM model is used to simulate the genesis and propagation of natural hydraulic fractures. The model provides insight into the relationship between fluid flow and propagation of fractures in strongly coupled systems. The LBDEM model captures the dominant dynamics of fluid-solid micromechanics of hydraulic fracturing and classes of problems that involve strongly coupled fluid-solid behavior.

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Section: Application Of Lbdem To Natural Hydraulic Fracturingmentioning

confidence: 99%

Direct simulation of fluid‐solid mechanics in porous media using the discrete element and lattice‐Boltzmann methods

Boutt¹,

Cook²,

McPherson³

et al. 2007

J. Geophys. Res.

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“…For tensile cracks to form by hydraulic fracturing, the pore fluid pressure must exceed the magnitude of the least principal stress by the tensile strength of the rock (e.g. Secor, 1965;Shaw, 1980). The condition for hydraulic fracturing is commonly written as P fluid Rs 3 CT, with T denoting tensile strength, s 3 the least principal stress and P fluid the pore fluid pressure.…”

Section: Microcrack Density As a Function Of Distance From The Centramentioning

confidence: 99%

“…For tensile cracks to form by hydraulic fracturing, the fluid pressure must exceed the magnitude of the least principal stress by the tensile strength of the rock (e.g. Secor, 1965;Shaw, 1980) or, in fracture mechanics terminology, exceed the fracture toughness of the rock. Upon cooling and crystallisation, the portion of volatiles in the pegmatitic melt that is not incorporated into minerals is liberated as a fluid phase (Burnham, 1979).…”

Section: Introductionmentioning

confidence: 99%

Magma-driven hydraulic fracturing and infiltration of fluids into the damaged host rock, an example from Dronning Maud Land, Antarctica

Engvik

Bertram

Kalthoff

et al. 2005

Journal of Structural Geology

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Excellent outcrops in Dronning Maud Land, Antarctica, provide unique insight into the mode and extent of fluid infiltration into metamorphic and plutonic rocks in the middle crust. The fluids are liberated from pegmatitic veins and give rise to alteration halos. In the alteration halos, the conspicuous change in colour is correlated with (1) hydration mineral reactions, and (2) high density of microcracks in quartz and feldspar exceeding that observed in the unaltered host rock by an order of magnitude. The field relations indicate that the veins originated as melt-driven hydraulic fractures, sealed by pegmatite and aplite crystallising from volatile-rich melts, with the alteration halo being the wake of the process zone formed at the tip of the propagating fractures. It is proposed that (1) the size of the alteration zone and the width of the vein are correlated, resulting in higher values of both these quantities for cracks propagating at higher velocities and consequently higher crack propagation toughnesses; (2) the damage zone is characterised by a transient state of high permeability which was short-lived due to rapid healing and sealing of microcracks; (3) the infiltration and retrogression of the high-grade rocks can be considered as a quasi-instantaneous process on geologic time scales with a duration of hours to weeks. q

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“…The maximum depth for hydrofracturing (z max ) as a function of λ can be calculated from the failure criterion for extensional fracturing of intact homogeneous rock, given by σ 3 ' = -T where T is the tensile strength of the rock, combined with the maximum differential stress for extension fracturing, given by σ^ -σ' 3 = AT (Secor, 1965). Combining these two equations, and recalling σ,' = σ, -P = (p r gz + p w gh) -P, yields the following relationship between λ and z max :…”

Section: \ -(2)mentioning

confidence: 99%

Structural Evolution of Upper Layer 2, Hole 896A

Harper¹,

Tartarotti²

1996

Proceedings of the Ocean Drilling Program, 148 Scientific Results

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An analysis of the state of stress in the upper ocean crust shows that high hydrostatic pore-fluid pressures will result from the thick overlying water column, providing that the upper crust is sufficiently permeable. High pore-fluid pore pressures will result in very low effective stresses in the upper ocean crust. Such conditions favor deformation by formation of extension fractures and mixed mode (combined extension and shear) fractures rather than by frictional sliding on faults. High pore-fluid pressures are considered very likely to have produced many of the structures in Hole 896A, including jigsaw-puzzle breccias and associated vein networks, cement-supported breccias, and fibrous veins. These structures record an overall volume increase, and their geometry and offset markers indicate formation as extensional fractures or, in some cases, mixed mode fracturing. The geometry and textures of jigsaw-puzzle breccias and associated vein networks suggest formation by longitudinal (axial) splitting, a type of brittle rock failure that occurs in rock deformation experiments done under stress conditions similar to those in the upper ocean crust (σ 2 ' and σ 3 ' < 0). Breccias can form by disaggregation during volume increase associated with extension or mixed mode fractures. The textures of many breccias formed in this way are very similar to those of sedimentary breccias and thus the sedimentary vs. tectonic origin of many breccias in the drill core is uncertain, especially because the margins of the breccias are not usually preserved in core. The fibrous veins generally postdate jigsaw-puzzle breccias and vein networks. They probably formed by repeated cycles of hydrofracturing and sealing of fractures (crack-seal mechanism). The extension directions indicated by both fibrous and nonfibrous veins are highly variable in orientation, even within a single piece, and vein networks suggest simultaneous extension in several directions. In addition, small faults having fibrous slickensides occurring below 334 m below seafloor indicate normal, reverse, and oblique slip. The style of brittle deformation observed in Hole 896A should produce microseismicity characterized by a nonuniform stress field and non-double-couple earthquakes. Such microseismicity characterized geothermal activity in the post-rifting stage at Krafla, Iceland.

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Role of fluid pressure in jointing

Cited by 545 publications

References 0 publications

Direct simulation of fluid‐solid mechanics in porous media using the discrete element and lattice‐Boltzmann methods

Direct simulation of fluid‐solid mechanics in porous media using the discrete element and lattice‐Boltzmann methods

Magma-driven hydraulic fracturing and infiltration of fluids into the damaged host rock, an example from Dronning Maud Land, Antarctica

Structural Evolution of Upper Layer 2, Hole 896A

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