Fluid overpressure and stress drop in fault zones

Guðmundsson, Ágúst

doi:10.1029/1998gl900228

Cited by 65 publications

(48 citation statements)

References 21 publications

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“…A hydrofracture is initiated (Gudmundsson, 1990) when the internal fluid excess pressure, p e , defined as the pressure in excess of the lithostatic stress p l , in a fluid source reaches the local in situ tensile strength, T 0 , of the host rock, typically between 0.5 and 6 MPa (Amadei & Stephansson, 1997). In higher stratigraphic levels, hydrofractures commonly develop a fluid overpressure due to buoyancy (Spence, Sharp & Turcotte, 1987;Gudmundsson, 1990Gudmundsson, , 1999Rubin, 1995;Ray, Sheth & Mallik, 2007), particularly when the fluid has a low density, such as geothermal water. Because hydrofractures commonly are extension fractures, they propagate perpendicular to the minimum principal compressive stress (maximum principal tensile stress) σ 3 (cf.…”

Section: B Fluid Transport Along Faults and Into The Layersmentioning

confidence: 99%

“…Active faults commonly transport crustal fluids (Byerlee, 1993;Barton, Zoback & Moos, 1995;Gudmundsson, 1999Gudmundsson, , 2000Haneberg et al 1999;Faybishenko, Witherspoon & Benson, 2000). Inactive and active fault zones with associated mineral veins offer good evidence of former fluid transport along faults (Gudmundsson, Fjeldskaar & Brenner, 2002;Brenner & Gudmundsson, 2004a).…”

Section: B Fluid Transport Along Faults and Into The Layersmentioning

confidence: 99%

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Geometry and formation of gypsum veins in mudstones at Watchet, Somerset, SW England

Philipp

2008

Geol. Mag.

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-Gypsum veins and faults were studied in red mudstones of the Upper Triassic Mercia Mudstone Group, in the Bristol Channel Basin, exposed in E-W-trending cliffs at Watchet on the Somerset Coast (SW England). In nodular gypsum horizons, individual gypsum nodules are connected by subhorizontal gypsum veins. In evaporite-free mudstone layers, however, dense anastomosing networks of gypsum veins occur. In a 300 m long profile dissected by 28 (mostly) normal faults with small displacements, 24 faults have veins following them, indicating palaeofluid transport along the fault planes. Ninety-seven cross-cutting relationships and mostly perpendicular vein fibres indicate that the veins are primarily extension fractures. The thickest veins in the vein network are subhorizontal (160 measurements), indicating a vertical orientation of the minimum principal compressive stress (horizontal basin compression). Such a stress state may have existed during basin inversion associated with Alpine compression (late Cretaceous to early Tertiary). I propose that the gypsum veins are the result of hydrofracturing. In the gypsum nodules, then presumably consisting of anhydrite, overpressure was generated related to the hydration of anhydrite to gypsum. Stress concentration around the nodules led to rupturing and injection of thin subhorizontal hydrofractures. Some of the calcium-sulphate saturated fluids were then transported upwards along the faults and gained access to evaporite-free mudstone layers where dense anastomosing vein networks developed. Most veins were arrested during their propagation by layers with contrasting mechanical properties (stress barriers). Some veins, however, propagated through the barriers along faults to shallower levels. The dense networks of mineral veins observed in Watchet indicate that hydrofractures can generate a very high temporary permeability in fluid reservoirs.

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Section: B Fluid Transport Along Faults and Into The Layersmentioning

confidence: 99%

Section: B Fluid Transport Along Faults and Into The Layersmentioning

confidence: 99%

Geometry and formation of gypsum veins in mudstones at Watchet, Somerset, SW England

Philipp

2008

Geol. Mag.

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“…Seismogenic faulting is commonly associated with zones of fluid overpressure (Gudmundsson, 1999). At the midcrustal depths, near the brittle-ductile transition, metamorphic dehydration may supply a major source of fluids.…”

Section: Introductionmentioning

confidence: 99%

Preliminary report on the Sanyi-Puli seismic zone conductivity anomaly and its correlation with velocity structure and seismicity in the Northwestern Taiwan

Chen

2014

Earth Planet Sp

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As part of seismotectonic investigations in Northwestern Taiwan, eight magnetotelluric (MT) soundings were conducted across the Sanyi-Puli seismic zone, a distinct NW-SE trending linear seismic zone in the fold-thrust belt of Northwestern Taiwan. A preliminary one-dimensional resistivity model according to the determinant MT response was computed, and the resistivity model includes a high-conductivity anomaly beneath this seismic zone. This conductivity anomaly raises the possibility of metamorphic dehydration triggering the seismic events in the seismic zone. The correlation between the conductivity anomaly and active seismicity in this area is tentatively discussed in this study.

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“…Fault zones in the Earth's upper crust contain complex structures-generally a fault core and a damage zone-that have distinct mechanical and permeability properties (Vermilye and Scholz, 1998;Gudmundsson, 1999Gudmundsson, , 2000Wibberley and Shimamoto, 2003;Faulkner et al, 2003;Cappa et al, 2007;Guglielmi et al, 2008;Mitchell et al, 2009;Cappa, 2009). The fault core is a low-permeability zone with small intergranular porosity, whereas the damage zone is a more permeable zone with a macroscopic fracture network.…”

Section: Introductionmentioning

confidence: 99%

Modeling of coupled deformation and permeability evolution during fault reactivation induced by deep underground injection of CO2

Cappa

Rutqvist

2011

International Journal of Greenhouse Gas Control

411

234

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The interaction between mechanical deformation and fluid flow in fault zones gives rise to a host of coupled hydromechanical processes fundamental to fault instability, induced seismicity, and associated fluid migration. In this paper, we discuss these coupled processes in general and describe three modeling approaches that have been considered to analyze fluid flow and stress coupling in fault-instability processes. First, fault hydromechanical models were tested to investigate fault behavior using different mechanical modeling approaches, including slip interface and finite thickness elements with isotropic or anisotropic elasto-plastic constitutive models. The results of this investigation showed that fault hydromechanical behavior can be appropriately represented with the least complex alternative, using a finite thickness element and isotropic plasticity. We utilized this pragmatic approach coupled with a strain-permeability model to study hydromechanical effects on fault instability during deep underground injection of CO 2 . We demonstrated how such a modeling approach can be applied to determine the likelihood of fault reactivation and to estimate the associated loss of CO 2 from the injection zone. It is shown that shearenhanced permeability initiated where the fault intersects the injection zone plays an important role in propagating fault instability and permeability enhancement through the overlying caprock.

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Fluid overpressure and stress drop in fault zones

Cited by 65 publications

References 21 publications

Geometry and formation of gypsum veins in mudstones at Watchet, Somerset, SW England

Geometry and formation of gypsum veins in mudstones at Watchet, Somerset, SW England

Preliminary report on the Sanyi-Puli seismic zone conductivity anomaly and its correlation with velocity structure and seismicity in the Northwestern Taiwan

Modeling of coupled deformation and permeability evolution during fault reactivation induced by deep underground injection of CO2

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