Stress control of hydraulic conductivity in fracture-saturated Swedish bedrock

Talbot, Christopher J.; Sirat, Manhal

doi:10.1016/s0013-7952(01)00047-3

Cited by 44 publications

(25 citation statements)

References 11 publications

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“…Highly fractured rock masses are treated as homogeneous anisotropic porous media when the concept of representative elementary volume (REV) is applicable. Lee et al (1995), Talbot and Sirat (2001), Zhou et al (2008) and Rong et al (2013) studied the stress effect on the permeability of fractured rock masses and showed that the in-situ rock stresses and the embedded depth can affect its permeability because of their effects on apertures. Leung and Zimmerman (2012) proposed a method for estimating two-dimensional macroscopic effective hydraulic conductivity by using parameters of fracture network, such as fracture density and aperture distribution.…”

Section: Introductionmentioning

confidence: 99%

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Investigation of the permeability anisotropy of 2D fractured rock masses

Ren

et al. 2015

Engineering Geology

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Section: Introductionmentioning

confidence: 99%

“…In fact, only a small portion of the fractures is conductive and contributes to fluid flow (Long and Billaux, 1987;Talbot and Sirat, 2001). Dense fracture networks are not necessarily hydraulically connected (Berkowitz, 2002).…”

Section: Introductionmentioning

confidence: 99%

Investigation of the permeability anisotropy of 2D fractured rock masses

Ren

et al. 2015

Engineering Geology

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“…If shear slip occurs on a critically stressed fracture, it can raise the permeability of the fracture through several mechanisms, including brecciation, shear dilation, and breakdown of seals (Barton et al 1995). Lately, similar correlations have been found at the KTB Scientific Drill Hole in Germany down to 7 km (Ito and Zoback 2000), and also at Äspö, Sweden, in the Precambrian rocks of the Baltic Shield deep in the Eurasian plate (Talbot and Sirat 2001). On the other hand, experience from injection experiments at the hot-dry rock geothermal sites in Soultz, France, and Rosemanowes, U.K., suggests that a pore-pressure increase of 5-6 MPa over ambient is needed to stimulate significant microseismicity (Evans et al 1999).…”

Section: Correlation Between Shear Stress and Permeability In Fracturmentioning

confidence: 60%

Coupled hydromechanical effects of CO2 injection

Rutqvist¹,

Tsang²

2005

Underground Injection Science and Technology

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INTRODUCTIONUnderground storage of carbon dioxide (CO 2 ) in permeable formations, such as deep saline aquifers, depleted oil and gas reservoirs, and coal seams, has been suggested as an important potential method for reducing the emission of greenhouse gases to the atmosphere (DOE 1999). The injection would take place at a depth below 800 m, so that the CO 2 would be within the temperature and pressure range of a supercritical fluid. As a supercritical fluid, CO 2 behaves like a gas with low viscosity but with a liquid-like density of 200-900 kg/m 3 , depending on pressure and temperature. Because supercritical CO 2 is less dense than water, deep underground disposal requires a sufficiently impermeable caprock above an underground storage zone to trap the injected CO 2 .Caprock integrity and reservoir leakage is a key issue for both short-and long-term performance of geological CO 2 storage. In the short term, leakage is an important safety issue during active CO 2 injection. In the long term, leakage impacts the sequestration effectiveness of the once-injected CO 2 . In general, two kinds of leakage mechanisms can be identified (Yamamoto and Takahashi, 2004): 1) Steady or slow leakage processes of buoyancy-driven gas flow at a rate that depends on formation permeability and fluid capillarity 2) Dynamic or rapid leakage processes along fluid paths created by interaction between formation and injected CO 2 For the slow-leakage mechanism, the fluid travels through the rock matrix, fractures, and abandoned boreholes present in the storage volume. The fluid path can be regarded as fixed in the short term, but may change slowly over the long term. Because of the limited toxicity of CO 2 , a slow leakage of CO 2 is allowable from the viewpoint of short-term safety. However, such leakage may reduce long-term usefulness of CO 2 sequestration. The second, rapid leakage mechanism has been observed in nature, caused by external forces such as earthquakes. Such rapid changes could include a breach in a caprock caused by mechanical changes such as hydraulic fracturing or fault slip. For CO 2 sequestration, a rapid change in the geologic system may increase CO 2 leakage so significantly that it may be detrimental to both short-term safety and long-term environmental conservation.In considering a site for CO 2 sequestration, it will be important to evaluate the effects of CO 2 storage on the formation, so as to minimize the risk of a breach occurring in the 1 system. First, injection of CO 2 will result in an increase in formation fluid pressure, especially around the injection source. Such a fluid pressure increase will causes locatel changes in the stress field, which, in turn, will induce mechanical deformations and possible irreversible mechanical failure in the caprock. This mechanical failure may involve shear along many of the existing fractures or creation of new fractures that reduce the sealing properties of the caprock system. Second, replacing the native formation fluid with CO 2 may cause changes in rock mechanic...

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“…Transmissivity, which is the extent to which fractures are hydraulically conductive, depends strongly on their aperture (Cook, 1992), which in turn is primarily, yet not solely, affected by the fracture orientation within the in situ stress field. Preexisting faults and fractures that are critically stressed for either tensile (Gudmundsson, Fjeldskaar, and Brenner, 2002) or shear failure Barton, Zoback, and Moos, 1995) within the in situ stress field are most likely to be open and hydraulically conductive (Ferrill et al, 1999;Talbot and Sirat, 2001). Generally, tensile failure is unlikely to be the dominant fracture reactivation mechanism below a depth of approximately 2000 m, as the high lithostatic overburden causes high differential stresses (Ferrill and Morris, 2003).…”

Section: Relevance Of the Stress Field For Egs 47mentioning

confidence: 99%