An asperity-deformation model for effective pressure

Gangi, Anthony F.; Carlson, R. L.

doi:10.1016/0040-1951(95)00167-0

Cited by 87 publications

(63 citation statements)

References 10 publications

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“…However, laboratory measurements often show effective stress coefficients systematically lower than one (Todd and Simmons, 1972;Christensen and Wang, 1985;Prasad and Manghnani, 1997;Siggins and Dewhurst, 2003). To explain these observations, some authors proposed models of effective stress which are inconsistent with theoretical results described above (Gangi and Carlson, 1996;Prasad and Manghnani, 1997).…”

Section: Introductionmentioning

confidence: 71%

“…Other authors even suggest that n is not always a constant and may itself depend on the confining stress and pressure (Gangi and Carlson, 1996;Prasad and Manghnani, 1997). An in-depth analysis of this disparity and of the concept of effective stress in general has been performed by Robin (1973), Carroll and Katsube (1983), Zimmerman (1991), and Berryman (1992Berryman ( , 1993.…”

Section: Introductionmentioning

confidence: 99%

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A simple derivation of the effective stress coefficient for seismic velocities in porous rocks

Gurevich

2004

GEOPHYSICS

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Section: Introductionmentioning

confidence: 71%

Section: Introductionmentioning

confidence: 99%

A simple derivation of the effective stress coefficient for seismic velocities in porous rocks

Gurevich

2004

GEOPHYSICS

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“…In most samples, the data points κ s (p f , p c ) collapsed on a rather well defined, declining line when plotted against p c À p f , suggesting that κ s can generally be considered a decreasing function of the differential pressure, p c À p f . This property was conjectured by Ghabezloo et al [2009] and can be justified based on the crack-asperity model of Gangi and Carlson [1996]. Finally, κ s does not appear to correlate to either porosity or permeability.…”

Section: Secant Epl Coefficientsmentioning

confidence: 87%

“…Consequently, determining the EPL accurately may be particularly difficult in rocks that are insensitive to pressure, since they tend to have δk much lower than ε k (Gangi and Carlson [1996] similarly concluded that the effective pressure cannot be determined if the rock pressure sensitivity is not known with sufficient precision). However, this is not a problem in practical applications.…”

Section: 1002/2013jb010485mentioning

confidence: 99%

“…Furthermore, it is well known that in most rocks, K depends on pressure, implying that κ in equation (1) is also pressure dependent [e.g., Todd and Simmons, 1972;Coyner, 1984;Zimmerman, 1991;Gangi and Carlson, 1996]. Thus, nonlinear EPLs should be expected for many rock properties [Robin, 1973] and, indeed, have been reported for permeability [Bernabé, 1986[Bernabé, , 1987[Bernabé, , 1988Warpinski and Teufel, 1992;Ghabezloo et al, 2009;Li et al, 2009aLi et al, , 2009b.…”

Section: Introductionmentioning

confidence: 99%

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Nonlinear effective pressure law for permeability

Xiao

Bernabé

et al. 2014

JGR Solid Earth

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The permeability k of porous rocks is known to vary with confining pressure pc and pore fluid pressure pf. But it is, in principle, possible to replace the two‐variable function k(pf, pc) by a function k(peff) of a single variable, peff(pf, pc), called the effective pressure. Our goal in this paper is to establish an experimental method for determining a possibly nonlinear, effective pressure law (EPL) for permeability, i.e., find the function κs(pf, pc) such that the effective pressure is given by peff = pc − κs(pf, pc) pf. We applied this method to a set of 26 sandstone cores from various hydrocarbon reservoirs in China. We found that κs greatly varied, from sample to sample, in magnitude and range, sometimes even reaching theoretically prohibited values (i.e., greater than 1 or lower than porosity). One interesting feature of κs(pf, pc) is that it could be approximately described in all rocks but one as a decreasing function κs(pc − pf) of Terzaghi's differential pressure. We also investigated the dependence of permeability on peff for each of our samples. Three models from the literature, i.e., exponential (E), power law (P), and the Walsh model (W), were tested. The (W) model was more likely to fit the experimental data of cores with a high pressure dependence of permeability whereas (E) occurred more frequently in low‐pressure‐sensitive rocks. Finally, we made various types of two‐ and three‐dimensional microstructural observations that generally supported the trend mentioned above.

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Constraints on the shallow velocity structure of the Lucky Strike Volcano, Mid-Atlantic Ridge, from downward continued multichannel streamer data

Arnulf

Harding

Kent

et al. 2014

J. Geophys. Res. Solid Earth

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The shallow velocity structure of the Lucky Strike segment of the Mid-Atlantic Ridge is investigated using seismic refraction and reflection techniques applied to downward continued multichannel streamer data. We present a three-dimensional velocity model beneath the Lucky Strike Volcano with unprecedented spatial resolutions of a few hundred meters. These new constraints reveal large lateral variations in P wave velocity structure beneath this feature. Throughout the study area, uppermost crustal velocities are significantly lower than those inferred from lower resolution ocean bottom seismometer studies, with the lowest values (1.8-2.2 km/s) found beneath the three central volcanic cones. Within the central volcano, distinct shallow units are mapped that likely represent a systematic process such as burial of older altered surfaces. We infer that the entire upper part of the central volcano is young relative to the underlying median valley floor and that there has been little increase in the layer 2A velocities since emplacement. Layer 2A thins significantly across the axial valley bounding faults likely as the result of footwall uplift. The upper crustal velocities increase with age, on average, at a rate of~0.875 km/s/Myr, similar to previous measurements at fast-spreading ridges, suggesting hydrothermal sealing of small-scale porosity is progressing at normal to enhanced rates.

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An asperity-deformation model for effective pressure

Cited by 87 publications

References 10 publications

A simple derivation of the effective stress coefficient for seismic velocities in porous rocks

A simple derivation of the effective stress coefficient for seismic velocities in porous rocks

Nonlinear effective pressure law for permeability

Constraints on the shallow velocity structure of the Lucky Strike Volcano, Mid-Atlantic Ridge, from downward continued multichannel streamer data

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