Determination of stiffness and other joint properties from roughness measurements

Swan, Graham

doi:10.1007/bf01030216

Cited by 152 publications

(56 citation statements)

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“…Assuming laminar flow and that fluid flow within the core is mainly controlled by fracture properties, the "cubic law" approach (Boussinesq, 1868;Snow, 1965) is chosen to derive appropriate local permeabilities (K MA ) based on the MSMA aperture calibration, which is defined as…”

Section: Image Processingmentioning

confidence: 99%

“…In the past, the stress dependency of fracture permeability and its hysteretic behavior due to stepwise loading and subsequent unloading were investigated by various authors (e.g., Gangi, 1978;Kranz et al, 1979;Snow, 1965). Various empirical models were developed that approximate stressdependent fracture permeability by adding roughness-based variables to the common cubic law approach (Bernabe, 1986;Gale, 1982;Gangi, 1978;Huo and Benson, 2015;Swan, 1983;Walsh, 1981;Witherspoon et al, 1980;Zimmerman et al, 1992).…”

Section: Introductionmentioning

confidence: 99%

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Simulating stress-dependent fluid flow in a fractured core sample using real-time X-ray CT data

et al. 2016

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Abstract. Various geoscientific applications require a fast prediction of fracture permeability for an optimal workflow. Hence, the objective of the current study is to introduce and validate a practical method to characterize and approximate single flow in fractures under different stress conditions by using a core-flooding apparatus, in situ X-ray computed tomography (CT) scans and a finite-volume method solving the Navier-Stokes-Brinkman equations. The permeability of the fractured sandstone sample was measured stepwise during a loading-unloading cycle (0.7 to 22.1 MPa and back) to validate the numerical results. Simultaneously, the pressurized core sample was imaged with a medical X-ray CT scanner with a voxel dimension of 0.5 × 0.5 × 1.0 mm 3 . Fracture geometries were obtained by CT images based on a modification of the simplified missing attenuation (MSMA) approach. Simulation results revealed both qualitative plausibility and a quantitative approximation of the experimentally derived permeabilities. The qualitative results indicate flow channeling along several preferential flow paths with less pronounced tortuosity. Significant changes in permeability can be assigned to temporal and permanent changes within the fracture due to applied stresses. The deviations of the quantitative results appear to be mainly caused by both local underestimation of hydraulic properties due to compositional matrix heterogeneities and the low CT resolution affecting the accurate capturing of sub-grid-scale features. Both affect the proper reproduction of the actual connectivity and therefore also the depiction of the expected permeability hysteresis. Furthermore, the threshold value CT mat (1862.6 HU) depicting the matrix material represents the most sensitive input parameter of the simulations. Small variations of CT mat can cause enormous changes in simulated permeability by up to a factor of 2.6 ± 0.1 and, thus, have to be defined with caution. Nevertheless, comparison with further CT-based flow simulations indicates that the proposed method represents a valuable method to approximate actual permeabilities, particularly for smooth fractures (< 35 µm). However, further systematic investigations concerning the applicability of the method are essential for future studies. Thus, some recommendations are compiled by also including suggestions of comparable studies.

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Section: Image Processingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Simulating stress-dependent fluid flow in a fractured core sample using real-time X-ray CT data

et al. 2016

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“…Witherspoon et al (1979), Barton and Bakhtar (1982)) and confirmed in theoretical studies (e.g. Neuzil and Tracy (1981) and Swan (1983)). Neuzil and Tracy (1981) attributed this size effect to a truncation of the aperture frequency distribution, implying that fewer of the largest, least-frequent flow channels would be included in a smaller sample.…”

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confidence: 51%

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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“…Existing models of the normal compliance of mismatched joints [Walsh and Grosenbaugh, 1979;Swan, 1983;Brown and $cholz, 1985], extensions of these for shear compliance [Yoshioika and Scholz, 1989], and some models of sliding friction [Biegel et (Figure l a), the probability that any asperity on the nominally flat surface will make contact with the flat surface is prob = I qo(z)dz,…”

Section: Introductionmentioning

confidence: 99%

“…For example, rock elastic and poroelastic properties are affected by the presence of mismatched joints because of their high normal compliance [Walsh and Grosenbaugh, 1979;Swan, 1983;Brown and Scholz, 1985]. Electrical resistivity of dry rock depends on the percent of contact across joints and fractures [Greenwood and Williamson, 1966].…”

Section: Introductionmentioning

confidence: 99%

A note on contact stress and closure in models of rock joints and faults

Beeler¹,

Hickman²

2001

Geophysical Research Letters

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Abstract. We have re-examined asperity deformation predicted by joint closure models based on Greenwood and Williamson [1966] which use a statistical representation of loaded, rough surfaces. Although such models assume small elastic strains within contacting asperities (Hertzian contact) and well predict the observed dependence of closure on normal stress, large elastic normal strains measured in experiments violate the model assumptions. This inconsistency between observations and models can be resolved. The model dependence of closure on macroscopic normal stress results primarily from the statistics of the surface topography, and the functional dependence of closure on normal stress can be independent of assumed contact-scale elastic interactions. Thus, a joint model of the Greenwood and Williamson kind, modified to allow a portion of the elastic deformation to occur outside of the asperity contact region, predicts macroscopic behavior consistent with Hertzian models. Contact stresses derived from previously published models of this kind may be in error.

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Determination of stiffness and other joint properties from roughness measurements

Cited by 152 publications

References 9 publications

Simulating stress-dependent fluid flow in a fractured core sample using real-time X-ray CT data

Simulating stress-dependent fluid flow in a fractured core sample using real-time X-ray CT data

Coupled hydromechanical effects of CO2 injection

A note on contact stress and closure in models of rock joints and faults

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