ISSN:
1420-9136
Keywords:
Physical properties of rocks
;
permeability
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
,
Physics
Notes:
Abstract Permeability, resistivity formation factor, and pore volume change were simultaneously measured on samples of Chelmsford granite subjected to confining pressure and pore pressure cycles. Using a technique described in a previous paper, the tangent coefficients of the effective pressure law for permeability α k and for formation factor α F were determined. α k and α F did not differ significantly from one another. They showed a strong stress history dependence as has already been observed for α k in several crystalline rocks. According to the definition of the effective pressure law used here, two physical properties with identical α's must be related through a one-to-one functional relationship. Hence, the observation above suggests that such a relationship may be empirically found between permeability and formation factor. Indeed, analysis of the data revealed that, to a good approximation, permeability was inversely proportional to the formation factor. The same relation has previously been observed in other crystalline rocks. This relationship was included in a recent version of the so-called equivalent channel model. Using this model, the specific surface area of the cracksA c/VS, the standard deviation of the distribution of asperities heightsh and the hydraulic radiusm o were evaluated. The following values were respectively found: 850 cm−1, 0.008 μm and 0.14 μm. The specific surface area of the cracks was independently estimated on micrographs of polished sections using a standard quantitative stereology method. The result was in good agreement with the values estimated from the transport properties data.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00881747
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