The effect of pressure on porosity and the transport properties of rock

Abstract

We reanalyze the flow model proposed by Wyllie and Rose (1950) in which the complicated flow network through the pore phase of rock is replaced by a single representative conduit. Although the model is a very simple representation of the complicated pore phase in rock, we find that it provides an adequate simulation of how the transport properties vary with external pressure. Expressions derived for fluid permeability k and formation factor F are combined to give an expression for the mean hydraulic radius of the pore phase. Using this expression, we show that the exponent r in the empirical relationship k oc F-' must fall in the range 1 < r < 3. Also, we use the expression for hydraulic radius to estimate the crack area per unit volume and the standard deviation of the height of the asperities on the microcrack surfaces for two granites. The values are in reasonable agreement with other estimates.

Changes in Electrokinetic Coupling Coefficients of Granite under Triaxial Deformation

“…The streaming current International Journal of Geophysics coefficient C c was approximately proportional to the square root of the permeability. This dependence can be explained by assuming that m 2 is proportional to 1/F = η/T 2 in (5) and (6) for the capillary model [17,27,32]. This assumption is supported by the experimental results that log k is linearly related to log F with slope of ∼ −2 for granite reported by Walsh and Brace [32].…”

Deep geoelectric survey of the Carnmenellis granite

“…In such circumstances the Carnmenellis granite must be viewed as comprising very resistive 'intact' rock and many voids such as joints, cracks and pores which are saturated with interstitial fluids. Both the flow of fluid (governed by the permeability of the rock) and the flow of electric current (governed by the resistivity of the rock) are then principally controlled by the nature of the void and fluid content (Walsh & Brace 1984). The applicability of the 'Brace' model appears to be confirmed by an examination of the resistivity laterologs from the geothermal wells at Rosemanowes quarry (supplied by the Camborne School of Mines).…”

Permeability in Rotliegend gas sandstones to gas and brine as predicted from NMR, mercury injection and image analysis

“…Electrical resistivity or diffusion measurements are used to estimate Γ by some authors e.g., Berryman and Blair (1987), Cornell and Katz (1953), Dullien (1975), Pape et al (2006), Walsh and Brace, (1984).…”