The Effect of Temperature and Confining Pressure on Single-Phase Flow in Consolidated Rocks (includes associated paper 9087 )
- Francis J. Casse (Franlab) | Henry J. Ramey Jr. (Stanford U.)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- August 1979
- Document Type
- Journal Paper
- 1,051 - 1,059
- 1979. Society of Petroleum Engineers
- 4.6 Natural Gas, 1.10 Drilling Equipment, 1.6.9 Coring, Fishing, 5.1.1 Exploration, Development, Structural Geology, 5.4.1 Waterflooding, 4.1.5 Processing Equipment, 5.2.1 Phase Behavior and PVT Measurements, 4.1.2 Separation and Treating
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Single-phase flow through consolidated rocks is conducted under conditions of elevated temperature and overburden pressure. Unique permeability reduction with increasing temperature is observed with distilled water, while a slight increase is noted with white mineral oil and no change is found with gas. With gas flow, slippage and turbulence at high temperatures also are investigated; results agree closely with theory.
In all reservoir engineering calculations, absolute permeability is a basic parameter and traditionally has been measured at room conditions, with the assumption that absolute permeability changes only with core loading pressure. As a result, most reservoir engineers use a single value of absolute permeability throughout a range of temperatures.
It was only in the late 1960s that changes in absolute permeability were observed with temperature. In 1968, Greenberg et al. reported data on the permeability to water of nine artificially consolidated hydrological porous medium samples for a limited temperature span [80 to 140 deg. F(26.7 to 60 deg. C)]. The Greenberg et al. results showed either slight-to-moderate decreases in permeability, no change at all with increasing temperature, or increases in permeability in two cases. No confining pressure was applied to the cores.
In 1969, Afinogenov reported a large reduction of permeability to oil with increased temperature, up to 100-fold between 70 and 200 deg. F(21.1 and 93.3 deg. C). He also observed extreme permeability reductions with increasing confining pressure for pressures ranging from 300 to 15,000 psi (2.1 to 103 MPa).
Qualitatively, these results agreed with those in previously published works, but quantitatively the decrease observed was much greater than one might expect. No attempt-was made to study the combined effect of temperature and confining pressure on absolute permeability.
The effect of radial and/or axial stress on various physical properties of rocks has been studied by several investigators. A review of earlier work was made in 1967 by Wilhelmi and Somerton. They measured pore and elastic properties of rocks simultaneously under a wide range of triaxial stress conditions. One of the first contributions in this area was made in 1952 by Fatt and Davis. They showed that permeability at 15,000-psi (103-MPa) confining pressure could be 25 to 60% smaller than the permeability at zero confining pressure, depending on the type of rocks studied.
In 1963, work on the effect of overburden pressure on permeability was extended by Gray et al. to sandstone permeability anisotropy. Permeability reduction was shown to be a function of the ratio of radial to axial stress, with maximum reduction evidenced under uniform stress - i.e., when the axial stress was equal to the radial stress. (The results reported here were obtained under conditions of uniform stress).
We usually consider the effect of the net confining pressure on absolute permeability. If k is defined as the fraction of pore pressure counteracting the confining pressure, the net confining pressure is the confining pressure less lambda x (pore pressure). Several investigaors found that the best correlating value is lambda = 0.85. Most temperature studies have considered a temperature range from 75 to 350 deg. F (23.9 to 176.7 deg. C).
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