Laboratory‐determined transport properties of Berea sandstone

Geophysics ◽  
1985 ◽  
Vol 50 (5) ◽  
pp. 775-784 ◽  
Author(s):  
William D. Daily ◽  
Wunan Lin

We report laboratory measurements of electrical resistivity ρ, water permeability k, and compressional wave velocity [Formula: see text] for both intact and fractured Berea sandstone samples as functions of temperature from 20°C to 200°C and effective pressure [Formula: see text] from 2.5 MPa to 50 MPa. For the intact sample, [Formula: see text] increases from 3.52 km/s to 4.16 km/s as [Formula: see text] goes from 3 to 50 MPa. With increasing temperature, [Formula: see text] decreases at rates of about 3 percent per 100°C at [Formula: see text] of 5 MPa and about 1.5 percent per 100°C at [Formula: see text] of 38 MPa. Data from the fractured sample are qualitatively similar, but velocities are about 10 percent lower. For both intact and fractured samples, ρ increases less than 15 percent as [Formula: see text] increases from 2.5 MPa to 50 MPa. Although both samples show a larger decrease in resistivity with increasing temperature, most of this change is attributed to the decrease in resistivity of the pore fluid over that temperature range. For both samples, k decreases with increasing pressure and temperature. The intact sample permeability varies from 23 mD at 3 MPa and 20°C to less than 1 mD at 50 MPa and 150°C. The permeability of the fractured sample varies from 676 mD at 3 MPa and 20°C to less than 1 mD at 40 MPa and 190°C. The effect of the fracture on k vanishes after several pressure cycles and above about 100°C. These laboratory data are used to demonstrate the possibility of using resistivity and velocity measurements to estimate in‐situ permeability of a reservoir.

Geophysics ◽  
1989 ◽  
Vol 54 (1) ◽  
pp. 76-81 ◽  
Author(s):  
D. Goldberg ◽  
B. Zinszner

We computed compressional‐wave velocity [Formula: see text] and attenuation [Formula: see text] from sonic log waveforms recorded in a cored, 30 m thick, dolostone reservoir; using cores from the same reservoir, laboratory measurements of [Formula: see text] and [Formula: see text] were also obtained. We used a resonant bar technique to measure extensional and shear‐wave velocities and attenuations in the laboratory, so that the same frequency range as used in sonic logging (5–25 kHz) was studied. Having the same frequency range avoids frequency‐dependent differences between the laboratory and in‐situ measurements. Compressional‐wave attenuations at 0 MPa confining pressure, calculated on 30 samples, gave average [Formula: see text] values of 17. Experimental and geometrical errors were estimated to be about 5 percent. Measurements at elevated effective pressures up to 30 MPa on selected dolostone samples in a homogeneous interval showed mean [Formula: see text] and [Formula: see text] to be approximately equal and consistently greater than 125. At effective stress of 20 MPa and at room temperature, the mean [Formula: see text] over the dolostone interval was 87, a minimum estimate for the approximate in‐situ conditions. We computed compressional‐wave attenuation from sonic log waveforms in the 12.5–25 kHz frequency band using the slope of the spectral ratio of waveforms recorded 0.914 m and 1.524 m from the source. Average [Formula: see text] over the interval was 13.5, and the mean error between this value and the 95 percent confidence interval of the slope was 15.9 percent. The laboratory measurements of [Formula: see text] under elevated pressure conditions were more than five times greater than the mean in‐situ values. This comparison shows that additional extrinsic losses in the log‐derived measurement of [Formula: see text], such as scattering from fine layers and vugs or mode conversion to shear energy dissipating radially from the borehole, dominate the apparent attenuation.


Geophysics ◽  
2009 ◽  
Vol 74 (2) ◽  
pp. WA93-WA101 ◽  
Author(s):  
Clive McCann ◽  
Jeremy Sothcott

Laboratory measurements of the attenuation and velocity dispersion of compressional and shear waves at appropriate frequencies, pressures, and temperatures can aid interpretation of seismic and well-log surveys as well as indicate absorption mechanisms in rocks. Construction and calibration of resonant-bar equipment was used to measure velocities and attenuations of standing shear and extensional waves in copper-jacketed right cylinders of rocks ([Formula: see text] in length, [Formula: see text] in diameter) in the sonic frequency range and at differential pressures up to [Formula: see text]. We also measured ultrasonic velocities and attenuations of compressional and shear waves in [Formula: see text]-diameter samples of the rocks at identical pressures. Extensional-mode velocities determined from the resonant bar are systematically too low, yielding unreliable Poisson’s ratios. Poisson’s ratios determined from the ultrasonic data are frequency corrected and used to calculate thesonic-frequency compressional-wave velocities and attenuations from the shear- and extensional-mode data. We calculate the bulk-modulus loss. The accuracies of attenuation data (expressed as [Formula: see text], where [Formula: see text] is the quality factor) are [Formula: see text] for compressional and shear waves at ultrasonic frequency, [Formula: see text] for shear waves, and [Formula: see text] for compressional waves at sonic frequency. Example sonic-frequency data show that the energy absorption in a limestone is small ([Formula: see text] greater than 200 and stress independent) and is primarily due to poroelasticity, whereas that in the two sandstones is variable in magnitude ([Formula: see text] ranges from less than 50 to greater than 300, at reservoir pressures) and arises from a combination of poroelasticity and viscoelasticity. A graph of compressional-wave attenuation versus compressional-wave velocity at reservoir pressures differentiates high-permeability ([Formula: see text], [Formula: see text]) brine-saturated sandstones from low-permeability ([Formula: see text], [Formula: see text]) sandstones and shales.


Geophysics ◽  
1961 ◽  
Vol 26 (1) ◽  
pp. 77-84 ◽  
Author(s):  
Andris Viksne ◽  
Joseph W. Berg ◽  
Kenneth L. Cook

Compressional wave velocities through 36 synthetic sandstone cores were measured and related to several of their physical properties, namely, porosity, manufacturing pressure, grain contacts, and amount of cement. The cores were composed of Ottawa sand grains averaging 0.12 mm in diameter and commercial Grefco cement; the manufacturing pressure was varied from 4,000 to 10,000 psi; the cement content by volume was varied from 10 to 100 percent; the effective porosities ranged between 2.1 and 30.4 percent; and the compressional wave velocities ranged between 9,170 and 17,420 ft.sec. All velocity measurements were taken at room temperature and atmospheric pressure using cores that contained only air in the pore space. The results are presented in graphic form, showing the relationship between the compressional wave velocity and manufacturing pressure, porosity, and cement content. For Grefco cement contents between 10.0 and 17.5 percent, the compressional wave velocity is controlled by the manufacturing pressure and the porosity. A change in manufacturing pressure of 1,000 psi changed the compressional wave velocity by one percent for cores having porosities of about 23 percent and by about 3 percent for cores having porosities of about 28 percent. A decrease in porosity of one percent increased the velocity by an average of 1.4 percent for effective porosities between 23 and 26 percent. The velocity is also dependent, to a great extent, on the number of grain contacts which is intimately associated with the manufacturing pressure, and the cement content which is intimately associated with the porosity. For cement contents greater than 17.5 percent by volume, the sand grains float in the cement, and the analogy between the synthetic sandstone cores and natural sandstones is questionable.


Geophysics ◽  
1997 ◽  
Vol 62 (4) ◽  
pp. 1163-1176 ◽  
Author(s):  
Manika Prasad ◽  
Murli H. Manghnani

Compressional‐wave velocity [Formula: see text] and quality factor [Formula: see text] have been measured in Berea and Michigan sandstones as a function of confining pressure [Formula: see text] to 55 MPa and pore pressure [Formula: see text] to 35 MPa. [Formula: see text] values are lower in the poorly cemented, finer grained, and microcracked Berea sandstone. [Formula: see text] values are affected to a lesser extent by the microstructural differences. A directional dependence of [Formula: see text] is observed in both sandstones and can be related to pore alignment with pressure. [Formula: see text] anisotropy is observed only in Berea sandstone. [Formula: see text] and [Formula: see text] increase with both increasing differential pressure [Formula: see text] and increasing [Formula: see text]. The effect of [Formula: see text] on [Formula: see text] is greater at higher [Formula: see text]. The results suggest that the effective stress coefficient, a measure of pore space deformation, for both [Formula: see text] and [Formula: see text] is less than 1 and decreases with increasing [Formula: see text].


Author(s):  
Jack K. Odum ◽  
William J. Stephenson ◽  
Kathy Goetz-Troost ◽  
David M. Worley ◽  
Arthur D. Frankel ◽  
...  

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