Scientific Quarterly Journal of Geosciences

Scientific Quarterly Journal of Geosciences

Wave Velocities in carbonate rock specimens of a hydrocarbon reservoir in the south of Iran

Document Type : Original Research Paper

Authors
Mahdi Ghassemi 1
Majid Nabi-Bidhendi 2
Jalal Khazanehdari 3
1 The Petroleum University of Technology
2 Institute of Geophysics, Tehran University, Tehran, Iran
3 PRIS, The University of Reading, England
Abstract
      In this research, effects of different parameters on elastic wave velocities were assessed for eight carbonate rock specimens and different theories applied to laboratory data. Ultrasonic measurements were made on the samples in both dry and saturated states. Pore pressure of fluid (kerosene) was kept constant at 5MPa and the range of effective pressures was from 5MPa to 60 MPa. Central wave frequency of P-wave was I MHz and that of S-wave 0.6 MHz. All the experiments were carried out in room temperature.
The results show that by saturating the samples, P-wave velocities will increase but S-wave velocities show negligible changes. An increase in effective pressure causes the velocities to rise in both dry and saturated states, though the rate of P-wave velocity increase is more than that of S-wave. Results also show that wave velocities will increase by increasing the density or decreasing the porosity.
We applied Gassmann and Biot theories to the laboratory data. The results showed that these theories were in agreement with the results of ultrasonic measurements. Gassmann deviation was between -3% and +1% . Biot dispersion for P- and S- wave velocities was less than 0.3 and 0.5 percent, respectively. We also concluded that wyllie´s time average equation did not show a good agreement with the laboratory data.
Keywords
P-wave and S-wave velocities
carbonate rocks
hydrocarbon reservoir
Gassmann and Biot theories

Subjects

Best, A. I., McCann, C. and Sothcott, J., 1994- The relationships between the velocities, attenuations and petrophysical properties of reservoir sedimentary rocks: Geophysical Prospecting, 42, 151-178.
Biot, M. A., 1956- Theory of propagation of elastic waves in a fluid-saturated porous solid. I. Low-frequency range: J. Acoust. Soc. Am. 28, 168-178.
Edjell, H. S., 1977- the Permian system as an oil & gas reservoir in Iran, Iraq & Arabia, Proc. Second Iranian Geological Symposium, Tehran, 161-201.
Gassmann, F., 1951- On the elasticity of porous media: Viertelijahrsschrift der Naturforschenden Gesellschaft in Zurich, 96, 1-23.
Kashfi, M. S., 2000- Greater Persian  Gulf Permian-Triassic stratigraphic nomenclature requires study: Oil and Gas Journal, Tusla, Nov., 6, 36-44.
Marion, D., Jizba, D., 1997- Acoustic properties of Carbonate rocks: use in quantitative interpretation of sonic and seismic measurements, in carbonate seismology: edited by Ibrahim Palaz and Kurt J. Marfurt, Soc. Explor. Geophys., 75-94.
Mavko, G. M. and Nur, A. M., 1978- the effect of nonelliptical cracks on the compressibility of rocks: J. Geophys. Res., 83, 4459-4468.
McCann, C., and Sothcott, J., 1992- Laboratory measurements of the seismic properties of sedimentary rocks, in Hurst, A., Worthington, P. F. and Griffiths, C., Eds., Geological applications of wire-line logs 2, Special Publication of the Geological Society of London.
O’Connell, R. J., and Budiansky, B., 1977- Viscoelastic properties of fluid saturated cracked solids: J. Geophys. Res. 82, 5719-5736, in Toksöz, M. N. and Johnston, D. H. Eds., 1981, Seismic wave attenuation: Geophysics reprint series, 2.
Schön, J. H., 1996- Physical properties of rocks, fundamentals and principles of petrophysics, in Handbook of geophysical exploration: Siesmic exploration, vol. 18.
Wang, Z., 1997- Seismic properties of carbonate rocks, in Carbonate seismology: edited by Palaz, I., Marfurt, K. J., Soc. Explor.Geophys., 22-52.
Wang, Z., 2000- The Gassmann equation revisited: Comparing laboratory data with Gassmann’s predictions, in Seismic and acoustic elocities in reservoir rocks (chapter 1): edited by Wang, Z., Nur, A., Soc. Explor. Geophys.
Wang, Z., and Nur, A.,1992- Elastic wave velocities in porous media: a theoretical recipe, in Wang, Z., and Nur, A., Eds., Seismic and acoustic velocities in reservoir rocks: Soc. Explor. Geophys., 1-35.
Winkler, K. W., and Plona, T. J., 1982- Techniques for measuring ultrasonic velocity and attenuation spectra in rocks under pressure: Jour. Geophys. Res., 87, 10776-10780.
Wyllie, M.R.J., Gregory, A.R., and Gardner, L.W., 1956- Elastic wave velocities in heterogeneous and porous media: Geophysics, 21, 41-70.
Scientific Quarterly Journal of Geosciences
Volume 14, Issue 56
Summer 2005, Vol. 12, No. 56
Summer 2005
Pages 134-145