Laboratory study of fluid viscosity induced ultrasonic velocity dispersion in reservoir sandstones
He Tao1, Zou Chang-Chun2, Pei Fa-Gen2, Ren Ke-Ying3, Kong Fan-Da1, and Shi Ge1
1. Key Laboratory of Orogenic Belts and Crustal Evolution, MOE (School of Earth and Space Sciences, Peking University), Beijing 100871, China.
2. Key Laboratory of Geo-detection (China University of Geosciences, Beijing), Ministry of Education, Beijing 100083, China.
3. Zhanjiang Branch of China National Offshore Oil Corporation Ltd., Zhanjiang 524057, China.
Abstract：
Ultrasonic velocities of a set of saturated sandstone samples were measured at simulated in-situ pressures in the laboratory. The samples were obtained from the W formation of the WXS Depression and covered low to nearly high porosity and permeability ranges. The brine and four different density oils were used as pore fluids, which provided a good chance to investigate fluid viscosity-induced velocity dispersion. The analysis of experimental observations of velocity dispersion indicates that (1) the Biot model can explain most of the small discrepancy (about 2 – 3%) between ultrasonic measurements and zero frequency Gassmann predictions for high porosity and permeability samples saturated by all the fluids used in this experiment and is also valid for medium porosity and permeability samples saturated with low viscosity fluids (less than approximately 3 mP•S) and (2) the squirt flow mechanism dominates the low to medium porosity and permeability samples when fluid viscosity increases and produces large velocity dispersions as high as about 8%. The microfracture aspect ratios were also estimated for the reservoir sandstones and applied to calculate the characteristic frequency of the squirt flow model, above which the Gassmann’s assumptions are violated and the measured high frequency velocities cannot be directly used for Gassmann’s fluid replacement at the exploration seismic frequency band for W formation sandstones.
HE Tao,ZOU Chang-Chun,PEI Fa-Gen et al. Laboratory study of fluid viscosity induced ultrasonic velocity dispersion in reservoir sandstones[J]. APPLIED GEOPHYSICS, 2010, 7(2): 114-126.
[1]
Ba, J., Cao, H., Yao, F. C., Nie, J. X., and Yang, H. Z., 2008, Double-porosity rock model and squirt flow in the laboratory frequency band: Applied Geophysics, 5(4), 261 - 276.
[2]
Batzle, M., Hofmann, R., Han, D., and Castagna, J., 2001, Fluids and frequency dependent seismic velocity of rocks: The Leading Edge, 20(2), 168 - 171.
[3]
Batzle, M. L., Han, D., and Hofmann, R., 2006, Fluid mobility and frequency-dependent seismic velocity - Direct measurements: Geophysics, 71(1), N1 - N9.
[4]
Batzle, M., and Wang, Z., 1992, Seismic properties of pore fluids: Geophysics, 57(11), 1396 - 1408.
[5]
Best, A. I., and McCann, C., 1995, Seismic attenuation and pore-fluid viscosity in clay-rich reservoir sandstones: Geophysics, 60(5), 1386 - 1397.
[6]
Biot, M. A., 1956, Theory of propagation of elastic waves in a fluid-saturated porous solid. I. Low-frequency range, II. Higher frequency range: Journal of the Acoustical Society of America, 28(2), 168 - 191.
[7]
Deng, J. X., Shi, G., and Yu, J., 2003, The research of the characteristics of ultrasonic velocity dispersion in fluid saturated rock: Acta Scicentiarum Naturalum Universitis Pekinesis (in Chinese), 39(6), 835 - 843.
[8]
Dvorkin, J., Mavko, G., and Nur, A., 1995, Squirt flow in fully saturated rocks: Geophysics, 60(1), 97 - 107.
[9]
Dvorkin, J., Nolen-Hoeksema, R., and Nur, A., 1994, The squirt-flow mechanism: Macroscopic description: Geophysics, 59(3), 428 - 438.
[10]
Dvorkin, J., and Nur, A., 1993, Dynamic poroelasticity: A unified model with the squirt and the Biot mechanisms: Geophysics, 58(4), 524 - 533.
[11]
Gassmann, F., 1951, Über die Elastizität poröser Medien: Veirteljahrsschrift der Naturforschenden Gesellschaft in Zürich, 96, 1 - 23.
[12]
Geertsma, J., and Smit, D. C., 1961, Some aspects of elastic wave propagation in fluid-saturated porous solids: Geophysics, 26(2), 169 - 181.
[13]
Gurevich, B., 2002, Effect of fluid viscosity on elastic wave attenuation in porous rocks: Geophysics, 67(1), 264 - 270.
[14]
Han, D., and Batzle, M., 2000a, Velocity, density and modulus of hydrocarbon fluids - empirical modeling: SEG Technical Program Expanded Abstracts, 19 (1), 1867-1870.
[15]
Han, D., and Batzle, M., 2000b, Velocity, density and modulus of hydrocarbon fluids - data measurement: SEG Technical Program Expanded Abstracts, 19(1), 1862 - 1866.
[16]
Hornby, B. E., 1998, Experimental laboratory determination of the dynamic elastic properties of wet, drained shales: Journal of Geophysical Research, 103(B12), 29945 - 29964.
[17]
Khazanehdari, J., and Sothcott, J., 2003, Variation in dynamic elastic shear modulus of sandstone upon fluid saturation and substitution: Geophysics, 68(2), 472 - 481.
[18]
Li, J. C., Shi, G., and Chen, S. Y., 2005, Experimental study on effects of viscosity and salinity of liquid on rock velocity anisotropy: Acta Scicentiarum Naturalum Universitis Pekinesis (in Chinese), 41(6), 851 - 858.
[19]
Mavko, G., and Nur, A., 1975, Melt squirt in the asthenosphere: Journal of Geophysical Research, 80, 1444 - 1448.
[20]
Mavko, G., and Jizba, D., 1991, Estimating grain-scale fluid effects on velocity dispersion in rocks: Geophysics, 56(12), 1940 - 1949.
[21]
Mavko, G., Mukerji, T., and Dvorkin, J., 2009, The rock physics handbook: Tools for seismic analysis in porous media (2nd edition): Cambridge University Press, New York, p.312.
[22]
Murphy, W. F., 1984, Acoustic measures of partial gas saturation in tight sandstones: Journal of Geophysical Research, 89, 11549 - 11559.
[23]
Murphy, W. F., Winkler, K. W., and Kleinberg, R. L., 1984, Frame modulus reduction in sedimentary rock: Geophysical Research Letters, 11(9), 805 - 808.
[24]
Nie, J. X., and Yang, D. H., 2008, Viscoelastic BISQ model for low-permeability sandstone with clay: Chinese Physics Letters, 25(8), 3079 - 3082.
[25]
Nie, J. X., Yang, D. H., and Ba, J., 2010, Velocity dispersion and attenuation of waves in low-porosity-permeability anisotropic viscoelastic media with clay: Chinese Journal of Geophysics (in Chinese), 53(2), 385 - 392.
[26]
Nie, J. X., Yang, D. H., and Yang, H. Z., 2008, A generalized viscoelastic Biot/squirt model for clay-bearing sandstones in a wide range of permeabilities: Applied Geophysics, 5(4), 249 - 260.
[27]
O’Connell, R. J., and Budiansky, B., 1977, Viscoelastic properties of fluid-saturated cracked solids: Journal of Geophysical Research, 82, 5719 - 5740.
[28]
Parra, J. O., 2000, Poroelastic model to relate seismic wave attenuation and dispersion to permeability anisotropy: Geophysics, 65(1), 202 - 210.
[29]
Peselnick, L., and Outerbridge, W. F., 1961, Internal friction in shear and shear modulus of Solenhofen limestone over a frequency range of 107 cycles per second: Journal of Geophysical Research, 66(2), 581 - 588.
[30]
Shi, G., and Yang, D. Q., 2002, Determination of the elastic wave velocities in porous rocks with the change of overburden pressure and its universal significance: Science in China, Ser.D, 45(7), 635 - 642.
[31]
Spencer, J. W., 1981, Stress relaxations at low frequencies in fluid saturated rocks: Attenuation and modulus dispersion: Journal of Geophysical Research, 86(B3), 1803 - 1812.
[32]
Wang, Z., and Nur, A., 1990, Dispersion analysis of acoustic velocities in rocks: The Journal of the Acoustical Society of America, 87(6), 2384 - 2395.
[33]
Wang, Z., and Nur, A. M., 1988, Velocity dispersion and the “local flow’’ mechanism in rocks: SEG Technical Program Expanded Abstracts, 7(1), 548 - 550.
[34]
Wei, X. C., Lu, M. H., Ba, J., and Yang, H. Z., 2008, Dispersion and attenuation of elastic waves in a viscous fluid-saturated anisotropic porous solid: Chinese Journal of Geophysics (in Chinese), 51(1), 213 - 220.
[35]
Winkler, K. W., 1985, Dispersion analysis of velocity and attenuation in Berea sandstone: Journal of Geophysical Research, 90, 6793 - 6800.
[36]
Winkler, K. W., 1986, Estimates of velocity dispersion between seismic and ultrasonic frequencies: Geophysics, 51(1), 183 - 189.
[37]
Yang, D. H., and Zhang, Z. J., 2002, Poroelastic wave equation including the Biot/squirt mechanism and the solid/fluid coupling anisotropy: Wave Motion, 35(3), 223 - 245.
[38]
Zhang, Y. Z., Chu, Z. H., Li, M., and Luo, M., 2001, An experimental study of acoustic dispersion of rock and extrapolation of the velocity: Chinese Journal of Geophysics (in Chinese), 44(1), 136 - 141.
2010, Vol. 7 
