Fluid-property discrimination with AVO: A Biot-Gassmann perspective

This analysis draws together basic rock physics, amplitude variations with offset (AVO), and seismic amplitude inversion to discuss how fluid‐factor discrimination can be performed using prestack seismic data. From both Biot and Gassmann theories for porous, fluid‐saturated rocks, a general formula is first derived for fluid‐factor discrimination given that both the P and S impedances are available. In essence, the two impedances are transformed so that they better differentiate between the fluid and rock matrix of the porous medium. This formula provides a more sensitive discriminator of the pore‐fluid saturant than the acoustic impedance and is especially applicable in hard‐rock environments. The formulation can be expressed with either the Lame constants and density, or the bulk and shear moduli and density. Numerical and well‐log examples illustrate the applicability of this approach. AVO inversion results are then incorporated to show how this method can be implemented using prestack seismic data. Fi...

[1]  Jon Downton,et al.  Improved AVO Fluid Detection And Lithology Discrimination Using Lamé Petrophysical Parameters; “λρ”, μρ, λμ Fluid Stack”, From P And S Inversions. , 1997 .

[2]  J. Garat,et al.  A Petrophysical Interpretation Using the Velocities of P and S Waves (Full-Waveform Sonic) , 1990 .

[3]  C. Frasier,et al.  SCATTERING OF ELASTIC WAVES FROM DEPTH‐DEPENDENT INHOMOGENEITIES , 1976 .

[4]  Paul G. Richards,et al.  Quantitative Seismology: Theory and Methods , 1980 .

[5]  Richard Verm,et al.  Lithology, color-coded seismic sections; the calibration of AVO crossplotting to rock properties , 1995 .

[6]  Ken Hedlin,et al.  Pore Space Modulus And Extraction Using AVO , 2000 .

[7]  S. N. Domenico,et al.  Effect of water saturation on seismic reflectivity of sand reservoirs encased in shale , 1974 .

[8]  J. Berryman.  Origin of Gassmann’s equations , 1999 .

[9]  R. Jeanloz,et al.  Introduction to the physics of rocks , 1994 .

[10]  W. J. Ostrander.  Plane-wave reflection coefficients for gas sands at nonnormal angles of incidence , 1984 .

[11]  Fred Hilterman,et al.  Seismic amplitude interpretation , 2001 .

[12]  William F. Murphy,et al.  Modulus decomposition of compressional and shear velocities in sand bodies , 1993 .

[13]  Steven R. Rutherford,et al.  Amplitude-versus-offset variations in gas sands , 1989 .

[14]  M. Biot.  General Theory of Three‐Dimensional Consolidation , 1941 .

[15]  J. P. Castagna,et al.  Shear-wave velocity estimation in porous rocks: theoretical formulation, preliminary verification and applications , 1992 .

[16]  A. R. Gregory,et al.  ELASTIC WAVE VELOCITIES IN HETEROGENEOUS AND POROUS MEDIA , 1956 .

[17]  Zhijing Wang,et al.  Seismic properties of pore fluids , 1992 .

[18]  T. Mukerji,et al.  The Rock Physics Handbook , 1998 .

[19]  J. Korringa,et al.  On the Dependence of the Elastic Properties of a Porous Rock on the Compressibility of the Pore Fluid , 1975 .

[20]  J. Castagna,et al.  Framework for AVO gradient and intercept interpretation , 1998 .

[21]  G. C. Smith,et al.  Detection of gas in sandstone reservoirs using AVO analysis: A 3-D seismic case history using the Geostack technique , 1994 .

[22]  J. Castagna,et al.  Relationships between compressional‐wave and shear‐wave velocities in clastic silicate rocks , 1985 .

[23]  H. W. Swan,et al.  A Closer Look At Hydrocarbon Indicators , 1993 .

[24]  F. Gaßmann.  Uber die Elastizitat poroser Medien. , 1961 .

[25]  G. C. Smith,et al.  Weighted stacking for rock property estimation and detection of gas , 1987 .