Estimation of elastic parameters using two-term fatti elastic impedance inversion

Abstract

Elastic impedance (EI) inversion has been widely used in industry to estimate kinds of elastic parameters to distinguish lithology or even fluid. However, it is found that conventional three-term elastic impedance formula is unstable even with slight random noise in seismic data, due to the ill-conditioned coefficient matrix of elastic parameters. We presented two-term Fatti elastic impedance inversion method, which is more robust and accurate than conventional three-term elastic impedance inversion. In our method, density is ignored to increase the robustness of inversion matrix. Besides, P-impedance and S-impedance, which are less sensitive to random noise, are inverted instead of V _P and V _S in conventional three-term elastic impedance. To make the inversion more stable, we defined the range of K value as a constraint. Synthetic tests claim that this method can obtain promising results with low SNR (signal noise ratio) seismic data. With the application of the method in a 2D line data, we achieved λρ, μρ and V _P/V _S sections, which matched the drilled well perfectly, indicating the potential of the method in reservoir prediction.

Keywords

two-term Fatti EI / random noise / K value

References

[1] Aki K., Richards P. G. Quantitative Seismology. W. H. Freeman and Company, San Francisco, 1980, 557.

[2] Bruce V., VerWest B., Masters R., . Elastic Impedance Inversion. Expanded Abstracts of 70th SEG Mtg., Calgary., 2000, 1580-1582.

[3] Cambois G. AVO Inversion and Elastic Impedance. SEG Technical Program Expanded Abstracts 2000, 2000, 142-145.

[4] Castagna J. P., Batzle M. L., Eastwood R. L. Relationships between Compressional-Wave and Shear-Wave Velocities in Clastic Silicate Rocks. Geophysics, 1985, 50(4): 571-581.

[5] Connolly P. Elastic Impedance. The Leading Edge, 1999, 18(4): 438-452.

[6] Downton, J. E., 2005. Seismic Parameter Estimation from AVO Inversion: [Dissertation]. University of Calgary, Calgary

[7] Fatti J. L., Smith G. C., Vail P. J., . Detection of Gas in Sandstone Reservoirs Using AVO Analysis: A 3-D Seismic Case History Using the Geostack Technique. Geophysics, 1994, 59(9): 1362-1376.

[8] Gardner G. H. F., Gardner L. W., Gregory A. R. Formation Velocity and Density—The Diagnostic Basics for Stratigraphic Traps. Geophysics, 1974, 39(6): 770-780.

[9] Greenberg M. L., Castagna J. P. Shear-Wave Velocity Estimation in Porous Rocks: Theoretical Formulation, Preliminary Verification and Applications. Geophysical Prospecting, 1992, 40(2): 195-209.

[10] Han D., Nur A., Morgan D. Effects of Porosity and Clay Content on Wave Velocities in Sandstones. Geophysics, 1986, 51(11): 2093-2107.

[11] Lu S. M., McMechan G. A. Elastic Impedance Inversion of Multichannel Seismic Data from Unconsolidated Sediments Containing Gas Hydrate and Free Gas. Geophysics, 2004, 69(1): 164-179.

[12] Mallick S. AVO and Elastic Impedance. The Leading Edge, 2001, 20(10): 1094-1104.

[13] Mallick S. Amplitude-Variation-With-Offset, Elastic-Impedence, and Wave-Equation Synthetics—A Modeling Study. Geophysics, 2007, 72(1): C1-C7.

[14] Mallick S., Huang X. R., Lauve J., . Hybrid Seismic Inversion: A Reconnaissance Tool for Deepwater Exploration. The Leading Edge, 2000, 19(11): 1230-1237.

[15] Ostrander W. J. Plane-Wave Reflection Coefficients for Gas Sands at Nonnormal Angles of Incidence. Geophysics, 1984, 49(10): 1637-1648.

[16] Santos L. T., Tygel M., Ramos A. C. B. Reflection Impedance. 64th Conference European Association of Geoscientists and Engineers. Expanded Abstracts, Florence, 2002, 182.

[17] Tsuneyama F., Mavko G. Elastic-Impedance Analysis Constrained by Rock-Physics Bounds. Geophysical Prospecting, 2007, 55(3): 289-306.

[18] Wang B., Yin X., Zhang F., . Elastic Impedance Equation Based on Fatti Approximation and Inversion. Progress in Geophysics, 2008, 23: 192-197.

[19] Whitcombe D. N. Elastic Impedance Normalization. Geophysics, 2002, 67(1): 60-62.

[20] Whitcombe D. N., Connolly P. A., Reagan R. L., . Extended Elastic Impedance for Fluid and Lithology Prediction. Geophysics, 2002, 67(1): 63-67.

[21] Xu S. Y., White R. E. A Physical Model for Shear-Wave Velocity Prediction. Geophysical Prospecting, 1996, 44(4): 687-717.