5TH International Congress on Technology - Engineering & Science - Kuala Lumpur - Malaysia (2018-02-01)

P-wave Reflection Coefficient For A Vti/vti Interface

Amplitude variation with offset (AVO) has become a commonly used seismic attribute in the petroleum exploration to reveal the lithology and estimate pore fluids underground. However, strata usually exhibit velocity anisotropy, thus the effect of anisotropy must be taken into account when applying the AVO analyzing. Rüger’s approximation of the P-wave reflection coefficient equation for a VTI/VTI interface is accurate and full of physical meaning with linear expression, now it is wildly used in oil industry. Based on Rüger’s approximation, a new anisotropic term of the P-wave reflection coefficient equation for a VTI/VTI interface is been derived in this study. The new derived anisotropic term is only function of the incident angle dependent phase velocity of P-wave. Both the new derived and Rüger’s approximations fit the exact solutions well for cases of the positive high and positive low acoustic impedance contrasts across the interface. For the case of the negative high acoustic impedance contrasts across the interface, the new derived approximation is better than Rüger’s approximation, since the new derived approximation weakens the influences of the anisotropic parameters delta and epsilon in the P-wave reflection coefficient thus reduces the overestimation of Rüger’s approximation. In addition, this new derived approximation has a simple and direct physical meaning which is useful in understanding the influence of anisotropy on the AVO response. Thus, a new, effective, simple and direct approximation for calculating the P-wave reflection coefficient for a VTI-VTI interface is proposed conclusively.
Young-Fo Chang, Jia-Wei Liu