Estimating Anisotropic Parameters from PP and PS Data - A Case Study

摘要

Anisotropic parameters are estimated using PP and PS converted-waves data. The data were acquired by digital MEMS (micro-electro-mechanical system) sensors over a volcanic gas reservoir in Northeast China with a mixed sand and shale sequence in the overburden. This gives rise to shear-wave splitting as well as anisotropic moveout effects. We find that the amount of splitting determined from the data can be correlated to the known gas reservoirs, revealing a potential for using shear-wave splitting to delineate gas reservoirs in volcanic rocks. Furthermore, we use a four-parameter theory to evaluate the effects of non-hyperbolic moveout due to an asymmetric raypath and transverse isotropy (TI). These four parameters include the PS converted wave stacking velocity (V_(C2)), the vertical velocity ratio (γ_0), the effective velocity ratio (γ_(eff)), and the anisotropy parameter (χ). This four-parameter theory leads to an improvement in imaging quality and correlation between the P-waves and converted-waves.