Converted wave AVO inversion for average velocity ratio and shear wave reflection coefficient

Abstract

Based on the empirical Gardner equation describing the relationship between density and compressional wave velocity, the converted wave reflection coefficient extrema attributes for AVO analysis are proposed and the relations between the extrema position and amplitude, average velocity ratio across the interface, and shear wave reflection coefficient are derived. The extrema position is a monotonically decreasing function of average velocity ratio, and the extrema amplitude is a function of average velocity ratio and shear wave reflection coefficient. For theoretical models, the average velocity ratio and shear wave reflection coefficient are inverted from the extrema position and amplitude obtained from fitting a power function to converted wave AVO curves. Shear wave reflection coefficient sections have clearer physical meaning than conventional converted wave stacked sections and establish the theoretical foundation for geological structural interpretation and event correlation. The method of inverting average velocity ratio and shear wave reflection coefficient from the extrema position and amplitude obtained from fitting a power function is applied to real CCP gathers. The inverted average velocity ratios are consistent with those computed from compressional and shear wave well logs.

An Improved Scheme of Frequency-Dependent AVO Inversion Method and Its Application for Tight Gas Reservoirs

“…The amplitude versus offset (AVO) is one of the most widely used geophysical techniques to predict oil and gas reservoirs [1]. Since Ostrander [2] developed the AVO technique to identify "bright spot" reservoirs, many scholars have studied AVO extensively and got many successful cases [3][4][5][6][7][8][9]. AVO approaches mentioned above are based on the assumption that subsurface rocks are elastic.…”