Characterization of Gas Clouds Using Non-linear Full Waveform Inversion

Abstract

Due to complex wave propagation, anelastic losses, multiple scattering and strong contrast, it becomes a belief that gas cloud area especially the overburden is not invertable. In this paper we demonstrate that the so-called overburden gas cloud is invertable using non-linear full waveform inversion; Case study shown are based on synthetic and field data example from Malaysian basin. In our inversion strategy, we aim to invert the gas cloud overburden reflectivity response to achieve an effective medium representation which will be implemented in the full waveform redatuming method (see companion paper, Ghazali 2013). The depth interval to be inverted is shallow and the purpose of the inversion was not to have a full quantitative interpretation of the shallow overburden, but only to describe the overburden in terms of properties in a way sufficient to derive full waveform redatuming operators that remove the overburden imprint on the deeper targets (Ghazali et al., 2009; Ghazali, 2011). The actual derivation of the redatuming operators is not within the scope of this paper