Reflection Full Waveform Inversion of Walkaway VSP – Abu Dhabi Case Study

Summary Applying FWI to borehole seismic data has a potential to be a helpful solution for various challenging situations as it gives us quantitative elastic properties in high resolution image. In this study, we conducted data pre-processing and isotropic acoustic FWI on the walkaway VSP acquired in very limited receiver’s geometry. In the pre-processing, general processing was conducted such as removal of random noise and PS converted wave, surface consistent amplitude correction and deconvolution. In addition to that, the polarity of up-going reflection in vertical component of geophone were flipped and the horizontal component was merged with vertical component to be consistent with the wavefield estimated in acoustic FWI. In the FWI, a part of gradient which is the contribution from all of downgoing wave was muted for positive use of up-going reflections because the target signal is only existing in the up-going reflection. The result of this study provided highly accurate and resoluble Pwave velocity image. The vertical resolution about 30 feet seems to be achievable. This study demonstrated well the high potential of FWI on borehole seismic for dealing with the various challenging situations.