Application of 2D elastic full waveform inversion to walkaway VSP data from a carbonate reservoir

To obtain high resolution P-wave and S-wave velocity models, 2D elastic full waveform inversion (FWI) was applied to a line extracted from a 3D walkaway VSP data, acquired in an oilfield offshore Abu Dhabi, in the United Arab Emirates. After pre-processing, the data were band-pass filtered with a minimum frequency of 3.5 Hz, and a maximum frequency of 20 Hz. A sequential inversion approach was used to mitigate non-linearities. The pre-proccessing of the data consisted in the removal of bad traces, followed by amplitudes and phase corrections. High resolution P-wave and S-wave velocity models that show good correlations with the available sonic logs were obtained. The geological interpretation of the results suggests that the area is made of a stack of layers associated with variation in lithology, and potentially in fluid content for some layers.