The sigma processing of seismic data has already proven its capability to remove noise and separate waves on pre and post stack seismic data (Piriac & al 2010, Gronwald & al 2009). In order to further validate this new technology for assessing the quality and performance of a seismic data processing step, we show in the following the first results of a case study currently underway on the AVO processing of pre-stack data on the Forties field (UK). The preconditioning of pre stack gathers (AVO noise reduction) requires a particular attention so that the amplitude versus offset relationship is not impacted before the AVO analysis (AVO consistency). This is verified with the sigma processing workflow that is presented below and this opens the way to the quality assessment and optimization of the derivation of the AVO attributes.