Long offset seismic data acquisition in shallow water allows the use of complex seismic tomography technology for gasfield prediction. The technology is based on the a complex processing of refracted and reflected waves. The effectiveness of the complex seismic data processing was evaluated on a test model and on seismic data acquired in a shallowwater zone of Ob Bay. Low velocity anomalies detected with seismic tomography correspond to anomalous dynamic parameters of seismic data and morphological evidences within this explored gasfield.