Salt Dome Caused Distortion of Seismic Reflection and Approaches to Eliminate Its Effects

The tremendous wave transit velocity difference between salt rock and its surrounding rock causes seismic reflection distortion for formations beneath it on seismic section in time domain, leading to fake structures and fake faults to be interpreted. By the aid of forward modeling, effects caused by the variation of salt thickness, wave transit velocity and existence of low velocity interbeds inside salt dome on seismic reflection under salt dome are analyzed. The case study of Zhanazhol oilfield about how to eliminate effects of seismic reflection distortion caused by salt dome during seismic interpretation are presented, in which these effects are eliminated through proper time-depth conversion with an average velocity field built based on stack velocity replacement with velocity calculated from VSP data and nearby synthetic seismograph.