Joint Solution for Improving Subsalt Imaging Using 3D Gravity and Seismic Data

Pre-stack depth migration (PSDM) is one of the most important technologies for accurate subsalt structure imaging. However, in the case of huge salt domes and low signal-to-noise ratios (SNR) of subsalt data, the key to accurate imaging of subsalt structure using PSDM is to establish an accurate velocity model. This paper presents a joint solution of 3D gravity and 3D seismic data. The SNR of seismic data above the several huge salt domes in the area is high, while the SNR below the salt domes is relatively low. Since the target is below the salt domes, the PSDM data can’t meet the needs of subsalt structure interpretation. We therefore carried out 3D gravity exploration to solve subsalt structural imaging accuracy problems jointly using 3D gravity data and 3D seismic data. Using the inversion result of 3D gravity formation separation, the cause of clutter in seismic reflections on the interior of salt domes is illustrated and the initial velocity model provided by 3D seismic data is revised in the study area. Through this revised initial velocity model, a new pre-stack depth migrated section with improved subsalt reflection SNR as well as better subsalt structure imaging is achieved. Along with the work flow of joint solution of gravity and seismic data, this paper also gives prerequisites for formation separation technique.