Seismic imaging of mud volcano boundary in the east of Caspian Sea by common diffraction surface stack method

Abstract

The problem of seismic imaging in complex structures such as folded faulting areas, salt domes, or mud volcano-bearing areas cannot be properly solved by the conventional seismic processing methods. The reverse time migration, Gaussian beam migration, the extended search strategy in the optimized common reflection surface (CRS) stack, and the partial CRS stack methods are among the new methods introduced for seismic imaging in complex structures. Among them, the CRS stack method is frequently used for seismic imaging. However, besides its great advantage in enhancing the quality of seismic section, it faces with some problem in imaging of complex structures, especially in the existence of conflicting dips. The CRS method transforms pre-processed multi-coverage data into a zero-offset section by summing along stacking surfaces instead of only along a common reflection point trajectory. The extended parameter search strategy in the CRS method and the partial CRS stack method were introduced to solve the problem of conflicting dips in the CRS method. However, some examples showed that these methods could not completely solve the problem of conflicting dips. In this study, a new introduced method is used to completely solve the problem of conflicting dips in complex structures. The new stacking surface is the approximation of diffraction response of a diffraction point. The surface is made by well-known three CRS attributes, where the radius of normal and normal incidence point waves is equals. The third parameter is the emergence angle of the central ray that the stacking surface is built for each angle, thus making an operator volume. Therefore, the operator gathers more energy that might get lost by other stacking surfaces. The new method was applied on a seismic data from a complex geological structure from northeast of Iran. This area contains mud volcano, an indicator for gas reservoir. Mud also absorbs the seismic energy and deteriorates the quality of the seismic section. Therefore, imaging the boundary of the mud volcano is questionable. By applying post-stack time migration on the stacked section obtained by the new method, the advantage of the stacking operator has been evaluated for imaging in complex structures. These advantages were more highlighted in depth migration applied on the new introduced operator volume common diffraction surface (CDS)-stacked section. The results showed that not only the boundary of the mud but also the faults that were completely unclear in previous results were imaged well.