A comparison of the classical OWWE migration methods: analysis of feasibility in subsalt plays exploration

Subsalt seismic imaging is particularly difficult due to the complex overburdens, caused by the movement of salt that usually results in steeply dipping structures, which along with strong lateral velocity contrast at the sediments-salt interface distort the structural position and the stratigraphic resolution of the subsalt reservoirs. Despite it was proven that two-way wave equation migration provides the best results illuminating these reservoirs, it has huge computational cost, especially in three dimensions. One-way wave equation (OWWE) migration techniques are good alternative in this case as providing the acceptable quality of seismic sections with an appropriate computational cost. To know the advantages and limitations of the OWWE techniques in subsalt imaging, three classical OWWE algorithms were evaluated for depth migration of prestack data (PSDM): phase-shift-plus-interpolation (PSPI), split-step Fourier (SSF), and Fourier finite-difference (FFD). These algorithms were tested with three different fully elastic synthetic models which simulates the structural complexity showed in subsalt plays. It was concluded that FFD gives very accurate results when the lateral velocity variation was strong with acceptable computational cost. The PSPI provided the best quality results but required about twice the computer time needed for FFD, and SSF was the fastest but clearly the least accurate.