Salt flank delineation by PS interferometric imaging

Abstract

We present the method of PS interferometric imaging (II) for delineating the flank of a salt dome from VSP data. Unlike traditional migration methods, interferometric PS imaging does not require the migration velocity model of the salt or upper sediments in order to image the salt flank. Synthetic elastic examples show that PS II can clearly delineate the upper and lower salt boundaries of a realistic salt body model. Results show that PS II is noticeably more accurate than the conventional migration method in the presence of static shifts and/or migration velocity errors. However, the illumination area of the PS transmitted waves is limited by the shot and geophone aperture. Thus wide shot offsets and deeper receiver wells are needed for comprehensive salt flank imaging. Interferometric imaging results for VSP data from the Gulf of Mexico demonstrate its superiority over the traditional migration method. For comparison, reduced time migration results are also presented, which are similar in quality to those obtained for interferometric imaging. We conclude that PS interferometric imaging of VSP data provides the geophysicist with a new tool by which to view salt flanks from both above and below the VSP geophone locations.