Reprocessing of line FFI-161 of the Brazos-Galveston area using Pro-MAX 2D to evaluate migration techniques

Abstract

ProMAX 2D, a software for the interactive and batch processing of two dimensional seismic data, was used to process approximately 25 km of seismic data from line FFI-161 of the Brazos-Galveston area of the Gulf of Mexico. The main objectives were to process the data to obtain optimum velocities that are good for stacking and migration, and to produce and compare migrated sections using different migration schemes. The dip moveout (DMO) process was incorporated in the processing stream to improve the velocity estimates. The DMO process was not very successful for two main reasons: the velocity gradients at shallow depth were too large and the deeper part of the section lacked large dips and continuous reflectors. Three migration algorithms namely, Memory Stolt F-K (a transform method), Kirchhoff Time (a summation method), and Fast Explicit FD Time (a finite-difference method), were used to migrate the stacked data. All three migration algorithms performed well in broadening the synclines in the section, defining fault ten-ninations and collapsing diffractions from faults. The fault terminations on the section produced by the Fast Explicit FD Time algorithm were better defined but the section suffered from smearing. Comparison of the sections produced by the Kirchhoff Time and the Memory Stolt F-K migration schemes revealed that the performance of the two schemes was the same for the same events on the stacked section except that the section from the Memory Stolt F-K was less noisy. The Memory Stolt F-K algorithm produced a section with the best picture contrast and was found to be the least computationally expensive. It is over 100 times faster than the Kirchhoff Time and over 25 times faster than the Fast Explicit FD Time. The Memory Stolt F-K algorithm using a stretch factor of 0.6 is the most suitable for line FFI-16 1.