SEISMIC PROCESSING OF U.S. EAST COAST DATA

Abstract

Seismic method is the mainstay of geophysical exploration. The main reasons for its success include its accuracy, the depth of penetration and the ability to generate high resolution image of subsurface, while being relatively economical at the same time. The present study uses the technique to study the subsurface structure and the geometry of reflectors across the eastern edge of North American shelf off the coast of U.S. The continental shelves are hotbeds for oil and gas exploration; and hence, here we would try to identify possible traps within region. Our area of interest includes two large sedimentary basins that underlie the said region, the Carolina trough and the Blake Plateau basin. Each of them marks a distinct geological province. The Carolina trough is dominated by a terrigenous-clastic depositional regime, whereas the Blake Plateau is transitional into a carbonate-platform depositional regime. Three profiles (lines 30, 31, and 32) were chosen such that they run across the shelf which would allow us to study the cross sectional view of the region. The obtained dataset is without geometry information and is heavily contaminated by reverberations and back-scattered noise. We first start by merging geometry information, editing out bad traces and correcting for geometric spreading, collectively termed as pre-processing. Then a series of filters, including deconvolution, dip filtering and radon transform, were applied to attenuate coherent noise. Deconvolution would also help in increasing the temporal resolution. Velocity analysis was performed and number of velocity models tested; and the best suiting one was used to migrate and finally stack the dataset. In the end, some final conditioning was done to further enhance the reflectors. We have observed three major reflectors in all the studied profiles, with many minor ones present in between. A major fault can be seen in the seismic section of line 32, which may favour formation of some minor structural traps. An amplitude shadow resembling gas chimney effect is also observed, which points toward a possible gas deposit in the region. The on-laps and off-laps evident in all three profiles are indicative sea-level changes