Application of sequence stratigraphy to Neritic sediments of the Niger delta

Sequence stratigraphy is an approach to correlation that emphasizes regional unconformities as the basis for subdividing sediments into time-equivalent packages called sequences. In Chevron's acreage in the northwestern Niger delta, three-dimensional (3-D) seismic data have been used to map each sequence-bounding unconformity based on the presence of a submarine canyon near the paleoshelf edge. Erosion lateral to each canyon is slight or even absent. Useful criteria for recognizing sequence boundaries in 3-D seismic data in neritic sediments of the niger delta are (1) truncation of underlying reflections, (2) drape, dip discordance, or onlap of younger reflections over topography on the sequence boundary, (3) contrast in seismic attributes across the sequence boundary, and (4) termination of faults at the sequence boundary. Published criteria for recognizing sequence boundaries from logs and paleontological data are being adaped to the Niger delta, where high-frequency fourth-order sequences are strongly developed. Identifying and mapping sequence boundaries is beneficial because sequence boundaries (1) may form truncation traps where shales of the younger sequence overlie truncated sands of the older sequence, (2) assist correlations across faults, (3) subdivide the section into units of genetically related sediments, and (4) provide an objective basis for regional correlations.