Seismic stratigraphy and attribute analysis of an offshore field, Niger Delta, Nigeria

Three-dimensional seismic and composite well log data from three wells were used to carry out log sequence/seismic stratigraphy and attribute analysis of an offshore field Niger Delta. The gamma ray and resistivity logs were used to delineate the reservoir sand bodies and carry out sequence analysis. From the log sequence analysis, two depositional sequences were delineated in wells 1 and 2 from 1,820 to 3,020 m and 1,860 to 3,000 m, respectively. The two depositional sequences were mapped on the seismic section at time windows 3.3 and 2.92 s for sequence 1, and for sequence 2 at 2.92 and 2.0 s, respectively. Time slice maps of sweetness attribute were generated to further investigate the hydrocarbon prospect of the field. The seismic facies analysis shows that the depositional setting in depositional sequence 1 is characterized by sheet- to lens-shaped variable amplitude and chaotic reflection characters while depositional sequence 2 is characterized by (i) sheet-like shaped medium to high amplitude, subparallel, continuous reflections, (ii) wedge-shaped low-to-medium amplitude, wavy, continuous reflections, and (iii) wedge-shaped high-amplitude, wavy, continuous reflections. Results from the seismic stratigraphy show that the depositional environment has prograded from the delta platform (delta front) in depositional sequence 2 down to the wave-dominated prodelta/slope (depositional sequence 1) in the shallow marine of the deltaic environment. The reservoir quality sand bodies within this field occur within the depositional sequence 2 and occur within all the systems tracts in this sequence.