Seismic Stratigraphy of X-field in the Niger Delta

James Chijioke Ukachukwu
University of Nigeria, Nsukka, Nsukka, Nigeria

The application of Seismic Stratigraphy in the Niger Delta made it possible to differentiate the three diachronous lithostratigraphic units (the Akata, Agada, and Benin Formations) in the subsurface of the Niger Delta. Three-dimensional (3-D) seismic sections of X-field in the Niger Delta reveal the internal geometry and depositional history of the tertiary sediments in the field. The X-field comprises the middle Miocene to late Pliocene super sequence. The super sequence is subdivided into sequence sets 1, 2 and 3.

Sequence set 1 (middle Miocene) comprises a prodelta sequence. Seismic reflection characteristics and well log data show that sediments must have been deposited in a marine environment. Sequence set 2 (late Miocene to early Pliocene) comprises of a sandy progradational sequence characterized by complex growth faulting. Evidence from well logs and seismic reflection characteristics show that sediment must have been deposited in a transitional environment. Sequence set 3 (Late Pliocene) is a progradational succession, representing a deltaic plain deposit. Well logs and evidence from biostratigraphic data shows that Sediments must have accumulated in a continental environment.

These three sequence sets forms a generally complex regressive offlap sequence of clastic sediments. Rapid sediment supply and shale tectonism must have resulted in the complex growth faulting nature of the delta. The growth faults indicate good trapping mechanism for the reservation of hydrocarbons. Sequence and facies mapping, well correlation and evidence from Biostratigraphic data suggest that the Niger Delta has an excellent reservoir potential.