Stratigraphic Interpretation Using Seismic Reflection and Well Log Data of ‘OGEY’ Field, Niger Delta, Nigeria

Abstract

The stratigraphic interpretation of ‘OGEY’ Field, deep offshore Niger Delta, Nigeria was carried out with a view of correlating the subsurface facies and deducing the environments of deposition of the field. This was done by using the concept of sequence and seismic stratigraphy. The data available and used for this study include digital 3-D seismic, well logs, biostratigraphic information and check shot data. Lithological identification was done with the aim of differentiating the shale and sandstone lithological units. This process was carried out using the gamma ray and resistivity logs. The reservoir sands were correlated across the wells after defining the reservoir's depositional environment to monitor their lateral continuity and probable structures within the well coverage area. The well log data was also tied with seismic sections for accurate geologic interpretation. Seismic facies analysis was done by combining the geometric information with the seismic attributes. The lithologies identified are sand, sandy shale and shale, respectively. The sequence boundaries identified were dated 20.4Ma, 17.7Ma, 15.50Ma, 12.10Ma and 10.35Ma while the Maximum Flooding surfaces were dated 19.4Ma, 15.9Ma, 12.80Ma, 10.4Ma, and 9.6Ma respectively. The result revealed three system tracts, which are LST, TST and HST, which indicated five depositional sequences. Four seismic sequences were observed in this field and they are SF1, SF2, SF3, and SF4. The environment of deposition for the field is deep offshore with depositional units ranging from turbidite sand to sheet sands, channel levee and overbank complex, canyon fills and mass transport deposits. The study concluded that the stratigraphic features of the field could be used to reevaluate the prospects and improve the production.