Sequence Stratigraphic Interpretation of XY-Field Onshore Niger Delta Basin Nigeria

C.E Okpala,T.A Ibitoye,O.W Osisanya,F.C Ighrakpata,A.S Saleh

doi:10.4314/jasem.v25i12.2

Abstract

Wireline logs and biostratigraphic data were integrated to attempt the sequence stratigraphy of “XY field” onshore Niger Delta Basin which revealed three depositional sequences. Four sequence boundaries and three maximum flooding surfaces dated (17.7, 16.7, 15.5, and 13.1Ma) and (17.4, 15.9, 15.0 Ma) respectively were identified in both Wells. The delineated sequences comprised Lowstand Systems Tracts (LST), Transgressive Systems Tracts (TST) and Highstand Systems Tracts (HST), which reflect depositional systems deposited during different phases of base level changes. The sands of LST and HST show good reservoir qualities while the shales of the TSTs could form potential reservoir seals. Integration of lithofacies and biofacies data suggests that the depositional environments ranges from transitional to Outer Neritic environment.

Highlights

MATERIAL AND METHODSThe interactive Schlumberger petrel software package (2013 version) was used for the analysis of well log data, while the stratabug software was utilized in the analysis of the biostratigraphic data
For several decades, majority of the geoscientific research carried out in the Niger Delta Basin, focused mainly on the lithostratigraphy and tectonic framework of the area which is why very few published research work on the sequence stratigraphy of wells in this area exist
With increasing interest in the Niger delta basin as a result of its great economic potential, there is need for more detailed understanding of the sequence stratigraphy of the existing wells to enhance correlation between these wells thereby reducing the risks involved in hydrocarbon exploration which may arise as a result of insufficient data

Summary

MATERIAL AND METHODS

The interactive Schlumberger petrel software package (2013 version) was used for the analysis of well log data, while the stratabug software was utilized in the analysis of the biostratigraphic data. A bell shaped log indicates increasing clay content (fining upward trend) which denotes an upward increasing gamma ray value and characteristics of fluvial deposits to transgressive facies It reflects upward decreasing depositional energy i.e. backstepping/ retrograding shoreline (Figure 4) (Emery, 1996). Basin floor fan (BFF): This is characterized on the gamma ray and resistivity logs by a blocky pattern (Figure 6) with relatively few breaks (unamalgated turbidite sand). It contains massive turbidite sand with the upper boundary characterize by hemi pelagic shale of channel over bank apron facies which forms a minor condensed section associated with peak abundance and diversity of deep water fauna.

AND DISCUSSION

Conclusion