Reservoir characteristics and palaeo depositional environment of Duski Field, onshore, Niger-Delta, Nigeria

Matthew E Nton,Salami Rotimi

doi:10.4314/gjgs.v14i1.5

Abstract

The Niger Delta is a prolific hydrocarbon producing belt in the southern Nigeria sedimentary basin on the continental margin of the Gulf of Guinea. This study used well log suites to delineate the hydrocarbon reservoirs, depositional environments and lithostratigraphy of the Duski Field, Onshore Niger Delta, Nigeria. A comprehensive interpretation of the three wells revealed five (5) reservoir units with low volume of shale and thickness variations between 24m and 60.20m. The average porosity values ranged from 12% to 34%, with high hydrocarbon saturation in all the reservoir sands. Generally, porosity and permeability values decrease with depth in all the wells. Cross-plots of water saturation (Sw) and porosity ( o ) (Buckles plot) revealed that some reservoirs were at irreducible water saturation; hence producing water-free hydrocarbons. Therefore the hydrocarbon accumulation of this field is commercially viable and promising. This study revealed that the reservoir sand units were deposited within marginal marine depositional environment which include fluvial channel, transgressive marine, progradational and deltaic settings. Keywords: Reservoir characteristics, depositional environment, Niger Delta

Highlights

The Niger Delta Basin occupies the Gulf of Guinea continental margin in equatorial West Africa between Latitudes 30 and 60 N and Longitudes 50 and 80 E
From the cross-plot of porosity vs water saturation (Fig.7), most of the points plotted along the hyperbolic curve and this implied that reservoir sand 1 in well A1 is at irreducible water saturation and the bulk volume of water (BVW) is at constant value of 6.39%; minimal quantity of water will be produced with hydrocarbon (Morris and Biggs, 1967)
The analysis revealed that the bell-shaped successions are thin, which may suggest that the sands were deposited in a transgressive marine setting

Summary

Introduction

The Niger Delta Basin occupies the Gulf of Guinea continental margin in equatorial West Africa between Latitudes 30 and 60 N and Longitudes 50 and 80 E. Such include; gamma ray log (lithology identification), volume of shale log (porosity correction), density and neutron logs (delineating fluid contacts), resistivity and water saturation logs (identifying pore fluid type). High deep resistivity readings corresponding to sand units indicated hydrocarbon bearing or freshwater zones while low deep resistivity readings, showed water bearing zones (Schlumberger, 1989).Usually, a definite identification of fluid type contained within the pore spaces of a formation is achieved by the observed relationship between the Neutron and Density logs.

Results

Conclusion