Reservoir Characterisation of the WND Field in the Niger Delta Basin, Nigeria: Background Study to Simulation

Okome, Gloria E (1998) Reservoir Characterisation of the WND Field in the Niger Delta Basin, Nigeria: Background Study to Simulation. MSc(R) thesis, University of Glasgow.

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The WND field located in the north-west proximal offshore of the Niger delta basin was discovered in 1988 and started production in 1995 with most of its oil production coming from the D-01 reservoir. The focus of this project is on the description of the D-01 reservoir and quantification of the hydrocarbon reserves and the role that the description has on understanding the reservoir performance. The integration of petrophysical data, seismic and production data has made it possible to delineate the D-01 reservoir and allowed for a better understanding of the architecture and sedimentary parameters that influence reservoir properties to optimize recovery of the hydrocarbon reserves. The aims of this research among others is to describe the reservoir, determine the oil- water contact in the reservoir, delineate the boundaries and extent of the reservoir in the field, as well as to estimate the oil reserves. Database for this project include mudlog, core, digital log curves, seismic and production data. The reservoir has been described and characterised, and this project yielded six lithostratigraphic facies associations, a depositional model, correlation cross sections through every well in the field, 2-D structure contour maps of the top and base horizons of the reservoir in time and depth, isopach and net-isopach maps, and a 3-D geologic model of the D-01 reservoir that honours all the available data for this project. The D-01 reservoir characterisation provides the geologic framework that can be used for reservoir management purposes in the WND field. Petrophysical analysis shows that the sands in this reservoir generally occur as blocky sandstone successions with minor upward fining, having moderate to high porosity and permeability, and low water saturation. Core data analysis and log interpretations have led to the identification of six lithostratigraphic facies associations for the sediments in this reservoir. It was discovered that the reservoir is made up of barrier bar sandstones (characterised by a coarsening upwards of grain size) and prodelta marine shales (exhibiting fining upward log trend) deposited in a prograding wave dominated middle-lower shoreface to prodelta environment. The marine shales deposited in the low energy environment hardly have any porosity and permeability, while the sandstone deposited in the higher energy environment are mostly found in the upper part of the sequence intercalated with very thin shale beds, and they turned out to be the best reservoir facies. Well-to-well correlation shows that the sands have good lateral continuity and the shale interbeds are not extensive laterally to act as vertical permeability barrier. The delineation and mapping of the extent of the D-01 reservoir in the WND field was done from seismic inteipretations made. 2-D and 3-D grids were constructed from which structure contour maps for the top and bottom of the reservoir were constructed. Isopach maps were also constructed for the gross reservoir thickness and net thickness defined by the oil-water contact. Interpretations from these contours show that the D-01 sands tend to develop more in the middle part of the field, this area is a good development target. Results of petrophysical analysis and seismic interpretations were integrated with available production data to construct a 3-D geological model that honours all the available data for this project. Recoverable estimates carried out compared with the available production shows that there is still 52,332,620 barrels of oil left in the reservoir to be recovered.

Item Type: Thesis (MSc(R))
Qualification Level: Masters
Additional Information: Adviser: G D Couples
Keywords: Petroleum engineering, Geological engineering
Date of Award: 1998
Depositing User: Enlighten Team
Unique ID: glathesis:1998-75428
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 19 Nov 2019 20:09
Last Modified: 19 Nov 2019 20:09

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