**Conflict of interest**

*Sedimentary Processes - Examples from Asia, Turkey and Nigeria*

cially for production wells proximal to the injectors.

**5. Conclusions**

The continued water injection through the injector wells in the field could be another source of water production which has adverse effect on oil recovery espe-

The oil rate, Qo, as well as the liquid rate declined at the onset of water production in 2001 and afterwards liquid rate had remained constant at different choke sizes. The oil rate declined further as water cut increased (**Figures 15**–**18**). The total cumulative oil production as at January 2011 is about 67.18 MMSTB; this represents 43.91% recovery factor. However, there is still recoverable oil remaining in the reservoir, which can

The conclusions drawn based on the results of this study are as stated below:

1.The key geological factors that aided fluid mobility especially vertical flow include: environments of deposition, rock properties, lateral continuity of reservoirs, limited and negligible shale barriers in the N5.2 sand, and network of fractures. Reservoir properties of N5.2 sand show that the facies is highly homogenous and exerts a greater impact on fluid flow across the reservoir. The results of anisotropy due to permeability within facies on oil production increases with vertical flow potential. Fracture networks created anisotropic condition in the reservoir resulting in dominant vertical flow created by vertical fracture permeability. The major drive mechanism in the field is water; vertical fracture permeability would have created a high mobility ratio resulting in both the injected and displacing fluid breaking through earlier at the producer sand.

2.A significant coning effect is observed where there is rapid increase in choke

3.Increase in vertical fracture permeability resulted to early breakthrough and

4.Geological conditions (fractures and excellent reservoir quality) and poor reservoir management accounted for high fluid movement as well as high

5.Seismic time-slicing methodology remains the approach to display the various seismic attributes, and useful in: identification of facies, selecting the best

aquifer-supported reservoirs and is aggravated in a fractured reservoir system.

drilling locations, and measuring the architecture of a reservoir.

6.Water coning effect is a significant reservoir phenomenon that occurs in

7.A synergy of a comprehensive geological and engineering investigation is a must at every stage in field development. It will provide full information

The platform for this research was provided by the O.B. Lulu Briggs Chair in Petroleum Geoscience at the Institute of Petroleum Studies, University of Port

size. It increases breakthrough time and decreases oil rate.

reduces oil rate after breakthrough.

needed to understand the subsurface.

watercut in the field.

**Acknowledgements**

only be recovered if certain field operational conditions are considered.

**24**

There is no conflict of interest in this research work.
