1.1 DESCRIPTION OF PROBLEM
Produced water is any water that is present in a reservoir with the hydrocarbon resource and is produced to the surface with the crude oil or natural gas. This water could either come from an aquifer or from injection wells in water flooding process. The production of this water alongside the oil from any reservoir is a condition that is natural in all reservoirs. It is expected that water production would increase with the life of the reservoir. However, a premature increase in the production of water in any reservoir is an undesirable condition. Excess or premature water production, exists with associated cost implication on the surface facilities, artificial lift systems, corrosion and scale problems. Another effect that ensues is a decrease in the recovery factors as oil is left behind the displacement front, thereby reducing the performance of the reservoir. All these along with the decrease in the quantity and quality of the oil imply a reduced profitability.
Globally, as at 2002, analysis showed that three barrels of water is produced to one barrel of oil and the cost of water handling ranges from 5 to 50 cents, where this cost is a function of the water cut (Bailey et al, 2000). It is therefore imperative that actions be taken to reduce this adverse effect, as this will not just lead to potential savings but its greatest values comes from potential increase in oil production and recovery. To control the produced water effectively, the source or the mechanism of the water problem must be identified. Diagnostic plots have been used successfully to identify the mechanism of water production and that is the focus of this work.
1.2 STUDY OBJECTIVES
Reservoir simulation would most likely describe a reservoir adequately but a quicker and cheaper way to analyse the performance of a reservoir is by the use of analytical and diagnostic plots, therefore, this research work is aimed at:
· Developing a work flow for the evaluation of water production mechanisms.
· Presenting the workflow by considering detailed step by step approach on how water production problems in the reservoir can be diagnosed to support water management planning for mitigation actions.
· The use of a couple of case studies to demonstrate the application of the workflow and diagnostic plots to identify water production characteristics.
· Formulating guidelines on how to mitigate water production and thereby optimizing well performance and oil recovery.