Evaluating Reservoirs For Secondary Recovery (Waterflooding), A Case Study of Nigerian Reservoir with Computer Aided Approach

Ubon S. Usen, Uju M. Ezendu, and Michael A. Osuagwu
University of Port Harcourt, Port Harcourt, Nigeria

The initial production of hydrocarbons from the underground reservoir is accomplished by the used of natural energy and is referred to as primary production.

Recoveries by natural drive mechanisms rarely exceed 30 to 40% and are often lower for oil reservoirs. This is why the need soon appeared to inject energy into these reservoirs to achieve better recovery.

The first processes employed waterflooding (Injection of water) named secondary recovery whose main purpose is to maintain the reservoir pressure but the initial oil operators based the prospect of waterflood of a field on analogy and rule of thumb which have great limitations and can be misleading.

This paper work shows that the use of "Analogy and Rule of Thumb" in evaluating prospects of waterflooding is faulty. So with modern reservoir engineering which enables us to determine the range of reservoir conditions which will result in favourable responds to waterflood efforts, and also to delineate the range of conditions under which waterflooding will be of doubtful success aided this research work.

It was observed from this research that the prediction of recovery rate in waterflooding is becoming increasingly important and studies show that two factors affects the success or failure of a waterflood to a much greater degree than all others. These factors are, in the other of importance, total cumulative waterflood recovery and rate of recovery.

In this study, the limit of the variation of the variable responsible for success or failure of waterflood in reservoirs are determined and empirical method, which is based on the performance 86 successful Oklahoma waterflood, is used in predicting the performance of the reservoirs during waterflooding. A standard computer program (Using Microsoft Visual Basic 6.0) that evaluates the prospect of waterflooding is developed.