available ccpy to permit the broadest possible availaitiiity.

In this paper, an empirical method that enables estimation of a critical choke, and corresponding production rate beyond which there is a high risk of early water breakthrough, is proposed. The method involves the plot of the log of the average of well test rates at various choke settings. All the reservoirs investigated in this manner indicated a characteristic hump shape with some notable features. Hence characteristic reservoir models corresponding to selected Niger Delta reservoirs were developed and validated with well tests of recent drills. Furthermore, a theoretical justification for this observation was realised by applying a slight mathematical manipulation of the Gilbert's correlation, which relates surface production with the choke. Finally, deductions from the correlation yielded a twophase flow shift factor that can be used to match Gilbert's correlation to actual performance.

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