UTILIZATION OF NODAL ANALYSIS TECHNIQUE FOR SELECTING THE OPTIMUM TUBING SIZE TO ACHIEVE AN OPTIMUM PRODUCTION RATE IN NATURALLY FLOWING WELL VIA MODELLING
1.1 BACKGROUND OF STUDY
Naturally flowing well is a well in which the formation pressure is sufficient to produce the oil at a commercial rate to the surface without requiring a pump. Most reservoirs are initially at pressures high enough to allow a well to flow naturally. In other words, it is a well that can flow to the surface unassisted. However, during the well‘s life, pressures will drop to a point where it will no longer flow by its own accord. At this point, methods including artificial lift and enhanced oil recovery (EOR) will be employed to ensure the maximum reserves are recovered.
Based on this project, a natural flowing well is going to be focused upon. Naturally flowing wells normally use the energy inherent in the reservoir. This is referred to as the reservoir drive mechanism. The drive mechanism of the reservoir affects some of the fluid properties such as the gas oil ratio (GOR), water oil ratio (WOR) and parameters like the reservoir pressure and the flowing life span.
1.1.1 DRIVE MECHANISMS FOR NATURALLY FLOWING WELLS AND THEIR RESPECTIVE CHARACTERISTICS.
- Water drive: A substantial percentage of petroleum reservoirs worldwide produce under water drive mechanism. In water drive, the energy responsible for production comes from the expansion of the aquifer underlying the reservoir. In some cases, water drive also results from the expansion of unknown hydrocarbon trapped within the aquifer or the expansion of connate water within the reservoir.
Characteristics of water drive
a) The reservoir pressure is high and fairly constant over a long period of time.
b) The GOR is low and fairly constant.
c) The production of water is fairly high.
d) The well has a long flowing lifespan.
e) Produces mostly under saturated oil and no gas at the wellbore.
f) It has a straight line IPR.