2.Production Capacity

The following is a simplification of procedures for predicting well performance. This discussion assumes a flow efficiency of one. A damaged well or other factors will effect the flow efficiency and could change the well's productivity. Productivity Index When the well flowing pressure (Pwf) is greater than bubble -point pressure (Pb) the fluid flow is similar to single phase flow, and the inflow performance curve is a straight line with slope J,as given by the productivity index, PI:

Where:

Q = the fluid test production rate.

Pwf = the well flowing pressure @ test rate Q.

Pr = the well static pressure.

Note: Pr and Pwf are terms which are always referenced to the same  specific vertical depth.

Inflow Performance Relationship

If Pwf is less than Pb, resulting in multi-phase flow, the IPR method should be used. The relationship is given by the following equation

This relationship was first used by W.E. Gilbert1 and further developed by J.V. Vogel2. Vogel developed a dimensionless reference curve that can be used to determine the IPR curve for a particular well.