Page 243 - Standard Handbook Petroleum Natural Gas Engineering VOLUME2

212 Reservoir Engineering

0 0.2 0.4 0.6 0.8 1.0
RATIO: OIL PRODUCING RATE TO MAX. RATE, q , FRACTION

Figure 5-130. Vogel IPR curve [224].

reservoir. When a zone of altered permeability exists near the wellbore, the
degree of damage (or improvement) is expressed in terms of a “skin effect” or
“skin factor.” (Skin effect will be discussed in more detail later.) A modification
to Vogel’s IPR curves has been proposed by Standing [225] for situations when
a skin effect is present (see Figure 5131). In this figure, Standing has provided
a series of IPR curves for flow efficiencies between 0.5 and 1.5, where flow
efficiency ,(FE) is defined as:
-
FE = P-Pwf-AP‘
-
P-Pwf (5-1 32)
where j5 is the average reservoir pressure, Pwf is the flowing bottomhole pressure,
and Ap, is the pressure drop in the skin region. Thus, the Vogel curve is for a
flow efficiency of 1.0.