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For a single-layer formation with low-compressibility fluid the PI does not depend on flowrate
and
WFP – Well Flow Performance plot is reperented by a straight line (Fig. 1)
This is a typical WFP – Well Flow Performance plot for water supply wells, water injectors and oil producers above bubble point.
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It can be interpreted as deterioration of near-reservoir zone permeability with fluid velocity growth.
The alternative way to define the
vs
correlation is to present
as a function of
:
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| Note |
|---|
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Despite of terminological similarity there is a big difference in the way WFP and Well Testing deal with formation pressure and flowrates which results in a big difference in productivity index definition and corresponding analysis. This difference is summarized in the table below:
| WFP | Well Testing |
|---|
| Formation pressure | – field-average pressure within the drainage area
| – pressure value at boudary of the drainage area
| | Flow rate | | | LaTeX Math Inline |
|---|
| body | q_t = B_w \, q_W + \frac{B_o - R_s B_g}{1 - R_v R_s} \, q_O + \frac{B_g - R_v B_o}{1 - R_v R_s} \, q_G |
|---|
|
– total flowrate at sandface | | Prroducivity Index | | LaTeX Math Inline |
|---|
| body | J = \frac{q_{\rm liq}}{p_R - p_{wf}} |
|---|
|
| LaTeX Math Inline |
|---|
| body | J_g = \frac{q_g}{p_R - p_{wf}} |
|---|
|
| | LaTeX Math Inline |
|---|
| body | J = \frac{q_t}{p_e - p_{wf}} |
|---|
|
|
|
VLP – Vertical Lift Performance
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