Normalised dimensionless difference between the sandface bottomhole pressure (BHP)
and the
sandface r
eservoir pressure | LaTeX Math Inline |
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| body | \displaystyle p({\bf r}, t) |_{{\bf r} \in \Gamma_s} |
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at the boundary
of
damaged reservoir zone :
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S = \frac{2 \pi \sigma}{q_t} \cdot \left[ p_{wf}(t) - p({\bf r}, t) |_{{\bf r} \in \Gamma_s} \right] |
where
It quantitatively characterises permeability change in a thin layer (usually < 1 m) around the well or around the fracture plane, caused by stimulation or deterioration during the reservoir invasion under drilling or well intervention or under routine production or injection.
It contributes to the total skin estimated in transient well testing.
For the radial-symmetric permeability change around the well it can be estimated from Hawkins equation:
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S_M = \left ( \frac{k}{k_s} - 1 \right ) \ \ln \left ( \frac{r_s}{r_w} \right ) |
where
The definition | LaTeX Math Block Reference |
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suggests that:
The most popular practical range of skin-factor variation is
.
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k_s = \frac{k}{ 1 + \frac{S_M}{ \ln \frac{r_s}{r_w} }} |
See Also
Petroleum Industry / Upstream / Subsurface E&P Disciplines / Well Testing / Pressure Testing
[ Well & Reservoir Surveillance ][ Skin-factor (total) ][ Skin-factor (geometrical) ]
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| displaytext | 1DR pressure diffusion of low-compressibility fluid |
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provides a good example how mechanical skin-factor affects pressure dynamics. |
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