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Fluid flow with fluid pressure 

LaTeX Math Inline
bodyp(t, {\bf r})
 is linearly changing  linearly changing in time:

LaTeX Math Block
alignmentleft
p(t, {\bf r}) = \psi({\bf r}) + A \cdot t, \quad A = \rm const


The fluid temperature  

LaTeX Math Inline
bodyT(t, {\bf r})
 is supposed to vary slowly enough to provide quasistatic equilibrium.


The fluid velocity 

LaTeX Math Inline
body{\bf u}(t, {\bf r})
 may not be stationary.

In the most general case (both reservoir and pipelines) the fluid motion equation is given by fluid velocity proportional to of fluid pressure and pressure gradient:

LaTeX Math Block
anchoru
alignmentleft
{\bf u}(t, {\bf r})= - MF({\bf r}, p, \nabla p) \nabla p

with right side dependent on time through the pressure variation.


In case of linear motion equation (the flow with velocity dependent on pressure  gradient only

LaTeX Math Inline
bodyM({\bf r}, p, \nabla p) = Mu} = {\bf u}({\bf r}, \nabla p)
) the PSS flow velocity will be stationary as the right side of
LaTeX Math Block Reference
anchoru
 is not dependant on time.

The fluid temperature  

LaTeX Math Inline
bodyT(t, {\bf r})
 is supposed to vary slowly enough to provide quasistatic equilibrium.


In terms of Well Flow Performance the PSS flow means:

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Fig. 1. PTA Diagnostic Plot for vertical well in single-layer homogeneous reservoir with impermeable circle boundary (PSS).

Pressure is in blue and log-derivative is in red.


See Also

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Petroleum Industry / Upstream /  Production / Subsurface Production / Field Study & Modelling / Production Analysis / PSS Diagnostics

Steady State (SS) well fluid flow regime ]