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Fig. 1. Example of log-derivative P' (in red) along with pressure drop P (in blue) for a typical DTR presented on PTA type-library log-log plot


The calculation algorithm of logarithmic derivative is brought in Logarithmic Derivative @model.


Note

In Well Testing applications the logarithmic derivative is often denoted as 

LaTeX Math Inline
bodyp' = t \, \frac{dp}{d t}
 which is misnomer as the usual mathematical convention for prime " ' " is the regular Derivative with respect to the argument
LaTeX Math Inline
bodyp' = \frac{dp}{d t}
.

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Tip

In Well Testing applications the logarithmic derivative is often denoted as 

LaTeX Math Inline
bodyp' = t \, \frac{dp}{d t}
 which is misnomer as the usual mathematical convention for prime " ' " is the regular Derivative with respect to the argument
LaTeX Math Inline
bodyp' = \frac{dp}{d t}
.


See Also

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Petroleum Industry / Upstream / Subsurface E&P Disciplines / Well Testing / Pressure Testing / Pressure Transient Analysis (PTA) /  PTA Diagnostic Plot

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