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Pressure difference between the current wellbore flowing current bottom-hole pressure
and the
wellbore flowing pressure bottom-hole pressure at time moment
when flowrate has changed :
| LaTeX Math Block |
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\delta p (t) = p_{wf}(t_0) - p_{wf}(t) |
Pressure drop is:
| | when production rate is increased or injection rate is decreased |
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| |
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| when production rate is decreased or injection rate is increased |
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On log-log plots the pressure drop is always pictured as positive (see Fig. 1).
 Image Added
|  Image Added
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Image Removed A sample typical DTR ( log-derivative P' in red) presented in log-log coordinates for PTA type-library analysis
In particular case when the well has been shut-in for a long time and bottom-hole pressure has stabilised by the time moment
and when well is opened for flow the pressure drop will be equal to pressure drawdown:| LaTeX Math Block |
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{\rm pressure } \, \, {\rm drop} = \delta p (t) = p_{wf}(t_0) - p_{wf}(t) = p_e - p_{wf}(t) = \Delta p(t) = {\rm pressure } \, \, {\rm drawdown} |
as the initial bottom-hole pressure value
represents formation pressure :
See Also
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Petroleum Industry / Upstream / Subsurface E&P Disciplines / Well Testing / Pressure Testing / Pressure Transient Analysis (PTA) / PTA Diagnostic Plot
[ Well & Reservoir Surveillance ] [ Pressure Diffusion ] [ Pressure drawdown ]
