Pressure difference between the current wellbore flowing pressure p_{wf} and the wellbore flowing pressure p_{wf}(t_0) at time moment t=t_0 when flowrate has changed :
\delta p (t) = p_{wf}(t_0) - p_{wf}(t) |
Fig. 1. A sample of typical DTR (pressure drop P in blue and log-derivative P' in red) presented in log-log coordinates for PTA type-library analysis |