Log-log plot of unit-rate drawdown survey pressure variation and pressure log-derivative
(see Fig. 1 and Fig. 2, for example).
The pressure log-derivative provides a zoomed insight into the pressure diffusion dynamics at different times which helps identifying the pressure diffusion model behind the pressure variation.
See PTA Type Library for a wide range of typical PTA Diagnostic Plots.
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Fig. 1. PTA Diagnostic Plot for vertical well in single-layer homogeneous reservoir without boundaries. Pressure is in blue and log-derivative is in red. | Fig. 2. PTA Diagnostic Plot for vertical well in single-layer homogeneous reservoir with impermeable circle boundary. Pressure is in blue and log-derivative is in red. | Fig. 3. PTA Diagnostic Plot for vertical well in single-layer homogeneous reservoir with constant pressure boundary. Pressure is in blue and log-derivative is in red. |
