Time interval of pressure transition when pressure variation drop
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\Deltadelta p = p_{wf}(0) - p_{wf}(t) \sim p_{wf}(0) - p_i - \frac{q_t}{4 \pi \sigma} \, \bigg[ - 2S + \gamma - \ln \bigg( \frac{4 \chi t}{r_w^2} \bigg) \bigg] |
and hence the pressure pressure log-derivative stays stays constant:
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\Deltadelta p ' = \frac{d \, \Delta p}{d \, \ln t} = \frac{q_t}{4 \pi \sigma} = \rm const |
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Since IARF is normally used to define a flow regime during a certain finite period of time, the term "infinite acting" is a misnomer.
This flow regime is native to pressure diffusion in pressure diffusion regime is native to radial fluid flow in vertical well, homogeneous reservoir and no boundary (see Fig. 1).
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The other popular occurrence of occurrence of IARF is before PSS (Fig. 2) and SS (Fig. 3).
Fig. 1. PTA Diagnostic Plot with IARF regime developing after 100 hrs | Fig. 2. PTA Diagnostic Plot with IARF regime developed between developing after 100 hrs and until PSS at 1,000 hrs | Fig. 3. PTA Diagnostic Plot with IARF regime | developed betweendeveloping after 100 hrs | anduntil SS at 1,000 hrs |
See Also
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Petroleum Industry / Upstream / Subsurface E&P Disciplines / Field Study & Modelling / Reservoir Flow Simulation
[ Pressure Testing ] [ Boundary Dominated Flow (BDF) ]