Well shut-in pressure during buildup (Horner plot)

Input(s)

$p_{i}$: Initial False Pressure (psi)

$Q_{o}$: Stabilized Well Flow Rate before Shut-in (STB/day)

$B_{o}$: Oil Formation Volume Factor (bbl/STB)

$\mathrm{k}$: Permeability $(\mathrm{mD})$

$\mu_{o}$: Oil Viscosity $(\mathrm{cP})$

$t_{p}$: Flowing Time before Shut-in (h)

$\Delta \mathrm{t}$: Shut-in Time (h)

h: Thickness (ft)

Output(s)

$p_{w s}$: Shut-in Pressure (psi)

Formula(s)

$$ p_{w s}=p_{i}-\left(\frac{162.6 * Q_{o} * \mu_{o} * B_{o}}{k * h}\right) * \log \left(\frac{t_{p}+\Delta t}{\Delta t}\right) $$

Reference(s)

Ahmed, T., McKinney, P.D. 2005. Advanced Reservoir Engineering, Gulf Publishing of Elsevier, Chapter: 1, Page: 56.