Pressure buildup equation (Horner equation)
Input(s)
\(P_{i}\): Initial Reservoir Pressure (psi)
\(Q_{o}\): Stabilized Well Flow Rate before Shut-in (bbl/d)
\(\mu_{o}\): Oil Viscosity \((\mathrm{cP})\)
\(B_{o}\): Oil Formation Volume Factor (rb/stb)
\(\mathrm{k}\): Permeability \((\mathrm{mD})\)
\(\mathrm{h}\): Height (ft)
\(t_{p}\): Flowing Time before Shut-in (day)
\(\Delta t\): Shut-in Time (day)
Output(s)
\(P_{w s}\): Pressure (psi)
Formula(s)
\[
P_{w s}=P_{i}-\left(\frac{162.6 * Q_{o} * B_{o} * \mu_{o}}{k * h}\right) * \log \left(\frac{t_{p}+\Delta t}{\Delta t}\right)
\]
Reference(s)
Ahmed, T., McKinney, P.D. 2005. Advanced Reservoir Engineering, Gulf Publishing of Elsevier, Chapter: 1, Page: 54 .