Permeability and skin factor from a constant-rate flow test

Input(s)

\(t_{a}\): Time at Pwf1 from given values or trendline (h)

\(t_{b}\): Time at Pwf 2 from given values or trendline (h)

\(p_{w}\): Well flowing Pressure at point 2 from given values or trend line (psi)

\(p_{w f}\): Well flowing Pressure at point 1 from given values or trendline (psi)

\(p_{i}\): Initial Pressure (psi)

\(\mathrm{p}_{\mathrm{hr}}\): Pressure Value at \(t=1 \mathrm{~h}(\mathrm{psi})\)

q: Flow Rate (STB/day)

B: Volume factor \((\mathrm{RB} / \mathrm{STB})\)

\(\mathrm{h}\): Thickness of reservoir \((\mathrm{ft})\)

\(\mu\): Viscosity of Oil (cP)

\(\varnothing\): Porosity (fraction)

\(c_{t}\): Compressibility (1/psi)

\(r_{w}\): Wellbore Radius (ft)

Output(s)

s: Skin Factor (dimensionless)

Formula(s)

Reference(s)

Pressure Buildup and Flow Tests in Wells, Matthews & Russell, Page: 57.