Single-phase or pseudo single-phase PVT model with the following correlations:

Total sandface flowrate:

q_t = q_s \, B

where  is fluid formation volume factor and  is  surface flowrate.

Fluid Mobility:

\left<\frac{k}{\mu} \right> =\frac{ k_{air} }{\mu}

where  is absolute formation permeability to air,  is dynamic fluid viscosity.

Total compressibility:

c_t = c_r + c

where  is formation compressibility and  is fluid compressibility.