The relation between the bottom-hole pressure p_{wf} and surface flow rate q during the stabilised reservoir flow:
q = J \, (p_r - p_{wf}) |
corresponding to linear IPR with constant productivity index :
(1) | J = \frac{2 \pi \sigma}{ \ln \frac{r_e}{r_w} + \epsilon+ S} |
where \sigma is transmissibility above bubble point
, \epsilon = 0.5 for steady-state SS flow and \epsilon = 0.75 for pseudo-steady state PSS flow.