A certain type of linear stabilised IPR:
| q = J \, (p_r - p_{wf}) |
with constant productivity index:
| (1) | J = \frac{2 \pi \sigma}{ \ln \frac{r_e}{r_w} + \epsilon+ S} |
where \sigma = \Big \langle \frac{k} {\mu} \Big \rangle \, h = k \, h\, \Big[ \frac{k_{rw}}{\mu_w} + \frac{k_{ro}}{\mu_o} \Big] – water-based or water-oil-based transmissbility above bubble point
,\epsilon = 0.5 for steady-state SS flow and \epsilon = 0.75 for pseudo-steady state PSS flow.