jumonville production on increase, page-17

ρ αρ α ρ ρ λρ (2)
where α is the void fraction (-), ρs is the density of
OIL (kg/m3), vs is the velocity of OIL, ρw is the
density of water (kg/m3), vw is the velocity of water,
P is the pressure (Pa), g is the gravitational
acceleration (m/s2), λ is the friction factor (-), and rw
is the well radius (m). The friction factor λ is
evaluated using a two-phase multiplier and is
independent of flow regime.

Oil VS steam.

more fun ... http://www.spe.org/atce/2007/tech_prog/documents/spe1103041.pdf