Work out wellhead pressure drop instantly with clear inputs, formula shown and shareable results.
Flowing wellhead pressure is reservoir pressure less the hydrostatic weight of the producing column and the tubing friction loss. When it falls below the pressure needed to enter the separator, the well needs artificial lift — gas lift, rod pump, or electric submersible pump.
Wellhead pressure
WHP = reservoir pressure - fluid gradient x depth - friction loss
It depends on the gas-liquid ratio: 0.43-0.45 psi/ft for water, around 0.35 for dead oil, and 0.15-0.30 for gassy oil where gas lightens the column. It falls as GOR rises.
Reservoir pressure declines and water cut rises, making the column heavier. Both push the hydrostatic loss above the available pressure, which is when artificial lift becomes necessary.