Work out mud weight instantly with clear inputs, formula shown and shareable results.
Mud weight must exceed the pore pressure gradient to keep formation fluids in place, with a trip margin of 0.2-0.5 ppg to cover swabbing when pulling pipe. It must stay below the fracture gradient or the formation breaks down and circulation is lost. The gap between the two is the drilling window.
Pore pressure gradient
Gradient (ppg) = pore pressure (psi) / (0.052 x TVD (ft))
Mud weight
Mud weight = pore gradient + trip margin; must remain below fracture gradient
Mud weight selection is a well control safety decision. It must be made by qualified personnel against a verified pore pressure and fracture gradient prognosis, with a tested barrier envelope in place.
Neither overbalance nor circulation can be maintained, and casing must be set. In narrow-margin wells, managed pressure drilling or dual-gradient techniques extend the window.
It converts pounds per gallon and feet to psi: 1 ppg over 1 foot exerts 0.05195 psi. It is the fundamental constant of well control arithmetic.