Petroleum Engineering Formulas
A source-linked petroleum engineering formula guide organized around drilling, reservoir, production, PVT, petrophysics, geomechanics, and hydraulic fracturing workflows.
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Hydrostatic Pressure from Mud Weight
Hydrostatic pressure from mud weight calculates the pressure exerted by a drilling-fluid column at true vertical depth using the standard oilfield 0.052 conversion factor.
Equivalent Circulating Density
Equivalent circulating density converts annular pressure loss into an effective mud-weight value at depth during circulation.
Initial Circulating Pressure
Initial circulating pressure estimates the pump pressure required at the start of a well-control circulation using slow circulating pressure and shut-in drillpipe pressure.
Maximum Allowable Annular Surface Pressure from Shoe EMW
Maximum allowable annular surface pressure estimates the casing-shoe pressure limit by comparing shoe equivalent mud weight with current mud hydrostatic pressure.
Kill Weight Mud Determination - Moore Equation
Kill weight mud determination estimates the mud density required to balance formation pressure after a kick using original mud weight, shut-in drillpipe pressure, and true vertical depth.
Vogel Inflow Performance Relationship
The Vogel IPR estimates oil well inflow rate under two-phase flow conditions using flowing bottomhole pressure and average reservoir pressure.
Productivity Index and Straight-Line IPR
Productivity index relates stabilized liquid production rate to reservoir-to-wellbore pressure drawdown and defines a straight-line inflow-performance relationship for a producing well.
Gas Formation Volume Factor
Gas formation volume factor converts gas volume between reservoir conditions and standard surface conditions using pressure, temperature, and gas z-factor.
Standing Oil Formation Volume Factor
Standing oil formation volume factor estimates the reservoir-barrel volume occupied by stock-tank oil and dissolved gas at reservoir pressure and temperature.
API Gravity
API gravity converts oil specific gravity into the API gravity scale used to classify crude oil density in petroleum engineering workflows.
Archie Water Saturation from Resistivity Logs
Archie water saturation estimates formation water saturation from resistivity-log measurements, porosity, formation-water resistivity, and Archie exponents.
Capillary Number
Capillary number compares viscous forces with capillary forces and is commonly used as a rock-fluid screening parameter in displacement and recovery calculations.
Steady-State Radial Liquid Flow Rate
Steady-state radial liquid flow rate estimates oil or liquid inflow toward a well from permeability, thickness, pressure drawdown, viscosity, formation volume factor, drainage radius, wellbore radius, and skin.
Darcy's Law for Linear Single-Phase Flow
Darcy's law for linear single-phase flow estimates volumetric flow rate through porous rock from permeability, flow area, pressure drop, viscosity, and flow length.
Original Oil in Place from General Oil Material Balance
Original oil in place from general oil material balance estimates OOIP by reconciling produced fluids, pressure change, expansion terms, and water influx in a reservoir material-balance relationship.
Pore Pressure Gradient - Rehm and McClendon
The Rehm and McClendon pore pressure gradient relationship estimates formation pore-pressure gradient from drilling or formation-evaluation indicators used in well planning.
Treatment Fracture Gradient - Hydraulic Fracturing
Treatment fracture gradient estimates the pressure gradient associated with hydraulic-fracturing treatment pressure at depth.
Joshi Horizontal Well Productivity Index
The Joshi horizontal well productivity index estimates steady-state oil deliverability for a centered horizontal well by combining horizontal and vertical flow resistance, drainage geometry, anisotropy, well length, fluid properties, and skin.