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Why annular velocity changes when the hole gets widerBingham plastic versus power law versus Herschel BulkleyHow to fit Herschel Bulkley parameters from viscometer readingsAnnular pressure loss through several hole sectionsDarcy versus Fanning friction factors in drilling calculationsWhat pipe eccentricity changes in annular flowExplore yield stress and the unyielded annular regionWhen a laminar annular model stops being appropriateSame flow rate different hole sizes a synthetic hydraulics studyWhy a good rheology fit can fail outside the measured rangeDrilling hydraulics practice problems and answer sheetConvert mud weight to pressure gradient with units shownGauge versus absolute pressure in petroleum calculationsCalculate hydrostatic pressure across two fluid columnsWhy shoe depth matters in a MAASP calculationSIDPP versus SICP what each pressure representsInitial versus final circulating pressure on a worksheetExplore how pressure equivalent density changes with depthHydrostatic pressure versus bottomhole pressureThe error from using measured depth for hydrostatic pressureOne surface pressure two different equivalent mud weightsPressure and depth basis worksheet for engineering studentsAnnular capacity versus annular volumeCement slurry yield versus slurry densityCalculate mixing water after rounding cement sacksHow to combine casing open hole and shoe track volumesExcess cement volume versus hole enlargementMeasured depth and diameter checks for a volume calculationExplore how hole diameter affects cement demandBarrels cubic feet and gallons in cement calculationsHow much a small washout changes a synthetic cement estimateWhy rounding at every step changes a cement worksheetMulti interval cement volume worksheet with worked answersPorosity versus permeability why storage is not flow capacitySteady state transient and pseudosteady state flowCalculate radial pressure drop with skin includedWhy well radius and drainage radius affect productivity differentlyHorizontal versus vertical well productivity under stated assumptionsFit permeability from core flood pressure and rate dataExplore the permeability viscosity and pressure tradeoffDarcy versus Forchheimer when inertia changes the equationThe productivity gain from doubling permeability in a synthetic caseTwo equally good permeability fits with different noisy dataDarcy flow practice set with field and SI unitsBuild a volumetric gas in place calculation from a rock volumeVolumetric versus material balance estimates of oil in placeNet to gross gross thickness and net pay in volumetricsGas expansion factor versus gas formation volume factorWhat water influx changes in a material balance interpretationBuckley Leverett breakthrough pore volumes explainedExplore gas in place sensitivity to porosity and saturationWhy one pressure point cannot establish a reservoir modelThe same rock volume with three different fluid volume basesHow input rounding propagates into a volumetric estimateReservoir volumetrics and material balance problem setExponential hyperbolic and harmonic decline explainedHow the hyperbolic b factor changes a forecastCalculate cumulative production from a decline curveWhy a decline forecast needs an end date and economic assumptionsModified hyperbolic decline and the terminal decline switchStretched exponential Duong and Arps choosing a decline modelExplore the same decline curve on monthly and annual time basesPreparing production data before a decline studySame first year different long term decline tailsWhy monthly rate samples do not exactly equal analytical cumulativeDecline curve teaching dataset and worked answer packEffective versus total porosity in saturation calculationsWhy a calculated water saturation can exceed oneWater resistivity temperature basis in a saturation workflowClean sand versus shaly sand choosing a saturation modelSonic porosity and matrix transit time assumptionsCapillary pressure versus relative permeabilityExplore saturation curve parameters without changing the rock dataGassmann fluid substitution what the inputs representTwo rocks with the same porosity and different Archie responseBrooks Corey versus van Genuchten on a shared synthetic casePetrophysics units and saturation practice packReservoir barrels versus stock tank barrelsStanding versus Vasquez Beggs comparing compatible PVT inputsBubble point versus dew point for petroleum fluidsGas gravity API gravity and specific gravityCalculate gas density with absolute pressure and temperatureGas formation volume factor and expansion factor worked togetherExplore gas Z correlations over reduced pressureDead oil versus live oil viscosity in a correlation workflowThe API coefficient switch in a synthetic solution gas studyWhy a small pressure datum mistake can distort a gas calculationPVT symbols units and calculation practice packProductivity index versus production rateGas deliverability pressure squared versus pseudopressureActual pipe velocity versus an erosional screening limitMixture density and gas volume basis in flowline calculationsSeparator gas capacity versus liquid retention timeResidence time versus retention volume in a vesselExplore how pipe diameter changes velocity and friction screeningWhat an inflow curve cannot tell you about a producing systemThree synthetic IPR curves from one test pointWhy the same standard gas rate has different pipe velocityProduction calculations problem set and screening checklistEffective stress versus total stress and the Biot coefficientMohr Coulomb failure envelopes with worked stress inputsMinimum and maximum hoop stress around a wellboreCarter leakoff coefficient time and area basesLeakoff spurt loss and fracture efficiencyFracture conductivity versus dimensionless conductivityExplore the square root of time in Carter leakoffVertical versus deviated wellbore stress assumptionsDoubling exposure time does not double Carter leakoffHow a stress sign convention changes an apparent failure resultRock mechanics and leakoff practice worksheetPeng Robinson versus SRK on the same supported mixturePhase fraction versus phase composition in a flash resultBubble dew and critical regions on a phase envelopeWhy phase stability is different from solver convergencePT PH and PS flash specifications explainedCharacterizing a C7 plus fraction for a flash modelExplore separator pressure and phase split on one synthetic feedCalibrating heavy end PVT parameters without hiding residualsSame feed two equations of state a reproducible comparisonWhat a heavier C7 plus assumption changes in a synthetic flashCompositional flash teaching cases with component balancesHoldup versus flowing gas fractionHydrostatic frictional and acceleration pressure termsRamey wellbore temperature profiles and heat transfer assumptionsWater hammer versus a steady pressure loss calculationHydrate onset versus wax appearance in a flow assurance modelWhy thermal history changes a shut in and restart calculationExplore gas slip and its effect on a thermal pressure profileMesh convergence and residuals in an annular CFD calculationThe same wellbore with three synthetic thermal historiesEquilibrium wax onset is not a wax deposition forecastMultiphase and thermal model selection worksheet

Core pages

Original technical studiesReproduce controlled synthetic engineering experiments with methods and downloadable data.Local simulation workbenchPrepare native PR/pure-crystal equilibrium and 3-D RANS duct cases; inspect checked result files.Linked calculation toolsRun source-backed linked calculations from one consistent case.PetroCalcHub TeamIdentify the publisher and the scope of implementation checks.Revision logRead material calculation and interface changes.Calculator librarySearch and open the complete calculator workspace.Engineering guidesRead source-backed engineering workflow guidance.ResourcesDownload and print engineering reference material.MethodologyUnderstand source, unit, and calculation review practices.AboutLearn who maintains PetroCalcHub and what it covers.CorrectionsReport a formula, unit, citation, or result problem.DisclaimerReview engineering-use responsibilities and limitations.PrivacyReview analytics, advertising, and browser-storage details.

Workflow collections

Coupled PR Vapor-Liquid-Liquid-Wax Flash CalculatorFinite-Inertia Eccentric Annular Navier-Stokes CFD CalculatorMixed-Gas Hydrate Onset and Cage Occupancy CalculatorPeng-Robinson Fluid Phase-Envelope Continuation CalculatorNonideal Two-Wax Multisolid Equilibrium CalculatorCoupled Concentric Helical Herschel-Bulkley Flow CalculatorEccentric Helical HB Creeping-Flow FEM CalculatorSingle-Phase Pipe Water-Hammer Transient CalculatorFormation Thermal History, Shut-In and Restart CalculatorFour-Cut Gamma C7+ Characterization and PR Flash CalculatorHeavy-End PR Interaction Parameter PVT Fit CalculatorFour-Cut C7+ Heat-Duty and Isenthalpic Flash CalculatorExpanded Gas and Isomer PR Flash CalculatorWet-Mixture Three-Phase PR Screening CalculatorPeng-Robinson Isentropic Expansion and Compression CalculatorHydrocarbon Bubble and Dew Pressure Band CalculatorThree-Stage Hydrocarbon Separator Train CalculatorCoupled Hydrocarbon Thermal and Pressure Profile CalculatorSlip-Aware Hydrocarbon Thermal Pressure Profile CalculatorHydrocarbon Homogeneous Equilibrium Critical Mass Flux CalculatorIdeal Single-Wax Solubility and Precipitation CalculatorPure-Water Ice Ih Melting Temperature and Margin CalculatorHerschel-Bulkley Rotational Couette Torque CalculatorC7+ Characterization and PR Flash CalculatorPeng-Robinson Heat-Duty and Isenthalpic Flash CalculatorSRK Heat-Duty and Isenthalpic Flash CalculatorPeng-Robinson Hydrocarbon PT Flash CalculatorSoave-Redlich-Kwong (SRK) Hydrocarbon PT Flash CalculatorYield-Stress Annular Laminar/Turbulent Friction CalculatorCoupled Water-Steam Thermal and Pressure Profile CalculatorEccentric Power-Law Annular Pressure Loss CalculatorRamey Wellbore Liquid Temperature Profile CalculatorBeggs-Brill Inclined Gas-Liquid Pressure Drop CalculatorHerschel-Bulkley Annular Pressure Loss CalculatorVertical Drift-Flux Gas-Liquid Pressure Profile CalculatorConcentric Laminar Annular Pressure Loss CalculatorHomogeneous Gas-Liquid Pressure Profile CalculatorLocal Porosity-Permeability Calibration CalculatorDAK and Hall-Yarborough Gas Z-Factor SolverHerschel-Bulkley Rheology Fitting CalculatorCement Volume and Sacks CalculatorArps Decline Curve Forecast CalculatorStanding vs Vasquez-Beggs PVT ComparisonLinked Drilling Hydraulics CalculatorPrintable calculation review checklistsWell control calculation workflowDrilling hydraulics workflowPVT calculation workflowPrintable petroleum engineering formula sheet

Topics with multiple in-depth references

Drilling Hydraulics (6)Fluid Flow in Porous Media (4)Fluid Properties (5)Gas Properties (4)Hydraulic Fracturing (2)In-Situ Stress and Rock Mechanics (7)Inflow Performance (4)Material Balance (2)Material Balance and Production (3)Permeability and Flow (4)Pressure Transient Analysis (5)PVT and Rock-Fluid Properties (4)PVT Properties (5)Reserves and Recovery (6)Resistivity Logs (2)Rock Properties (4)Well Control (8)Well Performance (11)

Engineering guides

Well Control Calculation WorkflowA source-checked well control calculation workflow for hydrostatic pressure, kill mud weight, initial circulating pressure, final circulating pressure, and MAASP checks.Drilling Hydraulics FormulasA drilling hydraulics formula guide for ECD, annular pressure loss, annular velocity, pump output, and pressure-window checks.Reservoir Engineering Formula GuideA reservoir engineering formula guide for Darcy flow, straight-line productivity index, Vogel IPR, material balance, and original oil in place checks.Petroleum PVT Calculator GuideA petroleum PVT calculator guide for gas formation volume factor, oil formation volume factor, real-gas density, API gravity, and reservoir-to-surface volume conversion checks.Joshi Horizontal Well Productivity GuideA source-backed guide to the Joshi horizontal well productivity equation, drainage geometry, anisotropy, effective radius, skin, and the limits of steady-state inflow screening.Shaly Sand Water Saturation GuideA practical comparison of Indonesian, Archie, and Simandoux water-saturation calculations for resistivity logs, with input checks for shale volume, shale resistivity, porosity, and water resistivity.Annular Hydraulics and Velocity GuideA drilling annular hydraulics guide connecting flow rate, annular geometry, average velocity, hole-cleaning limits, pump output, pressure loss, and equivalent circulating density.Black-Oil PVT Correlation GuideA black-oil PVT correlation guide for Vasquez-Beggs solution gas-oil ratio, bubble point, formation volume factors, gas properties, and Beggs-Robinson oil viscosity checks.API RP 14E Erosional Velocity GuideA careful API RP 14E erosional-velocity workflow covering mixture density, empirical C factor, actual velocity, utilization, pipe sizing, and the equation's documented screening limitations.Hydraulic Fracture Carter Leakoff GuideA hydraulic-fracturing leakoff guide for Carter square-root-time fluid loss, spurt loss, exposed area, time basis, fluid balance, fracture efficiency, and model limitations.How to Calculate Plateau Pressure for Water InfluxLearn how to calculate plateau pressure from reservoir pressure history and use pressure-step increments in van Everdingen-Hurst water influx calculations.TVD vs Measured Depth in Pressure and Volume CalculationsChoose TVD or measured depth for hydrostatic pressure, annular volume and friction, with a well diagram, interactive examples and calculator links.ECD vs EMW vs Mud Weight: Understanding the Pressure BudgetCompare mud weight, ECD and surface-pressure EMW with a pressure diagram, worked calculations and an interactive pressure budget at a stated TVD.How Archie Exponents Change Water SaturationExplore cementation exponent m and saturation exponent n with an Archie sensitivity table, worked example, pore diagram and interactive controls.Linear vs Radial Darcy Flow: Choosing the GeometryChoose a linear or radial Darcy model using flow diagrams, unit-aware worked examples and an interactive permeability comparison linked to both calculators.Calculate Cement Volume and Sacks Across Multiple Well SectionsBuild a section-by-section cement volume ledger, convert barrels to slurry sacks and mixing water, and explore excess and yield with a worked example.Nominal vs Effective Decline: Monthly and Annual ExamplesConvert effective annual decline to nominal daily decline for an exponential forecast, with monthly examples, a tangent diagram and an interactive rate curve.Z Factor vs Gas Compressibility CoefficientSeparate dimensionless Z from gas compressibility cg using a synthetic isothermal Z curve, signed pressure derivatives, a worked example and interactive slope controls.Vogel vs Straight-Line IPR: Choosing the ModelCompare Vogel and linear inflow assumptions, bubble-point regimes and normalized curves, with an interactive pressure-ratio slider and a 700 versus 500 STB/day example.What a Compositional Flash Calculation SolvesFollow a hydrocarbon PT flash from feed to liquid and vapor, with a six-component balance ledger, worked mole allocations and an interactive phase-split explorer.OOIP, OGIP, Recoverable Volume and Reserves: The DifferenceTrace rock volume to oil or gas in place, separate an assumed recovery fraction from reserves classification, and work a volumetric OGIP example with clear units.Fracture Gradient vs Fracture Pressure and Evaluation DepthBuild a treatment-pressure ledger from surface to fracture entry, distinguish pressure from a depth-normalized gradient, and explore friction at a defined TVD.Beggs–Brill vs Homogeneous Flow: What the Models AssumeCompare liquid holdup, no-slip fraction and pressure-loss components on the same short gas-liquid segment, with matched inlet conditions and an interactive model comparison.
In-depth calculator directory

Calculators with published engineering guidance

These records include a functioning calculator, formula and variables, a reproducible default result, individually written assumptions and limitations, common error checks, and source context.

Drilling Engineering

15 in-depth calculators

Open discipline collection

Annular Velocity from Pump Output

Annular velocity from pump output estimates the average drilling-fluid velocity in the annulus from flow rate and annular area.

Annular Volume Capacity of Pipe

Annular Volume Capacity of Pipe calculates annular volume capacity for drilling hydraulics workflows in drilling engineering. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

Equivalent Circulating Density

Equivalent circulating density converts annular pressure loss into an effective mud-weight value at depth during circulation.

Equivalent Mud Weight from Surface Pressure

Equivalent mud weight converts the combined pressure of a uniform mud column and applied surface pressure into a density at a selected true vertical depth. This surface-pressure calculation returns ppg, not the physical density of newly mixed mud.

Final Circulating Pressure

Final circulating pressure estimates circulating pressure after kill-weight mud reaches the bit at the planned kill rate.

Herschel-Bulkley Drilling Fluid Shear Stress

Evaluate shear-stress magnitude on the flowing branch of the Herschel-Bulkley drilling-fluid model from yield stress, consistency factor, shear rate and flow exponent. This adds a yield-power-law relation rather than substituting a Newtonian viscosity for drilling mud.

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.

Hydrostatic Pressure in Annulus Due to Slug

Hydrostatic Pressure in Annulus Due to Slug calculates hydrostatic pressure for well control workflows in drilling engineering. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

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.

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.

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.

Maximum Drilling Rate for Larger Holes

Maximum Drilling Rate for Larger Holes calculates maximum drilling rate for drilling hydraulics workflows in drilling engineering. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

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.

Stuck Pipe Free Point from Pipe Stretch - Method 1

Stuck Pipe Free Point from Pipe Stretch - Method 1 calculates estimated free pipe length for drillstring and rig mechanics workflows in drilling engineering. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

Velocity of Fluid in Annulus

Fluid velocity in an annulus converts circulating flow rate and concentric annular geometry into an average linear velocity between the hole or casing and the drillpipe or tubing.

Geomechanics and Fracturing

7 in-depth calculators

Open discipline collection

Biot-Willis Coefficient from Bulk Moduli

Evaluate the isotropic Biot-Willis poroelastic coefficient as one minus drained-frame bulk modulus divided by solid-grain bulk modulus. This gives the coefficient used in volumetric poroelastic coupling, not a fluid property or the heat-transfer Biot number.

Failure Criteria - Mohr-Coulomb Stress Components

Failure Criteria - Mohr-Coulomb Stress Components calculates shear stress on the plane for in-situ stress and rock mechanics workflows in geomechanics and fracturing. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

Fracture Gradient - Zoback and Healy

Fracture gradient estimates the pressure gradient required to initiate or propagate a fracture under a stated stress model.

Minimum Hoop Stress at the Wellbore Wall

Calculate minimum tangential stress at the wellbore wall from the two horizontal stresses, pore pressure, wellbore overbalance and thermal stress. The implemented expression is 3 Shmin - SHmax - 2 Po - dP - Sdt, with all inputs in psi.

Normal Hoop Stress at the Wellbore Wall

Normal Hoop Stress at the Wellbore Wall calculates hoop stress at the wellbore wall for in-situ stress and rock mechanics workflows in geomechanics and fracturing. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

Shale Compaction

Shale Compaction calculates compacted shale porosity for in-situ stress and rock mechanics workflows in geomechanics and fracturing. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

Tangential Stress Extremes at a Deviated Wellbore

Tangential Stress Extremes at a Deviated Wellbore calculates maximum tangential stress for in-situ stress and rock mechanics workflows in geomechanics and fracturing. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

Petrophysics

6 in-depth calculators

Open discipline collection

Archie Water Saturation from Resistivity Logs

Archie water saturation estimates formation water saturation from resistivity-log measurements, porosity, formation-water resistivity, and Archie exponents.

Brooks-Corey Drainage Capillary Pressure

Evaluate the uncapped Brooks-Corey drainage branch from positive entry pressure, effective wetting saturation and pore-size distribution index. The output is positive nonwetting-phase pressure minus wetting-phase pressure, with the entry threshold retained at full effective saturation.

Gassmann Saturated Rock Bulk Modulus

Compute saturated rock bulk modulus from drained-frame modulus, solid-grain modulus, connected porosity and effective pore-fluid modulus. Gassmann's relation provides a low-frequency rock-physics calculation, not a saturated sonic-log-to-static-modulus conversion.

Indonesian Water Saturation from Shaly Sand Logs

The Poupon-Leveaux Indonesian equation estimates water saturation in shaly formations by combining formation-water and shale conductivity terms with effective porosity, shale volume, true resistivity, and saturation exponents.

Sonic Porosity Raymer-Hunt-Gardner Method

Sonic Porosity Raymer-Hunt-Gardner Method calculates sonic porosity for rock properties workflows in petrophysics. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

van Genuchten Capillary Pressure

Evaluate positive nonwetting-minus-wetting capillary pressure from effective wetting saturation and the restricted van Genuchten shape relation m = 1 - 1/n. The pressure scale P_0 is the reciprocal of an inverse-pressure alpha, not a Brooks-Corey entry threshold.

Phase Behavior and Thermodynamics

12 in-depth calculators

Open discipline collection

Beggs-Robinson Live Oil Viscosity Correlation

The Beggs-Robinson live-oil correlation estimates saturated oil viscosity from dead-oil viscosity and solution gas-oil ratio through correlation coefficients that capture the viscosity-reducing effect of dissolved gas.

Formation Water Salinity from Density

Formation Water Salinity from Density calculates water salinity or solids concentration for fluid properties workflows in phase behavior and thermodynamics. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

Kinematic Viscosity for Saybolt Viscosimeter Measurements

Kinematic Viscosity for Saybolt Viscosimeter Measurements calculates kinematic viscosity for fluid properties workflows in phase behavior and thermodynamics. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

McCain Brine Gas-Solubility Salinity Correction

McCain Brine Gas-Solubility Salinity Correction calculates brine gas-solubility salinity correction factor for fluid properties workflows in phase behavior and thermodynamics. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

Papay Gas Z-Factor Correlation

Papay Gas Z-Factor Correlation calculates gas compressibility factor for gas properties workflows in phase behavior and thermodynamics. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

Real Gas Density

Real gas density estimates gas density at pressure and temperature using gas molecular weight or gravity and the real-gas z-factor.

Real Gas Isothermal Compressibility with Z-Factor Derivative

Calculate the real-gas isothermal compressibility coefficient from absolute pressure, z-factor and the pressure derivative of z at constant temperature. The output is an inverse-pressure coefficient in 1/psi, not the dimensionless compressibility factor z.

Real Gas Pseudopressure Difference for Constant Mu-Z

Real Gas Pseudopressure Difference for Constant Mu-Z calculates real gas pseudopressure difference for gas properties workflows in phase behavior and thermodynamics. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

Solution Gas-Oil Ratio - Standing Correlation

Estimate solution gas-oil ratio in scf/STB using the simplified Standing expression implemented on this page: gas specific gravity multiplied by [(p/18) x 10^(0.0125 API - 0.00091 t)]^1.2048. Pressure, temperature and gravity must describe the same fluid condition.

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.

Vasquez-Beggs Solution Gas-Oil Ratio from Pressure

The Vasquez-Beggs correlation estimates solution gas-oil ratio from pressure, temperature, oil API gravity, gas specific gravity, and the coefficient set selected for the oil-gravity range.

Wood Two-Phase Fluid Bulk Modulus

Calculate the pressure-equilibrated bulk modulus of a two-fluid pore mixture using the saturation-weighted harmonic relation. The second fluid fraction is one minus water saturation, so the two pore-volume fractions close exactly by construction.

Production Engineering

15 in-depth calculators

Open discipline collection

API RP 14E Erosional Velocity

The API RP 14E erosional velocity equation divides an empirical C factor by the square root of flowing mixture density to produce a screening velocity for gas-liquid production piping.

API RP 14E Two-Phase Flowline Pressure Drop

API RP 14E Two-Phase Flowline Pressure Drop calculates two-phase flowline pressure drop per 100 ft for well performance workflows in production engineering. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

Carter Leakoff Volume for Hydraulic Fracturing

The Carter leakoff equation estimates hydraulic-fracturing fluid volume lost to the formation from leakoff area, Carter leakoff coefficient, exposure time, and instantaneous spurt-loss thickness.

Gas Deliverability Pressure-Squared Drawdown

Gas Deliverability Pressure-Squared Drawdown calculates pressure-squared drawdown for inflow performance workflows in production engineering. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

Haaland Darcy Friction Factor

Estimate the Darcy friction factor for fully developed turbulent Newtonian pipe flow from Reynolds number and relative roughness. Haaland is an explicit approximation to the implicit Colebrook relation, not a laminar-flow or drilling-mud rheology model.

Horizontal Separator Length for Liquid Retention

Horizontal Separator Length for Liquid Retention calculates required liquid settling section length for well performance workflows in production engineering. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

Liquid-Liquid Vessel Retention Time

Liquid-Liquid Vessel Retention Time calculates retention time for well performance workflows in production engineering. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

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.

Range of Load - Sucker Rod Pump

Range of Load - Sucker Rod Pump calculates range of load for well performance workflows in production engineering. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

Rawlins-Schellhardt Gas Deliverability Rate

Rawlins-Schellhardt Gas Deliverability Rate calculates gas flow rate for inflow performance workflows in production engineering. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

Separator Gas Capacity at Standard Conditions

Separator Gas Capacity at Standard Conditions calculates gas capacity at standard conditions for well performance workflows in production engineering. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

Skin Factor Due to Reduced Crushed-Zone Permeability

Skin Factor Due to Reduced Crushed-Zone Permeability calculates skin factor due to reduced crushed-zone permeability for well performance workflows in production engineering. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

Treatment Fracture Gradient - Hydraulic Fracturing

Treatment fracture gradient estimates the pressure gradient associated with hydraulic-fracturing treatment pressure at depth.

Velocity of Fluid in Pipe

Velocity of Fluid in Pipe calculates velocity of fluid in pipe for well performance workflows in production engineering. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

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.

Reservoir Engineering

34 in-depth calculators

Open discipline collection

API Gravity

API gravity converts oil specific gravity into the API gravity scale used to classify crude oil density in petroleum engineering workflows.

Brooks-Corey Nonwetting Relative Permeability

Evaluate normalized nonwetting-phase relative permeability from effective wetting saturation and the Brooks-Corey pore-size distribution index. The nested saturation factor makes this relationship distinct from a single Corey oil or gas power law.

Buckley-Leverett Breakthrough Pore Volumes

Buckley-Leverett Breakthrough Pore Volumes calculates dimensionless breakthrough time for permeability and flow workflows in reservoir engineering. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

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.

Characteristic Time for Linear Diffusion in Reservoirs

Characteristic Time for Linear Diffusion in Reservoirs calculates characteristic diffusion time for pvt and rock-fluid properties workflows in reservoir engineering. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

Craft and Hawkins Vertical Well Critical Coning Rate

Craft and Hawkins Vertical Well Critical Coning Rate calculates critical oil rate without coning for well performance workflows in reservoir engineering. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

Cumulative Gas Production – Tarner’s Method

Cumulative Gas Production – Tarner’s Method calculates cumulative gas production for material balance and production workflows in reservoir engineering. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

Cumulative Oil Production – Undersaturated Oil Reservoirs

Cumulative Oil Production – Undersaturated Oil Reservoirs calculates cumulative oil production for pvt and rock-fluid properties workflows in reservoir engineering. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

Darcy-Forchheimer Superficial Velocity

Solve the local one-dimensional Darcy-Forchheimer pressure-gradient balance for nonnegative superficial velocity. The expression includes viscous and inertial resistance and uses a numerically stable positive quadratic root, including the zero-inertia Darcy limit.

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.

Dimensionless Pressure for Linear Flow Constant Rate General Case

Dimensionless Pressure for Linear Flow Constant Rate General Case calculates dimensionless linear flow pressure for pressure transient analysis workflows in reservoir engineering. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

Duong Oil Production Rate

Evaluate the original Duong time-rate relation on its fixed one-day reference basis using a fitted day-one oil rate, ratio-rate coefficient and exponent. This adds a fracture-dominated empirical curve, not another Arps exponent setting or an automatically fitted production forecast.

Fracture Conductivity During Bilinear Flow

Fracture Conductivity During Bilinear Flow calculates fracture conductivity for pressure transient analysis workflows in reservoir engineering. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

Gas Expansion Factor from Formation Volume Factor

Gas Expansion Factor from Formation Volume Factor calculates gas expansion factor for pvt properties workflows in reservoir engineering. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

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.

Gas Produced by Gas Expansion

Gas Produced by Gas Expansion calculates gas produced by gas expansion for material balance and production workflows in reservoir engineering. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

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.

Logistic Growth Cumulative Oil Production

Calculate cumulative oil production with the Clark-type logistic-growth relation using a fitted asymptote, half-production time and positive exponent. The half-time parameter replaces the original coefficient a with t_half raised to n, making the time units explicit.

Logistic Growth Oil Production Rate

Evaluate the derivative of a Clark-type logistic cumulative-production curve from its fitted asymptote, half-time and exponent. This is not necessarily a decline-only model: when the exponent exceeds one, rate first rises and subsequently declines.

Modified Hyperbolic Decline Rate

Evaluate an oil-rate curve that starts with hyperbolic decline and switches to terminal exponential decline when its nominal decline reaches the selected terminal coefficient. The transition preserves both rate and its time derivative, rather than splicing two unrelated forecasts.

Original Gas in Place - Volumetric Method

Original Gas in Place - Volumetric Method calculates original gas in place for reservoir volumetrics workflows in reservoir engineering. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

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.

Power-Law Exponential Decline Rate

Calculate a power-law exponential oil rate using a fitted amplitude, terminal decline coefficient, power-law coefficient and exponent. Unlike the stretched exponential form alone, this expression includes a separate terminal exponential term.

Pseudosteady-State Dimensionless Pressure Drop for Horizontal Well

Evaluate the implemented horizontal-well pressure expression from area-based dimensionless time, drainage area, lateral length and horizontal shape factor. The result is dimensionless pressure drop, not a pressure in psi or a productivity index.

Radial Pressure Distribution in Single-Phase Liquid Flow

Calculate pressure outside an ideal well from its skin-free steady-state radial liquid-flow relation. The pressure increases logarithmically with distance from the wellbore for nonnegative production, with constant permeability, thickness and compatible liquid properties.

Radius of Investigation

Radius of Investigation calculates radius of investigation for pressure transient analysis workflows in reservoir engineering. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

Skin Factor from Pressure Transient Semilog Analysis

Estimate liquid-well skin from a selected radial-flow semilog line using a fitted one-hour pressure intercept, slope magnitude and compatible rock/fluid properties. This implements the historical rounded MDH/log-time approximation, not a raw first-hour gauge-reading calculation or a full finite-preflow Horner solution.

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.

Stretched Exponential Decline Rate

Evaluate a stretched exponential production-rate curve from its fitted initial rate, characteristic time and exponent. This calculator adds a distinct time-rate model to the Arps family; it does not fit production history or estimate recoverable reserves.

Tight Gas Pore Volume from Squared-Pressure Decline

Tight Gas Pore Volume from Squared-Pressure Decline calculates pore volume for unconventional reservoirs workflows in reservoir engineering. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

van Everdingen-Hurst Single-Step Water Influx

van Everdingen-Hurst Single-Step Water Influx calculates cumulative water influx for pressure step for material balance workflows in reservoir engineering. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.

van Genuchten Nonwetting Relative Permeability

Calculate the INL van Genuchten nonwetting relative-permeability branch using effective wetting saturation and a fixed nonwetting connectivity exponent of one half. This completes the available wetting/nonwetting pair without treating all published nonwetting exponent variants as interchangeable.

van Genuchten-Mualem Wetting Relative Permeability

Calculate normalized wetting-phase relative permeability using the van Genuchten-Mualem relation with pore-connectivity exponent one half. The nonlinear saturation term differs from a single Corey power and shares its shape parameter with the restricted capillary-pressure model.

Water Influx Constant for van Everdingen-Hurst Aquifer

Water Influx Constant for van Everdingen-Hurst Aquifer calculates water influx constant for material balance workflows in reservoir engineering. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.