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Open calculators for drilling hydraulics, well control, reservoir engineering, PVT, production, petrophysics, and hydraulic fracturing workflows.

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Drilling Engineering14 formulasGeomechanics and Fracturing6 formulasPetrophysics3 formulasPhase Behavior and Thermodynamics11 formulasProduction Engineering14 formulasReservoir Engineering24 formulas

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Drilling Hydraulics5 formulasDrillstring and Rig Mechanics1 formulaFluid Flow in Porous Media3 formulasFluid Properties4 formulasGas Properties4 formulasHydraulic Fracturing2 formulasIn-Situ Stress and Rock Mechanics6 formulasInflow Performance4 formulasMaterial Balance2 formulasMaterial Balance and Production3 formulasPermeability and Flow1 formulaPressure Transient Analysis5 formulasPVT and Rock-Fluid Properties4 formulasPVT Properties5 formulasReservoir Volumetrics1 formulaResistivity Logs2 formulasRock Properties1 formulaUnconventional Reservoirs1 formulaWell Control8 formulasWell Performance10 formulas

In-depth petroleum engineering calculators

Showing 36 calculators with individually written engineering context, assumptions, limitations, examples, and source notes.

Drilling EngineeringWell ControlIn-depth reference

Hydrostatic Pressure from Mud Weight

HP=0.052MW⋅TVDHP = 0.052 MW \cdot TVD
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Drilling EngineeringDrilling HydraulicsIn-depth reference

Equivalent Circulating Density

ECD=MW+ΔPa0.052TVDECD = MW + \frac{\Delta P_a}{0.052TVD}
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Drilling EngineeringWell ControlIn-depth reference

Initial Circulating Pressure

ICP=SCRP+SIDPPICP=SCRP+SIDPP
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Drilling EngineeringWell ControlIn-depth reference

Maximum Allowable Annular Surface Pressure from Shoe EMW

MAASP=(MWmax−MW)0.052TVDshoeMAASP=(MW_{max}-MW)0.052TVD_{shoe}
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Drilling EngineeringWell ControlIn-depth reference

Kill Weight Mud Determination - Moore Equation

KWM=SIDPP0.052TVD+OMWKWM=\frac{SIDPP}{0.052TVD}+OMW
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Production EngineeringInflow PerformanceIn-depth reference

Vogel Inflow Performance Relationship

qo=qmax[1−0.2(PwfPr)−0.8(PwfPr)2]q_o = q_{max}\left[1 - 0.2\left(\frac{P_{wf}}{P_r}\right) - 0.8\left(\frac{P_{wf}}{P_r}\right)^2\right]
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Production EngineeringInflow PerformanceIn-depth reference

Productivity Index and Straight-Line IPR

J=qoPr−PwfJ = \frac{q_o}{P_r - P_{wf}}
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Reservoir EngineeringPVT PropertiesIn-depth reference

Gas Formation Volume Factor

Bg=0.02827zTPB_g = 0.02827 \frac{zT}{P}
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Phase Behavior and ThermodynamicsPVT PropertiesIn-depth reference

Standing Oil Formation Volume Factor

Bo=0.9759+0.00012F1.2B_o=0.9759+0.00012F^{1.2}
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Reservoir EngineeringPVT and Rock-Fluid PropertiesIn-depth reference

API Gravity

API=141.5SGo−131.5API = \frac{141.5}{SG_o} - 131.5
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PetrophysicsResistivity LogsIn-depth reference

Archie Water Saturation from Resistivity Logs

Sw=[(aϕm)(RwRt)]1/nS_w = \left[\left(\frac{a}{\phi^m}\right)\left(\frac{R_w}{R_t}\right)\right]^{1/n}
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Reservoir EngineeringPVT and Rock-Fluid PropertiesIn-depth reference

Capillary Number

Nc=μw⋅V⋅0.304886400⋅σowN_c = \frac{\mu_w \cdot V \cdot 0.3048}{86400 \cdot \sigma_{ow}}
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Reservoir EngineeringFluid Flow in Porous MediaIn-depth reference

Steady-State Radial Liquid Flow Rate

qo=0.00708kh(pe−pwf)μoBo[ln⁡(re/rw)+s]q_o=\frac{0.00708kh(p_e-p_{wf})}{\mu_oB_o[\ln(r_e/r_w)+s]}
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Reservoir EngineeringFluid Flow in Porous MediaIn-depth reference

Darcy's Law for Linear Single-Phase Flow

q=0.001127kAΔPμLq = \frac{0.001127 k A \Delta P}{\mu L}
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Reservoir EngineeringMaterial Balance and ProductionIn-depth reference

Original Oil in Place from General Oil Material Balance

N=F−WeEo+mEg+EfwN = \frac{F-W_e}{E_o+mE_g+E_{fw}}
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Drilling EngineeringWell ControlIn-depth reference

Pore Pressure Gradient - Rehm and McClendon

gp=0.398log⁡10(dcn−dco)+0.86g_p=0.398\log_{10}(d_{cn}-d_{co})+0.86
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Production EngineeringHydraulic FracturingIn-depth reference

Treatment Fracture Gradient - Hydraulic Fracturing

Gf=Pinj+ΔPh−ΔPf−ΔPpDG_f=\frac{P_{inj}+\Delta P_h-\Delta P_f-\Delta P_p}{D}
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Reservoir EngineeringWell PerformanceIn-depth reference

Joshi Horizontal Well Productivity Index

Jh=0.00708khhμoBo[ln⁡Rh+βhLln⁡(βh2rw)+s]J_h=\frac{0.00708k_hh}{\mu_oB_o\left[\ln R_h+\frac{\beta h}{L}\ln\left(\frac{\beta h}{2r_w}\right)+s\right]}
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PetrophysicsResistivity LogsIn-depth reference

Indonesian Water Saturation from Shaly Sand Logs

Sw=[1/RtVsh1−0.5VshRsh+ϕemaRw]2/nS_w=\left[\frac{\sqrt{1/R_t}}{\frac{V_{sh}^{1-0.5V_{sh}}}{\sqrt{R_{sh}}}+\sqrt{\frac{\phi_e^m}{aR_w}}}\right]^{2/n}
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Drilling EngineeringDrilling HydraulicsIn-depth reference

Velocity of Fluid in Annulus

va=Q2.448(Do2−Dp2)v_a = \frac{Q}{2.448(D_o^2-D_p^2)}
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Drilling EngineeringWell ControlIn-depth reference

Equivalent Mud Weight from Surface Pressure

EMW=Psurf0.052TVD+MWEMW=\frac{P_{surf}}{0.052TVD}+MW
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Drilling EngineeringDrilling HydraulicsIn-depth reference

Annular Volume Capacity of Pipe

Va=0.7854(Dh2−Do2)L808.5V_a=\frac{0.7854(D_h^2-D_o^2)L}{808.5}
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Reservoir EngineeringMaterial Balance and ProductionIn-depth reference

Gas Produced by Gas Expansion

Gp=43560Ahϕ(1−Swi)(1Bgi−1Bg)G_p=43560Ah\phi(1-S_{wi})\left(\frac{1}{B_{gi}}-\frac{1}{B_g}\right)
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Production EngineeringWell PerformanceIn-depth reference

Range of Load - Sucker Rod Pump

ROL=PPRL−MPRLROL=PPRL-MPRL
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Reservoir EngineeringMaterial BalanceIn-depth reference

Water Influx Constant for van Everdingen-Hurst Aquifer

B=1.119ϕctre2hfB=1.119\phi c_tr_e^2hf
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Reservoir EngineeringMaterial BalanceIn-depth reference

van Everdingen-Hurst Single-Step Water Influx

We=BΔpWeDW_e=B\Delta p W_{eD}
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Phase Behavior and ThermodynamicsPVT PropertiesIn-depth reference

Vasquez-Beggs Solution Gas-Oil Ratio from Pressure

Rs=C1γgpC2exp⁡(C3APIT+460)R_s=C_1\gamma_g p^{C_2}\exp\left(\frac{C_3API}{T+460}\right)
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Production EngineeringWell PerformanceIn-depth reference

API RP 14E Erosional Velocity

Ve=CρmV_e=\frac{C}{\sqrt{\rho_m}}
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Phase Behavior and ThermodynamicsFluid PropertiesIn-depth reference

Beggs-Robinson Live Oil Viscosity Correlation

μo=AμodB\mu_o=A\mu_{od}^{B}
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Production EngineeringHydraulic FracturingIn-depth reference

Carter Leakoff Volume for Hydraulic Fracturing

VL=AL(2CLt+Sp)V_L=A_L\left(2C_L\sqrt{t}+S_p\right)
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Drilling EngineeringWell ControlIn-depth reference

Hydrostatic Pressure in Annulus Due to Slug

P=VaVs(Ws−Wm)0.052P=V_aV_s(W_s-W_m)0.052
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Reservoir EngineeringFluid Flow in Porous MediaIn-depth reference

Radial Pressure Distribution in Single-Phase Liquid Flow

p(r)=pwf+141.2qoμoBokhln⁡(rrw)p(r)=p_{wf}+\frac{141.2q_o\mu_oB_o}{kh}\ln\left(\frac{r}{r_w}\right)
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Production EngineeringWell PerformanceIn-depth reference

Skin Factor Due to Reduced Crushed-Zone Permeability

sc=(kkdp−kkd)12hpNLpln⁡(rdprp)s_c=\left(\frac{k}{k_{dp}}-\frac{k}{k_d}\right)12\frac{h_p}{NL_p}\ln\left(\frac{r_{dp}}{r_p}\right)
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Production EngineeringWell PerformanceIn-depth reference

API RP 14E Two-Phase Flowline Pressure Drop

ΔP100=0.000336fW2Di5ρm\Delta P_{100}=\frac{0.000336fW^2}{D_i^5\rho_m}
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Production EngineeringInflow PerformanceIn-depth reference

Gas Deliverability Pressure-Squared Drawdown

Δp2=Pr2−Pwf2\Delta p^2=P_r^2-P_{wf}^2
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Reservoir EngineeringPVT PropertiesIn-depth reference

Gas Expansion Factor from Formation Volume Factor

Eg=35.37PzTE_g = 35.37 \frac{P}{zT}
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