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Drilling Engineering266 formulasGeomechanics and Fracturing90 formulasPetrophysics132 formulasPhase Behavior and Thermodynamics102 formulasProduction Engineering198 formulasReservoir Engineering303 formulas

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Directional Drilling33 formulasDrilling Hydraulics49 formulasDrilling Operations and Economics13 formulasDrillstring and Rig Mechanics17 formulasElectrical Properties32 formulasFluid Flow in Porous Media13 formulasFluid Properties34 formulasGas Properties23 formulasHydraulic Fracturing53 formulasIn-Situ Stress and Rock Mechanics72 formulasInflow Performance17 formulasInjection Wells13 formulasMaterial Balance20 formulasMaterial Balance and Production20 formulasMud and Cementing72 formulasNaturally Fractured Reservoirs18 formulasPermeability13 formulasPermeability and Flow11 formulasPressure Transient Analysis50 formulasPVT and Rock-Fluid Properties12 formulasPVT Properties50 formulasReserves and Recovery13 formulasReservoir Volumetrics19 formulasResistivity Logs39 formulasRock Properties76 formulasThermal Gradients11 formulasUnconventional Reservoirs22 formulasWaterflooding and EOR50 formulasWell Control82 formulasWell Performance144 formulas
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Drilling EngineeringWell Control

Hydrostatic Pressure from Mud Weight

HP=0.052MW⋅TVDHP = 0.052 MW \cdot TVD
MW (ppg)TVD (ft)
Details
Drilling EngineeringDrilling Hydraulics

Equivalent Circulating Density

ECD=MW+ΔPa0.052TVDECD = MW + \frac{\Delta P_a}{0.052TVD}
MW (ppg)dP_a (psi)TVD (ft)
Details
Drilling EngineeringWell Control

Initial Circulating Pressure

ICP=SCRP+SIDPPICP=SCRP+SIDPP
SCRP (psi)SIDPP (psi)
Details
Drilling EngineeringWell Control

Maximum Allowable Annular Surface Pressure from Shoe EMW

MAASP=(MWmax−MW)0.052TVDshoeMAASP=(MW_{max}-MW)0.052TVD_{shoe}
MW_max (ppg)MW (ppg)TVD_shoe (ft)
Details
Drilling EngineeringWell Control

Kill Weight Mud Determination - Moore Equation

KWM=SIDPP0.052TVD+OMWKWM=\frac{SIDPP}{0.052TVD}+OMW
SIDPP (psi)OMW (ppg)TVD (ft)
Details
Drilling EngineeringWell Control

Kick Analysis - Shut-In Drill Pipe Pressure

SIDPP=Pfp−MW⋅0.052⋅hSIDPP = P_{fp} - MW\cdot0.052\cdot h
P_fp (psi)MW (ppg)h (ft)
Details
Production EngineeringInflow Performance

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]
q_max (STB/day)P_wf (psi)P_r (psi)
Details
Production EngineeringInflow Performance

Productivity Index and Straight-Line IPR

J=qoPr−PwfJ = \frac{q_o}{P_r - P_{wf}}
q_o (STB/day)P_r (psi)P_wf (psi)
Details
Reservoir EngineeringPVT Properties

Gas Formation Volume Factor

Bg=0.02827zTPB_g = 0.02827 \frac{zT}{P}
z (dimensionless)T (°R)P (psia)
Details
Phase Behavior and ThermodynamicsPVT Properties

Standing Oil Formation Volume Factor

Bo=0.9759+0.00012F1.2B_o=0.9759+0.00012F^{1.2}
R_s (SCF/STB)gamma_g (fraction)gamma_o (fraction)t (°F)
Details
Reservoir EngineeringPVT and Rock-Fluid Properties

API Gravity

API=141.5SGo−131.5API = \frac{141.5}{SG_o} - 131.5
SG_o (dimensionless)
Details
PetrophysicsResistivity Logs

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}
a (dimensionless)phi (fraction)m (dimensionless)R_w (ohm m)R_t (ohm m)n (dimensionless)
Details
Reservoir EngineeringPVT and Rock-Fluid Properties

Capillary Number

Nc=μw⋅V⋅0.304886400⋅σowN_c = \frac{\mu_w \cdot V \cdot 0.3048}{86400 \cdot \sigma_{ow}}
mu_w (cP)V (ft/day)sigma_ow (dyn/cm)
Details
Reservoir EngineeringFluid Flow in Porous Media

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]}
k (mD)h (ft)p_e (psi)p_wf (psi)mu_o (cP)B_o (bbl/STB)
Details
Reservoir EngineeringFluid Flow in Porous Media

Darcy's Law for Linear Single-Phase Flow

q=0.001127kAΔPμLq = \frac{0.001127 k A \Delta P}{\mu L}
k (mD)A (ft²)DeltaP (psi)mu (cP)L (ft)
Details
Reservoir EngineeringMaterial Balance and Production

Original Oil in Place from General Oil Material Balance

N=F−WeEo+mEg+EfwN = \frac{F-W_e}{E_o+mE_g+E_{fw}}
F (RB)W_e (RB)E_o (RB/STB)m (dimensionless)E_g (RB/STB)E_fw (RB/STB)
Details
Drilling EngineeringWell Control

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
d_cn (dimensionless)d_co (dimensionless)
Details
Production EngineeringHydraulic Fracturing

Treatment Fracture Gradient - Hydraulic Fracturing

Gf=Pinj+ΔPh−ΔPf−ΔPpDG_f=\frac{P_{inj}+\Delta P_h-\Delta P_f-\Delta P_p}{D}
P_inj (psi)DeltaP_h (psi)DeltaP_f (psi)DeltaP_p (psi)D (ft)
Details
Production EngineeringInflow Performance

PI Test Skin Factor and Average Permeability

s=(kkj−1)[ln⁡(rerw)−0.75]s=\left(\frac{k}{k_j}-1\right)\left[\ln\left(\frac{r_e}{r_w}\right)-0.75\right]
P (psi)q (STB/day)P_wf (psi)k (mD)B (RB/STB)h (ft)
Details
Reservoir EngineeringFluid Flow in Porous Media

Steady-State Radial Liquid Productivity Index

J=0.00708khμoBo[ln⁡(re/rw)+s]J=\frac{0.00708kh}{\mu_oB_o[\ln(r_e/r_w)+s]}
k (mD)h (ft)mu_o (cP)B_o (bbl/STB)r_e (ft)r_w (ft)
Details
Drilling EngineeringWell Control

Additional Mud Returned by Slug

Vadd=(WsWm−1)VsV_{add}=\left(\frac{W_s}{W_m}-1\right)V_s
W_s (ppg)W_m (ppg)V_s (bbl)
Details
Production EngineeringWell Performance

Additional Pressure Drop in the Skin Zone

ΔPskin=141.2QoBoμoSkh\Delta P_{skin} = \frac{141.2 Q_o B_o \mu_o S}{k h}
Q_o (STB/day)B_o (bbl/STB)mu_o (cP)k (mD)h (ft)S (dimensionless)
Details
PetrophysicsResistivity Logs

Archie Flushed-Zone Water Saturation from Shallow Resistivity

Sxo=(aRmfϕmRxo)1/nS_{xo}=\left(\frac{aR_{mf}}{\phi^mR_{xo}}\right)^{1/n}
a (dimensionless)R_mf (ohm m)phi (fraction)m (dimensionless)R_xo (ohm m)n (dimensionless)
Details
Drilling EngineeringMud and Cementing

Cement Slurry Hydrostatic Pressure at Depth

Ph=GcemDP_h=G_{cem}D
G_cem (psi/ft)D (ft)
Details
Drilling EngineeringMud and Cementing

Cement Slurry Pressure Gradient from Density

Gcem=0.05195ρcemG_{cem}=0.05195\rho_{cem}
rho_cem (ppg)
Details
Production EngineeringInflow Performance

Composite IPR Productivity Index

Ji=q(Pr−Pb)+Pb1.8[1−0.2(PwfPr)−0.8(PwfPr)2]J_i=\frac{q}{(P_r-P_b)+\frac{P_b}{1.8}\left[1-0.2\left(\frac{P_{wf}}{P_r}\right)-0.8\left(\frac{P_{wf}}{P_r}\right)^2\right]}
q (STB/day)P_b (psi)P_wf (psi)P_r (psi)
Details
Production EngineeringWell Performance

Darcy-Weisbach Tubing Friction Pressure Drop

ΔPf=fDρLv22gcD⋅144\Delta P_f=\frac{f_D\rho Lv^2}{2g_cD\cdot144}
f_D (dimensionless)rho (lbm/ft3)L (ft)v (ft/s)D_i (in)
Details
Drilling EngineeringMud and Cementing

Differential Hydrostatic Pressure Between Cement Annulus and Mud in Casing

Pd=Pa−PcP_d=P_a-P_c
h_w (ft)h_f (ft)h_l (ft)h_t (ft)w_m (lb/gal)w_l (lb/gal)
Details
Drilling EngineeringWell Control

Dry Pipe Pulled Before Fill-Up for Pressure Drop

Ldry=ΔP(Cann+Cdp)0.052MWDdpL_{dry}=\frac{\Delta P(C_{ann}+C_{dp})}{0.052MWD_{dp}}
dP (psi)C_ann (bbl/ft)C_dp (bbl/ft)MW (ppg)D_dp (bbl/ft)
Details
Production EngineeringInflow Performance

Flow Coefficient During Drawdown

E=Pi−pwf−ΔpskinPi−pwfE=\frac{P_i-p_{wf}-\Delta p_{skin}}{P_i-p_{wf}}
P_i (psi)p_wf (psi)DeltaP_skin (psi)
Details
Production EngineeringWell Performance

Flow Efficiency with Skin Pressure Drop

E=p−pwf−141.2qBμskhp−pwfE = \frac{p-p_{wf}-\frac{141.2qB\mu s}{kh}}{p-p_{wf}}
p (psi)p_wf (psi)q (STB/day)B (RB/STB)mu (cP)s (dimensionless)
Details
PetrophysicsResistivity Logs

Hingle Crossplot True Resistivity

Rt=[ϕ(SwnaRw)1/m]−mR_t=\left[\phi\left(\frac{S_w^n}{aR_w}\right)^{1/m}\right]^{-m}
S_w (fraction)R_w (ohm m)phi (fraction)a (dimensionless)n (dimensionless)m (dimensionless)
Details
Drilling EngineeringWell Control

Hydrostatic Pressure Drop per Foot Pulling Dry Pipe

ΔPdry/ft=0.052MWDdpCann+Cdp\Delta P_{dry/ft}=\frac{0.052MWD_{dp}}{C_{ann}+C_{dp}}
MW (ppg)D_dp (bbl/ft)C_ann (bbl/ft)C_dp (bbl/ft)
Details
Drilling EngineeringWell Control

Hydrostatic Pressure Drop per Foot Pulling Wet Pipe

ΔPwet/ft=0.052MWCdp+DdpCann\Delta P_{wet/ft}=0.052MW\frac{C_{dp}+D_{dp}}{C_{ann}}
MW (ppg)C_dp (bbl/ft)D_dp (bbl/ft)C_ann (bbl/ft)
Details
Drilling EngineeringWell Control

Hydrostatic Pressure in Annulus Due to Slug

P=VaVs(Ws−Wm)0.052P=V_aV_s(W_s-W_m)0.052
V_a (ft/bbl)V_s (bbl)W_s (ppg)W_m (ppg)
Details
Reservoir EngineeringPressure Transient Analysis

Infinite-Acting Pseudoradial Bottomhole Flowing Pressure

Pwf=pi−162.6QoμoBokh[log⁡10t+log⁡10(kϕμoctrw2)−3.23+0.87S]P_{wf}=p_i-\frac{162.6Q_o\mu_oB_o}{kh}\left[\log_{10}t+\log_{10}\left(\frac{k}{\phi\mu_oc_tr_w^2}\right)-3.23+0.87S\right]
p_i (psi)Q_o (STB/day)B_o (bbl/STB)mu_o (cP)k (mD)h (ft)
Details