PetroCalcHubFree
Browse
132 indexed pages

Petrophysics Calculators

Use 132 petrophysics petroleum engineering calculators with formulas, units, default values, and source references.

Petrophysics calculators support porosity, saturation, resistivity, formation factor, shale correction, SP-log, nuclear-log, and core-log interpretation workflows.

132
Calculators
Free
No sign-in
Sources
Reviewable
PetrophysicsRock Properties

Acoustic Transit Time

Δt=106v\Delta t=\frac{10^6}{v}
Open calculator
PetrophysicsRock Properties

Adhesion Tension from Water-Oil Interfacial Tension

τ=σwocos⁡θ\tau=\sigma_{wo}\cos\theta
Open calculator
PetrophysicsRock Properties

Air Density for de Nouy Upper Phase Correction

ρair=4.324×10−2PT\rho_{air}=4.324\times10^{-2}\frac{P}{T}
Open calculator
PetrophysicsRock Properties

Amott-Harvey Wettability Index

IAH=Iw−IoI_{AH}=I_w-I_o
Open calculator
PetrophysicsRock Properties

Amplitude Transmission Coefficient in Seismic Reflection and Refraction

T=2Z1Z2+Z1T=\frac{2Z_1}{Z_2+Z_1}
Open calculator
PetrophysicsRock Properties

Apparent Gamma Ray Recorder Intensity

Ja(t)=J1+(J2−J1)(1−e−t/rc)J_a(t)=J_1+(J_2-J_1)(1-e^{-t/r_c})
Open calculator
PetrophysicsRock Properties

Apparent Interfacial Tension - de Nouy Ring Method

S=mg2lS=\frac{mg}{2l}
Open calculator
PetrophysicsElectrical Properties

Apparent Resistivity

R=GtΔV12IR=G_t\frac{\Delta V_{12}}{I}
Open calculator
PetrophysicsElectrical Properties

Archie Cementation Exponent from Formation Factor

m=ln⁡(F/a)ln⁡(1/ϕ)m=\frac{\ln(F/a)}{\ln(1/\phi)}
Open calculator
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}
Open calculator
PetrophysicsElectrical Properties

Archie Formation Factor from Porosity

F=1ϕmF = \frac{1}{\phi^m}
Open calculator
PetrophysicsElectrical Properties

Archie Resistivity Index from Water Saturation

RI=Sw−nRI = S_w^{-n}
Open calculator
PetrophysicsElectrical Properties

Archie True Formation Resistivity

Rt=RwϕmSwnR_t = \frac{R_w}{\phi^m S_w^n}
Open calculator
PetrophysicsElectrical Properties

Archie Water Saturation from Formation Factor

Sw=(FRwRt)1/nS_w = \left(\frac{FR_w}{R_t}\right)^{1/n}
Open calculator
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}
Open calculator
PetrophysicsResistivity Logs

Arps Formation Water Resistivity Temperature Correction

Rw2=Rw1T1F+6.77T2F+6.77R_{w2}=R_{w1}\frac{T_{1F}+6.77}{T_{2F}+6.77}
Open calculator
PetrophysicsRock Properties

Atlas Wireline Neutron Lifetime Log

Σ=3.15τ\Sigma=\frac{3.15}{\tau}
Open calculator
PetrophysicsResistivity Logs

Bulk Volume Water from Porosity and Water Saturation

BVW=ϕSwBVW=\phi S_w
Open calculator
PetrophysicsResistivity Logs

Carothers Formation Factor - Calcareous Sands

F=1.45ϕ1.70F=\frac{1.45}{\phi^{1.70}}
Open calculator
PetrophysicsResistivity Logs

Carothers Formation Factor - Shaly Sands

F=1.65ϕ1.33F=\frac{1.65}{\phi^{1.33}}
Open calculator
PetrophysicsResistivity Logs

Chalky Carbonate Formation Factor from Porosity

Fc=1ϕ2F_c=\frac{1}{\phi^2}
Open calculator
PetrophysicsResistivity Logs

Chevron Formation Factor from Porosity

F=1.13ϕ1.73F=\frac{1.13}{\phi^{1.73}}
Open calculator
PetrophysicsRock Properties

Clavier Shale Volume from Gamma Ray Index

Vsh=1.7−3.38−(IGR+0.7)2V_{sh}=1.7-\sqrt{3.38-(I_{GR}+0.7)^2}
Open calculator
PetrophysicsRock Properties

Coates NMR Permeability from Free-Fluid Ratio

k=(ϕNMRC)4(FFIBVI)2k=\left(\frac{\phi_{NMR}}{C}\right)^4\left(\frac{\mathrm{FFI}}{\mathrm{BVI}}\right)^2
Open calculator
PetrophysicsResistivity Logs

Compacted Carbonate Formation Factor from Porosity

FcO=1ϕaF_{cO}=\frac{1}{\phi^a}
Open calculator
PetrophysicsRock Properties

Composite Capture Cross Section of the Formation Schlumberger Thermal Decay Time Tool

Σ=4.55τ\Sigma=\frac{4.55}{\tau}
Open calculator
PetrophysicsRock Properties

Contact Angle from Interfacial Tensions

θ=cos⁡−1(σso−σswσwo)\theta=\cos^{-1}\left(\frac{\sigma_{so}-\sigma_{sw}}{\sigma_{wo}}\right)
Open calculator
PetrophysicsRock Properties

Corrected Interfacial Tension - de Nouy Ring Method

σ=SC\sigma=SC
Open calculator
PetrophysicsRock Properties

de Nouy Ring Interfacial Tension Correction Factor

C=0.7250+0.01452Sl2(ρD−ρd)+0.04534−1.679rRC=0.7250+\sqrt{\frac{0.01452S}{l^2(\rho_D-\rho_d)}+0.04534-\frac{1.679r}{R}}
Open calculator
PetrophysicsRock Properties

Density Log Porosity from Bulk Density

Φ=ρma−ρbρma−ρf\Phi=\frac{\rho_{ma}-\rho_b}{\rho_{ma}-\rho_f}
Open calculator
PetrophysicsElectrical Properties

Diffuse-Layer Thickness from Salt Concentration

xd=3n−1/2x_d=3n^{-1/2}
Open calculator
PetrophysicsElectrical Properties

Dual-Water Brine-Saturated Rock Conductivity

Co=1Fo(Cwf+fdlvQQv(Cwb−Cwf))C_o=\frac{1}{F_o}\left(C_{wf}+f_{dl}v_QQ_v(C_{wb}-C_{wf})\right)
Open calculator
PetrophysicsElectrical Properties

Effect of Clay on Conductivity

Co=CwF+CsC_o=\frac{C_w}{F}+C_s
Open calculator
PetrophysicsRock Properties

Effective Photoelectric Absorption Cross Section Index

Pe=(Z10)3.6P_e=\left(\frac{Z}{10}\right)^{3.6}
Open calculator
PetrophysicsElectrical Properties

Electric Resistance to Radial Current from a Wellbore

Re=ln⁡(re/rw)2πhσR_e=\frac{\ln(r_e/r_w)}{2\pi h\sigma}
Open calculator
PetrophysicsElectrical Properties

Electrical Conductivity from Resistivity

σ=1ρe\sigma = \frac{1}{\rho_e}
Open calculator
PetrophysicsElectrical Properties

Electrical Resistivity from Resistance Geometry

R=rALR = r \frac{A}{L}
Open calculator
PetrophysicsElectrical Properties

Electrochemical Potential - SP Log

Ec=2tClRTFln⁡(a1a2)E_c=2t_{Cl}\frac{RT}{F}\ln\left(\frac{a_1}{a_2}\right)
Open calculator
PetrophysicsElectrical Properties

Electrode Array Geometric Coefficient

Gt=4πr1r2r2−r1G_t=4\pi r_1\frac{r_2}{r_2-r_1}
Open calculator
PetrophysicsElectrical Properties

Electrokinetic Potential Across Mud Cake

Ek=xpyE_k=xp^y
Open calculator
PetrophysicsRock Properties

Electron Density Index for Gamma-Gamma Absorption Logging

ρe=2NeNA\rho_e=\frac{2N_e}{N_A}
Open calculator
PetrophysicsRock Properties

Epithermal Neutron Diffusion Coefficient

De=ξLe2ΣeD_e=\xi L_e^2\Sigma_e
Open calculator
PetrophysicsRock Properties

Epithermal Neutron Flux Distribution

ψe=NN4πDee−r/Ler\psi_e=\frac{N_N}{4\pi D_e}\frac{e^{-r/L_e}}{r}
Open calculator
PetrophysicsResistivity Logs

Equivalent Formation Water Resistivity from SP

Rwe=Rmfe10−SSP/K,K=61+0.133TFR_{we}=\frac{R_{mfe}}{10^{-SSP/K}},\quad K=61+0.133T_F
Open calculator
PetrophysicsRock Properties

Error Percentage of Porosity Measurements

Eϕ=ϕm−ϕpsϕm100E_\phi=\frac{\phi_m-\phi_{ps}}{\phi_m}100
Open calculator
PetrophysicsResistivity Logs

Fertl-Hammack Shaly Sand Water Saturation

Sw=(FRwRt)0.5−VshRw0.4ϕeRshS_w=\left(\frac{FR_w}{R_t}\right)^{0.5}-\frac{V_{sh}R_w}{0.4\phi_eR_{sh}}
Open calculator
PetrophysicsResistivity Logs

Flushed-Zone Apparent Formation Factor from Apparent Saturation

Fxo=FsSxo2F_{xo}=\frac{F_s}{S_{xo}^2}
Open calculator
PetrophysicsResistivity Logs

Flushed-Zone Water Saturation from Formation Factor

Sxo=(FRmfRxo)1/nS_{xo}=\left(\frac{FR_{mf}}{R_{xo}}\right)^{1/n}
Open calculator
PetrophysicsResistivity Logs

Formation Factor - Archie's Equation

F=TϕF = \frac{T}{\phi}
Open calculator
PetrophysicsElectrical Properties

Formation Factor from Water-Filled Rock Resistivity

F=RoRwF = \frac{R_o}{R_w}
Open calculator
PetrophysicsResistivity Logs

Formation Resistivity and Permeability - Carothers Limestones

k=4×108F3.65k=\frac{4\times10^8}{F^{3.65}}
Open calculator
PetrophysicsResistivity Logs

Formation Resistivity and Permeability - Carothers Sandstones

k=7×108F4.5k=\frac{7\times10^8}{F^{4.5}}
Open calculator
PetrophysicsElectrical Properties

Formation Water Resistivity from Resistivity Ratio Method

Rw=RtRxoRmfR_w=\frac{R_t}{R_{xo}}R_{mf}
Open calculator
PetrophysicsRock Properties

Fraction of Total Porosity Occupied by Clays

q=ΦS−ΦDΦSq=\frac{\Phi_S-\Phi_D}{\Phi_S}
Open calculator
PetrophysicsRock Properties

Fresh Water-Filled Porosity - Limestones

Φ=ρls−ρbρls−ρw\Phi=\frac{\rho_{ls}-\rho_b}{\rho_{ls}-\rho_w}
Open calculator
PetrophysicsRock Properties

Gamma Ray Log Shale Index

IGR=GR−GRclGRsh−GRclI_{GR}=\frac{GR-GR_{cl}}{GR_{sh}-GR_{cl}}
Open calculator
PetrophysicsRock Properties

Gas-Effect Corrected Porosity from Neutron-Density Logs

Φcorr=(ΦD2+ΦN22)0.5\Phi_{corr}=\left(\frac{\Phi_D^2+\Phi_N^2}{2}\right)^{0.5}
Open calculator
PetrophysicsElectrical Properties

Generalized Archie Formation Factor with Lithology Coefficient

F=aϕmF=\frac{a}{\phi^m}
Open calculator
PetrophysicsRock Properties

Half Thickness Value

h1/2=0.693αlh_{1/2}=\frac{0.693}{\alpha_l}
Open calculator
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}
Open calculator
PetrophysicsResistivity Logs

Humble Formation Factor from Porosity

F=0.62ϕ2.15F=\frac{0.62}{\phi^{2.15}}
Open calculator
PetrophysicsResistivity Logs

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}
Open calculator
PetrophysicsRock Properties

Integrated Radial Geometric Factor

G(r)=1−e−r/hˉG(r)=1-e^{-r/\bar{h}}
Open calculator
PetrophysicsRock Properties

Larionov Older-Rock Shale Volume from Gamma Ray Index

Vsh=0.33(22IGR−1)V_{sh}=0.33\left(2^{2I_{GR}}-1\right)
Open calculator
PetrophysicsRock Properties

Larionov Tertiary-Rock Shale Volume from Gamma Ray Index

Vsh=0.083(23.7IGR−1)V_{sh}=0.083\left(2^{3.7I_{GR}}-1\right)
Open calculator
PetrophysicsElectrical Properties

Lateral Device Geometric Coefficient

GL=4πAMANMNG_L=4\pi AM\frac{AN}{MN}
Open calculator
PetrophysicsRock Properties

Linear Absorption Attenuation Coefficient

αl=σN\alpha_l=\sigma N
Open calculator
PetrophysicsRock Properties

Liquid Permeability - Permeameter Lab Measurement

k=μVLAPtk = \frac{\mu V L}{A P t}
Open calculator
PetrophysicsRock Properties

Mean Free Path Photon Absorption

h=1αlh=\frac{1}{\alpha_l}
Open calculator
PetrophysicsElectrical Properties

Membrane Potential for SP Log

Em=RTFln⁡(a1a2)E_m=\frac{RT}{F}\ln\left(\frac{a_1}{a_2}\right)
Open calculator
PetrophysicsResistivity Logs

Movable Hydrocarbon Saturation from Flushed Zone

Shm=Sxo−SwS_{hm}=S_{xo}-S_w
Open calculator
PetrophysicsResistivity Logs

Mud Cake Resistivity from Mud and Filtrate Resistivity

Rmc=0.69Rmf(RmRmf)2.65R_{mc}=0.69R_{mf}\left(\frac{R_m}{R_{mf}}\right)^{2.65}
Open calculator
PetrophysicsResistivity Logs

Mud Filtrate Resistivity from Mud Resistivity

Rmf=KmRm1.07R_{mf}=K_mR_m^{1.07}
Open calculator
PetrophysicsRock Properties

Neutron Lethargy Logarithmic Energy Decrement

u=ln⁡(EoE)u=\ln\left(\frac{E_o}{E}\right)
Open calculator
PetrophysicsRock Properties

Neutron Porosity in a Shaly Formation

ΦN=ΦT+VshΦNsh\Phi_N=\Phi_T+V_{sh}\Phi_{Nsh}
Open calculator
PetrophysicsRock Properties

NMR Free-Fluid Index from Porosity Partition

FFI=MPHI−BVI\mathrm{FFI}=\mathrm{MPHI}-\mathrm{BVI}
Open calculator
PetrophysicsElectrical Properties

Non-Ideal Shale Membrane Efficiency from Shale Resistivity

meff=0.47+0.3Rshm_{eff}=0.47+0.3R_{sh}
Open calculator
PetrophysicsElectrical Properties

Non-NaCl Static Self Potential from Ion Activities

Essp=−Klog⁡10(aNa+(aCa+aMg)0.5aNam+(aCam+aMgm)0.5)E_{ssp}=-K\log_{10}\left(\frac{a_{Na}+(a_{Ca}+a_{Mg})^{0.5}}{a_{Nam}+(a_{Cam}+a_{Mgm})^{0.5}}\right)
Open calculator
PetrophysicsElectrical Properties

Normal Sonde Geometric Coefficient

GN=4πAMG_N=4\pi AM
Open calculator
PetrophysicsResistivity Logs

Oil Saturation from IE and CDN Resistivity Logs

So=1−RoRtS_o=1-\sqrt{\frac{R_o}{R_t}}
Open calculator
PetrophysicsRock Properties

Pair Production Gamma Ray Interactions

Ee=Ec−EE_e=E_c-E
Open calculator
PetrophysicsResistivity Logs

Partially Saturated Shaly Sand Resistivity Vsh Model

Rt=1(Vsh/Rsh)Sw+(1/F)Sw2/RwR_t=\frac{1}{(V_{sh}/R_{sh})S_w+(1/F)S_w^2/R_w}
Open calculator
PetrophysicsResistivity Logs

Phillips Formation Factor - Average Sands

F=1.45ϕ1.54F=\frac{1.45}{\phi^{1.54}}
Open calculator
PetrophysicsRock Properties

Photoelectric Absorption Cross Sectional Area

αpe=12.1Z3.6Eγ3.15\alpha_{pe}=\frac{12.1Z^{3.6}}{E_\gamma^{3.15}}
Open calculator
PetrophysicsResistivity Logs

Pickett Crossplot Log True Resistivity

log⁡10Rt=−mlog⁡10(ϕ)+log⁡10(Rw)−nlog⁡10(Sw)\log_{10}R_t=-m\log_{10}(\phi)+\log_{10}(R_w)-n\log_{10}(S_w)
Open calculator
PetrophysicsRock Properties

Poissons Ratio Seismic Arrival Time Method

ν=Vp2−2Vs22(Vp2−Vs2)\nu=\frac{V_p^2-2V_s^2}{2\left(V_p^2-V_s^2\right)}
Open calculator
PetrophysicsRock Properties

Porosity from Neutron Flux Response

ϕ=α−βlog⁡10(N)\phi=\alpha-\beta\log_{10}(N)
Open calculator
PetrophysicsResistivity Logs

Porter-Carothers Formation Factor - California Pliocene Logs

Fg=2.45ϕ1.08F_g=\frac{2.45}{\phi^{1.08}}
Open calculator
PetrophysicsResistivity Logs

Porter-Carothers Formation Factor - Gulf Coast Miocene Logs

Fc=1.97ϕ1.29F_c=\frac{1.97}{\phi^{1.29}}
Open calculator
PetrophysicsRock Properties

Pycnometer Volume Correction

Vg=Vk[1+Ω(Tt−Tk)]V_g=V_k\left[1+\Omega(T_t-T_k)\right]
Open calculator
PetrophysicsRock Properties

Rate of Radioactive Decay

N=Noe−CdtN=N_o e^{-C_d t}
Open calculator
PetrophysicsRock Properties

Raymer-Hunt Transform - Porosity Transit Time Relationship

Δt=((1−ϕ)2Δtma+ϕΔtf)−1\Delta t=\left(\frac{(1-\phi)^2}{\Delta t_{ma}}+\frac{\phi}{\Delta t_f}\right)^{-1}
Open calculator
PetrophysicsRock Properties

Relation Between Concentration of K Th or U and Recorded Total Gamma Ray Signal

γ=4CTh+8CU+CK\gamma=4C_{Th}+8C_U+C_K
Open calculator
PetrophysicsElectrical Properties

Relationship Between SSP and Rw - NaCl Predominant

SSP=−Ksplog⁡10(RmfeqRweq)SSP=-K_{sp}\log_{10}\left(\frac{R_{mfeq}}{R_{weq}}\right)
Open calculator
PetrophysicsRock Properties

Relative Centrifugal Force

RCF=(RPM265)2dRCF=\left(\frac{RPM}{265}\right)^2d
Open calculator
PetrophysicsRock Properties

Reservoir Wettability Characterization Rise-in-Core Method

cos⁡θ12=μ1ρ22−μ2ρ12ρ12ρ22CγL2L1m2t\cos\theta_{12}=\frac{\mu_1\rho_2^2-\mu_2\rho_1^2}{\rho_1^2\rho_2^2C\gamma_{L2L1}}\frac{m^2}{t}
Open calculator
PetrophysicsResistivity Logs

Residual Hydrocarbon Saturation from Flushed Zone

Shr=1−SxoS_{hr}=1-S_{xo}
Open calculator
PetrophysicsElectrical Properties

Resistivity Bed Reflection Coefficient

CR=R1−R2R1+R2C_R=\frac{R_1-R_2}{R_1+R_2}
Open calculator
PetrophysicsResistivity Logs

Resistivity Index - Archie's Law

RI=RtRoRI=\frac{R_t}{R_o}
Open calculator
PetrophysicsElectrical Properties

Resistivity Index from True and Water-Filled Resistivity

I=RtRoI=\frac{R_t}{R_o}
Open calculator
PetrophysicsElectrical Properties

Rock Conductivity for Clean Water-Bearing Rocks

Co=CwFC_o=\frac{C_w}{F}
Open calculator
PetrophysicsRock Properties

SDR NMR Permeability from T2 Geometric Mean

k=aϕNMR4T2gm2k=a\phi_{NMR}^4T_{2gm}^2
Open calculator
PetrophysicsResistivity Logs

Sethi Formation Factor - Clean Granular Formations

F=1ϕ2.05−ϕF=\frac{1}{\phi^{2.05-\phi}}
Open calculator
PetrophysicsRock Properties

Shale Index from Gamma Ray Spectrometry - Potassium

Ish,K=CK,log−CK,minCK,sh−CK,minI_{sh,K}=\frac{C_{K,log}-C_{K,min}}{C_{K,sh}-C_{K,min}}
Open calculator
PetrophysicsRock Properties

Shale Index from Gamma Ray Spectrometry - Thorium

Ish,Th=CTh,log−CTh,minCTh,sh−CTh,minI_{sh,Th}=\frac{C_{Th,log}-C_{Th,min}}{C_{Th,sh}-C_{Th,min}}
Open calculator
PetrophysicsRock Properties

Shale Index from Gamma Ray Spectrometry - Uranium-Free Gamma

Ish,Uf=GUf,log−GUf,minGUf,sh−GUf,minI_{sh,Uf}=\frac{G_{Uf,log}-G_{Uf,min}}{G_{Uf,sh}-G_{Uf,min}}
Open calculator
PetrophysicsResistivity Logs

Shell Formation Factor - Low-Porosity Carbonates

Fl=1ϕ1.87+0.019/ϕF_l=\frac{1}{\phi^{1.87+0.019/\phi}}
Open calculator
PetrophysicsResistivity Logs

Simandoux Total Shale Equation

Sw=0.4Rwϕe2[−VshRsh+(VshRsh)2+5ϕe2RwRt]S_w=\frac{0.4R_w}{\phi_e^2}\left[-\frac{V_{sh}}{R_{sh}}+\sqrt{\left(\frac{V_{sh}}{R_{sh}}\right)^2+\frac{5\phi_e^2}{R_wR_t}}\right]
Open calculator
PetrophysicsResistivity Logs

Simandoux Water Saturation from Shaly Sand Logs

Sw=−VshRsh+(VshRsh)2+4FRw(1−Vsh)Rt2FRw(1−Vsh)S_w=\frac{-\frac{V_{sh}}{R_{sh}}+\sqrt{\left(\frac{V_{sh}}{R_{sh}}\right)^2+\frac{4}{F R_w (1-V_{sh}) R_t}}}{\frac{2}{F R_w (1-V_{sh})}}
Open calculator
PetrophysicsRock Properties

Slowness of the Formation

Δt=tlLs−DbΔtm2(Ls2+Db2)−tl2Ls2+Db2\Delta t=\frac{t_lL_s-D_b\sqrt{\Delta t_m^2(L_s^2+D_b^2)-t_l^2}}{L_s^2+D_b^2}
Open calculator
PetrophysicsRock Properties

Sonic Compaction Correction Factor from Shale Transit Time

Cp=Δtshc100C_p=\Delta t_{sh}\frac{c}{100}
Open calculator
PetrophysicsRock Properties

Sonic First-Arrival Time in a Borehole

tlog=Lsvf+dh−(dt+2lc)vm1−(vmvf)2t_{log}=\frac{L_s}{v_f}+\frac{d_h-(d_t+2l_c)}{v_m}\sqrt{1-\left(\frac{v_m}{v_f}\right)^2}
Open calculator
PetrophysicsRock Properties

Sonic Porosity Raymer-Hunt-Gardner Method

Φsonic=CRHGΔt−ΔtmaΔt\Phi_{sonic}=C_{RHG}\frac{\Delta t-\Delta t_{ma}}{\Delta t}
Open calculator
PetrophysicsRock Properties

Spacing Between Transmitter and Receiver

(Ls)c=2soff1+Cmf1−Cmf(L_s)_c=2s_{off}\sqrt{\frac{1+C_{mf}}{1-C_{mf}}}
Open calculator
PetrophysicsElectrical Properties

Static Self Potential from NaCl Activities

Essp=−Klog⁡10(awamf)E_{ssp}=-K\log_{10}\left(\frac{a_w}{a_{mf}}\right)
Open calculator
PetrophysicsElectrical Properties

Static Spontaneous Potential from Equivalent Resistivities

SSP=−Klog⁡10(RmfeRwe)SSP=-K\log_{10}\left(\frac{R_{mfe}}{R_{we}}\right)
Open calculator
PetrophysicsRock Properties

Stieber Shale Volume from Gamma Ray Index

Vsh=IGR3−2IGRV_{sh}=\frac{I_{GR}}{3-2I_{GR}}
Open calculator
PetrophysicsResistivity Logs

Tortuosity from Resistivity Log Path Lengths

T=La2L2T=\frac{L_a^2}{L^2}
Open calculator
PetrophysicsRock Properties

Total Porosity from Pore Volumes

ϕ=Vi+VdVb\phi = \frac{V_i + V_d}{V_b}
Open calculator
PetrophysicsElectrical Properties

Total Rock Conductivity from Water Saturation

Ct=CwSwϕEC_t=C_wS_w\phi E
Open calculator
PetrophysicsRock Properties

True Sonic Porosity from Compaction Correction

Φt=ΦaCp\Phi_t=\frac{\Phi_a}{C_p}
Open calculator
PetrophysicsRock Properties

USBM Wettability Index

IU=log⁡10(A1A2)I_U=\log_{10}\left(\frac{A_1}{A_2}\right)
Open calculator
PetrophysicsRock Properties

Volumetric Photoelectric Absorption Cross Section

U=PeρeU=P_e\rho_e
Open calculator
PetrophysicsResistivity Logs

Water Salinity Index Ratio

Sw=CaCS_w=\frac{C_a}{C}
Open calculator
PetrophysicsResistivity Logs

Water Saturation from IE and CDN Resistivity Logs

Sw=RoRtS_w=\sqrt{\frac{R_o}{R_t}}
Open calculator
PetrophysicsResistivity Logs

Water Saturation from Neutron Capture Cross Section

Sw=(Σlog−Σma)−ϕ(Σh−Σma)ϕ(Σw−Σh)S_w=\frac{(\Sigma_{log}-\Sigma_{ma})-\phi(\Sigma_h-\Sigma_{ma})}{\phi(\Sigma_w-\Sigma_h)}
Open calculator
PetrophysicsResistivity Logs

Water-Saturated Shaly Sand Resistivity Vsh Model

Ro=1Vsh/Rsh+1/(FRw)R_o=\frac{1}{V_{sh}/R_{sh}+1/(FR_w)}
Open calculator
PetrophysicsRock Properties

Wavelength Equation

λ=Cf\lambda=\frac{C}{f}
Open calculator
PetrophysicsElectrical Properties

Waxman-Smits Clean-Sand Brine-Saturated Rock Conductivity

Co=1F(Ccl+Cw)C_o=\frac{1}{F}\left(C_{cl}+C_w\right)
Open calculator
PetrophysicsElectrical Properties

Wellbore Electric Voltage Generation

V=Ve,w−ΔVeln⁡(r/rw)ln⁡(re/rw)V=V_{e,w}-\Delta V_e\frac{\ln(r/r_w)}{\ln(r_e/r_w)}
Open calculator
PetrophysicsRock Properties

Wyllie Time-Average Sonic Porosity - Compacted Formations

Φs=Δt−ΔtmaΔtf−Δtma\Phi_s=\frac{\Delta t-\Delta t_{ma}}{\Delta t_f-\Delta t_{ma}}
Open calculator
PetrophysicsRock Properties

Wyllie Time-Average Sonic Porosity - Uncompacted Formations

Φs=(Δt−Δtma)/(Δtf−Δtma)Bcp\Phi_s=\frac{(\Delta t-\Delta t_{ma})/(\Delta t_f-\Delta t_{ma})}{B_{cp}}
Open calculator