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BASIC PETROPHYSICAL FORMULAE

BASIC PETROPHYSICAL FORMULAE. Compiled By:- Muhammad Zahid petrophysicist786@hotmail.com. POROSITY. Effective Porosity PHIE = PHIA * (1-Vshl) Density Porosity PHID = (RhoM - RHOB) / (RhoM - RhoF) Average Neutron Density Porosity PHIA = (PHID + PHIN) / 2 Gamma Ray Neutron Porosity

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BASIC PETROPHYSICAL FORMULAE

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  1. BASIC PETROPHYSICAL FORMULAE Compiled By:- Muhammad Zahid petrophysicist786@hotmail.com

  2. POROSITY • Effective Porosity • PHIE = PHIA * (1-Vshl) • Density Porosity • PHID = (RhoM - RHOB) / (RhoM - RhoF) • Average Neutron Density Porosity • PHIA = (PHID + PHIN) / 2 • Gamma Ray Neutron Porosity • Enter Values for PorMax, PorMin... • PorMax = 0.35 • PorMin = 0.02 • Enter Values in Counts Per Second or API... • CPS_PorMax = 75 • CPS_PorMin = 600 • B = log(PorMax/PorMin) / (CPS_PorMax - CPS_PorMin) • A = PorMax / 10 ^ (B*CPS_PorMax) • PHIGRN = A * 10 ^ (B * CPS)

  3. Sonic Porosity (Wyllie) • PHIS = (DT - DTma) / (DTfld - DTma) • Sonic Porosity (Wyllie) • Enter Compaction Coefficient below, • Cmp = 1.0 • PHIS = (1/Cmp) * (DT - DTma) / (DTfld - DTma) • Sonic Porosity (Empirical) • PHIS = 0.67 * (DT - DTma) / DT • Apparent Sonic Matrix • DTma = ( DT - PHIA * DTfld ) / (1 - PHIA) • Apparent Density Matrix • RHOMa = (RHOB - PHIA * RhoF) / (1 - PHIA) • Bulk Volume Water • BVW = PHIA * SwA. • Hydrocarbon Pore Volume • HCPV = (1-SwA) * PHIA • Hydrocarbon Pore Volume • SoPhiH = (1-SwA) * PHIA

  4. WATER RESISTIVITY • Archie Ro • Ro = a * Rw / (PHIA^m) • Apparent Water Resistivity • Rwa = RT * PHIA^m • Conductivity • COND = 1000/RT • Rw from Dual Water • RwDW = Rw * RwBnd / (Rw * Vshl + (1-Vshl) * RwBnd) • Ro from Dual Water • RoDW = (1 / (PHIA^m)) * (Rw * RwBnd / (Rw * Vshl + RwBnd * (1 - Vshl))) • Modified Simandoux Ro • If (Vshl < 1) • RoMS = 1/(PHIE^m / (a* Rw*(1-Vshl)) + Vshl/Rshl)

  5. Resistivity Temp Correction • T1 and T2 in 'F • R2 = R1 * (T1 + 6.77) / (T2 + 6.77) • Resistivity Temp Correction • T1 and T2 in 'C • R2 = R1 * (T1 + 21.5) / (T2 + 21.5)

  6. WATER SATURATION • Archie Water Saturation • SwA = sqrt( Rw / (RT * PHIA^2) ) • Archie Water Saturation • SwA = (a * Rw / ( RT * PHIA^m) )^(1/n) • Archie Water Saturation (Humble) • SwA = sqrt( .62 * Rw / (RT * PHIA ^2.15) ) • Archie Water Saturation • SwA = sqrt( Rw / (RT * PHID ^m) ) • Archie Water Saturation • SwA = sqrt(Ro / RT) • Archie Water Saturation • SwA = sqrt(Rw / Rwa) • SwA = min( 1, max( 0, SwA )

  7. Dual Water SwT & SwE • Calculate SwT Total Porosity • Y = Vshl * ( RwBnd - Rw ) / ( 2 * RwBnd ) • SwT = Y +( (Rw / ( RT * PHIA^2 ) ) + Y^2 )^.5 • SwT = min( 1, max( Vshl, SwT ) ) • Calculate SwE Effective Porosity • If ( Vshl < .75 ) • SwE = ( SwT - Vshl ) / ( 1 - Vshl ) • Modified Simandoux SwMS • If (Vshl < 1) • SwMS = (sqrt( (Vshl/Rshl)^2 + 4*PHIE^m/(a*Rw*(1-Vshl)*RT) ) - Vshl/Rshl)/(2*PHIE^m/(a*Rw*(1-Vshl)) )

  8. Indonesian SwI • SwI = sqrt(1/RT) / ( Vshl^(1- 0.5*Vshl) /sqrt(Rshl) + sqrt( PHIE^m / (a*Rw)) ) • Ratio Method Sw • Requires normalized SP, • Rmf/Rw ratio from SP... • K = ~ 61 + 0.1333 * <Temp> • K = -71 • RmfRwRatio = 10 ^ (SP / K) • Sw = Min( 1, ( (ResS/ResD) / (RmfRwRatio) ) ^(5/8) ) • Vshl = min(1, max(0, (GR-GRcln) / (GRshl-GRcln) )) • Vshl = min(1, max(0, (SP-SPcln) / (SPshl-SPcln) )) • Vshl = min(1, max(0, (RHOB - RhoM + PHIN * (RhoM - RhoF)) / (RhoShl - RhoM +HIshl * (RhoM - RhoF)) ))

  9. SHALE VOLUME • Calculate Vshl from Minimum of GR, SP & N/D • Vshl_GR = (GR-GRcln) / (GRshl-GRcln) ) • Vshl_SP = (SP-SPcln) / (SPshl-SPcln) )) • Vshl_ND = (RHOB - RhoM + PHIN * (RhoM - RhoF)) / (RhoShl - RhoM +HIshl * (RhoM - RhoF) • Vshl = Min(Vshl_GR , Min( Vshl_SP , Vshl_ND )) • Clavier Shale Correction • Vshl = 1.7 - (3.38 - (Vshl+0.7)^2)^0.5 • Steiber Shale Correction • Vshl = 0.5 * Vshl / (1.5 - Vshl)

  10. DT EQUATIONS • Faust's Equation for DT • DT_F = 1000/(2 * (DEPTH * RT) ^(1 / 6)) • Gardner's Equation for DT • DT_G = ((25 / RHOB) ^4) /140 • Sonic from Apparent Porosity • DT_P = DTma + PHIA * ( DTfld - DTma) • Sonic 3pt Average Curve • DTAve = (DT [-1] + DT + DT[1])/3 • Sonic 5pt Average Curve • DTAve = (DT[-2] + DT[-1] +DT + DT[1] + DT[2])/5 • Sonic 7pt Average Curve • DTAve = (DT[-3] + DT[-2] + DT[-1] +DT + DT[1] + DT[2]+ DT[3])/7

  11. PERMEABILITY • Tixier Permeability • K = (250 * PHIE^3/SwIrr)^2 • Timur Permeability • K = (100 * PHIE^2.25/SwIrr)^2 • Coates Permeability • K = (70 * PHIE^2 * (1- SwIrr)/SwIrr)^2

  12. MISCELLANEOUS • Oil in Barrels; Depth in Feet • BBL = 7758 * Acres * PHIA * (1 - SwA) • Gas in Mcfd; Depth in Feet • MCF = 43.560 * Acres * PHIA * (1 - SwA) • Oil in Barrels; Depth in Meters • BBL = 25450 * Acres * PHIA * (1 - SwA) • Gas in Mcfd; Depth in Meters • MCF = 142.9 * Acres * PHIA * (1 - SwA) • Oil in Barrels; Depth in Meters • BBL = 62890 * Hectares * PHIA * (1 - SwA) • Gas in Mcfd; Depth in Meters • MCF = 353.1 * Hectares * <Step> * PHIA * (1 - SwA) • Oil in Barrels with Pay criteria • If (PAY >0) • BBL = 7758 * Acres * PHIA * (1 - SwA) • Gas in Mcfd with PAY criteria • If (PAY >0) • MCF = 43.560 * Acres * PHIA * (1 - SwA)

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