Berikut adalah kompilasi rumus petrofisika (dari berbagai sumber) yang dapat digunakan dalam spreadsheet (excel dll). Tidak semua rumus harus digunakan, pilih yang sesuai dengan ketersediaan data, jenis kasus dan local knowledge. Pembaca diharapkan sudah cukup familiar dengan jenis - jenis data log, satuannya dan aplikasinya.

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)

POROSITY : Effective Porosity PHIE = PHIA * (1-Vshl) Density Porosity PHID = (RhoM - RHOB) / (RhoM - RhoF) Average Neutron Density Porosity PHIA = (PHID + PHIN) / 2 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

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)

RESISTIVITY TEMP CORRECTION (for Rw, Rmf) 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)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 ) 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 < 0.75 ) 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)) )

Indonesian Sw (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 * 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)) ))

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