FORMULA PETROFISIKA - KOMPILASI

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 * <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)) ))

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