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text-align: left; text-indent: 0pt; line-height: 43pt;">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
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)



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