Print this pageCalculation of 
Resistivity
of Irreducible Water for
Reserves Estimation
Frank W. Krieger, Peter J. Eadington, and Mark Lisk
A new fluid inclusion technique that allows determination of the resistivity
of irreducible water trapped during oil accumulation has been developed. The
technique is directly applicable to problems associated with the evaluation of
oil accumulations which arise when the salinity and thus the resistivity of
present day formation waters differ from those of the irreducible water trapped
during oil accumulation.
It is possible by measuring the ice melting temperature of samples of
formation water trapped during creation of three phase, oil-water-vapour
inclusions to calculate a salinity for the irreducible water and thus calculate
a resistivity to be used in reserves calculations.
Salinities of 71,000 to 85,000 parts per million have been measured on three phase inclusions in oil zone samples from the Papuan Foldbelt.
Present day salinities in the Papuan Foldbelt are about 10,000-12,000 parts per million indicating that oil charge occurred before the present day hydrologic system was emplaced.
Using salinity data from three phase inclusions results in resistivity values
of about 0.05 ohm/m for irreducible water while present day formation waters
have a resistivity of about 0.3 ohm/m at formation temperatures of 60°C.
Using the water saturation calculated from three phase fluid inclusion
salinity data compared with using the water saturation from present day
formation water
results in an estimated 25 % increase in reserves for oil fields
studied in the Papuan Foldbelt.
AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California