FORMATION RESISTIVITY FACTOR (a, m values)
Resistance of the simple brine is measured and resistivity at standard temperature of 77 deg F is calculated. The brine saturated samples are mounted as shown in the schematic with the porous plate at one end along with the end stems.
Samples are loaded in core holders and held at minimum confining stress (800 psig) and flushed with brine to ensure complete saturation. A porous plate capable of withstanding 200 psig air brine capillary pressure is inserted between the bottom end of the sample and the bottom end stem.
Resistivity of the sample is measured under ambient conditions (zero net confining stress).
Pressure is subsequently increased to reservoir stress of and reduction in pore volume and increase in the sample resistivity is monitored.
Resisitivty is monitored over a few days and stable readings were used in the calculations.
Formation resistivity factor is calculated and the "m" cememtation exponent value is calculated.
RESISTIVITY INDEX (RI, n values) AND CAPILARY PRESSURE
Using air as the displacing medium, the samples were desaturated at constant Air Brine Capillary pressure.
The pressures used are 0.5, 1, 2, 4, 8, 15, 35, 70, 150 psig.
At each pressure, resisitivty and residual water saturation in the sample is monitored over a few days and stable readings of saturation and resistivity were used in the calculations.