NOTE
Simultaneous Measurement of Capillary Pressure and Resistivity using the Centrifuge the top face of the rock increases since the density of the oil phase, r o , is less than the density of the water phase, r w (3). Oil is thus forced into the In this Note we describe a centrifuge apparatus for simultanerock and the displaced water collects in the lower graduated receiving cup.
ously measuring resistivities and capillary pressures of a partially
The change in the position of the oil-water interface in the lower cup is a saturated rock. Simultaneous measurement overcomes errors due measure of the saturation change in the rock and is illuminated by a strobe.
to sample handling and hysteresis. Our apparatus has a four-
A CCD camera assembly attached to the observation port is used to capture terminal electrode design that uses the centrifugal force to mainthe image of the interface. The image is acquired automatically by a com- tain good contact with the rock. We report data for an Indiana puter and processed to quantify its pixel position. Calibration runs were limestone sample up to 10,000 rpm, corresponding to a capillary conducted independently, using known quantities of the fluid to get the pressure of 720 kPa. α§ 1998 Academic Press pixels per unit volume.