consider a shale-free, dry, sandstone core plug. by measurement, the following data are known: d=254 cm, l= 6.00 cm, and mass (dry)=548 g. 1 knowing that the grain density of most sandstone is about 2.65 gm/cu. cm, estimate the porosity of the core plug. 2. the plug is completely saturated with 145,000-ppm nacl brine whose specific gravity is 1.1 the mass of the saturated core plug is now 60.38 g. calculate the porosity of the plug. 3. estimate the end-to-end resistance ofthe saturated core plug inohm at 80 degree fahrenheit. use chevron's formula for f when required. 4. by actual measurement, the end-to-end resistance of the plug is 83.3 ohm. calculate the ro value of the plug. 5. some of the brine is removed from the core plug: i. e, the core is partially desaturated. its mass now is 56.03 g. calculate the water saturation. 6. for anexponent n of 3, what would be the end-to-end resistance of the core?