Consider a shale-free, dry, sandstone core plug. By measure- ment, the following data are known: d=2.54 cm, L=5.00 cm, and mass (dry)=54.8 g. a. Knowing that the grain density of most sandstones is about 2.65 g/cm, estimate the porosity of the core plug. b. The plug is completely saturated with 145,000-ppm NaCl. brine whose specific gravity is 1.1. The mass of the satu- rated core plug is now 60.38 g. Calculate the porosity of the plug. c. Estimate the end-to-end resistance of the saturated core plug in 2 at 80F. d. By actual measurement, the end-to-end resistance of the plug is 83.3 2. Calculate the R, value of the plug. e. Some of the brine is removed from the core plug; i.e., the core is partially desaturated. Its mass is now 57.03 g. Cal- culate the water saturation. f. For an exponent n of 2, what would be the end-to-end resistance of the core and its true resistivity?