Average core analysis values for porosity, permeability, oil, gas, and water saturation should be determined for each facies recognized to identify those facies of greater and lesser reservoir quality (Figure 3a). In gas-bearing sandstones, very low values of porosity and permeability are acceptable and expected. While the average air permeability values rarely exceed 1.0 md (millidarcy) for tight gas reservoirs, a significant difference in permeability values often occurs between facies (Figure 3b). | Average core analysis values for porosity, permeability, oil, gas, and water saturation should be determined for each facies recognized to identify those facies of greater and lesser reservoir quality (Figure 3a). In gas-bearing sandstones, very low values of porosity and permeability are acceptable and expected. While the average air permeability values rarely exceed 1.0 md (millidarcy) for tight gas reservoirs, a significant difference in permeability values often occurs between facies (Figure 3b). |