Stress dependency of permeability, porosity and flow channels in anhydrite and carbonate rocks

This study investigates the effect of stress magnitude and stress history on porosity and permeability values of anhydride and carbonate rocks. Porosity and permeability properties are measured for twelve anhydride and carbonate core samples under stress loading and unloading conditions. The results of permeability measurements show that tighter core samples are more stress dependent while the anhydride samples are generally more sensitive to the stress. The gap between stress loading and unloading (hysteresis) is more considerable at lower effective stress values. The results also indicate that the hysteresis is more noticeable in the anhydride core samples. The gas slippage factor is also determined which specifies the flow channels systems of rocks. Three different flow channels systems are observed in the anhydride core samples while the carbonate core samples show one flow channels system. Porosity measurements show that, it has less sensitivity to the stress for both anhydride and carbonate core samples.