STRESS-DEPENDENCE OF THE PERMEABILITY, POROSITY, AND COMPRESSIBILITY OF FRACTURED CARBONATE ROCK

Although fractured reservoirs are important hydrocarbon resources, the increase in effective stress due to production causes fractures to be sealed and hence production rates decrease. A better understanding of permeability, porosity, and compressibility of fractures would be useful in optimizing production. This research paper describes experiments on carbonate fractured reservoir rocks by measuring the permeability, porosity, and compressibility of different types of fractures, based on their orientation, opening, density, and persistency. Fractured cylindrical rock samples from a south Iran oil reservoir were tested by helium gas apparatus in hydrostatic condition. Microscopic X-ray computerized tomography (CT) scanning was utilized to show fracture distribution and the network. The experimental results indicated that stress sensitivity of porosity in fractured rock is lower than that of permeability and compressibility. Different analytical models were applied to describe permeability, porosity, and compressibility with respect to effective stress. The analysis showed that the permeability and compressibility of fractured reservoirs are more dependent upon the orientation, opening, density, and persistency of fractures.

Automated summary

Fractured reservoirs are important hydrocarbon resources, but production-induced stress increase can lead to fracture sealing and decreased production rates. Experimental results show that the stress sensitivity of porosity in fractured rock is lower than that of permeability and compressibility. The permeability and compressibility of fractured reservoirs are more dependent upon the orientation, opening, density, and persistency of fractures.