Influence of Pores, Fractures and Pressure on Permeability and Elastic Wave Velocities in Rock

It is essential to know how fluid flow in pores and fracture networks in rock and elastic wave velocities respond to the elevated pressures found at depth for better understandeing of seismology, volcanology and rock engineering. In this study, we investigate the changes in fluid permeability and associated changes in P-wave and S-wave velocities at elevated effective pressure for both intact and fractured rock samples of two sandstones and two igneous rocks. It was shown that the wave velocities increased with increasing pressure for all cases. The permeability of igneous rock decreased with increasing pressure. On the other hand, the permeability of a porous sandstone remained essentially constant over the whole pressure range. For sandstone samples, it was also shown that the difference in permeability between intact and fractured samples was little. By contrast, the fluid permeability in fractured igneous rock samples was higher than that in intact rock sample. From our experimental results, it is concluded that the networks of pores control the permeability in sandstone, and that the networks of fractures have significant influence on permeability in igneous rock.