The permeability of whole and jointed Barre Granite

The permeability of whole and jointed Barre granite was measured at pressures up to 2 kbars. Jointed samples were actually split cylinders joined by surfaces with controlled surface roughness. Samples with induced tension fractures were also measured. The permeability of the whole rock ranged from about 10−6 to 10−7 darcies. The permeability of the jointed rock ranged from about 8 × 10−5 darcies at low pressure down to that of the whole rock at high pressures. Permeability was not a simple function of the difference between external confining pressure (Pc) and internal fluid pressure (Pf). Changes in permeability were found to be proportional to (b dPf − a dPc) where b/a