Permeability studies of argillaceous rocks

Because the rate of water movement in argillaceous rocks depends considerably on the conditions of measurement, the only permeability measurements of practical field significance for these rocks are those obtained while the sample was held at temperatures and pressures that duplicated natural subsurface conditions as closely as possible. In laboratory measurements described in this report, the permeabilities of argillaceous rocks from the lower Cretaceous of western Canada ranged from 10−7 to 10−4 millidarcy decreasing as the rocks became more clayey. Since argillaceous rocks tend to be compressible, flow rates through these rocks were dependent upon the difference between confining and average fluid pressures. Furthermore, the flow rates changed more with temperature than would be expected from the normal changes of water viscosity with temperature. This anomalous flow behavior suggests that the water in clayey rocks has a structure that is different from the structure of bulk water.