Transient flow through porous rocks studied by PEPI

The transient behaviour of fluid flow through porous rocks is examined using the high speed π-modified echo-planar imaging technique (PEPI). Spatially resolved flow maps show the change in velocity, as the bulk flow rate is increased or decreased in large steps in the approach to steady state for two sandstone samples of different porosity and permeability. Different rise and fall settling times are observed for these rocks. In addition, the area occupied by significant flow and the variance of the velocity distributions are calculated during the transient state.