Studies of fluid transport in porous rocks by echo-planar MRI

Attempts to quantify the permeability constant that appears in Darcy's equation in terms of the porosity, tortuosity and surface area have been made by Kozeny and Carman. These results in turn have been translated by Seevers into expressions involving spin-lattice relaxation times. When this work was done originally in the mid-1960s, NMR imaging and spatially localised T₁ maps had not been invented. Therefore, bulk T₁ average values were used and it is not surprising to see substantial deviations from predicted permeabilities in bore core material. In this paper we re-examine the Kozeny-Carman and Seevers theories in the light of new techniques development for the localised measurement of both T₁ maps and fluid velocity maps. New results show spatially correlated T₁ and flow maps obtained from Bentheimer sandstone samples. These are discussed in terms of a localised permeability constant. By this means we show that the relationship between T₁ and permeability does not hold at the local level for isolated pixels within a larger specimen.