Permeability measurement by the pulse-decay method: Effects of poroelastic phenomena and non-linear pore pressure diffusion

Permeability values inferred from data obtained by the pulse-decay, or transient pulse method, might be affected by two phenomena not previously considered to be important: poroelastic coupling between sample cores and pore fluid, and non-linear pore pressure diffusion associated with large pore pressure gradients. The theoretical reasons for these complications are discussed, as well as the results of two simple experiments designed to test the theory. Poroelastic effects introduce an inherent sample-size dependence into the transient-pulse method: experiments suggest such a dependence, but possibly masked by material inhomogeneity. Non-linear pore pressure diffusion limits the size of the pore pressure pulse that may be used in the pulse-decay scheme; this is well-demonstrated by experimental results. Furthermore, direct measurements of poroelastic strains associated with pulse propagation show very good agreement with predictions of linear poroelasticity theory.