Patent ID: 7388373

Claim:
A method of determining the permeability of an underground medium from NMR logs, comprising calibrating NMR logs from NMR and permeability measurements of rock fragments from said medium, comprising: A) a calibration stage including: a) direct permeability measurement in the laboratory from the rock fragments comprising measuring the pressure variations within a vessel filled with a fluid containing the rock fragments after it has been communicated for a predetermined time with a tank containing the same fluid under pressure, measuring the volume effectively absorbed by the rock fragments and modelling the evolution of the pressure or of the volume in the vessel, from initial values selected for the permeability of the rock fragments, that are iteratively adjusted so that the modelled pressure evolution best adjusts with the measured cuttings permeability evolution b) measurement of parameters of signals obtained by NMR of the rock fragments, and c) calculation of the parameters of a selected empirical relation that relates the value of the permeability to parameters deduced from the signals obtained by NMR, using the direct measurements performed on the rock fragments, and B) obtaining permeability logs by using parameterization to determine the permeability of the medium only from NMR logs for which no direct permeability measurements are available.