Determination of the permeability of a subterranean medium involving NMR permeability measurements on stone cuttings of the medium

摘要

A calibration stage involves measuring the permeability of the rock fragments directly in a laboratory; measuring signals obtained by NMR from the rock fragments, and calculating an empirical relationship between the permeability and parameters deduced from the NMR signals. The permeability of the rock can then be found using only NMR diagraphs, with no direct measurements of permeability : The direct measurement of permeability in the laboratory of the rock fragments includes the measurement of pressure variations inside a receiver filled with a fluid containing the rock fragments after it has been put in contact for a defined time with a reservoir of the same fluid under pressure. The volume effectively absorbed by the rock fragments is measured and a model created of the evolution of pressure or volume in the receiver, from the initial values chosen for permeability of the rock fragments and adjusted iteratively so the modelled evolution matches the measured evolution of permeability of the rock debris. At least one longitudinal and/or transverse relaxation time is measured for the NMR signals.