NUCLEAR MAGNETIC RESONANCE SENSING APPARATUS AND TECHNIQUES

摘要

A method and apparatus are disclosed for using nuclear magnetic resonance (NMR) techniques to obtain information relating to fluids present near geologic structures. A modular NMR tester which can be located within a standard modular logging tool is used for direct downhole NMR measurements of various parameters of fluid samples of geologic formations near the walls (12) of a borehole. The tester has a vessel (20) made of a non-conductive material and a surrounding permanent magnet (16) that creates a uniform static magnetic field within the test chamber of the vessel (20). An RF coil (26) embedded in the walls of the vessel (20) induces an excitation field with a direction perpendicular to the static magnetic field. Fluids located proximate the borehole (12) are introduced into a test chamber (20) of the tester. NMR signals from the excited nuclei in the fluids are detected to obtain data for calculating a number of important fluid parameters and for the interpretation of wireline MRIL measurements.