Fremgangsmåte og apparat for logging av hydrokarbonreservoarer

摘要

A method, of logging a borehole, for use in a cased oil well for detecting the gas/oil or water/oil contact in a hydrocarbon reservoir, using a neutron capture technique to detect one or more properties of fluid includes comparing the count rates from two or more radiation detectors spaced at respective first and second distances from an isotopic source of continuous neutron radiation. The contact detection criteria are arranged to be substantially independent of borehole fluid characteristics. Apparatus (10) for carrying out the method includes a logging tool (10) having an isotopic source (16) and two spaced detectors (17,18).