Behind casing water flow detection using pulsed neutron oxygen activation
 Measurement of the linear flow velocity and volume flow rate of undesired behind casing water flow is provided. A well tool having a 14 MEV pulsed neutron source is used to irradiate the earth formations behind well casing with bursts of high energy neutrons. This irradiation activates elemental oxygen nuclei comprising the molecular structure of the undesired flow. Dual spaced gamma ray detectors located above or below the neutron source detect the decay of unstable isotope nitrogen 16 produced by the oxygen activation in the time intervals between the neutron bursts. Background radiation due to prompt N-.sigma. radiation is thus largely avoided. From the detected nitrogen 16 characteristic gamma rays the linear flow velocity of the undesired flow is determined. By combining this with an estimation of the distance R to the undesired flow region from the detectors, the volume flow rate V may be deduced. 
Texaco Inc.
E G G
E21B G01F G01V
inventional inventional inventional
Harold E. Dan M. Hans J.
Peelman Arnold Paap