Behind casing water volume flow rate measurement using concentric gamma ray detectors
 Measurement of the distance from a gamma ray detector to a gamma ray source for location of a channel of undesired behind casing water flow in a producing well is provided. Coaxially aligned dual cylindrical gamma ray detector crystals are used at one or more longitudinally spaced locations in the borehole to detect the characteristic gamma rays from the decay of radioactive nitrogen 16 produced by the activation of elemental oxygen nuclei comprising the molecular structure of undesired water flow. The ratio of counts at the outer coaxial detector to those at the inner coaxial detector is then interpreted in terms of R, the distance from the detector to the water flow channel. This distance information may then be combined with the linear flow velocity of such undesired water flow to derive an indication of the volume flow rate V of such flow. 
Texaco Inc.
G G E
G01V G01F E21B
inventional inventional inventional
Dan M. Hans J.
Arnold Paap