Detection of behind casing water flow at an angle to the axis of a well borehole

摘要

Methods and apparatus are disclosed herein for detecting undesired water flow at an angle to the axis of a well borehole. The borehole envisons is irradiated with 14 MEV neutrons resulting in the in situ creation of the radioactive tracer element N16 in the flowing water. Two spaced gamma ray detectors are used to sense gamma rays produced by the decay of this radioactive isotope. The distance from the center of each detector to the center of the flowing water is used to establish the angle of flow with respect to the well tool, the linear flow rate of the flow v and the volume flow rate V of the undesired water flow.