Method and apparatus for determining well fluid flow velocity using a nonradioactive tracer

摘要

Method of determining the flow velocity of fluid flowing within the borehole of a well, traversing subsurface formations of the earth, with a nonradioactive tracer. A population of neutrons is generated in a stream of fluid so as to engulf a detector capable of detecting neutron capture. A substance of large thermal neutron capture cross section is injected into a stream of fluid a known distance upstream from a detector. Measurement of the elapsed time for the capturing substance to travel a known distance, and, by neutron capture, produce a minimum indication at the detector indicating the presence of said capturing substance at its location of closest proximity to the detector, allows calculation of the velocity of said stream of fluid.