NEUTRON-ABSORBING GAMMA RAY WINDOW IN A DOWNHOLE TOOL

摘要

Methods and downhole tools involving neutron-absorbing gamma ray windows are provided. One such method involves emitting neutrons from a neutron source in a downhole tool in a well into a surrounding geological formation. This may produce formation gamma rays through interactions between the neutrons and elements of the geological formation. The formation gamma rays may be detected by a gamma ray detector when the gamma rays pass via a gamma ray window that includes a neutron-absorbing material disposed in a substrate material of the downhole tool. The gamma ray window may be both more transmissive of gamma rays than the substrate material and less transmissive of neutrons than a window without the neutron-absorbing material. This may decrease a neutron flux that would otherwise reach the gamma ray detector and the tool materials surrounding it and thus would otherwise lead to a background signal contaminating a signal corresponding to the detected formation gamma rays.

主权项

1. A method comprising:
emitting neutrons from a neutron source in a downhole tool in a well into a surrounding geological formation to produce formation gamma rays through interactions between the neutrons and elements of the geological formation; and detecting the formation gamma rays in a gamma ray detector via a gamma ray window disposed in a substrate material of the downhole tool, wherein the gamma ray window comprises a neutron-absorbing material and is both more transmissive of gamma rays than the substrate material and less transmissive of neutrons than were the gamma ray window without the neutron-absorbing material, to decrease a neutron flux that would otherwise reach the gamma ray detector while enhancing a probability that the formation gamma rays reach the gamma ray detector.