Measurement of downhole gamma radiation by reduction of compton scattering

摘要

Systems, methods and devices for evaluating an earth formation intersected by a borehole. The method includes using a first radiation responsive component to detect gamma rays having an energy below a threshold energy; using a second radiation responsive component configured to detect gamma rays that traverse the first radiation responsive component; generating a reduced-Compton gamma ray spectrum by generating an anticoincidence gamma ray spectrum indicative of the gamma rays detected by the first radiation responsive component and the gamma rays detected by the second radiation responsive component. The anticoincidence gamma ray spectrum represents those gamma rays of the gamma rays detected by the second radiation responsive component that are not detected in coincidence with the gamma rays detected by the first radiation responsive component.

主权项

1. An apparatus for evaluating an earth formation intersected by a borehole, the apparatus comprising:
a first radiation responsive component configured to detect gamma rays; a second radiation responsive component configured to detect gamma rays that traverse the first radiation responsive component, wherein the second radiation responsive component is disposed within the first radiation responsive component, and wherein the gamma rays that traverse the first radiation responsive component include at least gamma rays that interact with the first radiation component and are indicative of Compton scattering in the formation; and a processor configured to:
generate a reduced-Compton gamma ray spectrum mitigating effects on the gamma ray spectrum resulting from Compton scattering in the formation by generating an anticoincidence gamma ray spectrum responsive to the gamma rays detected by the first radiation responsive component and the gamma rays detected by the second radiation responsive component, wherein the anticoincidence gamma ray spectrum is indicative of those gamma rays of the gamma rays detected by the second radiation responsive component that are not detected in coincidence with the same gamma rays detected by the first radiation responsive component, wherein those gamma rays of the gamma rays detected by the second radiation responsive component that are not detected in coincidence with the same gamma rays detected by the first radiation responsive component are indicative of Compton scattering in the formation.