Composition-Matched Inelastic or Capture Spectroscopy Tool

摘要

Composition-matched downhole tools and methods for using such tools are provided. One such method includes emitting neutrons using a neutron source in the downhole tool to generate formation gamma rays in a surrounding formation. At the same time, however, some of the neutrons may interact with different parts of the downhole tool to form tool gamma rays. The gamma ray spectra of at least some of the formation gamma rays and the tool gamma rays may be detected using a gamma ray detector. The tool gamma rays from the different parts of the tool may have a substantially similar spectral shape. As such, a processor may be used to analyze the spectra of the tool gamma rays using a single tool background standard, thereby simplifying the analysis and improving the precision of the results.

主权项

1. A method comprising:
emitting neutrons using a neutron source in a downhole tool into a surrounding formation to generate formation gamma rays, wherein some of the neutrons interact with a material of a first tool part of the downhole tool to generate first tool gamma rays and wherein some of the neutrons interact with a material of a second tool part of the downhole tool to generate second tool gamma rays; detecting gamma ray spectra of at least some of the formation gamma rays, the first tool gamma rays, and the second tool gamma rays using a gamma ray detector, wherein the first tool gamma rays and the second tool gamma rays detected by the detector have a substantially similar spectral shape in a spectral energy range of interest; and using a processor to analyze the spectra of the first tool gamma rays and the second tool gamma rays using a single tool background standard.