Simulations of a spectral gamma-ray logging tool response to a surface source distribution on the borehole wall
- Highland Scientific Ltd., Ashland, OR (United States)
- Los Alamos National Lab., NM (United States)
We have developed Monte Carlo and discrete ordinates simulation models for the large-detector spectral gamma-ray (SGR) logging tool in use at the Nevada Test Site. Application of the simulation models produced spectra for source layers on the borehole wall, either from potassium-bearing mudcakes or from plate-out of radon daughter products. Simulations show that the shape and magnitude of gamma-ray spectra from sources distributed on the borehole wall depend on radial position with in the air-filled borehole as well as on hole diameter. No such dependence is observed for sources uniformly distributed in the formation. In addition, sources on the borehole wall produce anisotropic angular fluxes at the higher scattered energies and at the source energy. These differences in borehole effects and in angular flux are important to the process of correcting SGR logs for the presence of potassium mudcakes; they also suggest a technique for distinguishing between spectral contributions from formation sources and sources on the borehole wall. These results imply the existence of a standoff effect not present for spectra measured in air-filled boreholes from formation sources. 5 refs., 11 figs.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 10103391
- Report Number(s):
- LA-UR-91-3657; CONF-911106-16; ON: DE92003727
- Resource Relation:
- Conference: 1991 Institute of Electrical and Electronic Engineers (IEEE) nuclear science symposium and medical imaging conference,Santa Fe, NM (United States),2-9 Nov 1991; Other Information: PBD: [1991]
- Country of Publication:
- United States
- Language:
- English
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