Baker Hughes Corporation

Mikhail A Fedorin

David J Jacobi

Richard R Pemper

John Longo

Xiaogang Han

Freddy Mendez

Brian J LeCompte

Alfred I Khisamutdinov

Gary A Feuerbacher

The present disclosure relates to borehole logging methods and apparatuses for estimating at least one parameter of interest of a volume of interest of an earth formation using nuclear radiation. The method may include obtaining an energy spectrum; using at least one processor to remove at least one energy spectrum component using a method selected from a spectral decomposition and spectral windows method; and estimating the concentration of at least one radionuclide using the energy spectrum after the removal. The estimation of the at least one radionuclide concentration may include using the other of the method selected form the removal. The apparatus may include at least one processor configured to perform the method.

Density derived from spectra of natural radioactivity

A method for estimating a lithotype of an earth formation, the method includes: obtaining at least two different energy spectra of radiation received from the earth formation using the logging tool, each energy spectrum having at least one of a natural gamma-ray spectrum, a fast neutron-induced inelastic spectrum, and a thermal neutron induced capture spectrum; establishing at least one geochemically-based constraint related to elemental spectral yields to be determined; determining the elemental spectral yields from the at least two different energy spectra by decomposing the at least two different energy spectra over weighted sum of monoelemental standards wherein at least one weight is constrained by the at least one geochemically-based constraint and each weight represents a proportion of one monoelemental standard; converting the elemental spectral yields to elemental concentrations; and using a classifier to receive the elemental concentrations as input and to provide a lithotype as output.

Use of chemically and geologically consistent constraints for obtaining elemental chemistry downhole

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Novosibirsk, Russia

Mikhail A Fedorin