Methods and apparatus for constituent analysis of earth formations

Patent · Tue Mar 02 04:00:00 EST 1982

OSTI ID:5214206

Hertzog, R C; Nelligan, W B

In the illustrative embodiments of the invention disclosed, the composition of an earth formation is investigated by repetitively irradiating the formation with bursts of fast neutrons and generating an energy spectrum of the gamma rays resulting from the inelastic scattering of such neutrons by nuclei of the formation. The inelastic scattering gamma ray spectrum is analyzed by comparing it with a composite spectrum, made up of standard spectra of constituents postulated to comprise the formation, to determine the proportions in the formation of the postulated constituents. A background energy spectrum is generated from gamma rays detected during periods between neutron bursts and is utilized to provide one or more standard background spectra for use in the analysis of the inelastic scattering gamma ray spectra. The standard background spectrum or spectra are preferably updated on a repetitive basis to reflect the current background component in the detected inelastic scattering gamma ray spectrum. More reliable information is thereby obtained of the presence of oil in the formation through the derivation of such indicators as the carbon/oxygen ratio, calcium/silicon ratio and the like. Constituent analysis may also be made of the detected background gamma ray spectrum to determine the proportions of the formation constituents contributing to such spectrum, and the standards for the most significant background contributors or the composite spectrum produced by such standard spectra may be used among the standard spectra for the inelastic scattering spectrum analysis in lieu of the detected background spectrum itself.

• Assignee: Schlumberger Technology Corp
• Patent Number(s): US 4317993
• OSTI ID: 5214206
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
ALKALINE EARTH METALS
BARYONS
CALCIUM
CARBON
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
ELEMENTS
ENERGY SPECTRA
FAST NEUTRONS
FERMIONS
GAMMA RADIATION
HADRONS
INELASTIC SCATTERING
IONIZING RADIATIONS
METALS
NEUTRON LOGGING
NEUTRONS
NONMETALS
NUCLEONS
OIL WELLS
OXYGEN
RADIATIONS
RADIOACTIVITY LOGGING
SCATTERING
SEMIMETALS
SILICON
SPECTRA
WELL LOGGING
WELLS