Method for investigating the composition of an earth formation traversed by a borehole

Patent · Tue May 06 04:00:00 EDT 1986

OSTI ID:5517222

Grau, J A

A method is described for investigating an earth formation traversed by a borehole, comprising: (a) placing a logging tool, including an high-energy neutron source and an energy-responsive gamma ray detector, in the borehole opposite the formation to be investigated; (b) irradiating the borehole and surrounding formation with neutrons from the source; (c) detecting gamma rays resulting from the neutron irradiation with the gamma ray detector; (d) generating an energy spectrum of the detected gamma rays, the energy spectrum including (1) a contribution due to neutron interactions with the formation elements, (2) a contribution due to neutron interactions with the borehole elements, and (3) a contribution due to neutron interactions with the logging tool elements; and (e) comparing the detected gamma ray spectrum with a composite spectrum, made up of a combination of weighted standard spectra of elements postulated to have contributed to the detected gamma ray spectrum and including among the standard spectra a tool background spectrum representing substantially only the tool contribution, to determine the relative proportions in the detected gamma ray spectrum of the gamma ray yields for one or more of the postulated elements.

• Assignee: Schlumberger Tech. Corp., New York, NY
• Patent Number(s): US 4587424
• OSTI ID: 5517222
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
03 NATURAL GAS
030200 -- Natural Gas-- Reserves
Geology
& Exploration
440101 -- Radiation Instrumentation-- General Detectors or Monitors & Radiometric Instruments
440400 -- Well Logging Instrumentation
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
47 OTHER INSTRUMENTATION
BARYONS
BOREHOLES
CAVITIES
COMPARATIVE EVALUATIONS
DETECTION
ELEMENTARY PARTICLES
EQUIPMENT
FERMIONS
GAMMA DETECTION
GEOLOGIC DEPOSITS
HADRONS
IRRADIATION
MEASURING INSTRUMENTS
MINERAL RESOURCES
NATURAL GAS DEPOSITS
NEUTRON LOGGING
NEUTRON SOURCES
NEUTRON-GAMMA LOGGING
NEUTRONS
NUCLEONS
PARTICLE SOURCES
PETROLEUM DEPOSITS
RADIATION DETECTION
RADIATION DETECTORS
RADIATION SOURCES
RADIOACTIVITY LOGGING
RESOURCES
WELL LOGGING
WELL LOGGING EQUIPMENT