Method and apparatus for epithermal neutron porosity well logging

Patent · Tue Sep 24 04:00:00 EDT 1991

OSTI ID:5682786

Hertzog, R C; Loomis, W A; Wraight, P

This patent describes a method for investigating the porosity of a subsurface earth formation surrounding a borehole. It comprises repetitively irradiating the borehole and earth formation with discrete bursts of high energy neutrons from a neutron source, which neutrons interact with nuclei of the materials in the borehole and the formation to produce therein populations of epithermal neutrons; detecting the populations of epithermal neutrons at near and far locations in the borehole spaced apart longitudinally by different distances from the neutron source; generating count signals indicative of the magnitudes of the detected epithermal neutron populations at the respective near and far locations; detecting the decay of the epithermal neutron populations following the neutron bursts at least at one location in the borehole and generating signals representative thereof; deriving from the decay signals a signal indicative of the slowing down time of epithermal neutrons in the formation of the at least one location; and deriving from the near and far count signals and the slowing down time signal a measurement signal representative of the porosity of the formation surrounding the borehole inherently compensated for the effects of tool standoff on the responses of the logging tool.

• Assignee: Schlumberger Technology Corp., New York, NY (United States)
• Patent Number(s): A; US 5051581
• Application Number: PPN: US 7-517268
• OSTI ID: 5682786
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
07 ISOTOPE AND RADIATION SOURCES
070204 -- Radiation Sources-- Industrial Uses
Radiometric
440400 -- Well Logging Instrumentation
47 OTHER INSTRUMENTATION
BARYONS
DRILLING
ELEMENTARY PARTICLES
EPITHERMAL NEUTRONS
FERMIONS
HADRONS
INTERACTIONS
NEUTRON LOGGING
NEUTRONS
NUCLEONS
OIL WELLS
RADIOACTIVITY LOGGING
WELL DRILLING
WELL LOGGING
WELLS