Measurement of subsurface formation lithology, including composition and fluids, using gamma spectroscopy and thermal neutron decay

Patent · Tue Dec 30 04:00:00 EST 1975

OSTI ID:4047924

Scott, H D

Gamma ray spectra of earth formations surrounding an open or cased well borehole are obtained by exciting subsurface formation elements around the borehole with pulsed neutrons and detecting the gamma rays resulting from capture in the subsurface formation of thermalized neutrons from a capture gamma spectroscopy (C.G.S.) well log source. The spectra of gamma rays so obtained are analyzed to form logs of the elements which contribute significantly to the spectra. Simultaneously, the time rate of decay of the number of gamma rays resulting from capture of the thermal neutrons in the formation is obtained to derive a measure of the macroscopic thermal neutron capture cross-section of the formation. The gamma rays obtained from the formation are then compensated for variations the thermal neutron capture cross-section obtained for the formation. From the logs of elements and the macroscopic thermal neutron capture cross- section of the formation, quantitative measurements of the primary formation parameters of formation water salinity, water saturation, porosity, major matrix components and ratios of formation constituents of the earth formations are obtained. (auth)

• Research Organization: Originating Research Org. not identified
• NSA Number: NSA-33-029395
• Assignee: to Texaco Inc.
• Patent Number(s): US 3930154
• OSTI ID: 4047924
• Country of Publication: United States
• Language: English

Related Subjects

*WELL LOGGING-- PULSED NEUTRON TECHNIQUES
440105* --Instrumentation--Radiation Instrumentation-- Radiometric Instruments
BOREHOLES
CAPTURE
GAMMA SPECTROSCOPY
MOISTURE
N40110 --Chemistry--Analytical & Separations Chemistry--Activation & Nuclear Reaction Procedures
N44420 - -Environmental & Earth Sciences--Radiometric Techniques--Soil
N46200* --Instrumentation--Radiometric Instruments
NEUTRON REACTIONS
NUCLEAR REACTION ANALYSIS
POROSITY
SALINITY