Measurement of subsurface formation lithology, including shaliness, using capture gamma spectroscopy

Patent · Tue Dec 23 04:00:00 EST 1975

OSTI ID:4049521

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 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 macroscopic thermal neutron capture cross-section of the formations is also known or obtained, either from the C.G.S. log or other previous logs. The spectra of gamma rays obtained from the formation are analyzed to form logs of the elements which contribute significantly to the spectra. From these logs, a partial macroscopic thermal neutron capture cross- section of the elements contributing to the gamma rays of the spectrum is obtained. The partial macroscopic thermal neutron capture cross-section so obtained is then compared with the capture cross-section of the formation to obtain an indication of the shaliness of the formation. (auth)

• Research Organization: Originating Research Org. not identified
• NSA Number: NSA-33-029208
• Assignee: to Texaco Inc.
• Patent Number(s): US 3928763
• OSTI ID: 4049521
• Country of Publication: United States
• Language: English

Related Subjects

*WELL LOGGING-- PULSED NEUTRON TECHNIQUES
440101* --Instrumentation--Radiation Instrumentation-- General Detectors & Monitors
BOREHOLES
CAPTURE
GAMMA SPECTROSCOPY
LITHOLOGY
N40110 --Chemistry--Analytical & Separations Chemistry--Activation & Nuclear Reaction Procedures
N44420 --Environmental & Earth Sciences--Radiometric Techniques--Soil
N46110* --Instrumentation--Radiation Detection Instruments-- General Detectors & Monitors
NEUTRON REACTIONS
NUCLEAR REACTION ANALYSIS
POROSITY
SALINITY
SHALES