Method and apparatus for pulsed neutron spectral analysis using spectral stripping

Patent · Mon Jan 22 23:00:00 EST 1979

OSTI ID:6231250

Hopkinson, E C

A pulsed neutron generator in a well logging instrument is pulsed at a clock frequency of 20 KHz. Inelastic scatter gamma rays are detected during a first time interval coinciding with the neutron source being on and capture gamma rays are measured during a second interval subsequent to the end of each neutron burst. Only a single detected pulse, assuming detection occurs, is transmitted during each of the two detection intervals. Sync pulses are generated in the well logging instrument scaled down to a frequency of 200 Hz for transmission to the earth's surface. At the earth's surface, the scaled-down sync pulses are applied to a phase-locked loop system for regenerating the sync pulses to the same frequency as that of the clock frequency used to pulse the neutron source and to open the detection gates in the borehole instrument. The regenerated sync pulses are used in the surface instrumentation to route the pulses occurring in the inelastic interval into one section of a multichannel analyzer memory and the pulses occurring in the capture interval into another section of the multichannel analyzer. The use of memory address decoders, subtractors and ratio circuits enables both a carbon/oxygen ratio and a silcon/calcium ratio to be struck substantially free of background radiation and substantially unaffected by downscattering of high energy gamma rays.

• Assignee: Dresser Industries, Inc.
• Patent Number(s): US 4136279
• OSTI ID: 6231250
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
440400 -- Well Logging Instrumentation
47 OTHER INSTRUMENTATION
COMPUTER CALCULATIONS
DATA ANALYSIS
NEUTRON LOGGING
NEUTRON-GAMMA LOGGING
OIL WELLS
PULSED NEUTRON TECHNIQUES
RADIOACTIVITY LOGGING
SYNCHRONIZATION
WELL LOGGING
WELLS