Radiant energy – Calibration or standardization methods
Patent
1994-10-11
1997-01-07
Fields, Carolyn E.
Radiant energy
Calibration or standardization methods
250264, 250266, 2502694, 25039001, G01V 510, G01T 300
Patent
active
055919677
ABSTRACT:
The invention relates to an apparatus and method for verifying the operability of neutron detectors and associated pulse generating circuits in a neutron logging tool prior to committing the tool to the well borehole. The method comprises the steps of exposing the neutron detectors to a source or sources of gamma rays, determining the rate of detected gamma rays by counting detector output pulses, and comparing the detected rate to an expected value thereby to verify the operations of the detectors. In the apparatus in accordance with the invention, the gamma ray source(s) may be contained inside the tool near or mounted on the detectors themselves. In an alternate embodiment, the gamma ray source(s) may be externally applied to the tool at the surface during verification procedures. Counting of detected gamma rays is based on detection of detector pulser amplitudes falling in a range defined by first and second thresholds where gamma rays are those pulses falling in the range, while pulses outside the range, i.e., greater than the second threshold, represent detected neutrons.
REFERENCES:
patent: 3511994 (1970-05-01), Jonsson et al.
patent: 3710166 (1973-01-01), Perelman et al.
patent: 5180917 (1993-01-01), Wraight
patent: 5422480 (1995-06-01), Schultz
Wiley et al, "Recommendations for Neutron Logging from the SPWLA Subcommittee for Log Calibration Guidelines", The Log Analyst, May-Jun. 1988, pp. 204-215.
Calibration, Checking and Physical Corrections For A New Dual-Spaced Neutron Porosity Tool, by M. P. Smith--27th Annual SPWLA Symposium in Houston, Texas, Jun. 1986.
Fundamentals of Helium-3 Filled Proportional Counters for Neutron Detection--Reuter-Stokes (no date), Twinsburg, Ohio, trade brochure.
Fields Carolyn E.
Halliburton Company
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