Thomas J Burnett

US Patent:

54517796, Sep 19, 1995

Filed:

Dec 15, 1993

Appl. No.:

8/167672

Inventors:

Ronald L. Spross - Humble TX
Thomas Burnett - Humble TX

Assignee:

Baroid Corporation - Houston TX

International Classification:

G01V 512

US Classification:

250266

Abstract:

A method and apparatus for determining at least one characteristic of a formation is provided which includes storing a plurality of counts received from both a long space radiation detector and a short space radiation detector. The counts are detected during a plurality of short duration time periods which are brief compared to rotary drilling speed. A count rate mean is determined and used to sort each of the plurality of count measurements into one of at least three bins. Count information accumulated in at least one of the bins is used to calculate a corrected density. A short space collimator enhances the count rate of singly scattered gamma rays detected by the short space detector and blocks gamma rays from the formation radially outwardly of the short space detector to improve spine-rib correction characteristics for relatively short standoffs. The method of sorting the plurality of short duration time period measurements improves the accuracy for short standoffs to larger standoffs.