The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Nov. 26, 1991
Filed:
Apr. 04, 1991
L Scott Allen, Dallas, TX (US);
William R Mills, Plano, TX (US);
Daivd C Stromswold, Addison, TX (US);
Mobil Oil Corporation, Fairfax, VA (US);
Abstract
A borehole logging tool is lowered into a borehole traversing a subsurface formation and a neutron detector measures the die-away of nuclear radiation in the formation. A model of the die-away of nuclear radiation is produced using exponential terms varying as the sum of borehole, formation and thermal neutron background components. Exponentially weighted moments of both the die-away measurements and die-away model are determined and equated. The equated moments are solved for the ratio of the borehole to formation amplitude components of the measurements. The formation decay constant is determined from at least the formation and thermal neutron background terms of the weighted measurement and model moments. The determined borehole to formation amplitude ratio is used to correct the determined formation decay constant for the effects of detector standoff from the borehole wall. A porosity log of the formation is produced which is corrected for detector standoff from the borehole wall as a function of the standoff corrected formation decay constant calibrated in borehole models of known porosities.