Apparatus for producing a porosity log of a subsurface formation corrected for detector standoff

U.S. Patent Number: 5300770

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. Intensity signals are produced representing the die-away of nuclear radiation as the logging tool traverses the borehole A signal processor, employing at least one neural network, processes the intensity signals and produces a standoff-corrected epithermal neutron lifetime signal to correct for standoff from the borehole wall encountered by the detector as the logging tool traverses the borehole. The signal processor further generates a porosity signal from the standoff-corrected epithermal neutron lifetime signal derived from measurements in borehole models at known porosities and conditions of detector standoff. A log is generated of such porosity signal versus depth as the logging tool traverses the borehole.

Inventors: Allen; L. Scott (Dallas, TX); Mills; William R. (Plano, TX)

Assignee: Mobil Oil Corporation (Fairfax, VA)

Application Number: 07/927,109

Issued: 1994-04-05

Expired: 2006-04-05

Classes: 250/269.5 ; 250/256; 250/262; 250/268; 702/12; 702/8; 706/10; 706/16; 706/928; 706/929

Field of search: 250/270,269,268,262,256 364/422 395/11,22,928,929

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