Focused detection logging technique

Claim 1

A well logging method comprising the steps of: (a) emitting from a given location gamma radiation in at least one tightly collimated beam toward the media surrounding a borehole; (b) detecting at a predetermined distance from said location gamma radiation that is tightly collimated to a plurality of paths focused to a zone of intersection with and aligned to intersect with said emitted gamma radiation beam so that the radiation detected includes singly scattered gamma radiation produced by the intersection of emitted gamma radiation and the media at said zone of intersection; (c) misaligning the beam emitted from said location and the tightly collimated paths to prevent their intersection; (d) detecting at said predetermined distance, with the emitted beam and the tightly collimated paths misaligned, principally gamma radiation multiply scattered by the interaction of the emitted gamma radiation and the media; and (e) subtracting the gamma radiation detected during misalignment from the gamma radiation detected during alignment to obtain a measurement of said singly scattered gamma radiation which is related to a density characteristic of the media at the zone of intersection.

Claim 3

A method of well logging using at least one source emitting gamma radiation and at least one gamma radiation detector located at a predetermined distance from the source comprising the steps of: (a) tightly collimating the gamma radiation emitted by said source to at least one beam directed toward the media adjacent a borehole; (b) tightly collimating the gamma radiation detected by said detector to a plurality of paths focused to a zone of intersection with and aligned to intersect with said emitted gamma radiation beam so that the spectrum of gamma radiation detected includes singly scattered gamma radiation produced by the interaction of emitted gamma radiation and the media at the zone of intersection; (c) misaligning the beam emitted by said source and the tightly collimated paths to prevent their intersection so that the radiation detected by said detector is principally gamma radiation multiply scattered by the interaction of the emitted gamma radiation and the media; and (d) subtracting the gamma radiation detected during misalignment from the gamma radiation detected during alignment to obtain a measurement of said singly scattered gamma radiation which is related to a density characteristic of the media at the zone of intersection.

Claim 4

A method of well logging using at least one source emitting gamma radiation and at least one gamma radiation detector located at a predetermined distance from the source comprising the steps of: (a) tightly collimating the gamma radiation emitted by said source to at least one beam directed toward the media adjacent a borehole; (b) tightly collimating the gamma radiation detected by said detector to a plurality of paths focused to a zone of intersection with and aligned to intersect with said emitted gamma radiation beam so that the spectrum of gamma radiation detected includes singly scattered gamma radiation produced by the interaction of emitted gamma radiation and the media at the zone of intersection; (c) misaligning the beam emitted by said source and the tightly collimated paths to prevent their intersection so that the radiation detected by said detector is principally gamma radiation multiply scattered by the interaction of the emitted gamma radiation and the media; and (d) subtracting the gamma radiation detected during misalignment from the gamma radiation detected during alignment to obtain a measurement of said singly scattered gamma radiation which is related to a density characteristic of the media at the zone of intersection.

Claim 5

A method of well logging using at least one source emitting gamma radiation and at least one gamma radiation detector located at a predetermined distance from the source comprising the steps of: (a) tightly collimating the gamma radiation emitted by said source to at least one beam directed toward the media adjacent a borehole; (b) tightly collimating the gamma radiation detected by said detector to a plurality of paths that are (1) spherically focused to a zone of intersection with and aligned to intersect with said beam and (2) azimuthally symmetrical about the beam axis so that the spectrum of gamma radiation detected includes singly scattered gamma radiation produced by the interaction of emitted gamma radiation and the media at said zone of intersection; (c) misaligning the beam emitted by said source and the tightly collimated paths to prevent their intersection so that the radiation detected by said detector is principally gamma radiation multiply scattered by the interaction of the emitted gamma radiation and the media; and (d) subtracting the gamma radiation detecting during misalignment from the gamma radiation detected during alignment to obtain a measurement of said singly scattered gamma radiation which is related to a density characteristic of the media at the zone of intersection.

Claim 6

A method of well logging using at least one source emitting gamma radiation and at least one gamma radiation detector located at a predetermined distance from the source comprising the steps of: (a) tightly collimating the gamma radiation emitted by said source to at least one beam directed toward the media adjacent a borehole; (b) tightly collimating the gamma radiation detected by said detector to a plurality of paths that are (1) spherically focused to a zone of intersection with and aligned to intersect with said beam and (2) azimuthally symmetrical about the beam axis so that the spectrum of gamma radiation detected includes singly scattered gamma radiation produced by the interaction of emitted gamma radiation and the media at said zone of intersection; (c) misaligning the beam emitted by said source and the tightly collimated paths to prevent their intersection so that the radiation detected by said detector is principally gamma radiation multiply scattered by the interaction of the emitted gamma radiation and the media; and (d) subtracting the gamma radiation detecting during misalignment from the gamma radiation detected during alignment to obtain a measurement of said singly scattered gamma radiation which is related to a density characteristic of the media at the zone of intersection.

Claim 7

A method of well logging using at least one source emitting gamma radiation and at least one gamma radiation detector comprising the steps of: (a) tightly collimating the emitted gamma radiation to a first beam directed toward the media adjacent a borehole; (b) tightly collimating the detected gamma radiation to a plurality of paths that are focused to a zone of intersection with and aligned to intersect with the first beam so that the spectrum of gamma radiation detected includes singly scattered gamma radiation produced by the interaction of emitted gamma radiation and the media at the zone of intersection; (c) tightly collimating the emitted gamma radiation to a second beam directed toward an earth formation adjacent a borehole; (d) tightly collimating the detected gamma radiation to a plurality of paths that are focused to a zone of intersection with and aligned to intersect with the second beam so that the spectrum of gamma radiation detected includes singly scattered gamma radiation produced by the interaction of emitted gamma radiation and the media at the zone of intersection; (e) misaligning the first and second beams and their respective focused detection paths to prevent their intersection so that the radiation detected is background gamma radiation; and (f) determining from the aligned gamma radiation and the misaligned gamma radiation a density characteristic of the media.

Claim 8

A method of well logging using at least one source emitting gamma radiation and at least one gamma radiation detector comprising the steps of: (a) tightly collimating the emitted gamma radiation to a first beam directed toward the media adjacent a borehole; (b) tightly collimating the detected gamma radiation to a plurality of paths that are focused to a zone of intersection with and aligned to intersect with the first beam so that the spectrum of gamma radiation detected includes singly scattered gamma radiation produced by the interaction of emitted gamma radiation and the media at the zone of intersection; (c) tightly collimating the emitted gamma radiation to a second beam directed toward an earth formation adjacent a borehole; (d) tightly collimating the detected gamma radiation to a plurality of paths that are focused to a zone of intersection with and aligned to intersect with the second beam so that the spectrum of gamma radiation detected includes singly scattered gamma radiation produced by the interaction of emitted gamma radiation and the media at the zone of intersection; (e) misaligning the first and second beams and their respective focused detection paths to prevent their intersection so that the radiation detected is background gamma radiation; and (f) determining from the aligned gamma radiation and the misaligned gamma radiation a density characteristic of the media.

Claim 9

An apparatus for logging a borehole to determine a characteristic of the media surrounding the borehole, the apparatus having at least one source emitting gamma radiation and at least one gamma radiation detector located at a predetermined distance from the source, comprising: (a) means for tightly collimating the gamma radiation emitted by said source to at least one beam directed toward the media adjacent a borehole; (b) means for tightly collimating the gamma radiation detected by said detector to a plurality of paths focused to a zone of intersection with and aligned to intersect with said emitted gamma radiation beam so that the spectrum of gamma radiation detected includes singly scattered gamma radiation produced by the interaction of emitted gamma radiation and the media at the zone of intersection; (c) means for misaligning the beam emitted by said source and the tightly collimated paths to prevent their intersection so that the radiation detected by said detector is principally gamma radiation multiply scattered by the intersection of the emitted gamma radiation and the media; and (d) means for subtracting the gamma radiation detected during misalignment from the gamma radiation detected during alignment to obtain a measurement of said singly scattered gamma radiation which is related to a density characteristic of the media at the zone of intersection.

Claim 10

An apparatus for logging a borehole to determine a characteristic of the media surrounding the borehole, the apparatus having at least one source emitting gamma radiation and at least one gamma radiation detector located at a predetermined distance from the source, comprising: (a) means for tightly collimating the gamma radiation emitted by said source to at least one beam directed toward the media adjacent a borehole; (b) means for tightly collimating the gamma radiation detected by said detector to a plurality of paths focused to a zone of intersection with and aligned to intersect with said emitted gamma radiation beam so that the spectrum of gamma radiation detected includes singly scattered gamma radiation produced by the interaction of emitted gamma radiation and the media at the zone of intersection; (c) means for misaligning the beam emitted by said source and the tightly collimated paths to prevent their intersection so that the radiation detected by said detector is principally gamma radiation multiply scattered by the intersection of the emitted gamma radiation and the media; and (d) means for subtracting the gamma radiation detected during misalignment from the gamma radiation detected during alignment to obtain a measurement of said singly scattered gamma radiation which is related to a density characteristic of the media at the zone of intersection.

Claim 11

An apparatus for logging a borehole to determine a characteristic of the media surrounding the borehole, the apparatus having at least one source emitting gamma radiation and at least one gamma radiation detector located at a predetermined distance from the source, comprising: (a) means for tightly collimating the gamma radiation emitted by said source to at least one beam directed toward the media adjacent a borehole; (b) means for tightly collimating the gamma radiation detected by said detector to a plurality of paths that are (1) spherically focused to a zone of intersection with and aligned to intersect with said beam and (2) azimuthally symmetrical about the beam axis so that the spectrum of gamma radiation detected includes signly scattered gamma radiation produced by the interaction of emitted gamma radiation and the media at said zone of intersection; (c) means for misaligning the beam emitted by said source and the tightly collimated paths to prevent their intersection so that the radiation detected by said detector is principally gamma radiation multiply scattered by the interaction of the emitted gamma radiation and the media; and (d) means for subtracting the gamma radiation detected during misalignment from the gamma radiation detecting during alignment to obtain a measurement of said singly scattered gamma radiation which is related to a density characteristic of the media at the zone of intersection.

Claim 12

An apparatus for logging a borehole to determine a characteristic of the media surrounding the borehole, the apparatus having at least one source emitting gamma radiation and at least one gamma radiation detector located at a predetermined distance from the source, comprising: (a) means for tightly collimating the gamma radiation emitted by said source to at least one beam directed toward the media adjacent a borehole; (b) means for tightly collimating the gamma radiation detected by said detector to a plurality of paths that are (1) spherically focused to a zone of intersection with and aligned to intersect with said beam and (2) azimuthally symmetrical about the beam axis so that the spectrum of gamma radiation detected includes signly scattered gamma radiation produced by the interaction of emitted gamma radiation and the media at said zone of intersection; (c) means for misaligning the beam emitted by said source and the tightly collimated paths to prevent their intersection so that the radiation detected by said detector is principally gamma radiation multiply scattered by the interaction of the emitted gamma radiation and the media; and (d) means for subtracting the gamma radiation detected during misalignment from the gamma radiation detecting during alignment to obtain a measurement of said singly scattered gamma radiation which is related to a density characteristic of the media at the zone of intersection.

Claim 13

An apparatus for logging a borehole to determine a characteristic of the media surrounding the borehole, the apparatus having at least one source emitting gamma radiation and at least one gamma radiation detector, comprising: (a) means for tightly collimating the emitted gamma radiation to a first beam directed toward the media adjacent a borehole; (b) means for tightly collimating the detected gamma radiation to a plurality of paths that are focused to a zone of intersection with and aligned to intersect with the first beam so that the spectrum of gamma radiation detected includes singly scattered gamma radiation produced by the interaction of emitted gamma radiation and the media at the zone of intersection; (c) means for tightly collimating the emitted gamma radiation to a second beam directed toward an earth formation adjacent a borehole; (d) means for tightly collimating the detected gamma radiation to a plurality of paths that are focused to a zone of intersection with an aligned to intersect with the second beam so that the spectrum of gamma radiation detected includes singly scattered gamma radiation produced by the interaction of emmitted gamma radiation and the media at the zone of intersection; (e) means for misaligning the first and second beams and their respective focused detection paths to prevent their intersection so that the radiation detected is background gamma radiation; and (f) means for determining from the aligned gamma radiation and the misaligned gamma radiation a density characteristic of the media.

Claim 14

An apparatus for logging a borehole to determine a characteristic of the media surrounding the borehole, the apparatus having at least one source emitting gamma radiation and at least one gamma radiation detector, comprising: (a) means for tightly collimating the emitted gamma radiation to a first beam directed toward the media adjacent a borehole; (b) means for tightly collimating the detected gamma radiation to a plurality of paths that are focused to a zone of intersection with and aligned to intersect with the first beam so that the spectrum of gamma radiation detected includes singly scattered gamma radiation produced by the interaction of emitted gamma radiation and the media at the zone of intersection; (c) means for tightly collimating the emitted gamma radiation to a second beam directed toward an earth formation adjacent a borehole; (d) means for tightly collimating the detected gamma radiation to a plurality of paths that are focused to a zone of intersection with an aligned to intersect with the second beam so that the spectrum of gamma radiation detected includes singly scattered gamma radiation produced by the interaction of emmitted gamma radiation and the media at the zone of intersection; (e) means for misaligning the first and second beams and their respective focused detection paths to prevent their intersection so that the radiation detected is background gamma radiation; and (f) means for determining from the aligned gamma radiation and the misaligned gamma radiation a density characteristic of the media.