Large depth-of-investigation pulsed neutron measurements and enhanced reservoir saturation evaluation
AssigneeSaudi Arabian Oil Company
InventorYahia Ahmed Eltaher
Life of this patent
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Abstract
A method, including emitting from a source of ultrafast neutrons within a logging tool deployed in a borehole, a pulse of ultrafast neutrons into an irradiated portion of a formation surrounding the borehole. The method further includes detecting, with one or more gamma ray detectors located at increasing distances from the source of ultrafast neutrons, a flux of stimulated gamma rays generated within the irradiated portion of the formation by the pulse of ultrafast neutrons; and determining, from the detected flux of stimulated gamma rays, one or more petrophysical properties of the irradiated portion of the formation.
Claims23
A method, comprising:
- emitting, from a source of ultrafast neutrons within a logging tool deployed in a borehole, a pulse of ultrafast neutrons into an irradiated portion of a formation surrounding the borehole, wherein the irradiated portion of the formation is a cylindrical volume with a greater external radius than a radius of a cylindrical volume irradiated by a neutron with a lower energy than the ultrafast neutrons;
- detecting, with one or more gamma ray detectors located at increasing distances from the source of ultrafast neutrons, a flux of stimulated gamma rays generated within the irradiated portion of the formation by the pulse of ultrafast neutrons;
- determining, from the detected flux of stimulated gamma rays, one or more petrophysical properties of the irradiated portion of the formation.
A logging tool system, comprising:
- a computer processor;
- a wireline connected to the computer processor;
- a logging tool housing;
- a source of ultrafast neutrons mounted in the logging tool housing that emits a pulse of ultrafast neutrons into an irradiated portion of a formation surrounding the borehole, wherein the irradiated portion of the formation is a cylindrical volume with a greater external radius than a radius of a cylindrical volume irradiated by a neutron with a lower energy than the ultrafast neutrons;
- one or more gamma ray detectors mounted in the logging tool housing at one or more distances from the source of ultrafast neutrons that detect and determine a characteristic of a flux of stimulated gamma rays stimulated in a formation by the pulse of ultrafast neutrons;
- and
- a non-transitory computer memory that receives and stores a characteristic of the flux of stimulated gamma rays detected by the plurality of gamma ray detector.
A logging tool system, comprising:
- a logging tool housing connected to the bottom-hole assembly of a drill-string;
- a computer processor mounted in the logging tool housing;
- a source of ultrafast neutrons mounted in the logging tool housing that emits a pulse of ultrafast neutrons into an irradiated portion of a formation surrounding the borehole, wherein the irradiated portion of the formation is a cylindrical volume with a greater external radius than a radius of a cylindrical volume irradiated by a neutron with a lower energy than the ultrafast neutrons;
- one or more gamma ray detectors mounted in the logging tool housing at one or more distances from the source of ultrafast neutrons that detect and determine a characteristic of a flux of stimulated gamma rays stimulated in a formation by the pulse ultrafast neutrons;
- and
- a non-transitory computer memory that receives and stores the characteristic of the flux of stimulated gamma rays detected by the gamma ray detector.
Dependencies are inferred from the claim text.