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US 4,542,292 AGranted
Correction of natural gamma radiation logs for the effects of gamma ray emission from and attenuation by the borehole fluid
AssigneeSchlumberger Technology Corporation
InventorDarwin V. Ellis
Life of this patent
Estimating the term…
Abstract
Disclosed are a method and a system for natural gamma radiation well logging in which the radiation detected in five energy windows is converted into a log of thorium, uranium and potassium (Th,U,K) which is corrected for the presence of gamma radiation emitting materials (e.g., potassium) and strong gamma radiation attenuators (e.g., barite and/or hematite) in the borehole fluid.
Claims37
A well logging method comprising the steps of:
- deriving a log of natural gamma radiation detected in respective energy windows in a selected depth interval of a borehole containing borehole fluid comprising at least one of (i) a gamma ray emitting substance and (ii) a substance which is a strong attenuator of gamma rays;
- converting the windows log into a log of selected gamma radiation emitting subsurface materials in the formations surrounding the borehole which is substantially corrected for at least one of said (i) emitting substance in the borehole fluid and (ii) strongly attenuating substance in the same borehole fluid;
- and
- producing a tangible representation of said subsurface materials log.
1 more element
A well logging method comprising the steps of:
- deriving a log of radiation detected in respective energy windows for a selected depth interval of a borehole which traverses subsurface formations and is packed with borehole fluid containing a substance emitting radiation and a substance strongly attenuating radiation;
- generating from said windows log an estimate of the effect thereon of at least one of said substances;
- and
- producing from said windows log a log of respective radiation emitting materials in the subsurface formations surrounding the borehole interval which is substantially corrected for said estimate of the effect on the windows log of said at least one substance.
1 more element
A well logging method comprising the steps of:
- deriving a log of natural gamma radiation detected in respective energy windows for a selected depth interval of a borehole which traverses subsurface formations and contains borehole fluid comprising a substance emitting natural gamma radiation and a substance strongly attenuating said radiation;
- finding from the windows log respective estimates of the effects of said substances on the windows log, and optimizing said estimates for consistency with each other and with the windows log;
- and
- utilizing said windows log and said optimized estimates to produce a log of respective selected subsurface materials which are in the formations surrounding the borehole interval and which emit natural gamma radiation.
1 more element
A well logging method comprising the machine-implemented steps of:
- deriving a log of natural gamma radiation detected in respective energy windows in a selected depth interval of a borehole which traverses subsurface earth formations and contains borehole fluid comprising at least one of (i) a substance which emits gamma rays and (ii) a substance which strongly attenuates gamma rays;
- utilizing the window log to find an estimate of at least one of (i) the increase in the detected radiation represented by the windows log due to the gamma ray emitting substance in the borehole fluid and (ii) the attenuation of the detected radiation represented by the windows log due to the strongly attenuating substance in the borehole fluid;
- and
- correcting the window log by removing therefrom at least one of said increase and attenuation based on said estimate, and converting the resulting corrected windows log into a log of selected gamma ray emitting materials in the formations surrounding the selected borehold interval.
1 more element
A well logging method comprising the steps of:
- deriving a log of natural gamma radiation detected in selected energy windows by a logging tool passed through a selected depth interval of a borehole which extends through subsurface earth formations and contains borehole fluid;
- wherein said borehole fluid contains at least one of (i) a gamma ray emitting substance and (ii) a substance which strongly attenuates gamma radiation;
- converting said energy windows log into a log of selected gamma radiation emitting subsurface materials which is substantially corrected for deleterious effects of at least one of said emitting substance and attenuating substance in said borehole fluid;
- and
- producing a tangible representation of said corrected log of the selected subsurface materials.
2 more elements
A well logging system comprising:
- means for deriving a log of natural gamma radiation detected in respective energy windows in a selected depth interval of a borehole containing borehole fluid comprising at least one of (i) a gamma ray emitting substance and (ii) a substance which is a strong attenuator of gamma rays;
- and
- means for converting the windows log into a log of selected gamma radiation emitting subsurface materials in the formations surrounding the borehole which is substantially corrected for of at least one of said (i) emitting substance in the borehold fluid and (ii) strongly attenuating substance in the same borehole fluid, and for producing a tangible representation of said subsurface materials log.
Dependencies are inferred from the claim text.