Apparatus and method for determining thermal neutron capture cross section of a subsurface formation from a borehole using multiple detectors
AssigneeBaker Hughes Incorporated
InventorsAllen Gilchrist, Darryl E. Trcka
Life of this patent
Estimating the term…
Abstract
A well logging instrument including a plurality of detectors having different precisions and accuracies, the more precise detectors generally having lower accuracies. The detectors are responsive to the interaction of radiation from a suitable source on the instrument with earth formations. Outputs from the plurality of detectors are smoothed and combined to provide processed measurements with improved accuracy and precision.
Claims33
A method for determining a parameter of interest of an earth formation with a logging tool having an energy source and a plurality of detectors for making measurements resulting from interaction of said energy source with said earth formation, the method comprising:
- (a) making a first measurement indicative of said parameter of interest at a first of said plurality of detectors, said first measurement having a first precision;
- (b) making a second measurement indicative of said parameter of interest at a second of said plurality of detectors, said second measurement having a second precision not greater than said first precision;
- (c) forming a weighted sum of said first and second measurements to give a processed measurement having a higher precision than the first measurement;
- and
- (d) recording the processed measurement on a suitable medium.
A method for determining a parameter of interest of an earth formation with a logging tool having a source for irradiating said earth formation, and a plurality of detectors spaced apart from the source for making measurements resulting from interaction of said energy source with said earth formation, the method comprising:
- (a) making a first, second and third set of measurements indicative of said parameter of interest with first, second and third detectors, said first, second and third measurements each having a precision, resolution and accuracy;
- (b) forming a weighted sum of said first, second and third measurements to give a processed measurement having a higher precision than the most precise of said measurements and having a higher accuracy than the least accurate of said measurements;
- and
- (c) recording the processed measurement on a suitable medium.
An apparatus for determining a parameter of interest of an earth formation comprising:
- (a) a logging tool configured to be conveyed into a borehole in said earth formation, said logging tool including a source which propagates energy into said earth formation;
- (b) a first detector on said logging tool spaced apart from the source at a first distance, said first detector configured to make a first measurement indicative of an interaction of said energy with said earth formation, said first measurement having a first precision;
- (c) a second detector on said logging tool spaced apart from the source at a second distance greater than the first distance, said second detector configured to make a second measurement indicative of said parameter of interest, said second measurement having a second precision not greater than said first precision;
- and
- (d) a processor configured to form a weighted sum of said first and second measurements to give a processed measurement having a higher precision than the first measurement.
A system for determining a parameter of interest of an earth formation comprising:
- (a) a logging tool including a neutron source configured to irradiate said earth formation;
- (b) a first detector on said logging tool spaced apart from the source at a first distance, said first detector configured to make a first measurement indicative of an interaction of said energy source with said earth formation, said first measurement having a first precision;
- (c) a second detector on said logging tool spaced apart from the source at a second distance greater than the first distance, said second detector configured to make a second measurement indicative of said parameter of interest, said second measurement having a second precision not greater than said first precision;
- (d) a conveyance device configured to convey said tool into said borehole;
- (e) a processor configured to form a weighted sum of said first and second measurements to give a processed measurement having a higher precision than said first measurement.
Dependencies are inferred from the claim text.