Spectral alignment method for induced gamma ray logging
AssigneeSchlumberger Technology Corporation
InventorFabien Haranger
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Abstract
A method for gain correcting a gamma ray spectrum includes acquiring a gamma ray spectrum including gamma ray counts distributed into a plurality of energy channels, evaluating the acquired gamma ray spectrum to determine an energy of a calibration feature therein, comparing the energy of the calibration feature in the acquired spectrum to a standard spectral energy to determine a deviation between the energy of the calibration feature and the standard spectral energy, and adjusting the acquired spectrum so that the energy of the calibration feature is equal to the standard spectral energy to obtain a gain calibrated spectrum.
Claims20
A method for gain correcting gamma ray spectra, the method comprising:
- acquiring a gamma ray spectrum including gamma ray counts distributed into a plurality of energy channels;
- evaluating the acquired gamma ray spectrum to determine an energy of a calibration feature therein;
- comparing the energy of the calibration feature in the acquired gamma ray spectrum to a standard spectral energy to determine a deviation between the energy of the calibration feature and the standard spectral energy;
- and
- adjusting the acquired gamma ray spectrum so that the energy of the calibration feature is equal to the standard spectral energy to obtain a gain calibrated spectrum.
A system for logging a wellbore, the system comprising:
- a neutron source and a gamma ray detector deployed in a logging tool body;
- and
- a processor including instructions configured to:
- acquire a gamma ray spectrum including gamma ray counts distributed into a plurality of energy channels;
- evaluate the acquired gamma ray spectrum to determine an energy of a calibration feature therein;
- compare the energy of the calibration feature in the acquired gamma ray spectrum to a standard spectral energy to determine a deviation between the energy of the calibration feature and the standard spectral energy;
- and
- adjust the acquired gamma ray spectrum so that the energy of the calibration feature is equal to the standard spectral energy to obtain a gain calibrated spectrum.
A method for calibrating gamma ray spectra, the method comprising:
- acquiring a gamma ray spectrum including gamma ray counts distributed into a plurality of energy channels;
- evaluating the acquired gamma ray spectrum to determine an energy of a predetermined feature therein;
- computing a ratio of the energy of the predetermined feature in the acquired gamma ray spectrum to a standard spectral energy;
- and
- multiplying a spectral axis of the acquired gamma ray spectrum by the ratio so that the energy of the predetermined feature is equal to the standard spectral energy to obtain a gain calibrated spectrum.
Dependencies are inferred from the claim text.