Baker Hughes, a Ge Compnay, LLC

Weatherford Technology Holdings, LLC

Matthew McCleskey

Natasa Mekic

Methods and tools for determining one or more parameters of an earth formation using time-of-flight (TOF) measurements of fast neutrons through the formation are disclosed. The disclosed tools feature a neutron source capable of emitting a population of fast neutrons having a distribution of neutron energies and one or more neutron detectors. The TOF of the fast neutrons travelling from the neutron source to the detector(s) and traversing a portion of the formation is measured and binned as a function of TOF (which is a function of neutron energy). By determining which neutron energies are attenuated by the intervening formation, the composition of the intervening formation is determined.

Neutron time of flight wellbore logging

Estimating a parameter of interest, comprising intermittently generating a calibration radiation source in the carrier, the calibration radiation source comprising a radioisotope producing radiation to which the radiation sensor is exposed. Methods include measuring a calibration response from the radiation sensor with measurement circuitry during the exposure to produce calibration information, and measuring another response from the radiation sensor with the measurement circuitry to produce measurement information after the radioisotope has decayed to a reduced radiation level such that the measurement information is substantially unaffected by the radioisotope. The radioisotope may be a positron emitter producing radiation by annihilation of the positrons emitted from the radioisotope. The radiation produced may thus be gamma rays.

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Anderson, TX, United States of America

Matthew McCleskey