Abstract: A method for operating a pulsed neutron generator including an ionizer with an electron emitting cathode and a grid wherein the cathode and grid are disposed in a sealed chamber. At least one of the following is applicable to the ionizer; a distance between the cathode and the grid, a cathode current and/or a potential on the grid are selected such that the ionizer operates at most about one-half the space charge limited current for a grid current selected to provide a predetermined amount of neutron production.

Abstract: A method for formation logging includes acquiring measurements of neutron-induced signals having azimuthal information using a neutron tool; processing the measurements into a plurality of azimuthal sector data for each acquisition interval; and deriving a selected parameter from the plurality of azimuthal sector data. A logging tool includes a housing adapted to move in a borehole; a circuitry having memories for storing neutron-induced measurements; a neutron source disposed in the housing; and at least one detector bank disposed in the housing spaced apart from the neutron source, wherein each of the at least one detector bank comprises at least one detector disposed around a periphery of the housing such that the at least one detector is more sensitive to signals from an azimuthal direction, and wherein count rates detected by each of the at least one detector are separately stored in the memories.

Abstract: A method for formation logging includes acquiring measurements of neutron-induced signals having azimuthal information using a neutron tool; processing the measurements into a plurality of azimuthal sector data for each acquisition interval; and deriving a selected parameter from the plurality of azimuthal sector data. A logging tool includes a housing adapted to move in a borehole; a circuitry having memories for storing neutron-induced measurements; a neutron source disposed in the housing; and at least one detector bank disposed in the housing spaced apart from the neutron source, wherein each of the at least one detector bank comprises at least one detector disposed around a periphery of the housing such that the at least one detector is more sensitive to signals from an azimuthal direction, and wherein count rates detected by each of the at least one detector are separately stored in the memories.

Abstract: Techniques for monitoring a pulsed neutron source include measuring a burst count rate while the pulsed neutron source is turned on using a monitor detector disposed proximate the pulsed neutron source; measuring a decay count rate while the neutron source is turned off using the monitor detector; and deriving a source strength indicator from the burst count rate and the decay count rate. A pulsed neutron tool includes a tool body; a pulsed neutron source disposed in the tool body; a monitor detector disposed in the tool body proximate the pulsed neutron source; at least one measurement detector disposed in the tool body at a predetermined distance from the pulsed neutron source; and circuitry disposed in the tool body for controlling the pulsed neutron source, the monitor detector, and the at least one measurement detector.

Abstract: A method is disclosed for operating a well logging tool having a controllable radiation source operatively coupled to a power source. The method includes monitoring at least one condition in a wellbore, and operatively disconnecting the power source from the radiation source when the at least one condition changes. Also disclosed is a downhole measurement assembly, which includes a radiation source, a power source, and at least one interlock operatively connected between the power source and the radiation source, where the at least one interlock is adapted to selectively arm and disarm the radiation source.

Abstract: A method is disclosed for operating a well logging tool having a controllable radiation source operatively coupled to a power source. The method includes monitoring at least one condition in a wellbore, and operatively disconnecting the power source from the radiation source when the at least one condition changes. Also disclosed is a downhole measurement assembly, which includes a radiation source, a power source, and at least one interlock operatively connected between the power source and the radiation source, where the at least one interlock is adapted to selectively arm and disarm the radiation source.