Abstract: A system that may identify when a pulsed neutron generator is operating while disposed in an undesirable environment, such as in air, may include a pulsed neutron generator designed to emit neutrons in an environment. The system may also include a radiation detector designed to take measurements of the neutrons. The system may also include data processing circuitry designed to determine if the environment surrounding the pulsed neutron generator is air based at least in part on a neutron signal obtained by the radiation detector. The determination may include comparing one or more characteristics of the neutron signal with corresponding reference characteristics.

Abstract: A method for evaluating cement in a cased wellbore in a geological formation includes placing a downhole tool into the cased wellbore, where the cased wellbore has been cased using a cement that contains a particular material. The method includes emitting neutrons using the downhole tool, wherein the neutrons interact with the particular material via inelastic scattering or capture of neutrons and cause the material to emit an energy spectrum of the gamma rays associated with the material or wherein the time-based measurement of gamma rays or neutrons is influenced by the presence of the material. The method includes using the downhole tool to detect radiation radiation, such as the energy spectrum of the gamma rays, or a die-away pattern of the gamma rays or neutrons that indicates a presence of the particular material and enable to estimate a parameter of the cement.

Abstract: A downhole tool includes a radiation generator configured to output radiation using electrical power received from a power supply. A first portion of the radiation is emitted into a surrounding sub-surface formation. The downhole tool also includes a radiation detector coupled proximate the radiation generator. The radiation detector includes a micromesh gaseous detector, and the radiation detector is configured to output a measurement signal based at least in part on interaction between a second portion of the radiation output by the radiation generator and the radiation detector. Additionally, the downhole tool includes a control system communicatively coupled to the radiation generator and the radiation detector. The control system is configured to determine measured characteristics of the radiation output from the radiation generator based at least in part on the measurement signal and to control operation of the radiation generator based at least in part on the measured characteristics.

Abstract: A system that may identify when a pulsed neutron generator is operating while disposed in an undesirable environment, such as in air, may include a pulsed neutron generator designed to emit neutrons in an environment. The system may also include a radiation detector designed to take measurements of the neutrons. The system may also include data processing circuitry designed to determine if the environment surrounding the pulsed neutron generator is air based at least in part on a neutron signal obtained by the radiation detector. The determination may include comparing one or more characteristics of the neutron signal with corresponding reference characteristics.

Abstract: A method for evaluating cement in a cased wellbore in a geological formation includes placing a downhole tool into the cased wellbore, where the cased wellbore has been cased using a cement that contains a particular material. The method includes emitting neutrons using the downhole tool, wherein the neutrons interact with the particular material via inelastic scattering or capture of neutrons and cause the material to emit an energy spectrum of the gamma rays associated with the material or wherein the time-based measurement of gamma rays or neutrons is influenced by the presence of the material. The method includes using the downhole tool to detect radiation radiation, such as the energy spectrum of the gamma rays, or a die-away pattern of the gamma rays or neutrons that indicates a presence of the particular material and enable to estimate a parameter of the cement.

Abstract: This disclosure is related to a downhole tool to be lowered into a wellbore, having a longitudinal axis and an outer surface, the tool including: a particle detection assembly having at least one particle detector for detecting at least a predetermined type of particles, wherein the particle detectors of the assembly are each wrapped around at least one detecting portion forming an angular portion of the tool azimuthal plane perpendicular to the longitudinal axis of the tool so that the detection assembly substantially forms a ring, at least a window transparent to the particle type and extending between the outer surface and the particle detection assembly.

Abstract: A downhole tool includes a radiation generator configured to output radiation using electrical power received from a power supply. A first portion of the radiation is emitted into a surrounding sub-surface formation. The downhole tool also includes a radiation detector coupled proximate the radiation generator. The radiation detector includes a micromesh gaseous detector, and the radiation detector is configured to output a measurement signal based at least in part on interaction between a second portion of the radiation output by the radiation generator and the radiation detector. Additionally, the downhole tool includes a control system communicatively coupled to the radiation generator and the radiation detector. The control system is configured to determine measured characteristics of the radiation output from the radiation generator based at least in part on the measurement signal and to control operation of the radiation generator based at least in part on the measured characteristics.

Abstract: This disclosure is related to a downhole tool to be lowered into a wellbore, having a longitudinal axis and an outer surface, the tool including: a particle detection assembly having at least one particle detector for detecting at least a predetermined type of particles, wherein the particle detectors of the assembly are each wrapped around at least one detecting portion forming an angular portion of the tool azimuthal plane perpendicular to the longitudinal axis of the tool so that the detection assembly substantially forms a ring, at least a window transparent to the particle type and extending between the outer surface and the particle detection assembly.

Abstract: Systems and methods are provided for an integrated caliper measurement obtained based on caliper measurements from at least two downhole tools. In one example, a system for obtaining such an integrated caliper includes several caliper tools and data processing circuitry. The caliper tools may respectively obtain caliper measurements of a wellbore. The data processing circuitry may assign respective weights to the respective caliper measurements and combine the weighted caliper measurements to obtain an integrated caliper measurement. The confidence factors may be determined based at least partly on at least two of a plurality of weighting functions. These weighting functions may each relate a confidence of the caliper measurements to an environmental or drilling characteristic occurring when the caliber measurements are obtained.