A borehole neutron imaging tool having a two-dimensional array of neutron detector crystals, wherein said tool includes at least a source of neutrons; at least one collimated imaging detector to record images created by incident neutrons; sonde-dependent electronics; and a plurality of tool logic electronics and power supply units. A method for borehole neutron imaging, the method including controlling the direction of incident neutrons onto the imaging array; imaging said borehole surroundings; and creating a composite image of the materials surrounding the formation.

A method can include receiving neutron data and density data for a borehole in a geologic formation; determining a migration length value for a layer of the geologic formation based at least in part on the neutron data; forward modeling at least the layer based at least in part on the migration length value and the density data; and outputting, based at least in part on the forward modeling, modeled neutron data for the layer.

A well logging tool includes a neutron generator to generate and emit energetic neutrons using substantially exclusively a T-T fusion reaction. The well logging tool can include measuring instrumentation for measurement and logging of formation parameters based on elastic scattering in subsurface formations of neutrons emitted by the neutron generator. The neutron generator can have a concentric layout, in which a cylindrical target structure loaded with tritium particles is located co-axially in an elongate cylindrical housing, with mobile tritium ions being accelerated radially inwardly into impact with the target structure. Production of the mobile tritium ions may be by field ionization through operation of a nano-structure field ionization array.

A method for determining a tubing deviation from nuclear measurement data includes acquiring neutron measurement data from a wellbore. The method also includes identifying one or more features from the neutron measurement data. The method further includes determining, based at least in part on a pattern matching algorithm, that the one or more features are indicative of a tubular deviation. The method also includes determining, based at least in part on a comparison between the one or more features, a deviation amount.

A system includes a tool for measuring properties of a formation. The tool includes a tool body, a neutron source to emit neutrons disposed within the tool body, a neutron detector disposed within the tool body spaced apart from the neutron source, and a neutron shield arranged in operational relationship to the neutron detector, the neutron shield defines an exterior surface and an interior volume, the neutron shield to prevent neutrons having an energy below a first predetermined threshold from traveling from the exterior surface to the interior volume. The neutron shield is movably coupled to the tool body, wherein the neutron shield defines a non-occluded position relative to the neutron detector such that the neutron detector is at least partially outside the interior volume, and the neutron shield defines an occluded position relative to the neutron detector such that the neutron detector is disposed within the interior volume.

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.

The present disclosure describes a method for surveillance of a horizontal well, including: monitoring a first set of measurement data from a pulsed neutron tool and a second set of measurement data from an array tool, wherein: the first set of measurement data indicate a holdup of the second liquid globally inside the horizontal well, and the second set of measurement data show a plurality of velocities measured at a set of corresponding locations inside the horizontal well; and interpolating the first set of measurement data to identify an interface between the first liquid and the second liquid; establish an estimated holdup of the second liquid in the cross-section of the horizontal well; and combining the estimated holdup of the second liquid with velocities measured at locations inside the horizontal well that correspond to the second layer to generate a flow weighted estimate of the second liquid inside the horizontal well.

A downhole multi-modality inspection system includes a first imaging device operable to generate first imaging data and a second imaging device operable to generate second imaging data. The first imaging device includes a first source operable to emit energy of a first modality, and a first detector operable to detect returning energy induced by the emitted energy of the first modality. The second imaging device includes a second source operable to emit energy of a second modality, and a second detector operable to detect returning energy induced by the emitted energy of the second modality. The system further includes a processor configured to receive the first imaging data and the second imaging data, and integrate the first imaging data with the second imaging data into an enhanced data stream. The processor correlates the first imaging data and the second imaging data to provide enhanced data for detecting potential wellbore anomalies.

A method can include receiving neutron data and density data for a borehole in a geologic formation; determining a migration length value for a layer of the geologic formation based at least in part on the neutron data; forward modeling at least the layer based at least in part on the migration length value and the density data; and outputting, based at least in part on the forward modeling, modeled neutron data for the layer.

A combining mechanism for borehole logging tool data that employs modality merging to combine the output data of various borehole logging tools to provide a combined result and automated interpretation is provided, said mechanism comprising: at least one mechanism for assigning interpretive values to individual processed data types; at least one mechanism for combining the interpretive value data sets; and, at least one mechanism for providing an interpretation. A method of combining borehole logging tool data that employs modality merging to combine the output data of various borehole logging tools to provide a combined result and automated interpretation is also provided, said method comprising: assigning interpretive values to individual processed data types; combining the interpretive value data sets; and, providing an interpretation.