Abstract: A downhole tool can include a photon beam source configured to transmit a photon beam into materials lining a wellbore. The materials may comprise fluid, casing, and cement. A photon detector in the tool is configured to count detected photons received at a predetermined angle from the materials. The density of the borehole material may be determined in response to the number of detected photons. Changes in a distribution of a plurality of photon count ratio values may indicate the standoff distance. Additional apparatus, systems, and methods are disclosed.

Abstract: A system for determining a wettability associated with a subterranean formation can include a dielectric logging tool, a resistivity logging tool, a pulsed neutron tool, and a computing device. The dielectric logging tool can transmit a first data set associated with the subterranean formation. The resistivity logging tool can transmit a second data set associated with the subterranean formation. The pulsed neutron tool can transmit a third data set associated with the subterranean formation. The computing device can be in communication with the dielectric logging tool, the resistivity logging tool, and the pulsed neutron tool. The computing device can receive the first data set, the second data set, and the third data set and determine the wettability associated with the subterranean formation based on the first data set, the second data set, and the third data set.

Abstract: Determining a value indicative of hydrogen index. At least some of the example embodiments are methods including obtaining an inelastic count rate and a capture count rate of a gamma detector for a particular borehole depth in a formation, calculating a ratio of an inelastic count rate to a capture count rate for the particular borehole depth, and determining a value indicative of hydrogen index based on the ratio of the inelastic count rate to the capture count rate for the particular borehole depth.

Abstract: Determining a value indicative of hydrogen index. At least some of the example embodiments are methods including obtaining an inelastic count rate and a capture count rate of a first gamma detector for a particular borehole depth, obtaining an inelastic count rate and a capture count rate of a second gamma detector for the particular borehole depth, calculating a ratio of an inelastic count rate to a capture count rate for the first gamma detector, thereby creating a first value, calculating a ratio of an inelastic count rate to a capture count rate for the second gamma detector, thereby creating a second value, calculating a ratio of the first and second values, and determining a value indicative of hydrogen index based on the ratio of the first and second values.

Abstract: A fiber optic distributed sensing system for installation within a wellbore is provided. The system includes a first set of downhole sensors having one or more nuclear sensors with nuclear field sensitivity. The system additionally includes, a second set of downhole sensors having one or more ElectroMagnetic (EM) sensors with electromagnetic field sensitivity. The fiber optic distributed sensing system also includes a processor system configured to receive data measurements from the first and second sets of sensors and configured to conjointly process the data measurements into representations of physical attributes of the wellbore.

Abstract: A tool can include an X-ray tomography device to evaluate cement in a downhole environment. The X-ray tomography device includes an X-ray beam source configured to transmit an X-ray beam at a first predetermined angle. The beam angle may be set by a capillary device coupled to the X-ray beam source. An energy dispersive, multi-pixel photon detector is configured to count detected backscatter photons received at a second predetermined angle and determine an energy spectrum for the detected photons. A density map of the cement may be generated in response to the number of detected photons. Additional apparatus, systems, and methods are disclosed.

Abstract: The disclosed embodiments include downhole neutron generators and methods to utilize downhole neutron generators in a downhole environment. In one embodiment, a downhole neutron generator includes a heating element to dissipate heat to a first transition metal, which heats up the first transition metal and facilitates the first transition metal to absorb deuterium and tritium gases flowing proximate said transition metal. The downhole neutron generator also includes a second transition metal separated from the target foil, where the second transition metal is doped with of deuterium and the tritium ions, and a laser to direct optical pulses onto a surface of the first transition metal to produce deuterium and the tritium ions from the absorbed deuterium and tritium, where said ions traverse through a back surface of the first transition metal to the second transition metal to interact with the doped deuterium and the tritium ions to initiate fusion reaction.

Abstract: In some embodiments, an apparatus and a system, as well as a method and an article, may operate to receive energy impinging on an outer surface of a photon detector having a columnar structure, and to direct the energy within the columnar structure to a position-sensitive readout to image the energy, wherein the position-sensitive readout has position-sensitive elements, and wherein individual ones of the elements are associated with at least one column in the columnar structure to provide intrinsic collimation of the energy from the outer surface to selected portions of the readout. Additional apparatus, systems, and methods are described.

Abstract: A method for monitoring tubing wall thickness includes conveying a tool through a tubular string in a borehole, the tool including a photon source that directs a photon beam along a radial path toward a wall of the borehole, the tool further including an array of collimated detectors that measure Compton backscattering rates at respective distance bins along the radial path. The method further includes calculating a sequence of ratios between measurements from neighboring detectors. The method further includes identifying one or more local extrema in the sequence, each extremum representing a boundary between different materials. The method further includes determining a wall thickness of the tubular string from absolute or relative positions of the one or more extrema. The method further includes displaying a representation of the wall thickness.

Abstract: A method may comprise providing a wellbore penetrating a subterranean formation, the wellbore being lined with a pipe and having a cement between the pipe and the wellbore, wherein the cement contains a defect; providing a control spectrum of gamma radiation count rates as a function of energy for a control, wherein the control comprises the cement without the defect; emitting gamma rays into the pipe and the cement having the defect from a source of a nuclear tool disposed in the wellbore; detecting count rates of gamma radiation scattered back from the pipe and the cement having the defect with a detector of the nuclear tool as a function of energy to produce a sample spectrum; and deriving one or more physical attributes related to the defect based on a comparison of the sample spectrum and the control spectrum.

Abstract: A well logging tool includes a neutron generator having a housing, a gas source, a field ionization array, and an extraction ring. The housing defines an ion source chamber, and the gas source delivers ionizable gas to the ion source chamber. The field ionization array directly ionizes the ionizable gas to produce ions in the ion source chamber. The extraction ring produces an ion beam using the ions to initiate a fusion reaction that results in neutron emission from the neutron generator. Additional apparatus, methods, and systems are disclosed.

Abstract: A photon radiation detection systems utilizes scintillating fibers to detect downhole radioactivity along a wellbore. The system includes a light detection unit, extended light guide, and a scintillating fiber radiation detector extending along a wellbore. The scintillating fiber radiation detector may be a permanent part of the wellbore completion, or may be deployed via a downhole conveyance. The detected light photons may be utilized to evaluate the formation, cement layer or tubular string.

Abstract: A neutron generator includes a gas control interface and a vacuum chamber coupled to the gas control interface. The neutron generator also includes a target rod disposed within the vacuum chamber and having a longitudinal axis aligned with a central axis of the vacuum chamber, and further including a target disposed on a surface of the target rod facing the getter. The neutron generator also includes a planar ion source adjacent to the gas control interface and disposed between the target and the gas control interface. The planar ion source includes an array grid that is offset from the target and generally perpendicular to the longitudinal axis of the target rod.

Abstract: The disclosed embodiments include downhole gamma-ray generators and methods to utilize downhole gamma-ray generators in a downhole environment. In one embodiment, a downhole gamma-ray generator includes a target foil formed from a first material. The downhole gamma-ray generator also includes a second layer deposited along a back surface of the target foil. The downhole gamma-ray generator further includes a laser system operable to direct optical pulses onto a front surface of the target foil to ionize atoms of the first material, where electrons produced by ionization of the first material propagate through the target foil and decelerates when the electrons interact with the high density material, and where the deceleration of the electrons produces gamma-rays that are utilized to obtain one or more formation properties of a downhole formation.

Abstract: A method for material evaluation may include detecting photons from gamma ray interactions with material in an annular region between a geological formation and a casing. An energy spectrum is generated from the detected photons. A difference between materials may then be detected based on a comparison of the generated energy spectrum with a reference spectrum for a known material (e.g., good cement, known fluid).

Abstract: Disclosed are apparatus, systems, and methods for determining the completeness of the cement sheath or gravel-pack annulus of a borehole based on gamma counts or count rates measured with a pulsed neuron tool deployed in the borehole in conjunction with a quantitative relationship between certain gamma count (rate) ratios and a parameter of completeness. In various embodiments, the determination utilizes the ratio of the net long inelastic count (rate) and the near capture count (rate), or the ratio of the net near inelastic count (rate) and the long capture count (rate). Additional apparatus, systems, and methods are disclosed.

Abstract: In some embodiments, an apparatus and a system, as well as a method and article, may operate to detect gamma radiation as detected gamma radiation, and to determine a relative level of potassium decay energy within a selected band of energy levels, with respect to a combination of at least two of potassium, uranium, or thorium. Further operations may include adjusting at least one of a detector supply voltage or an analyzer gain to place the potassium decay energy at a selected energy level location when the relative level of potassium decay energy exceeds a predetermined threshold, the threshold based on an energy level of a combination of detected gamma radiation within the selected band of energy levels. Additional apparatus, systems, and methods are disclosed.

Abstract: Various apparatus or methods are arranged to operate a tool downhole in a well, where the tool has a detection package operable to detect gamma rays. Deviation of energy spectra of detected gamma rays in each selected energy window of a set of selected energy windows with respect to reference energy spectra of the respective selected energy window can be detected. One or more properties of one or more regions around the tool can be determined from the deviations, the regions being between the tool and a source of the detected gamma rays in a formation around the well. Additional apparatus, systems, and methods having a gamma ray detection package can operate in a variety of applications.

Abstract: Various apparatus or methods are arranged to operate a tool downhole in a well, where the tool has a detection package operable to detect gamma rays. Spectra peaks of the detected gamma rays can be determined in each of selected energy windows. Distribution of radiation tracer can be determined in one or more regions around the tool from ratios of the spectra peaks. Additional apparatus, systems, and methods having a gamma ray detection package can operate in a variety of applications.

Abstract: Methods and systems including establishing a wellbore heterogeneity profiling factor (HPF), establishing a cement quality curve representing a volumetric void space of a completion profile, and comparing the wellbore HPF and the cement quality curve, thereby determining a cement volumetric void space in a wellbore at a target depth having the completion profile.