Abstract: A downhole tool operable for conveyance within a wellbore extending into a subterranean formation, and for obtaining one or more measurements of the subterranean formation, wherein the downhole tool comprises a sensor, a pressure housing containing the sensor and mounted on an external surface of the downhole tool, and a sliding stabilizer covering the pressure housing.

Abstract: Disclosed is a radiation logging tool, comprising a tool housing; a compact generator that produces radiation; a power supply coupled to the compact generator; and control circuitry. Embodiments of the compact generator comprise a generator vacuum tube comprising a source generating charged particles, and a target onto which the charged particles are directed; and a high voltage supply comprising a high voltage multiplier ladder located laterally adjacent to the generator vacuum tube. The high voltage supply applies a high voltage between the source and the target to accelerate the charged particles to a predetermined energy level. The compact generator also includes an electrical coupling between an output of the high voltage supply and the target of the generator vacuum tube to accommodate the collocated positions of the generator vacuum tube and the high voltage power supply.

Abstract: A method for determining a fractional volume of at least one component of a formation includes entering into a computer a number of detected radiation events resulting from imparting neutrons into the formation at an energy level of at least 1 million electron volts (MeV). The detected radiation events correspond to at least one of an energy level of the imparted neutrons and thermal or epithermal energy neutrons. A measurement of at least one additional petrophysical parameter of the formation is made. The at least one additional petrophysical parameter measurement and at least one of a fast neutron cross-section and a thermal neutron cross-section determined from the detected radiation events are used in the computer to determine the fractional volume of the at least one component of the formation. In another embodiment, the fast neutron cross-section and the thermal neutron cross-section may be used on combination to determine the fractional volume.

Abstract: A scintillator type radiation detector package is provided including a scintillation crystal directly coupled to the window of a photomultiplier. A scintillator package is also provided having a longer life at wellbore temperature with minimal deterioration of a hygroscopic scintillation crystal(s). Direct optical coupling of the scintillator to the photomultiplier reduces the amount of light lost at coupling interfaces and improved detection resolution over the conventional structures having separate packages for crystal and photomultiplier.

Abstract: Devices and methods for a rugged semiconductor radiation detector are provided. The semiconductor detector may include a hermetically sealed housing and a semiconductor disposed within the housing that has a first surface and a second surface opposite one another. A first metallization layer may at least partially cover the first surface of the semiconductor and a second metallization layer may at least partially cover the second surface of the semiconductor. The first metallization layer or the second metallization layer, or both, do not extend completely to an edge of the semiconductor, thereby providing a nonconductive buffer zone. This reduces electrical field stresses that occur when a voltage potential is applied between the first metallization layer and the second metallization layer and reduces a likelihood of electrical failure (e.g., due to arcing).

Abstract: A presence of cement may be identified based on a downhole tool that may emit neutrons into a wellbore having at least one cement casing. The neutrons may interact with the particular material via inelastic scattering, inelastic neutron reactions, capture of neutrons and/or neutron activation through one of these reactions and cause a material to emit an energy spectrum of gamma rays, and wherein the downhole tool is configured to detect an energy spectrum of the gamma rays that is specific to at least one of a plurality of elements and associated a region within the wellbore. An amount of elements, such as calcium and silicon, may be determined from the gamma ray spectra that may indicate a present of cement within the wellbore.

Abstract: A method for evaluating wellbore conduit condition includes using measurements of at least one of (i) inelastic gamma rays made during emission a burst of neutrons into the conduit from within the conduit at at least one spaced apart location from a position of the emission and (ii) epithermal neutrons or capture gamma rays therefrom detected at at least two spaced apart locations from the position of the emission within a selected time after the emission. The at least one of the measurements of inelastic gamma rays and epithermal neutron or capture gamma ray counts are characterized to estimate an amount of loss of iron in the conduit.

Abstract: The disclosure relates to a method for correcting a downhole natural gamma-ray measurement performed in a wellbore. A gamma-ray measurement including at least a gamma-ray count rate is obtained by a gamma-ray detector disposed in a bottom hole assembly having a mud channel inside of the assembly, such that mud flows downwards in the mud channel and upwards outside of the assembly and a neutron source situated above the gamma-ray detector and activating the mud.

Abstract: A downhole densitometer is used to determine one or more characteristics of a flowing fluid. The densitometer has one or more downhole x-ray sources and one or more downhole x-ray detectors. A fluid is allowed to flow past the x-ray sources. X-rays emitted by the x-ray sources and that have travelled through the flowing fluid are detected by the x-ray detectors. Characteristics of the flowing fluid are determined based on the detected x-rays. The densitometer may also have reference detectors used to measure a reference signal. The measured reference signal is used to normalize source emissions. The densitometer may be used as a permanent monitor and it may be used in conjunction with other sensors such as a flow-rate sensor or a capacitance sensor. The x-ray source may be, for example, a pyroelectric source, a radioisotopic source, or a traditional x-ray tube source.

Abstract: A system for a downhole tool includes an X-ray generator that outputs X-ray radiation into a surrounding sub-surface formation using electrical power received from a power supply and a detector device adjacent the X-ray generator. The detector device includes a first detector with a first radiation sensitivity that outputs a first measurement signal based on interaction between a first portion of the X-ray radiation and the first detector. The detector device also includes a second detector with a second radiation sensitivity adjacent the first detector, where the second detector outputs a second measurement signal based on interaction between a second portion of the X-ray radiation and the second detector.

Abstract: A method for separating and quantifying gamma ray induced and neutron induced responses in a radiation detector includes detecting radiation in a radiation field comprising neutrons and gamma rays. The detected events are converted into a detector pulse amplitude spectrum. The pulse amplitude spectrum is decomposed into contributions from detected gamma rays and detected neutrons using gamma ray standard spectra and neutron standard spectra and a spectral fitting procedure which results in a best fit between a weighted sum of the contributions and the detector pulse amplitude spectrum. The fitting procedure includes determining fitting parameters for each of the standard spectra wherein at least one of the fitting parameters is different for the gamma ray standard spectra and the neutron standard spectra. In one embodiment, the fitting parameter is spectral gain.

Abstract: Devices and methods for a rugged semiconductor radiation detector are provided. The semiconductor detector may include a hermetically sealed housing and a semiconductor disposed within the housing that has a first surface and a second surface opposite one another. A first metallization layer may at least partially cover the first surface of the semiconductor and a second metallization layer may at least partially cover the second surface of the semiconductor. The first metallization layer or the second metallization layer, or both, do not extend completely to an edge of the semiconductor, thereby providing a nonconductive buffer zone. This reduces electrical field stresses that occur when a voltage potential is applied between the first metallization layer and the second metallization layer and reduces a likelihood of electrical failure (e.g., due to arcing).

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: Devices and methods for a rugged semiconductor radiation detector are provided. The semiconductor detector may include a hermetically sealed housing and a semiconductor disposed within the housing that has a first surface and a second surface opposite one another. A first metallization layer may at least partially cover the first surface of the semiconductor and a second metallization layer may at least partially cover the second surface of the semiconductor. The first metallization layer or the second metallization layer, or both, do not extend completely to an edge of the semiconductor, thereby providing a nonconductive buffer zone. This reduces electrical field stresses that occur when a voltage potential is applied between the first metallization layer and the second metallization layer and reduces a likelihood of electrical failure (e.g., due to arcing).

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 well-logging tool may include a sonde housing, and a radiation generator carried by the sonde housing. The radiation generator may include a generator housing, a target carried by the generator housing, a charged particle source carried by the generator housing to direct charged particles at the target, and at least one voltage source coupled to the charged particle source. The at least one voltage source may include a voltage ladder comprising a plurality of voltage multiplication stages coupled in a bi-polar configuration, and at least one loading coil coupled at at least one intermediate position along the voltage ladder. The well-logging tool may further include at least one radiation detector carried by the sonde housing.

Abstract: Disclosed is a radiation logging tool, comprising a tool housing; a compact generator that produces radiation; a power supply coupled to the compact generator; and control circuitry. Embodiments of the compact generator comprise a generator vacuum tube comprising a source generating charged particles, and a target onto which the charged particles are directed; and a high voltage supply comprising a high voltage multiplier ladder located laterally adjacent to the generator vacuum tube. The high voltage supply applies a high voltage between the source and the target to accelerate the charged particles to a predetermined energy level. The compact generator also includes an electrical coupling between an output of the high voltage supply and the target of the generator vacuum tube to accommodate the collocated positions of the generator vacuum tube and the high voltage power supply.

Abstract: Systems and methods for estimating absolute elemental concentrations of a subterranean formation from neutron-induced gamma-ray spectroscopy are provided. In one example, a system for estimating an absolute yield of an element in a subterranean formation may include a downhole tool and data processing circuitry. The downhole tool may include a neutron source to emit neutrons into the formation, a neutron monitor to detect a count rate of the emitted neutrons, and a gamma-ray detector to obtain gamma-ray spectra deriving at least in part from inelastic gamma-rays produced by inelastic scattering events and neutron capture gamma-rays produced by neutron capture events. The data processing circuitry may be configured to determine a relative elemental yield from the gamma-ray spectra and to determine an absolute elemental yield based at least in part on a normalization of the relative elemental yield to the count rate of the emitted neutrons.

Abstract: A scintillator type radiation detector package is provided including a scintillation crystal directly coupled to the window of a photomultiplier. A scintillator package is also provided having a longer life at wellbore temperature with minimal deterioration of a hygroscopic scintillation crystal(s). Direct optical coupling of the scintillator to the photomultiplier reduces the amount of light lost at coupling interfaces and improved detection resolution over the conventional structures having separate packages for crystal and photomultiplier.

Abstract: Systems, methods, and devices for inelastic gamma-ray logging are provided. In one embodiment, such a method includes emitting neutrons into a subterranean formation from a downhole tool to produce inelastic gamma-rays, detecting a portion of the inelastic gamma-rays that scatter back to the downhole tool to obtain an inelastic gamma-ray signal, and determining a property of the subterranean formation based at least in part on the inelastic gamma-ray signal. The inelastic gamma-ray signal may be substantially free of epithermal and thermal neutron capture background.