Abstract: A subsurface logging tool that is deployable in a wellbore that traverses a formation includes a gamma-ray scintillation detector with a thallium-based scintillator material. The scintillator material is suitable for high-temperature downhole environments (i.e., above 70° C.). As such, the scintillator material improves the performance of oilfield measurement(s) at temperatures above 70° C. and at least up to 175° C., when compared with the use of the other materials. The scintillator material may have an effective atomic number of at least sixty. The scintillator material may have the chemical formula Tl2LiY1-xCexCl6, where x is 0 to 1. Lithium (Li) may be partially or completely replaced by another alkali metal or by indium (In). Yttrium (Y) is partially or completely replaced by another rare earth element. Chlorine (Cl) is partially or completely replaced by another halide.

Abstract: Methods and related systems are described for gamma-ray detection. A gamma-ray detector is made depending on its properties and how those properties are affected by the data analysis. Desirable properties for a downhole detector include; high temperature operation, reliable/robust packaging, good resolution, high countrate capability, high density, high Z, low radioactive background, low neutron cross-section, high light output, single decay time, efficiency, linearity, size availability, etc. Since no single detector has the optimum of all these properties, a downhole tool design preferably picks the best combination of these in existing detectors, which will optimize the performance of the measurement in the required environment and live with the remaining non-optimum properties.

Abstract: A subsurface logging tool that is deployable in a wellbore that traverses a formation includes a gamma-ray scintillation detector with a thallium-based scintillator material. The scintillator material is suitable for high-temperature downhole environments (i.e., above 70° C.). As such, the scintillator material improves the performance of oilfield measurement(s) at temperatures above 70° C. and at least up to 175° C., when compared with the use of the other materials. The scintillator material may have an effective atomic number of at least sixty. The scintillator material may have the chemical formula Tl2LiY1-xCexCl6, where x is 0 to 1. Lithium (Li) may be partially or completely replaced by another alkali metal or by indium (In). Yttrium (Y) is partially or completely replaced by another rare earth element. Chlorine (Cl) is partially or completely replaced by another halide.

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: Devices may include a scintillation detection device including a scintillator, a photon detector at least partially enclosed by the scintillator, and at least one reflector at least partially enclosing the scintillator. In another aspect, an oilfield wellbore device may include an oilfield string with at least one scintillation detection device on the string and a pressure housing enclosing the one or more scintillation detection devices. In another aspect, a method of measuring radiation in an oil and gas well may include conveying at least one scintillation detection device to at least one zone of interest in the oil and gas well and recording data from at least one scintillation detection device as a function of location in the well.

Abstract: Methods and downhole tools involving neutron-absorbing gamma ray windows are provided. One such method involves emitting neutrons from a neutron source in a downhole tool in a well into a surrounding geological formation. This may produce formation gamma rays through interactions between the neutrons and elements of the geological formation. The formation gamma rays may be detected by a gamma ray detector when the gamma rays pass via a gamma ray window that includes a neutron-absorbing material disposed in a substrate material of the downhole tool. The gamma ray window may be both more transmissive of gamma rays than the substrate material and less transmissive of neutrons than a window without the neutron-absorbing material. This may decrease a neutron flux that would otherwise reach the gamma ray detector and the tool materials surrounding it and thus would otherwise lead to a background signal contaminating a signal corresponding to the detected formation gamma rays.

Abstract: Devices may include a scintillation detection device including a scintillator, a photon detector at least partially enclosed by the scintillator, and at least one reflector at least partially enclosing the scintillator. In another aspect, an oilfield wellbore device may include an oilfield string with at least one scintillation detection device on the string and a pressure housing enclosing the one or more scintillation detection devices. In another aspect, a method of measuring radiation in an oil and gas well may include conveying at least one scintillation detection device to at least one zone of interest in the oil and gas well and recording data from at least one scintillation detection device as a function of location in the well.

Abstract: Methods and related systems are described for gamma-ray detection. A gamma-ray detector is made depending on its properties and how those properties are affected by the data analysis. Desirable properties for a downhole detector include; high temperature operation, reliable/robust packaging, good resolution, high countrate capability, high density, high Z, low radioactive background, low neutron cross-section, high light output, single decay time, efficiency, linearity, size availability, etc. Since no single detector has the optimum of all these properties, a downhole tool design preferably picks the best combination of these in existing detectors, which will optimize the performance of the measurement in the required environment and live with the remaining non-optimum properties.

Abstract: Methods and related systems are described for gamma-ray detection. A gamma-ray detector is made depending on its properties and how those properties are affected by the data analysis. Desirable properties for a downhole detector include; high temperature operation, reliable/robust packaging, good resolution, high countrate capability, high density, high Z, low radioactive background, low neutron cross-section, high light output, single decay time, efficiency, linearity, size availability, etc. Since no single detector has the optimum of all these properties, a downhole tool design preferably picks the best combination of these in existing detectors, which will optimize the performance of the measurement in the required environment and live with the remaining non-optimum properties.

Abstract: A method for estimating an aspect of a formation using a nuclear spectroscopy tool includes placing a nuclear spectroscopy tool into a borehole and emitting neutrons such that some of the neutrons generate gamma rays from a formation adjacent the nuclear spectroscopy tool and some of the neutrons generate gamma rays from elements within the nuclear spectroscopy tool. An energy spectrum of gamma rays induced by the emitted neutrons can be detected. The energy spectrum includes a background having a plurality of measured spectral components. A background ratio between at least one spectral component of the background and another measured spectral component can be determined or estimated in accordance with environmental measurements. The detected gamma ray spectra can be analyzed using a combination of standard spectra and subtracting at least one spectral component of the background in accordance with the background ratio.

Abstract: Methods and downhole tools involving neutron-absorbing gamma ray windows are provided. One such method involves emitting neutrons from a neutron source in a downhole tool in a well into a surrounding geological formation. This may produce formation gamma rays through interactions between the neutrons and elements of the geological formation. The formation gamma rays may be detected by a gamma ray detector when the gamma rays pass via a gamma ray window that includes a neutron-absorbing material disposed in a substrate material of the downhole tool. The gamma ray window may be both more transmissive of gamma rays than the substrate material and less transmissive of neutrons than a window without the neutron-absorbing material. This may decrease a neutron flux that would otherwise reach the gamma ray detector and the tool materials surrounding it and thus would otherwise lead to a background signal contaminating a signal corresponding to the detected formation gamma rays.

Abstract: Composition-matched downhole tools and methods for using such tools are provided. One such method includes emitting neutrons using a neutron source in the downhole tool to generate formation gamma rays in a surrounding formation. At the same time, however, some of the neutrons may interact with different parts of the downhole tool to form tool gamma rays. The gamma ray spectra of at least some of the formation gamma rays and the tool gamma rays may be detected using a gamma ray detector. The tool gamma rays from the different parts of the tool may have a substantially similar spectral shape. As such, a processor may be used to analyze the spectra of the tool gamma rays using a single tool background standard, thereby simplifying the analysis and improving the precision of the results.

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: Collocated radiation sensing is provided. In one possible implementation, a tool to be placed in a wellbore includes a first source of nuclear radiation and a second source of nuclear radiation. The tool also includes one or more sensors configured to discriminate between radiation emitted by the first and second sources and correctly attribute the radiation to the source from which the radiation was emitted. The one or more sensors are collocated to be within a range of radiation scattered from the first source and the second source by an environment of the formation.

Abstract: Borehole logging tools and systems that include a scintillator positioned to interact with scattered source neutrons that are received from a target formation. The scintillator emits luminescence in response to interaction with the scattered neutrons. The scintillator includes an aluminofluoride host material (e.g., LiCAF). In a specific embodiment, the aluminofluoride host material is doped with europium. In a further specific embodiment, a processor distinguishes scattered neutrons from gamma rays based upon identifying a peak within an output signal from the scintillator. In yet another specific embodiment, a system includes a first scintillator and a second scintillator. The processor subtracts luminescence generated by the second scintillator from luminescence generated by the first scintillator to identify a neutron response of the first scintillator.

Abstract: Apparatus and method for detecting radiation-of-interest, such as neutron radiation, employs a gas chamber, a gas that responds to ionizing particles by producing electrons and ions, a cathode that attracts ions, and a supporting layer with a conductive pathway. The conductive pathway collects electrons and responds to electrons that drift towards the conductive pathway by inducing production of further electrons and ions within the gas. The electrons that are collected at the conductive pathway and/or the ions that drift away from the conductive pathway will induce an electrical signal, which can be used to detect the radiation-of-interest.

Abstract: A method for improving precision of measurement of material composition of formations determined by gamma ray spectral an analysis includes determining an accurate value of an amount of a selected by analyzing a spectrum of gamma rays detected from the formations using a technique that directly relates the gamma ray spectrum to the amount of the material. A precise value of the amount of the material is determined by analyzing the spectrum of detected gamma rays that indirectly relates the gamma ray spectrum to the amount of the material. A function relating the accurate value to the precise value over a selected axial interval along the wellbore is determined. The function is applied to the accurate value at at least one selected axial position along the wellbore to determine an accurate and precise value of the amount of the material.

Abstract: A combined thermal neutron and epithermal neutron radiation detector includes a plurality of neutron detecting elements arranged such that a first set of the detecting elements is disposed closer to a source of neutron flux scatted from a material or formation to be analyzed than a second set of detecting elements. The neutron detecting elements have a material therein susceptible to capture of thermal neutrons for detection. Signal outputs of the first set of are interconnected and signal outputs of the second set are separately interconnected to provide a signal output corresponding to each of thermal neutron flux and epithermal neutron flux entering the detector.

Abstract: Composition-matched downhole tools and methods for using such tools are provided. One such method includes emitting neutrons using a neutron source in the downhole tool to generate formation gamma rays in a surrounding formation. At the same time, however, some of the neutrons may interact with different parts of the downhole tool to form tool gamma rays. The gamma ray spectra of at least some of the formation gamma rays and the tool gamma rays may be detected using a gamma ray detector. The tool gamma rays from the different parts of the tool may have a substantially similar spectral shape. As such, a processor may be used to analyze the spectra of the tool gamma rays using a single tool background standard, thereby simplifying the analysis and improving the precision of the results.

Abstract: Methods and related systems are described for gamma-ray detection. A gamma-ray detector is made depending on its properties and how those properties are affected by the data analysis. Desirable properties for a downhole detector include; high temperature operation, reliable/robust packaging, good resolution, high countrate capability, high density, high Z, low radioactive background, low neutron cross-section, high light output, single decay time, efficiency, linearity, size availability, etc. Since no single detector has the optimum of all these properties, a downhole tool design preferably picks the best combination of these in existing detectors, which will optimize the performance of the measurement in the required environment and live with the remaining non-optimum properties.