Elemental concentrations in subterranean formations may be determined using neutron spectroscopy. For example, neutrons may be emitted by a downhole tool into the formation and produce gamma rays via inelastic scattering of fast neutrons or capture of slow neutrons. The borehole surrounding a downhole tool may introduce artifacts in the neutron spectroscopy measurement. Embodiments of the present disclosure are directed to techniques that reduce artifacts signals in downhole tools that include one or multiple detectors based at least in part on the inelastic and capture measurements.

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.

Systems and methods for determining the composition of an earth formation are disclosed. One or more spectra that correspond to gamma radiation that is detected at each of multiple depths in a wellbore are generated, the contributions of each of multiple detection elements to the one or more spectra are determined, and the weight fractions of each of multiple compounds that are associated with the detection elements are calculated. The weight fraction calculations are based on a number density ratio value for the compound's associated detection element, which allows the weight fraction to be calculated directly from the contribution of the compound's associated detection element without a normalization factor.

A method for determining formation hydrogen index includes using as input to a computer measurements of numbers of burst gamma rays (gamma rays detected during operation of a pulsed neutron source) and numbers of thermal neutron capture gamma rays made at two different axial spacings from the pulsed neutron source. A ratio of the numbers of burst gamma rays and a ratio of the numbers of thermal neutron capture gamma rays is determined. A corrected ratio of the numbers of thermal neutron capture gamma rays using the ratio of numbers of burst gamma rays is determined. The formation hydrogen index is determined from the corrected ratio.

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.

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.

The present invention relates to a method for producing a cross-linked moulded body from UHMWPE, comprising the steps of: providing a moulded body from UHMWPE which is added with an antioxidant; heating the moulded body to a temperature of 100 C. or more; and irradiating the moulded body in order to cross-link the UHMWPE in the moulded body. The irradiation of the moulded body is carried out with x-ray radiation. The invention also relates to a method for producing an implant or an implant part, in particular an inlay for an artificial hip joint, comprising the performance of the above method and the machining of the cross-linked moulded body.

Systems and methods for determining the composition of an earth formation are disclosed. One or more spectra that correspond to gamma radiation that is detected at each of multiple depths in a wellbore are generated, the contributions of each of multiple detection elements to the one or more spectra are determined, and the weight fractions of each of multiple compounds that are associated with the detection elements are calculated. The weight fraction calculations are based on a number density ratio value for the compound's associated detection element, which allows the weight fraction to be calculated directly from the contribution of the compound's associated detection element without a normalization factor.

A method for obtaining elemental concentration and determining the formation density uses a tool having multiple dual-function detectors that can detect both neutrons and gamma rays simultaneously. The method includes emitting neutrons into the formation, detecting neutron and gamma ray signals from the formation and discriminating the neutron signal and the gamma ray signal, obtaining the space, time and energy dependent fluence rates for fast neutrons and thermal neutrons, obtaining gamma ray energy spectra from initial inelastic gamma rays and backscattered inelastic gamma rays from one or more detectors. The formation density can be calculated based on one or more ratios between the gamma ray count rates at the one or more detectors to the gamma ray count rate at the near detector.

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.