A computer-implemented method that uses a preprogrammed neural network and a trained neural network computer program product to predict and then compared borehole and formation sigmas, when using a pulse neutron source and at least three dual-function radiation detectors. These dual-function radiation detectors are used for detecting both neutrons and gamma rays and further pre-programmed to distinguish between neutrons and gamma rays by using pulse shape discrimination techniques. The trained neural network computer program product can be used on above-surface systems, as well as below surface systems like borehole assemblies in logging-while-drilling systems. Once thermal neutron time-decay signals and capture gamma ray time-decay signals are measured by the at least three-dual function radiation detectors, a non-transitory computer readable memory device with the trained neural network computer program product is used to obtain a true borehole sigma and true formation sigma as the measurements are not affected by near-wellbore environments.

A computer-implemented method that uses a preprogrammed neural network and a trained neural network computer program product to predict and then compared borehole and formation sigmas, when using a pulse neutron source and at least three dual-function radiation detectors. These dual-function radiation detectors are used for detecting both neutrons and gamma rays and further pre-programmed to distinguish between neutrons and gamma rays by using pulse shape discrimination techniques. The trained neural network computer program product can be used on above-surface systems, as well as below surface systems like borehole assemblies in logging-while-drilling systems. Once thermal neutron time-decay signals and capture gamma ray time-decay signals are measured by the at least three-dual function radiation detectors, a non-transitory computer readable memory device with the trained neural network computer program product is used to obtain a true borehole sigma and true formation sigma as the measurements are not affected by near-wellbore environments.

A well integrity inspection system configured to inspect a well structure including multiple concentric layers. The well integrity inspection system includes an inspection probe positioned in the well structure. The inspection probe includes a plurality of excitation assemblies for transmitting a plurality of radiation emissions into the well structure. The plurality of excitation assemblies includes at least a neutron excitation assembly and an X-ray excitation assembly. The inspection probe also includes a plurality of detection assemblies configured to receive a plurality of backscatter radiation returns from the well structure. The plurality of detection assemblies includes at least a neutron detection assembly and an X-ray detection assembly. The well integrity inspection system further including a processor operatively coupled to the inspection probe. The processor is configured to determine a well integrity parameter of the well structure based on at least one of the plurality of backscatter radiation returns.

Methods and devices for estimating at least one property of a volume of interest of an earth formation from a radiation based measurement. Methods include using an optimization procedure to determine an optimal mineralogical model in dependence upon a secondary dependence relation between tool measurements, the mineralogical model including a mineralogical composition of the volume. The secondary dependence relation may include a relation between a plurality of estimated elemental concentrations for the volume. The mineralogical composition may include a concentration of each mineral of a plurality of minerals of the volume. The relation may include a ratio of a first elemental concentration of the plurality of estimated elemental concentrations and a second elemental concentration of the plurality of estimated elemental concentrations. Methods may include using at least one cost function to determine the optimal mineralogical model, wherein the at least one cost function is determined using the relation.

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.

Systems and methods include a computer-implemented method for creating artificial real-time gamma ray (GR) images for well placement. Real-time azimuthal density data is determined from drilling of a well. An azimuthal density data set is generated using the real-time azimuthal density data. The azimuthal density data set is generated with a greater sampling rate than a real-time sampling rate of the real-time azimuthal density data. An azimuthal density curve depth match is performed using the azimuthal density data set. Performing the azimuthal density curve depth match includes creating a depth shift match table. A high-resolution sector near-bit gamma ray (GR) image is generated using the azimuthal density curve depth match and the depth shift match table. The high-resolution sector near-bit GR image is oriented to a top of a wellbore for the well.

A wellbore inspection apparatus and a corresponding method of operation are described. The wellbore inspection apparatus comprises a neutron generator that produces, by a fusion reaction, a neutron and a corresponding charged particle. An associated particle imaging (API) detector comprises a particle detector array that detects the corresponding charged particle. The particle detector array comprises a plurality of particle detector elements that facilitate determining a trajectory of the neutron based upon a detection, by a particular one of the plurality of particle detector elements, of the corresponding charged particle. A gamma-ray detector assembly comprises a set of gamma-ray detector elements, and a set of collimating structures, where adjacent pairs of the set of collimating structures define a gamma-ray path for a gamma-ray arising from an inelastic collision of the neutron.

A downhole inspection system includes a neutron imaging device operable to generate data for detecting potential wellbore anomalies and an electromagnetic imaging device operable to generate data for detecting potential wellbore eccentricity. The neutron imaging device includes a neutron generator operable to emit neutrons, and a neutron detector fixed relative to the neutron generation unit and operable to detect backscattered neutrons from a surrounding environment. The electromagnetic imaging device includes at least one transmitter for generating electromagnetic pulse, and at least one receiver for detecting returning electromagnetic pulse. Correlation of the neutron imaging data with the electromagnetic imaging data provides additional data regarding the potential wellbore anomalies.

A wellbore inspection device includes a radiation generation source operable to emit neutrons, and a radiation detector fixed relative to the radiation generation source and operable to detect backscattered neutron radiation from a surrounding environment. The radiation detector includes a plurality of individually addressable detector elements arranged in one or more concentric rings. Respective amounts of backscattered neutron radiation detected by the individually addressable detector elements within a ring is indicative of the azimuthal direction of the detected backscattered neutron radiation, and the respective amount of backscattered neutron radiation detected by the individually addressable detector elements of two or more concentric rings is indicative of an energy level of the backscattered neutron radiation. The inspection device determines whether a potential anomaly is present in or around the wellbore, based at least in part on the respective amounts of backscattered radiation detected by the individually addressable detector elements.

The disclosure provides methods of measuring an intrinsic CO ratio in a geological formation by disposing, proximate the formation, a petrophysical tool including at least one gamma-ray detector, reading a carbon gamma-ray peak for the geological formation and an oxygen gamma-ray peak for the geological formation, determining a measured CO ratio of the geological formation from the carbon gamma-ray peak and the oxygen gamma-ray peak, and correcting the measured CO ratio by applying a corrective algorithm specific for the petrophysical tool or the type of petrophysical tool to obtain an intrinsic CO ratio of the geological formation. The corrective algorithm is derived by a mathematical analysis of measured CO ratios of a sample with a known intrinsic CO ratio using the same petrophysical tool or a petrophysical tool representative of a same type of petrophysical tool. Additional methods and systems using this method are provided.