Abstract: A system is disclosed for correcting Uranium-free gamma logs. The system may receive data about a subterranean formation from a gamma-ray-logging process in a wellbore. The system may apply a photoelectric-suppression estimator to the data to determine a photoelectric-suppression factor using stored mud parameters and a wellbore diameter value. The data may be corrected by the system by using the photoelectric-suppression factor to generate a Uranium-free, gamma-ray log. The system may output the Uranium-free, gamma-ray log for determining characteristics of the subterranean formation.

Abstract: Embodiment disclosed herein include systems and methods for azimuthally imaging a borehole, A logging tool having one or more gamma radiation sensors is disposed at a depth position within a borehole, with the one or more gamma radiation sensors positioned to measure gamma radiation within multiple azimuthally offset sectors. The gamma radiation sensors measure gamma radiation at one or more positions within each of the azimuthally offset sectors. A spectral gamma radiation profile is determined for three radioelements at the one or more positions within each of the azimuthally offset sectors based on the gamma radiation measurements.

Abstract: A system is disclosed for correcting Uranium-free gamma logs. The system may receive data about a subterranean formation from a gamma-ray-logging process in a wellbore. The system may apply a photoelectric-suppression estimator to the data to determine a photoelectric-suppression factor using stored mud parameters and a wellbore diameter value. The data may be corrected by the system by using the photoelectric-suppression factor to generate a Uranium-free, gamma-ray log. The system may output the Uranium-free, gamma-ray log for determining characteristics of the subterranean formation.

Abstract: Embodiment disclosed herein include systems and methods for azimuthally imaging a borehole, A logging tool having one or more gamma radiation sensors is disposed at a depth position within a borehole, with the one or more gamma radiation sensors positioned to measure gamma radiation within multiple azimuthally offset sectors. The gamma radiation sensors measure gamma radiation at one or more positions within each of the azimuthally offset sectors. A spectral gamma radiation profile is determined for three radioelements at the one or more positions within each of the azimuthally offset sectors based on the gamma radiation measurements.

Abstract: System and methods for calibrating gamma ray tools using blanket field calibrator models is provided. A counting rate of a first gamma ray tool is simulated based on a model of a first blanket calibrator. When it is determined that the simulated counting rate matches a measured counting rate associated with the first gamma ray tool, a tally multiplier and a corresponding material specification for the model of the first blanket calibrator is determined. A counting rate for a second gamma ray tool is simulated based on the tally multiplier and the material specification determined for the model of the first blanket calibrator. A sensitivity factor for the second gamma ray tool is determined based on the simulation. The second gamma ray tool is calibrated according to a nominal blanket activity calculated from the sensitivity factor of the second gamma ray tool.

Abstract: Disclosed embodiments include a gamma logging detector assembly that includes a detector support structure comprising one or more high density alloy materials and including a first cylindrical drill collar segment and a second cylindrical drill collar segment each having a radius of at least R1. A third cylindrical drill collar segment is disposed axially between the first and second cylindrical drill collar segments to form an annular channel over the third cylindrical drill collar segment and between the first and second cylindrical drill collar segments. The third cylindrical drill collar segment includes an inwardly defined open cavity and a radius, R2, that is less than R1. An annular pressure sleeve comprising one or more low density alloy materials is disposed within the annular channel.

Abstract: Disclosed embodiments include a gamma logging detector assembly that includes a detector support structure comprising one or more high density alloy materials and including a first cylindrical drill collar segment and a second cylindrical drill collar segment each having a radius of at least R1. A third cylindrical drill collar segment is disposed axially between the first and second cylindrical drill collar segments to form an annular channel over the third cylindrical drill collar segment and between the first and second cylindrical drill collar segments. The third cylindrical drill collar segment includes an inwardly defined open cavity and a radius, R2, that is less than R1. An annular pressure sleeve comprising one or more low density alloy materials is disposed within the annular channel.

Abstract: A spectrometer for downhole applications can be calibrated without using radioactive sources. A spectrum of measured gamma ray counts can be received from a spectrometer in a calibration mode. A spectrum-to-window ratio can be used to determine a relationship between voltage level applied to a photoreceptor of the spectrometer and gain factors. A voltage level associated with a gain factor of one can be identified for use by the spectrometer in a non-calibration mode. The measured gamma ray counts and reference shapes for a plurality of radioactive elements can be used in a least squares fit process to determine an offset to apply to the spectrometer in the non-calibration mode.

Abstract: Aspects of the subject technology relate to a system configured to apply a voltage setting to a sensor of a downhole tool. The system is configured to identify an active gain control model for a temperature-sensitive sensor for a downhole tool, receiving temperature data for the downhole tool, and apply a high voltage setting for the first sensor based on the temperature data and the active gain control model. The system is further configured to collect sensor data from the sensor operating in a wellbore using the high voltage setting and update the active gain control model based on the sensor data.

Abstract: System and methods for calibrating gamma ray tools using blanket field calibrator models is provided. A counting rate of a first gamma ray tool is simulated based on a model of a first blanket calibrator. When it is determined that the simulated counting rate matches a measured counting rate associated with the first gamma ray tool, a tally multiplier and a corresponding material specification for the model of the first blanket calibrator is determined. A counting rate for a second gamma ray tool is simulated based on the tally multiplier and the material specification determined for the model of the first blanket calibrator. A sensitivity factor for the second gamma ray tool is determined based on the simulation. The second gamma ray tool is calibrated according to a nominal blanket activity calculated from the sensitivity factor of the second gamma ray tool.

Abstract: Aspects of the subject technology relate to a system configured to apply a voltage setting to a sensor of a downhole tool. The system is configured to identify an active gain control model for a temperature-sensitive sensor for a downhole tool, receiving temperature data for the downhole tool, and apply a high voltage setting for the first sensor based on the temperature data and the active gain control model. The system is further configured to collect sensor data from the sensor operating in a wellbore using the high voltage setting and update the active gain control model based on the sensor data.

Abstract: A non-rotatable, downhole imaging tool, an imaging system including the non-rotatable imaging tool and methods of determining information about a wellbore employing the non-rotatable imaging tool are provided herein. One example of a non-rotatable imaging tool is disclosed that has a central axis and horizontal planes perpendicular to the central axis, and further includes: (1) a radiation detector positioned proximate the central axis and uniquely on one of the horizontal planes, and (2) a collimator configured to limit exposure of the radiation detector to a single azimuthal area along a circumference of the downhole imaging tool on the one of the horizontal planes.

Abstract: A system includes a logging tool assembly having a geochemical logging tool with a neutron source and a gamma ray detector, wherein the geochemical logging tool collects formation property measurements as a function of position in a borehole. The system also includes a processor that receives the formation property measurements and that derives a geochemical photoelectric log based at least in part on the formation property measurements. The system also includes an output that displays the geochemical photoelectric log to a user.

Abstract: A spectrometer for downhole applications can be calibrated without using radioactive sources. A spectrum of measured gamma ray counts can be received from a spectrometer in a calibration mode. A spectrum-to-window ratio can be used to determine a relationship between voltage level applied to a photoreceptor of the spectrometer and gain factors. A voltage level associated with a gain factor of one can be identified for use by the spectrometer in a non-calibration mode. The measured gamma ray counts and reference shapes for a plurality of radioactive elements can be used in a least squares fit process to determine an offset to apply to the spectrometer in the non-calibration mode.

Abstract: A non-rotatable, downhole imaging tool, an imaging system including the non-rotatable imaging tool and methods of determining information about a wellbore employing the non-rotatable imaging tool are provided herein. One example of a non-rotatable imaging tool is disclosed that has a central axis and horizontal planes perpendicular to the central axis, and further includes: (1) a radiation detector positioned proximate the central axis and uniquely on one of the horizontal planes, and (2) a collimator configured to limit exposure of the radiation detector to a single azimuthal area along a circumference of the downhole imaging tool on the one of the horizontal planes.

Abstract: A system includes a logging tool assembly having a geochemical logging tool with a neutron source and a gamma ray detector, wherein the geochemical logging tool collects formation property measurements as a function of position in a borehole. The system also includes a processor that receives the formation property measurements and that derives a geochemical photoelectric log based at least in part on the formation property measurements. The system also includes an output that displays the geochemical photoelectric log to a user.

Abstract: A system and method for determining kerogen porosity of a formation for downhole operations is described herein. The method includes calculating a first formation characteristic and a second formation characteristic at a processor of an information handling system. The method further includes determining a kerogen porosity of the formation based, at least in part, on the first formation characteristic and the second formation characteristic. And the method also includes performing a downhole operation based, at least in part, on the determined kerogen porosity.

Abstract: Systems and methods for determining kerogen porosity of a formation for downhole operations are described herein. An example method may include obtaining core pyrolysis data from a wellbore disposed in a formation. A thermal characteristic of the formation proximate to the wellbore, such as a time-temperature burial history of the formation, may also be determined. A kerogen porosity of the formation may be calculated based, at least in part, on the pyrolysis data and the thermal characteristic, and a downhole operation may be performed based, at least in part, on the calculated kerogen porosity.

Abstract: A gamma-ray spectrometer calibration system comprises a photomultiplier tube and analysis electronics. The photomultiplier tube provides one or more reference signals that are analyzed relative to a spectrum by the analysis electronics to calibrate a gamma-ray spectrometer. Additional apparatus, methods, and systems are disclosed.

Abstract: The subject technology relates to estimating borehole contributions to measured calcium and sulfur elemental yields by using a small number of mud properties available from wellsite mud reports at the time of logging. Neutron-induced gamma ray spectroscopy logs may be measured and, more specifically, estimating the borehole contributions to the measured calcium and sulfur elemental yields. The subject technology provides for predicting relative borehole yields as a function of borehole size and a set of properties that describe the composition of various complex drilling mud mixtures based on the elemental atomic number density for the drilling mud. The subject technology generates borehole bias vectors from analysis of the simulated tool responses, and applies a borehole bias vector to a relative elemental yield vector to correct a calcium yield and/or a sulfur yield. Other methods, systems, and computer-readable media are also disclosed.