A method for making natural gamma ray measurements includes deploying a logging while drilling tool including an electrical neutron output of the electrical neutron source is modulated and the natural gamma ray sensor is used to make a corresponding gamma ray measurement during at least a portion of the modulation. The gamma ray measurement is processed to obtain a corrected total natural gamma ray measurement of the subterranean formation.

An apparatus for in-line mud logging is adapted to be in material communication with a conveyor used for conveying drilling fluid and/or drill cuttings from a well. An analysis body, disposed in the path of material falling from the conveyor has a sample accumulation tray for collecting a sample of material falling from the conveyor, and a gamma-ray detector for acquiring gamma-ray spectra from the sample of material. A weight sensor detects weight of the sample of material. A sample removal device is used to remove the sample of material from the sample accumulation tray after a desired sample interval. Signals from the gamma-ray detector and the weight sensor are communicated to a control unit.

An apparatus for in-line mud logging is adapted to be in material communication with a conveyor used for conveying drilling fluid and/or drill cuttings from a well. An analysis body, disposed in the path of material falling from the conveyor has a sample accumulation tray for collecting a sample of material falling from the conveyor, and a gamma-ray detector for acquiring gamma-ray spectra from the sample of material. A weight sensor detects weight of the sample of material. A sample removal device is used to remove the sample of material from the sample accumulation tray after a desired sample interval. Signals from the gamma-ray detector and the weight sensor are communicated to a control unit.

A system for real-time or near real-time analysis of drilling fluid, drill cuttings and/or mud gas transported from a well to a mud circulation system has a hydrocarbon analysis device for in-line measuring hydrocarbon content in the material and an in-line gamma-ray detection apparatus. The in-line gamma-ray detection apparatus is disposed in the path of material transported from the well. A control unit for real-time or near real-time receives and correlates signals from the hydrocarbon analysis device and the in-line gamma-ray detection apparatus.

A system for real-time or near real-time analysis of drilling fluid, drill cuttings and/or mud gas transported from a well to a mud circulation system has a hydrocarbon analysis device for in-line measuring hydrocarbon content in the material and an in-line gamma-ray detection apparatus. The in-line gamma-ray detection apparatus is disposed in the path of material transported from the well. A control unit for real-time or near real-time receives and correlates signals from the hydrocarbon analysis device and the in-line gamma-ray detection apparatus.

A method for making natural gamma ray measurements of a subterranean formation includes causing a natural gamma ray sensor on an LWD tool to acquire a spectral gamma ray measurement while a neutron source emits neutrons. The measurements are evaluated to compute first and second drilling fluid activation corrections using corresponding first and second correction methodologies. The first and second corrections are processed to compute a third drilling fluid activation correction which is applied to the gamma ray measurements to compute a corrected total natural gamma ray measurement.

A method for making natural gamma ray measurements of a subterranean formation includes causing a natural gamma ray sensor on an LWD tool to acquire a spectral gamma ray measurement while a neutron source emits neutrons. The measurements are evaluated to compute first and second drilling fluid activation corrections using corresponding first and second correction methodologies. The first and second corrections are processed to compute a third drilling fluid activation correction which is applied to the gamma ray measurements to compute a corrected total natural gamma ray measurement.

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.

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.

A calibrator is positioned on a logging tool at an angular orientation with respect to the logging tool. The calibrator has a radioactive source of gamma radiation distributed inside the calibrator. A first detector count rate is determined based on a detector in the logging tool detecting gamma radiation. One or more of the calibrator and logging tool is rotated by a first number of degrees. A second detector count rate is determined based on the detector in the logging tool detecting gamma radiation. One or more of the calibrator and logging tool is rotated by second number of degrees. A third detector count rate is determined based on the detector in the logging tool detecting gamma radiation. The first, second, and third detector count rates are averaged to determine a calibration gain factor based on the average detector count rate and a known indication of gamma radiation emitted by the calibrator.