There is provided herein a system and method for automatically determining a path within a target rock unit of a directionally drilled well (a target well) using log readings, e.g., gamma log readings, taken in the target well as compared with log readings (a typelog) taken in a well that penetrates the target rock unit (an offset well). Most specifically, in some embodiments the path of the target well within the target rock unit will be obtained by solving a minimum travel distance problem which uses distances that are based on differences between well log readings in the target and offset wells. Solution of this problem will yield a collection of stratigraphic blocks lengths and dips that define a path of a well in a subsurface through the target formation or rock unit.

Various apparatus or methods are arranged to operate a tool downhole in a well, where the tool has a detection package operable to detect gamma rays. Deviation of energy spectra of detected gamma rays in each selected energy window of a set of selected energy windows with respect to reference energy spectra of the respective selected energy window can be detected. One or more properties of one or more regions around the tool can be determined from the deviations, the regions being between the tool and a source of the detected gamma rays in a formation around the well. Additional apparatus, systems, and methods having a gamma ray detection package can operate in a variety of applications.

Various apparatus or methods are arranged to operate a tool downhole in a well, where the tool has a detection package operable to detect gamma rays. Deviation of energy spectra of detected gamma rays in each selected energy window of a set of selected energy windows with respect to reference energy spectra of the respective selected energy window can be detected. One or more properties of one or more regions around the tool can be determined from the deviations, the regions being between the tool and a source of the detected gamma rays in a formation around the well. Additional apparatus, systems, and methods having a gamma ray detection package can operate in a variety of applications.

The disclosure presents a process for determining an initial gain of a gamma detector located within a wellbore of a well system. The technique can utilize the subterranean formation characteristics at the gamma detector. The process can sweep, at a step value, across a determined high voltage range. At each sweep step, gamma events can be detected and counted over a detection time interval. The collected gamma events can then be utilized to perform an in-situ plateau test from which a high voltage can be determined, e.g., knee of the plateau curve. The determined high voltage can then be used as the initial gain. Additional fine gain control functions can be executed to further adjust the gain. In an alternative aspect, the collected gamma events can be utilized to perform diagnostics to infer faults or issues with the gamma detector assembly while it is down-hole.

The disclosure presents a process for determining an initial gain of a gamma detector located within a wellbore of a well system. The technique can utilize the subterranean formation characteristics at the gamma detector. The process can sweep, at a step value, across a determined high voltage range. At each sweep step, gamma events can be detected and counted over a detection time interval. The collected gamma events can then be utilized to perform an in-situ plateau test from which a high voltage can be determined, e.g., knee of the plateau curve. The determined high voltage can then be used as the initial gain. Additional fine gain control functions can be executed to further adjust the gain. In an alternative aspect, the collected gamma events can be utilized to perform diagnostics to infer faults or issues with the gamma detector assembly while it is down-hole.

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.

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.

The disclosure presents a process for determining an initial gain of a gamma detector located within a wellbore of a well system. The technique can utilize the subterranean formation characteristics at the gamma detector. The process can sweep, at a step value, across a determined high voltage range. At each sweep step, gamma events can be detected and counted over a detection time interval. The collected gamma events can then be utilized to perform an in-situ plateau test from which a high voltage can be determined, e.g., knee of the plateau curve. The determined high voltage can then be used as the initial gain. Additional fine gain control functions can be executed to further adjust the gain. In an alternative aspect, the collected gamma events can be utilized to perform diagnostics to infer faults or issues with the gamma detector assembly while it is down-hole.

The disclosure presents a process for determining an initial gain of a gamma detector located within a wellbore of a well system. The technique can utilize the subterranean formation characteristics at the gamma detector. The process can sweep, at a step value, across a determined high voltage range. At each sweep step, gamma events can be detected and counted over a detection time interval. The collected gamma events can then be utilized to perform an in-situ plateau test from which a high voltage can be determined, e.g., knee of the plateau curve. The determined high voltage can then be used as the initial gain. Additional fine gain control functions can be executed to further adjust the gain. In an alternative aspect, the collected gamma events can be utilized to perform diagnostics to infer faults or issues with the gamma detector assembly while it is down-hole.

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.