Schlumberger Technology Corporation

Avtandil Tkabladze

Christian Stoller

Kenneth Edward Stephenson

Michael Lynn Evans

Sicco Beekman

Matthieu Simon

David Rose

John J Simonetti

Justin Dale Mlcak

Justin Mlcak

Donna Simonetti

Kenneth E Stephenson

A downhole tool is provided with a neutron generator configured to emit neutrons into a geological formation. The downhole tool includes one or more neutron detectors configured to detect neutrons that return to the downhole tool after interacting with the geological formation. The downhole tool also includes one or more gamma ray detectors configured to detect gamma rays from the geological formation that form when neutrons are inelastically scattered by the geological formation. Measurements from a combination of detectors of at least one of the one or more neutron detectors and at least one of the one or more gamma ray detectors are used to determine formation density. A first formation density determined using a first combination of detectors is used to compensate a second formation density determined using a second combination of detectors.

Compensated neutron gamma density

Systems, methods, and devices are provided for radiation detector windows that have an improved shape or density and/or provide collimation of radiation that passes through. Thus, a radiation-based logging tool may include a source that emits radiation and a detector that detects, through a detector window, a first portion of the radiation scattered off of a geological formation. The detector window may include a dome having a first surface and a second surface and a support structure that provides support for the dome. The detector window may include a window insert that shields the detector from a second portion of the radiation.

Lower-density or collimating well-logging radiation detector windows

Systems, methods, and devices for inelastic gamma-ray logging are provided. In one embodiment, such a method includes emitting neutrons into a subterranean formation from a downhole tool to produce inelastic gamma-rays, detecting a portion of the inelastic gamma-rays that scatter back to the downhole tool to obtain an inelastic gamma-ray signal, and determining a property of the subterranean formation based at least in part on the inelastic gamma-ray signal. The inelastic gamma-ray signal may be substantially free of epithermal and thermal neutron capture background.

Optimization of neutron-gamma tools for inelastic gamma-ray logging

The techniques and device provided herein relate to regulating a source generator in X-ray based measurement for downhole applications. A source stream of photons is produced, via a generator of an X-ray system of a logging tool. A direct channel allows for the passage of a stream of photons, where a high energy filter filters a low energy part of the stream of photons. The resultant stream is measured by a reference detector to identify a high energy peak in a spectrum measurement derived based upon the resultant photon stream. From there, a normalized difference between a plurality of windows of the high energy peak is determined and subsequent output of the generator is based upon the normalized difference.

X-Ray generator regulation with high energy tail windows

A system includes a data processing system including a processor operatively coupled to a memory. The processor is configured to receive a first dataset indicative of spectral information regarding photons received from a first detector of a formation density tool. The processor is configured to receive a second dataset indicative of a total count rate of photons from a second detector of the formation density tool. The processor is configured to determine physical characteristics of a geological formation based on the spectral information and the total count rate. The processor is configured to display the physical characteristics of the geological formation in a display.

Formation density tool with a detector operating in total count mode

Systems, methods, and devices for determining a neutron-gamma density (NGD) measurement of a subterranean formation that is accurate in both liquid- and gas-filled formations are provided. For example, a downhole tool for obtaining such an NGD measurement may include a neutron generator, a neutron detector, two gamma-ray detectors, and data processing circuitry. The neutron generator may emit neutrons into a formation, causing a fast neutron cloud to form. The neutron detector may detect a count of neutrons representing the extent of the neutron cloud. The gamma-ray detectors may detect counts of inelastic gamma-rays caused by neutrons that inelastically scatter off the formation. Since the extent of the fast neutron cloud may vary depending on whether the formation is liquid- or gas-filled, the data processing circuitry may determine the density of the formation based at least in part on the counts of inelastic gamma-rays normalized to the count of neutrons.

Neutron-gamma density through normalized inelastic ratio

The techniques and device provided herein relate to regulating a source generator in an X-ray based equipment. In particular, an X-ray system is provided that comprises an X-ray generator and a reference detector system that regulates the output of the X-ray generator. The reference detector system comprises a direct channel that allows at least a portion of the photons to directly reach the detector crystal and a plurality of fluorescent channels, such that photon flux entering the reference detector from the fluorescent channels is negligibly impacted by variations of beam spots, shapes and/or positions.

X-ray generator output regulation

X-ray generator regulation with high energy tail windows

Optimization of neutron-gamma tools for inelastic-gamma ray logging

A system is disclosed for downhole logging. The system comprises a photon source configured to generate photons at different endpoint energies; at least one radiation detector configured to detect photons after interactions with a wellbore, a geological formation surrounding the wellbore, or both; an energy detection system configured to determine an endpoint energy of the photon source; and a processing system configured to determine properties of a wellbore, a geological formation, or both, based on photons detected at the at least one radiation detector and the endpoint energy determined by the energy detection system.

Method and apparatus for operating a downhole tool with an electronic photon source at different endpoint energies

Systems, methods, and devices for determining neutron-gamma density (NGD) measurement of a subterranean formation that is accurate in both liquid- and gas-filled formations are provided. For example, a downhole tool for obtaining such an NGD measurement may include a neutron generator, neutron detector, two gamma-ray detectors, and data processing circuitry. Neutron generator may emit neutrons into a formation, causing a fast neutron cloud to form. Neutron detector may detect a count of neutrons representing the extent of the neutron cloud. Gamma-ray detectors may detect counts of inelastic gamma-rays caused by neutrons that inelastically scatter off the formation. Since the extent of the fast neutron cloud may vary depending on whether the formation is liquid- or gas-filled, data processing circuitry may determine the density of the formation based at least in part on the counts of inelastic gamma-rays normalized to the count of neutrons.

A well-logging device may include a housing to be positioned within a larger borehole of a subterranean formation and thereby define a stand-off distance with respect to the larger borehole. The well-logging device may also include at least one radiation source carried by the housing to direct radiation into the subterranean formation, and radiation detectors carried by the housing in azimuthally spaced relation to detect radiation from the subterranean formation. The well-logging device may further include a controller to cooperate with the radiation detectors to determine at least one property of the subterranean formation corrected for the stand-off distance.

Well-logging apparatus including azimuthally spaced radiation detectors

A well-logging device may include a housing to be positioned within a borehole of a subterranean formation, and at least one radiation source carried by the housing to direct radiation into the subterranean formation. The well-logging device may also include noble gas-based radiation detectors carried by the housing in azimuthally spaced relation to detect radiation from the subterranean formation. A controller may determine at least one property of the subterranean formation based upon the detected radiation from the noble gas-based radiation detectors.

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Sugar Land, TX, United States of America

Avtandil Tkabladze