Systems and methods for downhole logging with enhanced sensitivity and azimuthal resolution

Patent metadata

Field	Value
Publication number	US-11066926-B2
Application number	US-201916590796-A
Country	US
Kind code	B2
Filing date	Oct 2, 2019
Priority date	Oct 5, 2018
Publication date	Jul 20, 2021
Grant date	Jul 20, 2021

Abstract

A downhole logging tool includes a radiation generation source operable to emit radiation into a formation surrounding the tool, a radiation detector fixed relative to the radiation generation source and operable to detect backscattered radiation from the formation surrounding the tool, and a sleeve positioned around the radiation detector to shield the radiation detector from a first portion of the backscattered radiation. The sleeve includes at least one aperture for exposing the radiation detector to a second portion of the backscattered radiation, in which the second portion of the backscattered radiation emanates from an inspected region of the formation facing the at least one aperture. A signal measured at the radiation detector corresponds to the inspected region of the formation, and the position of the at least one aperture is changeable with respect to the formation to distinctly inspect different regions of the formation.

First claim

We claim:

1. A downhole logging tool, comprising:
a radiation generation source operable to emit radiation into a formation surrounding the tool;
a radiation detector fixed relative to the radiation generation source and operable to detect backscattered radiation from the formation surrounding the tool; and
a sleeve positioned radially around the radiation detector to shield the radiation detector from a first portion of the backscattered radiation, the sleeve comprising a plurality of layers rotatable with respect to each other, each layer having one or more layer apertures that form at least one aperture in the sleeve when aligned, the at least one aperture exposing the radiation detector to a second portion of the backscattered radiation, the second portion of the backscattered radiation emanating from an inspected region of the formation facing the at least one aperture, wherein a signal detected at the radiation detector corresponds to the inspected region of the formation, and wherein the position of the at least one aperture is changeable with respect to the formation to distinctly inspect different regions of the formation.

2. The system of claim 1 , wherein the sleeve and the least one aperture are rotatable with respect to the radiation detector or the formation.

3. The system of claim 1 , wherein the sleeve includes one or more sections openable to create the at least one aperture.

4. The system of claim 1 , wherein the positions of the at least one aperture of the detector corresponds respectively to one or more azimuthal directions with respect to the formation and are changeable across a plurality of different azimuthal directions.

5. The system of claim 1 , wherein the positions of the at least one aperture with respect to the formation are changeable across a plurality of different axial positions.

6. The system of claim 1 , wherein a complete aperture occurs when the layer apertures of the plurality of layers are aligned.

7. The system of claim 6 , wherein a partial aperture occurs where at least a layer aperture of a first layer of the plurality of layers is aligned with a non-aperture portion a second layer of the plurality of layers.

8. A system for performing downhole logging operations in a well, comprising:
a downhole suspension device;
an inspection tool coupled to and lowerable into the well via the suspension device, the inspection tool comprising:
a radiation source operable to emit radiation;
a radiation detector operable to detect backscattered radiation generated as a result of the radiation emitted from the radiation source; and
a sleeve positioned radially around the radiation detector, the sleeve comprising a plurality of layers rotatable with respect to each other, each layer having one or more layer apertures that form at least one aperture in the sleeve when aligned, wherein the position of the at least one aperture is changeable with respect to the well.

9. The system of claim 8 , wherein the sleeve and the least one aperture are rotatable with respect to the radiation detector.

10. The system of claim 8 , wherein the sleeve includes one or more windows openable to create the at least one aperture.

11. The system of claim 8 , wherein the position of the at least one aperture is changeable across a plurality of different azimuthal positions of the well.

12. The system of claim 8 , wherein the position of the at least one aperture is changeable across a plurality of different axial positions of the well.

13. The system of claim 8 , wherein a complete aperture occurs when the layer apertures of the plurality of layers are aligned.

14. The system of claim 13 , wherein a partial aperture occurs where at least a layer aperture of a first layer of the plurality of layers is aligned with a non-aperture portion a second layer of the plurality of layers.

15. A method of performing downhole logging, comprising:
positioning an inspection tool in a well, the inspection tool comprising a radiation generation source, a radiation detector, and a sleeve positioned radially around the radiation detector at a first position with respect to the well, the sleeve comprising a plurality of layers rotatable with respect to each other, each layer having one or more layer apertures that form at least one aperture in the sleeve when aligned;
emitting radiation from the radiation generation source;
detecting backscattered radiation received at the radiation detector via the at least one aperture;
determining a first measurement based on the detected backscattered radiation;
associating the first measurement with a first region of the well corresponding to the first position; and
determining one or more characteristics of the first region of the well based at least in part on the first measurement.

16. The method of claim 15 , further comprising:
changing the position of the at least one aperture to a second position with respect to the well, the second position corresponding to a second region of the well;
determining a second measurement based on the backscattered radiation;
associating the second measurement with the second region of the well; and
determining one or more characteristics of the second portion of the well based at least in part on the second measurement.

17. The method of claim 16 , further comprising:
moving the position of the at least one aperture axially or azimuthally with respect to the well.

18. The method of claim 15 , further comprising:
tracking the position of the at least one aperture; and
constructing an aperture function based at least in part on the tracked position.

19. The method of claim 18 , further comprising:
rotating the sleeve around the detector to change the position of the at least one aperture with respect to the well.

20. The method of claim 18 , further comprising:
rotating the inspection tool to change the position of the at least one aperture with respect to the well.

Assignees

• Baker Hughes Oilfield Operations Llc

Inventors

• Ramirez Marc
• Inanc Feyzi

Classifications

• G01V5/107 Primary

  and detecting reflected or back-scattered neutrons · CPC title

• G01V5/08 Primary

  using primary nuclear radiation sources or X-rays {(, e.g. for inducing radioactivity; investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays, neutrons G01N23/00)} · CPC title

• E21B47/017

  Protecting measuring instruments · CPC title

• E21B47/11 Primary

  using tracers; using radioactivity · CPC title

• G01V5/14

  using a combination of several sources, e.g. a neutron and a gamma source · CPC title