Downhole photon radiation detection using scintillating fibers
A photon radiation detection systems utilizes scintillating fibers to detect downhole radioactivity along a wellbore. The system includes a light detection unit, extended light guide, and a scintillating fiber radiation detector extending along a wellbore. The scintillating fiber radiation detector may be a permanent part of the wellbore completion, or may be deployed via a downhole conveyance. The detected light photons may be utilized to evaluate the formation, cement layer or tubular string.
1. A downhole photon radiation detection system, comprising:
a light detection unit positioned at a surface location;
a scintillating fiber radiation detector extending along a wellbore drilled in a formation; and
an extended light guide extending along the wellbore to optically couple the light detection unit to the scintillating fiber radiation detector.
2. A system as defined in claim 1 , wherein the scintillating fiber radiation detector is permanently positioned along the wellbore.
3. A system as defined in claim 2 , wherein the scintillating fiber radiation detector:
forms part of a casing string extending along the wellbore; or
is cemented between the casing string and formation.
4. A system as defined in claim 1 , wherein the scintillating fiber radiation detector forms part of a wireline, slickline, production string or coiled tubing assembly.
5. A system as defined in claim 1 , wherein the scintillating fiber radiation detector is a single scintillating fiber.
6. A system as defined in claim 1 , wherein the scintillating fiber radiation detector comprises an array of scintillating fibers.
7. A system as defined in claim 6 , wherein the scintillating fibers in the array are sensitive at different positions along the wellbore.
8. A system as defined in claim 6 , wherein the scintillating fibers in the array are doped with different scintillator dopants.
9. A system as defined in claim 1 , wherein the light detection unit measures scintillation light and has absorption characteristics that peak at about a scintillation light wavelength and wherein the light detection unit includes at least one processor.
10. A system as defined in claim 1 , further comprising:
an optical coupler that couples the extended light guide and the scintillating fiber radiation detector, the optical coupler being connected to a first end of the scintillating fiber radiation detector; and
an optical mirror connected to a second end of the scintillating fiber radiation detector, the second end being opposite the first end.
11. A system as defined in claim 1 , further comprising:
a first optical coupler that couples the extended light guide and the scintillating fiber radiation detector, the first optical coupler being connected to a first end of the scintillating fiber radiation detector;
a second optical coupler that couples the second end of the scintillating fiber radiation detector to a second extended light guide; and
a second light detection unit optically coupled to the scintillating fiber radiation detector via the second optical coupler, the second light radiation detector unit being positioned at the surface location.
12. A system as defined in claim 1 , wherein a source of radiation is:
the formation;
a radiation source deployed along a downhole string; or
a radiation source which forms a permanent part of the wellbore.
13. A downhole photon radiation detection method, comprising:
interacting photon radiation with a scintillating fiber radiation detector positioned along a wellbore;
converting the radiation to light photons;
conveying the light photons from the scintillating fiber radiation detector to a light detection unit positioned at a surface location using an extended light guide that optically couples the scintillating fiber radiation detector and the light detection unit; and
detecting the light photons using the light detection unit;
utilizing the detected light photons to perform a wellbore operation.
14. A method as defined in claim 13 , wherein the radiation is generated by:
a radiation source positioned along a downhole string;
a radiation source forming part of the wellbore; or
a formation in which the wellbore is positioned.
15. A method as defined in claim 13 , wherein the wellbore operation comprises an evaluation of a formation, cement layer or casing string.
16. A method as defined in claim 13 , wherein the wellbore operation is determining a position of radioactivity along the wellbore.
17. A method as defined in claim 13 , wherein the scintillating fiber radiation detector has been permanently positioned in the wellbore.
18. A method as defined in claim 13 , wherein the scintillating fiber radiation detector is deployed using a wireline, slickline or coiled tubing.
19. A downhole photon radiation detection method, comprising:
conveying light photons emitted by a scintillating fiber radiation detector that extends along a wellbore to a light detection unit positioned at a surface location using an extended light guide that optically couples the scintillating fiber radiation detector to the light detection unit;
converting the light photons detected at the light detection unit into electrical signals; and
performing a well logging operation based on processing of the electrical signals.
20. A method as defined in claim 19 , wherein the scintillating fiber radiation detector is permanently positioned downhole.
21. A method as defined in claim 19 , wherein the scintillating fiber radiation detector forms part of a wireline, slickline or coiled tubing string positioned downhole.
22. A method as defined in claim 19 , further comprising logging a position of radioactivity along the wellbore.
23. A method as defined in claim 19 , further comprising detecting different radiation characteristics along the wellbore.