Multi-barrier wellbore integrity inspection system with eccentricity correction

1. A downhole inspection system, comprising:

a tool string lowerable into a wellbore;

a neutron imaging device forming at least a portion of the tool string, the neutron imaging device operable to generate data for detecting potential wellbore anomalies, wherein the neutron imaging device comprises:

a neutron generator operable to emit neutrons; and

a neutron detector fixed relative to the neutron generation unit and operable to detect backscattered neutrons from a surrounding environment;

an electromagnetic pulse imaging device forming another portion of the tool string, the electromagnetic pulse imaging device operable to generate data for detecting wellbore eccentricities, wherein the electromagnetic pulse imaging device comprises:

at least one transmitter coil for generating an electromagnetic pulse; and

at least one receiver coil for detecting returning electromagnetic waves; and

a processor configured to receive data from the neutron imaging device and data from the electromagnetic imaging device, and correlate the neutron imaging data and the electromagnetic imaging data to determine if a detected potential wellbore anomaly is attributable to tool eccentricity in the wellbore.

2. The system of claim 1 , wherein the processor is located remotely from the tool string.

3. The system of claim 1 , wherein the neutron imaging device and the electromagnetic imaging device are axially aligned with the wellbore.

4. The system of claim 1 , wherein the electromagnetic imaging device includes three transmitter and receiver coil pairs arranged axially symmetrically with respect to the tool string.

5. The system of claim 1 , wherein the electromagnetic imaging device includes one transmitter coil and a plurality of receiver coils arranged symmetrically with respect to the transmitter coil.

6. The system of claim 1 , wherein the wellbore includes a casing with a plurality of layers.

7. The system of claim 1 , wherein respective time delays between generation of the electromagnetic pulse and detection of the returned electromagnetic waves around the wellbore are used in determining eccentricity of the plurality of casing layers.

8. The system of claim 1 , wherein the neutron detector comprises a plurality of individually addressable detector elements arranged in a ring, the ring axially aligned with at least one of the tool string, the neutron generator, or the wellbore, wherein respective amount of backscattered neutrons detected by the individually addressable detector elements is indicative of an azimuthal direction of the detected backscattered neutrons.

9. The system of claim 1 , wherein the neutron detector comprises a plurality of individually addressable detector elements arranged in a plurality of concentric rings, wherein the respective amount of backscattered neutrons detected by the individually addressable detector elements of two or more concentric rings is indicative of an energy level of the backscattered neutrons.

10. The system of claim 9 , wherein the neutron imaging device and the electromagnetic imaging device are co-axially aligned.

11. The system of claim 9 , wherein the neutron detector comprises a plurality of individually addressable detector elements arranged in a ring axially symmetric to the neutron generator.

12. A downhole inspection system, comprising:

a neutron imaging device operable to generate data for detecting potential wellbore anomalies, wherein the neutron imaging device comprises:

a neutron generator operable to emit neutrons; and

a neutron detector fixed relative to the neutron generation unit and operable to detect backscattered neutrons from a surrounding environment;

an electromagnetic imaging device operable to generate data for detecting wellbore eccentricity, wherein the electromagnetic imaging device comprises:

at least one transmitter for generating electromagnetic pulse; and

at least one receiver for detecting returning electromagnetic pulse,

wherein correlation of the neutron imaging data with the electromagnetic imaging data provides additional data regarding the potential wellbore anomalies.

13. The system of claim 12 , wherein the neutron imaging data is indicative of whether potential wellbore anomalies are present.

14. The system of claim 13 , wherein the electromagnetic imaging data is indicative of whether a potential wellbore casing eccentricity is present.

15. The system of claim 14 , wherein correlation of the neutron imaging data and the electromagnetic imaging data is indicative of determine whether an actual wellbore anomaly is present, wherein the actual wellbore anomaly is structural and not due to casing eccentricity.

16. A method of inspecting a wellbore, comprising:

positioning a neutron imaging device in a wellbore having a casing comprising one or more layers;

emitting neutrons into a portion of a wellbore environment;

detecting backscattered neutrons from the portion of the wellbore environment;

generating neutron data for the portion of the wellbore, based at least in part on the detected backscattered neutrons;

positioning an electromagnetic pulse imaging device in the portion of the wellbore;

generating electromagnetic pulses towards the portion of the wellbore;

detecting returning electromagnetic pulses generated from eddy currents induced in the casing at the portion of the wellbore;

generating electromagnetic data for the portion of the wellbore based at least in part on the detected returning electromagnetic pulses;

determining if casing eccentricity is present in the portion of the wellbore based on the electromagnetic data; and

correlating the neutron data and the electromagnetic data to determine if a wellbore anomaly is present, wherein the potential wellbore anomaly is structural and not due to casing eccentricity.

17. The method of claim 16 , further comprising:

lowering a tool string into the wellbore, wherein the neutron imaging device and electromagnetic imaging device are a part of the same tool string.

18. The method of claim 16 , further comprising:

lowering the neutron imaging device into the wellbore during a first tool run; and

lowering the electromagnetic imaging device into the wellbore during a second tool run.

19. The method of claim 16 , further comprising:

determining whether an eccentricity is present in the one or more layers of the wellbore casing; and

determining whether a potential anomaly is present in or around the wellbore based at least in part on the respective amounts of backscattered radiation detected by the individually addressable detector elements.

20. The method of claim 19 , further comprising:

determining that the potential anomaly coincides with the eccentricity; and

determining that the potential anomaly is due to the eccentricity and not an actual anomaly in the wellbore.