Devices and methods to communicate information from below a surface cement plug in a plugged or abandoned well

1. A system for transmitting information indicative of a wellbore condition across a surface cement plug in a plugged off wellbore, the surface cement plug having an axial length within the wellbore and having an upper axial end and a lower axial end, the system comprising:

an electromagnetic signal transmitter located within the wellbore proximate the lower axial end of the surface cement plug, the electromagnetic signal transmitter receiving information indicative of the wellbore condition and transmitting the information into the lower axial end of the surface cement plug as an electromagnetic wave signal which is transmitted through the surface cement plug via induction or galvanic telemetry; and

an electromagnetic signal receiver located proximate the upper axial end of the surface cement plug to receive the electromagnetic wave signal from the upper axial end of the surface cement plug.

2. The system of claim 1 further comprising a wellbore condition sensor located within the wellbore to detect the wellbore condition and provide information indicative of the wellbore condition to the electromagnetic signal transmitter.

3. The system of claim 2 further comprising a controller that is operably interconnected with the wellbore condition sensor and electromagnetic signal transmitter, the controller receiving data from the wellbore condition sensor and encoding the data for transmission as an electromagnetic signal by the electromagnetic signal transmitter.

4. The system of claim 3 wherein the controller is disposed within a data sub within the plugged off wellbore.

5. The system of claim 3 further comprising a duplex transmission system which allows communication of an electromagnetic signal from the upper axial end of the surface cement plug to the lower axial end of the surface cement plug and having:

an electromagnetic signal transmitter located proximate the upper axial end of the surface cement plug to transmit the electromagnetic signal; and

an electromagnetic signal receiver located within the wellbore proximate the lower axial end of the surface cement plug, the electromagnetic signal receiver further being operably interconnected with the controller to provide a command to the controller.

6. The system of claim 1 wherein:

the electromagnetic signal transmitter comprises an induction telemetry transmitter coil which induces a time-varying electric current signal in the surface cement plug and/or areas of earth surrounding the surface cement plug; and

the electromagnetic signal receiver comprises an induction telemetry receiver coil to receive the electric current signal via electrical induction.

7. The system of claim 1 wherein:

the electromagnetic signal transmitter comprises a galvanic telemetry current generation arrangement which includes:

an current injector defined between the surface cement plug and a metallic casing within the wellbore, the current injector having an upper axial end and a lower axial end;

a first current injection electrode located proximate the lower axial end;

a second injection electrode located proximate the upper axial end from which an electrical current signal is flowed into the surface cement plug when an electrical potential is applied across the insulated gap; and

the electromagnetic signal receiver comprises a galvanic telemetry receiver electrode.

8. The system of claim 7 wherein the current injector comprises an insulated gap.

9. The system of claim 7 wherein the current injector comprises a toroidal coil.

10. The system of claim 7 further comprising a surface cement plug that is at least partially comprised of a highly conductive cement.

11. The system of claim 1 further comprising:

a completion plug within the wellbore to close off the wellbore, the completion plug being located below the surface cement plug;

an exterior sensor disposed between the completion plug and the surface cement plug, the exterior sensor to detect leakage across the completion plug; and

the exterior sensor being operably interconnected with the electromagnetic signal transmitter so that a signal representative of leakage can be transmitted by the electromagnetic signal transmitter.

12. The system of claim 1 wherein the wellbore condition comprises one from the group consisting of: pressure, temperature, presence of gas, oil, water, CO 2 , H 2 S, cement integrity, flow behind casing and casing condition.

13. A system for transmitting information indicative of a wellbore condition across a surface cement plug in a plugged off wellbore, the surface cement plug having an axial length within the wellbore and having an upper axial end and a lower axial end, the system comprising:

a wellbore condition sensor located within the wellbore to detect the wellbore condition and provide information indicative of the wellbore condition to an electromagnetic signal transmitter;

the electromagnetic signal transmitter located within the wellbore proximate the lower axial end of the surface cement plug, the electromagnetic signal transmitter receiving information indicative of the wellbore condition and transmitting the information into the lower axial end of the surface cement plug as an electromagnetic wave signal via induction or galvanic telemetry;

an electromagnetic signal receiver located proximate the upper axial end of the surface cement plug to receive the electromagnetic wave signal from the upper axial end of the surface cement plug.

14. The system of claim 13 wherein:

the electromagnetic signal transmitter comprises an induction telemetry transmitter coil which induces a time-varying electric current signal in the surface cement plug and/or areas of earth surrounding the surface cement plug; and

the electromagnetic signal receiver comprises an induction telemetry receiver coil to receive the electric current signal via electrical induction.

15. The system of claim 13 wherein:

the electromagnetic signal transmitter comprises a galvanic telemetry current generation arrangement which includes:

a current injector defined between the surface cement plug and a metallic casing within the wellbore, the current injector having an upper axial end and a lower axial end;

a first current injection electrode located proximate the lower axial end;

a second injection electrode located proximate the upper axial end from which an electrical current signal is flowed into the surface cement plug when an electrical potential is applied across the current injector; and

the electromagnetic signal receiver comprises a galvanic telemetry receiver electrode.

16. The system of claim 15 wherein the current injector comprises an insulated gap.

17. The system of claim 15 wherein the current injector comprises a toroidal coil.

18. The system of claim 13 further comprising:

a completion plug within the wellbore to close off the wellbore, the completion plug being located below the surface cement plug;

an exterior sensor disposed between the completion plug and the surface cement plug, the exterior sensor to detect leakage across the completion plug; and

the exterior sensor being operably interconnected with the electromagnetic signal transmitter so that a signal representative of leakage can be transmitted by the electromagnetic signal transmitter.

19. The system of claim 13 further comprising a controller that is operably interconnected with the wellbore condition sensor and electromagnetic signal transmitter, the controller receiving data from the wellbore condition sensor and encoding the data for transmission as an electromagnetic signal by the electromagnetic signal transmitter.

20. A method of communicating wellbore condition information across a surface cement plug from within a wellbore that has been plugged off with the surface cement plug, the method comprising the steps of:

sensing at least one wellbore condition; and

communicating the wellbore condition information into the lower axial end of the surface cement plug in the form of an electromagnetic wave signal via induction or galvanic telemetry which is received from the upper axial end of the surface cement plug.

21. The method of claim 20 wherein the step of communicating the wellbore condition information across the surface cement plug comprises:

energizing an induction telemetry transmitter coil which induces a time-varying electric current signal through the surface cement plug and/or areas of earth surrounding the surface cement plug; and

receiving the electric current signal with an induction telemetry receiver coil.

22. The method of claim 20 wherein the step of communicating the wellbore condition information across the surface cement plug comprises:

energizing a galvanic current injection electrode to inject a time-varying electric current signal into the surface cement plug; and

receiving the electric current signal with a galvanic telemetry receiver electrode.