Formation evaluation system and method

• US 20070052551A1
• Filed: 08/23/2005
• Published: 03/08/2007
• Est. Priority Date: 08/23/2005
• Status: Active Grant

• Current Assignee: Schlumberger Technology Corporation (SLB)
• Original Assignee: Schlumberger Technology Corporation (SLB)
• Inventors: Lovell, John, Bogath, Christopher, Pringnitz, Steven
• Granted Patent: US 7,495,446 B2
• Time in Patent Office: Days
• US Class Current: 340/854.600
• CPC Class Codes: G01V 11/002 Details, e.g. power supply systems for logging instruments, transmitting or recording data, specially adapted for well logging, also if the prospecting method is irrelevant means for transmitting well survey signals E21B47/12; signal transmission systems in general G08C; transmission in general H04B

Abstract

A formation evaluation system for a subterranean formation penetrated by a wellbore. The formation evaluation system is provided with a downhole tool and a sensor. The downhole tool is positionable in the wellbore. The downhole tool has a downhole electromagnetic unit for communication with a surface electromagnetic unit. The sensor determines at least one wellsite parameter from the electromagnetic signal. The downhole tool and the surface electromagnetic unit are adapted to pass electromagnetic signals there between. The electromagnetic signals pass through the subterranean formation whereby the sensor determines the at least one wellsite parameter from the electromagnetic signal.

Claims

1. A formation evaluation system for a subterranean formation penetrated by a wellbore, comprising:

a downhole tool positionable in the wellbore, the downhole tool having a downhole electromagnetic unit for communication with a surface electromagnetic unit; and

a sensor for determining at least one wellsite parameter from the electromagnetic signal;

wherein the downhole tool and the surface electromagnetic unit are adapted to pass electromagnetic signals there between, the electromagnetic signals passing through the subterranean formation whereby the sensor determines the at least one wellsite parameter from the electromagnetic signal.

2. The formation evaluation system of claim 1, wherein the downhole electromagnetic unit comprises:

an antenna;

a control circuitry operably connected to the antenna for directing the electromagnetic signals to the antenna whereby an electromagnetic field is generated and modulated for communicating the electromagnetic signals to the surface electromagnetic communication unit; and

a processor operatively connected to the control circuitry.

3. The formation evaluation system of claim 2, wherein the sensor determines a data signal indicative of the at least one wellsite parameter, and wherein the processor causes the data signal to be directed to the control circuitry for communication to the surface electromagnetic unit.

4. The formation evaluation system of claim 2, wherein the antenna includes at least two conductive members, and an insulative member electrically isolating the two conductive members, the control circuitry being operably connected to at least one of the conductive members for directing signals to the at least one conductive member.

5. The formation evaluation system of claim 2, wherein the antenna includes a coil for creating the electromagnetic signals via inductive coupling.

6. The formation evaluation system of claim 2, wherein the antenna uses a voltage potential to create the electromagnetic signals.

7. The formation evaluation system of claim 2, wherein the signals directed to the antenna by the control circuitry include a carrier having a relatively low frequency being receivable by the surface electromagnetic unit.

8. The formation evaluation system of claim 2, wherein the processor periodically directs signals to the control circuitry for communication to the antenna, and wherein the sensor collects data to generate the data signal in one period, and communicates the data signal to the processor for communication to the control circuitry in a subsequent period.

9. The formation evaluation system of claim 1, wherein at least one of the electromagnetic signals is a measurement signal and at least one of the electromagnetic signals is a carrier signal, the measurement signal being superimposed on the carrier signal and wherein the sensor can detect the measurement signal in the presence of the carrier signal.

10. The formation evaluation system of claim 8, wherein the measurement signal is at a higher frequency than the carrier signal.

11. The formation evaluation system of claim 8, wherein the detection of the measurement signal is made by measuring the difference between two signals;

wherein said first signal is the measurement signal superimposed upon the carrier signal; and

wherein the said second signal is an approximation of said carrier signal.

12. The formation evaluation system of claim 1, wherein at least one of the electromagnetic signals is a measurement signal and at least one of the electromagnetic signals is a carrier signal, the measurement signal being separate from the carrier signal.

13. The formation evaluation system of claim 1, wherein the sensor monitors the properties of the electromagnetic signal to determine at least one wellsite parameter from the electromagnetic signal.

14. The formation evaluation system of claim 1, wherein the downhole electromagnetic unit includes control circuitry, and wherein the sensor monitors properties of the control circuitry to determine at least one wellsite parameter from the electromagnetic signal.

15. The formation evaluation system of claim 14, wherein the sensor is integral to the control logic.

16. The formation evaluation system of claim 14, wherein the sensor is separate from the control logic.

17. The formation evaluation system of claim 1, wherein the sensor is located down hole.

18. The formation evaluation system of claim 1, wherein the sensor is operatively connected to the downhole electromagnetic unit.

19. The formation evaluation system of claim 1, wherein the sensor is separate from the downhole electromagnetic unit and located remotely therefrom.

20. The formation evaluation system of claim 1, further comprising a second downhole tool located remotely from the downhole tool, and wherein the sensor is located on the second downhole tool.

21. The formation evaluation system of claim 1, wherein the sensor is located within the subterranean formation.

22. The formation evaluation system of claim 1, wherein the sensor is operatively connected to the surface electromagnetic unit.

23. The formation evaluation system of claim 1, wherein the at least one wellsite parameter includes a resistivity measurement.

24. A method of evaluating a subterranean formation penetrated by a wellbore, comprising:

positioning a downhole tool in the wellbore;

passing at least one electromagnetic signal between a downhole electromagnetic unit of the downhole tool and a surface electromagnetic unit, the electromagnetic signal passing through the subterranean formation; and

determining at least one wellsite parameter from the at least one electromagnetic signal.

25. The method of claim 24, further comprising the step of encoding the at least one electromagnetic signal with data indicative of the at least one wellsite parameter.

26. The method of claim 24, wherein the at least one wellsite parameter includes a resistivity measurement.

27. The method of claim 24, wherein the step of determining at least one wellsite parameter is defined further as monitoring a control circuit of the downhole electromagnetic unit to determine at least one wellsite parameter of the at least one electromagnetic signal.

28. The method of claim 27, wherein the at least one wellsite parameter of the at least one electromagnetic signal is a current.

29. The method of claim 27, wherein the at least one wellsite parameter of the at least one electromagnetic signal is a voltage.

30. The method of claim 24 wherein the step of determining and the step of passing are made concurrently.

31. The method of claim 24 wherein the at least one electromagnetic signal is passed from the downhole electromagnetic unit of the downhole tool to the surface electromagnetic unit.

32. The method of claim 24 wherein the at least one electromagnetic signal is passed from the surface electromagnetic unit to the downhole electromagnetic unit of the downhole tool.

33. The method of claim 24, further comprising the step of superimposing a high frequency signal on top of a low frequency carrier signal to generate the at least one electromagnetic signal.

34. A method of evaluating a subterranean formation having a wellbore penetrating the subterranean formation, comprising the steps of:

deploying a downhole tool into the wellbore;

transmitting a first electromagnetic encoded telemetry signal through the subterranean formation between a downhole tool and a surface unit;

calculating a wellsite parameter from the first encoded electromagnetic telemetry signal;

encoding at least one subsequent electromagnetic telemetry signal with data correlated with the calculated wellsite parameter;

transmitting at least one subsequent electromagnetic telemetry signal through the subterranean formation between a downhole tool and a surface unit;

receiving the second electromagnetic telemetry signal by a surface electromagnetic unit; and

determining the wellsite parameter from the at least one subsequent electromagnetic telemetry signal.