BATTERY SWITCH FOR DOWNHOLE TOOLS

• US 20060126249A1
• Filed: 12/13/2004
• Published: 06/15/2006
• Est. Priority Date: 12/13/2004
• Status: Active Grant

• Current Assignee: Schlumberger Technology Corporation (SLB)
• Original Assignee: Schlumberger Technology Corporation (SLB)
• Inventors: BOLING, BRIAN E.
• Granted Patent: US 7,667,942 B2
• Time in Patent Office: Days
• US Class Current: 361/103
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence

Abstract

An electrical circuit for a downhole tool may include a battery, a load electrically connected to the battery, and at least one switch electrically connected in series with the battery and to the load. The at least one switch may be configured to close when a tool temperature exceeds a selected temperature.

Claims

1. An electrical circuit for a downhole tool, comprising:

a battery;

a load electrically connected to the battery; and

at least one switch electrically connected in series with the battery and the load,

wherein the at least one switch is configured to close when a tool temperature exceeds a selected temperature.

2. The electrical circuit of claim 1, wherein the at least one switch is further configured to open when the tool temperature is below the selected temperature.

3. The electrical circuit of claim 1, wherein the selected temperature is selected to be higher than a lowest point in a preferred operating range for the battery.

4. The electrical circuit of claim 1, wherein the selected temperature is about seventy degrees Celsius.

5. The electrical circuit of claim 1, wherein the selected temperature is about one hundred degrees Celsius.

6. The electrical circuit of claim 1, wherein the at least one switch comprises an integrated circuit temperature sensor.

7. The electrical circuit of claim 1, wherein the at least one switch comprises a thermistor.

8. The electrical circuit of claim 1, wherein the at least one switch comprises a resistive temperature detector.

9. The electrical circuit of claim 1, wherein the at least one switch comprises a thermostat.

10. The electrical circuit of claim 9, wherein the thermostat is a bimetallic thermostat.

11. The electrical circuit of claim 1, wherein the at least one switch comprises a relay.

12. The electrical circuit of claim 1, wherein the at least one switch comprises a transistor.

13. The electrical circuit of claim 1, further comprising a control electronics operatively connected to the at least one switch, wherein the control electronics is configured to control the at least one switch to close when the tool temperature exceeds the selected temperature.

14. The electrical circuit of claim 13, wherein the control electronics is electrically connected to the battery in parallel with at least one switch and the load.

15. The electrical circuit of claim 1, wherein at least one switch is electrically connected between a positive terminal of the battery and the load.

16. The electrical circuit of claim 1, wherein at least one switch is electrically connected between the load and a negative terminal of the battery.

17. The electrical circuit of claim 1, wherein at least one switch comprises a first switch and a second switch, wherein the first switch is electrically connected between a positive terminal of the battery and the load, the second switch is electrically connected between the load and a negative terminal of the battery.

18. The electrical circuit of claim 17, further comprising a control electronics operatively connected to the first switch and the second switch, wherein the control electronics is configured to control the first and second switches to close when the tool temperature exceeds the selected temperature.

19. The electrical circuit of claim 18, wherein the control electronics is electrically connected to the battery in parallel with the first switch, the second switch, and the load.

20. The electrical circuit of claim 19, further comprising a secondary load electrically connected to the battery in parallel with the first switch and the load, wherein the secondary load is operatively coupled to the control electronics.

21. The electrical circuit of claim 20, wherein the secondary load comprises a memory.

22. The electrical circuit of claim 1, further comprising a connector electrically connected to the load to bypass the at least one switch, wherein the connector is adapted to connect with an external power source.

23. The electrical circuit of claim 22, further comprising a first diode electrically connected to the battery and in series with the at least one switch and adapted to operate cooperatively with a second diode connected in series with in the external power source to prevent the battery from supplying power to the load when the external power source is connected.

24. The electrical circuit of claim 1, further comprising a depassivation switch electrically connected to the battery in series with the at least one switch and parallel to the load.

25. The electrical circuit of claim 24, further comprising a current limiting resistance electrically connected to the battery and in series with the depassivation switch and parallel to the load.

26. The electrical circuit of claim 1, wherein the battery comprises a high-temperature battery.

27. The electrical circuit of claim 26, wherein the high-temperature battery comprises a lithium thionyl chloride battery.

28. The electrical circuit of claim 1, wherein the at least one switch comprises a first switch and a second switch, wherein the first switch is electrically connected between a positive terminal of the battery and the load, the second switch is electrically connected between a negative terminal of the battery, and further comprising:

a control electronics electrically connected to the battery in parallel with the first switch, the second switch, and the load, wherein the control electronics is operatively connected to the first switch and the second switch and configured to control the first and second switches to close when the tool temperature exceeds the selected temperature;

a depassivation switch electrically connected to the battery in series with the first and second switches and parallel to the load;

a current limiting resistance electrically connected to the battery and in series with the depassivation switch and parallel to the load;

a connector electrically connected to the load to bypass the first and second switches, wherein the connector is adapted to connect with an external power source;

a first diode electrically connected to the battery and in series with one of the first and second switches, the first diode adapted to operate cooperatively with a second diode connected in series with the external power source to prevent the battery from supplying power when the external power source is connected; and

a memory electrically connected to the battery in parallel with the first switch and the load, wherein the second load draws a substantially small current from the battery.

29. A method for preventing power loss in a battery in a downhole tool positioned in a wellbore penetrating a subsurface formation, comprising:

measuring a tool temperature; and

closing at least one switch in a battery circuit when the tool temperature exceeds a selected temperature.

30. The method of claim 29, further comprising selecting the selected temperature to be above a lowest point in a preferred operating range for the battery.

31. The method of claim 29, further comprising opening the at least one switch when the tool temperature falls below the selected temperature.

32. The method of claim 31, wherein the closing the at least one switch comprises using a hysteresis routine to prevent repeated opening and closing of the at least one switch when the tool temperature is near the selected temperature.

33. The method of claim 29, further comprising closing a depassivation switch.

34. A downhole tool, comprising:

a battery;

a tool component electrically connected to the battery; and

at least one switch electrically connected between the battery and the tool component,

wherein the at least one switch is configured to close when a tool temperature exceeds a selected temperature.

35. The downhole tool of claim 34, wherein the at least one switch comprises a first switch and a second switch, wherein the first switch is electrically connected between the positive terminal of the battery and the tool component and the second switch is electrically connected between the tool component and a negative terminal of the battery.

36. The downhole tool of claim 34, further comprising a control electronics operatively connected to the at least one switch and configured to control the at least one switch to close when the tool temperature exceeds a selected temperature.

37. The downhole tool of claim 36, wherein the control electronics is electrically connected to the battery in parallel with the at least one switch and the tool component.

38. The downhole tool of claim 34, further comprising a depassivating switch electrically connected to the battery in series with the at least one switch and in parallel with the tool component.

39. The downhole tool of claim 34, further comprising an external connector electrically connected to the tool component and adapted to connect with an external power source.

40. The downhole tool of claim 39, further comprising a first diode electrically connected to the battery in series with the at least one switch and adapted to operate cooperatively with a second diode connected in series with the external power source to prevent the battery from supplying power when the external power source is connected.

41. The downhole tool of claim 34, wherein the battery comprises a high-temperature battery.

42. The downhole tool of claim 41, wherein the high-temperature battery comprise a lithium thionyl chloride battery.

43. The downhole tool of claim 34, wherein the downhole tool comprises a drilling tool.

44. The downhole tool of claim 34, wherein the downhole tool comprises a wireline tool.