Downhole high-impedance alternator

Patent metadata

Field	Value
Publication number	US-2016348478-A1
Application number	US-201415114839-A
Country	US
Kind code	A1
Filing date	Mar 14, 2014
Priority date	Mar 4, 2014
Publication date	Dec 1, 2016
Grant date	—

Abstract

System and method for supplying downhole power using a high-impedance alternator. The system includes a high-impedance alternator coupled with a rectifier at its output terminals, and a current fed power converter coupled with the rectifier providing a regulated voltage to a downhole load.

First claim

What is claimed is:

1 . A system for supplying electric power to a downhole load in a wellbore, comprising:
a downhole high-impedance alternator supplying power to the downhole load, the downhole high-impedance alternator having a predefined minimum reactance and a predefined minimum resistance; wherein the predefined minimum reactance and the predefined minimum resistance are sufficiently high to cause the high-impedance alternator to emulate a current source over a given output voltage range.

2 . The system of claim 1 , further comprising a rectifier coupled with the downhole high-impedance alternator at the output terminals of the downhole high-impedance alternator and configured to rectify any output current provided by the high-impedance alternator.

3 . The system of claim 2 , further comprising a current fed converter coupled with the rectifier, the current fed converter providing a regulated output voltage to the downhole load.

4 . The system of claim 1 , wherein the predefined minimum reactance of the high-impedance alternator is comprised of an armature reactance, the armature reactance being sufficiently high to cause the high-impedance alternator to emulate the current source over the given output voltage range.

5 . The system of claim 1 , wherein the predefined minimum resistance of the high-impedance alternator comprises an armature resistance of a predefined percentage of an armature reactance.

6 . The system of claim 1 , wherein the high-impedance alternator varies the output current by approximately 1.4:1 for an input shaft speed that has a variation of 2:1.

7 . The system of claim 1 , wherein the high-impedance alternator has a power factor of approximately 85 percent or higher.

8 . The system of claim 1 , wherein the downhole load requires energy storage and the high-impedance alternator provides a portion of the energy storage required by the downhole load.

9 . The system of claim 1 , wherein the high-impedance alternator provides a peak efficiency of approximately 99 percent when measured at a peak power point on a loading curve.

10 . The system of claim 1 , wherein the high-impedance alternator includes a rotor generating a magnetic field and an armature having armature windings thereon, the armature saturating at a point on a loading curve of the high-impedance alternator that has an operating voltage value greater than an operating voltage of a peak power point on the loading curve.

11 . The system of claim 1 , wherein the high-impedance alternator is capable of normal operation under both open circuit and short circuit load conditions without causing damage to the high-impedance alternator or propagating the fault to other downhole equipment.

12 . A method for supplying electric power to a downhole load in a wellbore, comprising:
providing a high-impedance alternator down a borehole, the high-impedance alternator having a predefined minimum reactance and a predefined minimum resistance; coupling the high-impedance alternator with a rectifier at the output terminals of the high-impedance alternator, the rectifier configured to rectify an output current provided by the high-impedance alternator; and coupling a current fed converter with the rectifier bridge, the current fed converter providing a regulated output voltage to the downhole load.

13 . The method of claim 12 , further comprising configuring the high-impedance alternator such that the predefined minimum reactance comprises an armature reactance adequate to cause the alternator to emulate a current source over a given output voltage range.

14 . The method of claim 12 , further comprising configuring the high-impedance alternator such that the predefined minimum resistance comprises an armature resistance of a predefined percentage of its reactance.

15 . The method of claim 12 , wherein for an input that has a variation of 2:1, the output current of the high-impedance alternator varies by approximately 1.4:1.

16 . The method of claim 12 , further comprising operating the high-impedance alternator with a power factor of approximately 85 percent or higher.

17 . The method of claim 12 , wherein the downhole load requires energy storage, further comprising using the high-impedance alternator to provide a portion of the energy storage required by the downhole load.

18 . The method of claim 12 , further comprising operating the high-impedance alternator to provide a peak efficiency of approximately 99 percent when measured at a peak power point on a loading curve.

19 . The method of claim 12 , wherein the high-impedance alternator includes a rotor generating magnetic field and an armature having armature windings thereon, further comprising saturating the armature at a point on a loading curve of the high-impedance alternator that has an operating voltage value greater than that of the peak power point on the loading curve.

20 . The method of claim 12 , further comprising operating the high-impedance alternator normally under both open circuit and short circuit load conditions without causing damage to the high-impedance alternator.

21 . A structure for drilling a subsurface formation, comprising:
a drilling platform centered over the subsurface formation; a conduit extending from a deck of the drilling platform into a wellbore within the subsurface formation; a hoisting apparatus installed on the drilling platform; a drill string supported by the hoisting apparatus, the drill string having a drill bit and one or more tools or sensors mounted thereon; a high-impedance alternator mounted at a predefined location on the drill string, the high-impedance alternator having a predefined minimum reactance and a predefined minimum resistance; and a rectifier coupled with the high-impedance alternator at the output terminals of the high-impedance alternator and configured to rectify an output current provided by the high-impedance alternator; wherein the predefined minimum reactance and the predefined minimum resistance are sufficiently high to cause the high-impedance alternator to emulate a current source over a given output voltage range.

22 . The structure of claim 21 , further comprising a turbine connected to the high-impedance alternator, the turbine configured to be driven by drilling mud pumped down the drill string, wherein the alternator is configured to prevent an electrical fault occurring on the one or more tools or sensors from propagating to the turbine.

23 . The structure of claim 21 , further comprising a downhole engine connected to the high-impedance alternator and configured to drive the high-impedance alternator, wherein the alternator is configured to prevent an electrical fault occurring on the one or more tools or sensors from propagating to the downhole engine.

24 . The structure of claim 21 , further comprising a current fed converter coupled with the rectifier, the current fed converter providing a regulated output voltage to the one or more tools or sensors mounted on the drill string.

25 . The structure of claim 21 , further comprising a linear shunt regulator coupled with the rectifier, the linear shunt regulator providing a regulated output voltage to the one or more tools or sensors mounted on the drill string.

Assignees

• Halliburton Energy Services Inc

Inventors

• Goodman George D

Classifications

• E21B41/0085 Primary

  Adaptations of electric power generating means for use in boreholes · CPC title

• E21B41/00

  Equipment or details not covered by groups E21B15/00 - E21B40/00 · CPC title

• E21B4/04

  Electric drives (E21B4/12 takes precedence) · CPC title