Magnetic sensor correction for field generated from nearby current

Patent metadata

Field	Value
Publication number	US-2016299252-A1
Application number	US-201414777899-A
Country	US
Kind code	A1
Filing date	Oct 22, 2014
Priority date	Oct 22, 2014
Publication date	Oct 13, 2016
Grant date	—

Abstract

An example method of calibrating a downhole tool includes stimulating a known current through a power circuit provided in the downhole tool, the power circuit extending between and communicably coupling a power source and a load. A conductor magnetic field is generated as the known current flows through the power circuit and the conductor magnetic field is detectable by a magnetic sensor included in the downhole tool to obtain sample measurements of Earth's magnetic field. A magnitude of the conductor magnetic field is then measured to obtain a measured value for the conductor magnetic field, and a relationship between the known current and the measured value is determined to calculate a correction factor for the sample measurements based on the relationship. A computer in the downhole tool is then programmed to apply the correction factor to the sample measurements in response to operational currents measured in the power circuit during operation.

First claim

What is claimed is:

1 . A downhole tool, comprising:
a body; a power source coupled to the body; a load coupled to the body; a power circuit extending between and electrically coupling the power source and the load to conduct current provided by the power source to and from the load, wherein, when current flows through the power circuit, a conductor magnetic field is generated; a magnetic sensor coupled to the body to obtain sample measurements of Earth's magnetic field, wherein the magnetic sensor is positioned on the body such that the conductor magnetic field affects operation of the magnetic sensor; a current sensor communicably coupled to the power circuit to measure the current in the power circuit; and a computer communicably coupled to the magnetic sensor and the current sensor for receiving current measurements from the current sensor and applying a correction factor to the sample measurements based on the current measurements to negate effects of the magnetic field on the sample measurements.

2 . The downhole tool of claim 1 , wherein the downhole tool comprises a tool selected from the group consisting of a directional drilling tool, a measure-while-drilling tool, a logging-while-drilling tool, one or more wireline tools, and any combination thereof.

3 . The downhole tool of claim 1 , wherein the power source is selected from the group consisting of one or more batteries, a generator, a fuel cell, a capacitive bank, or any combination thereof.

4 . The downhole tool of claim 1 , wherein the load comprises an electricity-consuming device selected from the group consisting of a sensor, a motor, an actuator, a downhole electronic device, a telemetry module, and any combination thereof.

5 . The downhole tool of claim 1 , wherein the power circuit comprises a positive conductor and a negative conductor.

6 . The downhole tool of claim 5 , wherein one or both of the positive and negative conductors comprise a self-shielding structure selected from the group consisting of a coaxial cable, a twisted pair of wires, a bus bar, and a strip line.

7 . The downhole tool of claim 5 , wherein the positive and negative conductors are fixed relative to the magnetic sensor.

8 . The downhole tool of claim 5 , wherein the body is cylindrical and the positive and negative conductors are angularly offset from the magnetic sensor about a circumference of the body at a maximum angular distance.

9 . A method of calibrating a downhole tool, comprising:
stimulating a current through a power circuit provided in the downhole tool, the power circuit extending between and electrically coupling a power source and a load, wherein the power source and the load are each coupled to a body of the downhole tool; generating a conductor magnetic field as the current flows through the power circuit, the conductor magnetic field being detectable by a magnetic sensor coupled to the body and used to obtain sample measurements of Earth's magnetic field; measuring a magnitude of the conductor magnetic field to obtain a measured value for the conductor magnetic field; determining a relationship between the current and the measured value; and calculating a correction factor for the sample measurements based on the relationship.

10 . The method of claim 9 , wherein stimulating the current through the power circuit comprises stimulating a known current through the power circuit.

11 . The method of claim 9 , wherein stimulating the current through the power circuit further comprises measuring an intensity of the current with a current sensor.

12 . The method of claim 9 , wherein determining the relationship comprises comparing an intensity of the current with the magnitude of the conductor magnetic field.

13 . The method of claim 9 , wherein measuring the magnitude of the conductor magnetic field comprises measuring the magnitude of the conductor magnetic field with the magnetic sensor.

14 . The method of claim 9 , further comprising:
introducing the downhole tool into a wellbore and flowing an operational current through the power circuit to operate the load, whereby an operational conductor magnetic field is generated based on an operational current intensity; obtaining the sample measurements of the Earth's magnetic field with the magnetic sensor; measuring the operational current intensity with a current sensor communicably coupled to the power circuit while the magnetic sensor obtains the sample measurements; and receiving a signal indicative of the operational current intensity with a computer associated with the downhole tool and applying the correction factor to the sample measurements with the computer based on the operational current intensity, and thereby negating effects of the operational conductor magnetic field on the sample measurements.

15 . The method of claim 14 , further comprising dynamically calibrating the downhole tool while the downhole tool is located within the wellbore.

16 . The method of claim 15 , wherein dynamically calibrating the downhole tool comprises:
stimulating a known current in the power circuit while the downhole tool is located in the wellbore and thereby generating an additional conductor magnetic field; measuring an intensity of the known current with the current sensor; comparing a measured value of the intensity of the known current to a static sample measurement obtained by the magnetic sensor; determining a new relationship between the known current and the measured value of the intensity of the known current; and calculating a new correction factor for the sample measurements based on the new relationship.

17 . The method of claim 16 , further comprising applying the new correction factor to the sample measurements in response to operational currents measured in the power circuit during operation.

18 . The method of claim 9 , wherein the power circuit comprises a positive conductor and a negative conductor, the method further comprising self-shielding one or both of the positive conductor and a negative conductors to provide a self-shielding structure, wherein the self-shielding structure is selected from the group consisting of a coaxial cable, a twisted pair of wires, a bus bar, and a strip line.

19 . The method of claim 9 , wherein the power circuit comprises a positive conductor and a negative conductor, the method further comprising coupling the positive and negative conductors to the body such that movement of the positive and negative conductors relative to the magnetic sensor is prevented.

20 . A method, comprising:
introducing a downhole tool into a wellbore, the downhole tool having a body, a power source coupled to the body, and a load coupled to the body; flowing an operational current through a power circuit to operate the load, a power circuit extending between and electrically coupling the power source and the load, whereby an operational conductor magnetic field is generated based on an intensity of the operational current; obtaining sample measurements of the Earth's magnetic field with a magnetic sensor coupled to the body, wherein the magnetic sensor is positioned on the body such that the operational conductor magnetic field affects operation of the magnetic sensor; measuring the intensity of the operational current with a current sensor communicably coupled to the power circuit while the magnetic sensor obtains the sample measurements; receiving a signal indicative of the intensity of the operational current with a computer c

Assignees

• Halliburton Energy Services Inc

Inventors

• Zacharko Jonathan Peter
• Fulford Robert Scott

Classifications

• E21B47/092

  by detecting magnetic anomalies · CPC title

• G01V3/38

  Processing data, e.g. for analysis, for interpretation, for correction · CPC title

• E21B7/04

  Directional drilling · CPC title

• E21B47/024

  of devices in the borehole (determining slope or direction of the borehole E21B47/022) · CPC title

• E21B41/0085

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