Variation H coils calibration method for triaxial magnetometers

Patent metadata

Field	Value
Publication number	US-11802476-B2
Application number	US-202017097352-A
Country	US
Kind code	B2
Filing date	Nov 13, 2020
Priority date	Nov 14, 2019
Publication date	Oct 31, 2023
Grant date	Oct 31, 2023

Abstract

A directional tool and method of surveying a wellbore with the directional tool in a borehole string. A first sensor of the directional tool is disposed in a non-homogeneous ambient magnetic field. A first applied magnetic field is applied to the first sensor. A first measurement is obtained at the first sensor while the first sensor is disposed within the non-homogeneous ambient magnetic field and with the first applied magnetic field applied. A second applied magnetic field is applied to the first sensor. A second measurement is obtained at the first sensor while the first sensor is disposed within the non-homogeneous ambient magnetic field and with the second applied magnetic field applied. The directional tool is calibrated based on the first and second measurement. A downhole survey measurement is obtained with the calibrated directional tool in the wellbore.

First claim

What is claimed is:

1. A method of surveying a wellbore with a directional tool, comprising:
disposing a first sensor of the directional tool in a non-homogeneous ambient magnetic field prior to use of the directional tool in a borehole string, wherein the non-homogeneous ambient magnetic field comprises an ambient earth's magnetic field that is disturbed by a magnetic material or a magnetic source;
applying a first applied magnetic field to the first sensor;
obtaining a first measurement at the first sensor while the first sensor is disposed within the non-homogeneous ambient magnetic field and with the first applied magnetic field applied;
applying a second applied magnetic field to the first sensor;
obtaining a second measurement at the first sensor while the first sensor is disposed within the non-homogeneous ambient magnetic field and with the second applied magnetic field applied;
calibrating the directional tool based on the first measurement and the second measurement;
placing the directional tool in a borehole; and
obtaining a downhole survey measurement with the calibrated directional tool in the wellbore.

2. The method of claim 1 , wherein at least one of the first applied magnetic field and the second applied magnetic field is zero.

3. The method of claim 1 , wherein the borehole string is a drill string and further comprising drilling the wellbore with the drill string using the downhole survey measurements.

4. The method of claim 1 , further comprising:
disposing a second sensor in the non-homogeneous ambient magnetic field;
applying the first applied magnetic field to the second sensor;
obtaining a third measurement at the second sensor, while the second sensor is disposed within the non-homogeneous ambient magnetic field and with the first applied magnetic field applied;
applying the second applied magnetic field to the second sensor;
obtaining a fourth measurement at the second sensor while the second sensor is disposed within the non-homogeneous ambient magnetic field and with the second applied magnetic field applied; and
calibrating the directional tool based on the first, second, third, and fourth measurement.

5. The method of claim 4 , wherein the second sensor is a calibrated sensor.

6. The method of claim 1 , wherein calibrating includes determining one or more calibration parameters, the one or more calibration parameters being a function of at least one of a sensitivity of the first sensor and a misalignment of the first sensor with respect to the directional tool.

7. The method of claim 4 , wherein the directional tool has a first longitudinal axis, further comprising determining a sensor reference angle between the first longitudinal axis and an axis of the second sensor and calibrating the directional tool based on the determined sensor reference angle.

8. The method of claim 4 , wherein the directional tool has a first longitudinal axis and the second sensor is in a calibrated reference directional tool having a second longitudinal axis, further comprising determining a tool reference angle between the first longitudinal axis and the second longitudinal axis and calibrating the directional tool based on the determined tool reference angle.

9. The method of claim 8 , wherein the tool reference angle is smaller than 10 degrees.

10. The method of claim 8 , wherein the directional tool and the calibrated reference directional tool are of the same design with respect to at least one of dimensions, magnetic sources, and magnetic material distribution.

11. The method of claim 1 , wherein the directional tool has a first longitudinal axis and the first applied magnetic field and the second applied magnetic field are substantially aligned to the first longitudinal axis.

12. The method of claim 1 , wherein the first sensor has a response to the first applied magnetic field or the second applied magnetic field that is defined by a first-degree polynomial.

13. The method of claim 1 , further comprising applying the first applied magnetic field and the second applied magnetic field along at least one of the x-axis of the directional tool, the y-axis of the directional tool and the z-axis of the directional tool.

14. A method of surveying a wellbore with a directional tool in a borehole string, comprising:
disposing a first sensor of the directional tool in a non-homogeneous ambient magnetic field prior to use of the directional tool in the borehole string;
applying a first applied magnetic field to the first sensor;
obtaining a first measurement at the first sensor while the first sensor is disposed within the non-homogeneous ambient magnetic field and with the first applied magnetic field applied;
applying a second applied magnetic field to the first sensor;
obtaining a second measurement at the first sensor while the first sensor is disposed within the non-homogeneous ambient magnetic field and with the second applied magnetic field applied;
calibrating the directional tool based on the first measurement and the second measurement; and
placing the directional tool in a borehole; and
obtaining a downhole survey measurement with the calibrated directional tool in the wellbore,
wherein the directional tool has a first longitudinal axis, further comprising: determining a bias of the first sensor from a measurement of the first sensor obtained with the first longitudinal axis aligned parallel to the earth's magnetic field and a measurement of the first sensor obtained with the first longitudinal axis aligned anti-parallel to the earth's magnetic field.

15. The method of claim 1 , further comprising determining a misalignment of the first sensor with respect to the directional tool from the calibration.

16. The method of claim 1 , further comprising using the calibrated directional tool to determine a magnetic gradient in the wellbore.

17. The method of claim 1 , wherein calibrating includes determining one or more calibration parameters, the one or more calibration parameters being a function of temperature and wherein the one or more calibration parameters are determined for a first temperature and a second temperature.

18. The method of claim 1 , wherein the directional tool includes a wire configured to carry a current and wherein calibrating includes determining one or more calibration parameters, wherein the one or more calibration parameters being a function of the current and wherein the one or more calibration parameters are determined for a first current through the wire and for a second current through the wire.

19. A directional tool for use in a borehole string for surveying a wellbore, comprising:
a first sensor calibrated prior to use of the directional tool in the wellbore, the first sensor calibrated by:
disposing the first sensor in a non-homogeneous ambient magnetic field, wherein the non-homogeneous ambient magnetic field comprises an ambient earth's magnetic field that is disturbed by a magnetic material or a magnetic source;
applying a first applied magnetic field to the first sensor;
obtaining a first measurement at the first sensor, while the first sensor is disposed within the non-homogeneous ambient magnetic field and with the first applied magnetic field applied;
applying a second applied magnetic field to the first sensor;
obtaining a second measurement at the first sensor while the first sensor is disposed within the non-homogeneous ambient magnetic field and with the second applied magnetic field applied; and
calibrating the directional tool based on the first mea

Assignees

• Herrera Bano Veronica Vanessa
• Tackmann Gunnar
• Kruspe Thomas
• Kunkiel Thomas
• Baker Hughes Oilfield Operations Llc

Inventors

• Herrera Baño Verónica Vanessa
• Tackmann Gunnar
• Kruspe Thomas
• Kunkiel Thomas

Classifications

• E21B47/092 Primary

  by detecting magnetic anomalies · CPC title

• E21B47/13

  by electromagnetic energy, e.g. radio frequency · CPC title

• G01R33/0094

  Sensor arrays · CPC title

• G01V3/26

  operating with magnetic or electric fields produced or modified either by the surrounding earth formation or by the detecting device (with electromagnetic waves G01V3/30) · CPC title

• G01R33/0017 Primary

  Means for compensating offset magnetic fields or the magnetic flux to be measured; Means for generating calibration magnetic fields · CPC title