Method for near field electromagnetic proximity determination for guidance of a borehole drill

• US 5,923,170 A
• Filed: 03/26/1998
• Issued: 07/13/1999
• Est. Priority Date: 04/04/1997
• Status: Expired due to Term

• Current Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Original Assignee: Vector Magnetics, Inc.
• Inventors: Kuckes, Arthur F.
• Primary Examiner(s): Strecker, Gerard
• Application Number:
  US09/047,926
• Time in Patent Office: 474 Days
• Field of Search: 324/247, 324/326, 324/329, 324/334, 324/336, 324/343, 324/345, 324/346, 324/207.17, 324/207.26, 175/40, 175/45, 175/61, 175/62, 342/459, 702/150
• US Class Current: 324/326
• CPC Class Codes: E21B 47/0228 using electromagnetic energy or detectors therefor
• CPC Class Codes: G01V 3/081 the magnetic field is produced by the objects or geological structures characterised by the method of magnetic field measurement G01R33/00
• CPC Class Codes: G01V 3/28 using induction coils

Abstract

A method and apparatus for precise measurement of the distance and direction from a magnetic field sensor to a nearby magnetic field source includes an elongated iron core solenoid driven by a repetitive, nonsinusoidal current source. In the near field the solenoid has two spaced, temporally varying magnetic poles, and measurement of the distance and direction to this source includes analysis of field components which vary in synchronism with the current source.

Claims

1. A method for electromagnetic proximity determination, comprising:

supplying a time-varying current having a repetitive waveform with periods of positive and negative current to a ferromagnetic solenoid source deployed in a borehole, said current at said solenoid source generating a non-sinusoidal, time-varying magnetic field with a known solenoid source strength parameter;

detecting three vector components of the time-varying magnetic field at a sensor in a second, nearby borehole;

obtaining from each of said three vector components an ensemble of individual magnetic field measurement values;

determining times of polarity reversal of the field components;

processing the ensemble of magnetic field measurement values for each of said three vector components with respect to the times of field polarity reversal over at least one of said periods of positive and negative current in said solenoid source to obtain field strength parameters; and

using said field strength parameters and the said solenoid source strength parameter to determine the distance between said solenoid source and said sensor.

2. The method of claim 1, wherein the step of processing said ensemble measurement values provides time synchronization between the field measurement values and said time varying current.

3. The method of claim 2 wherein said time varying current waveform is asymmetrical to permit determination of polarity synchronization between the magnetic field measurement values and the said solenoid source.

4. The method of claim 2 further including providing a time synchronized weighing factor to determine said field strength parameters.

5. The method of claim 1 wherein said processing effectively eliminates measurement values near times of polarity reversal of the field components.

6. The method of claim 1, wherein measurement processing is done in a borehole.

7. The method of claim 6, further including transmitting processed signals from the borehole to a surface location.

8. The method of claim 1, further including:

determining the orientation of said solenoid source;

determining the radial component of the magnetic field of said solenoid source; and

determining the direction to said solenoid using said determinations of said radial field components and solenoid source orientation.

9. The method of claim 1 further including determining field measurement parameters utilizing a time synchronized weighing factor.

10. The method of claim 8, further including eliminating measurement data taken near times of polarity reversal of the source to provide said field strength parameters.

11. A method of near-field proximity determination for guidance of a borehole drill, comprising:

energizing a target solenoid in a target borehole with a time-varying current having a repetitive waveform to produce a corresponding time-varying magnetic field;

obtaining an ensemble of measurements of said magnetic field in a second, nearby borehole;

adjusting said measurements by excluding measurements taken during transition periods of said time-varying current and said time-varying magnetic field;

synchronizing the measured magnetic field with said time-varying current waveform; and

determining from the synchronized measured field the distance from said borehole to said solenoid.

12. The method of claim 11, further including determining the direction from said borehole to said solenoid.

13. The method of claim 11, further including obtaining an ensemble of current waveform, measurements by measuring said time-varying current and periodically sampling the measured current.

14. The method of claim 13, wherein obtaining an ensemble of measurements of said magnetic field includes measuring said field and periodically sampling the field measurements.

15. The method of claim 14, wherein synchronizing the measured field with the measured current waveform includes producing a time shift of said field measurements to maximize the value of the sum of the ensemble of measurements.

16. The method of claim 12, further including locating the target solenoid in a target borehole at a distance from said second borehole approximately equal to the length of said solenoid.

17. The method of claim 16, further including guiding drilling of said second borehole with respect to said target borehole in accordance with said determined distance and direction.

18. The method of claim 11, wherein energizing said target solenoid includes driving said solenoid with a time-varying current having a nonsinusoidal waveform to produce two spaced, temporally varying magnetic poles.

19. The method of claim 18, wherein energizing said target solenoid includes driving and solenoid with an alternating current to drive said solenoid to saturation first in one direction and then in the opposite direction during each alternating current cycle.

20. The method of claim 19, wherein energizing said target solenoid includes driving said solenoid at a frequency sufficiently low that said corresponding magnetic field is produced in synchronism with said drive current.

21. The method of claim 19, wherein energizing said target solenoid includes driving said solenoid to produce a corresponding magnetic field which varies in synchronization with said current source but which is not proportional to said current.