Flux orientation locating in a drilling system

• US 6,838,881 B2
• Filed: 12/29/2003
• Issued: 01/04/2005
• Est. Priority Date: 03/01/1991
• Status: Expired due to Fees

• Current Assignee: Merlin Technologies Incorporated
• Original Assignee: Merlin Technologies Incorporated
• Inventors: Mercer, John E.
• Primary Examiner(s): Patidar, Jay
• Assistant Examiner(s): Aurora, Reena
• Application Number:
  US10/747,467
• Publication Number:
  US 20040140809A1
• Time in Patent Office: 372 Days
• Field of Search: 324326-329, 175/45
• US Class Current: 324/326
• CPC Class Codes: E21B 47/0228 using electromagnetic energy or detectors therefor
• CPC Class Codes: E21B 47/0232 at least one of the energy sources or one of the detectors being located on or above the ground surface
• CPC Class Codes: G01C 9/06 Electric or photoelectric indication or reading means
• CPC Class Codes: G01C 9/20 the indication being based on the inclination of the surface of a liquid relative to its container
• CPC Class Codes: G01V 3/08 operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices with electromagnetic waves G01V3/12
• 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 3/15 specially adapted for use during transport, e.g. by a person, vehicle or boat
• CPC Class Codes: G01V 3/165 operating with magnetic or electric fields produced or modified by the object or by the detecting device with electromagnetic waves G01V3/17

Abstract

An above ground locator includes an apparatus for determining the strength of the locating signal at a selected point relative to the boring tool. The apparatus includes an antenna arrangement configured for measuring the strength of the locating signal at the selected point along first and second orthogonally opposed receiving axes to produce first and second received signals. A phase shifting arrangement phase shifts the first and second received signals in a predetermined way to generate first and second phase shifted signals, respectively. Thereafter, a summing arrangement adds the first and second phase shifted received signals to generate an output signal which is a vector sum of the first and second received signals. In one feature, third and fourth signals derived from the first and second signals are used to eliminate balance point ambiguity which is present using the first and second signals alone. In another feature, signals corresponding to first, second, third and fourth axes are compared in a way which confines the possible locations of an above ground point to one particular type of region out of a plurality of different types of regions. Tracking of the boring tool may be accomplished in a number of described ways since the regions occur in a specific sequence along the intended path with respect to the location of the boring tool.

Claims

1. In a system for locating a boring tool which is disposed within the ground, said boring tool being configured for transmitting a locating signal, a method of determining the strength of the locating signal at a selected point relative to the boring tool, said method comprising the steps of:

a) measuring the strength of the locating signal at said selected point along first and second orthogonally opposed receiving axes to produce first and second received signals;

b) phase shifting said first and second received signals in a predetermined way to generate first and second phase shifted signals; and

c) summing the first and second phase shifted received signals to generate an output signal which is a vector sum of the first and second received signals.

2. The method of claim 1 wherein said phase shifting step is performed by

i) subjecting said first received signal to one phase shift in a first angular direction by a particular angular magnitude to generate said first phase shifted signal, and

ii) phase shifting said second received signal by another phase shift equal to said particular angular magnitude but in a second angular direction that is the opposite of said first angular direction to generate said second phase shifted signal.

3. In a system for locating a boring tool which is disposed within the ground, said boring tool being configured for transmitting a locating signal, an apparatus for determining the strength of the locating signal at a selected point relative to the boring tool, said apparatus comprising:

a) an antenna arrangement configured for measuring the strength of the locating signal at said selected point along first and second orthogonally opposed receiving axes to produce first and second received signals;

b) a phase shifting arrangement for phase shifting said first and second received signals in a predetermined way to generate first and second phase shifted signals, respectively; and

c) a summing arrangement for summing the first and second phase shifted received signals to generate an output signal which is a vector sum of the first and second received signals.

4. The apparatus of claim 3 wherein said phase shifting arrangement is configured for

i) subjecting said first received signal to one phase shift in a first angular direction by a particular angular magnitude to generate the first phase shifted signal, and

ii) phase shifting said second received signal by another phase shift equal to said particular angular magnitude but in a second angular direction that is the opposite of said first angular direction to generate the second phase shifted signal.