Detecting underground objects

• US 6,552,548 B1
• Filed: 06/14/1999
• Issued: 04/22/2003
• Est. Priority Date: 06/15/1998
• Status: Expired due to Fees

• Current Assignee: Radiodetection Limited
• Original Assignee: Radiodetection Limited
• Inventors: Fling, Richard William, Lewis, Andrew Biggerstaff
• Primary Examiner(s): Lefkowitz, Edward
• Assistant Examiner(s): Aurora, Reena
• Application Number:
  US09/332,783
• Time in Patent Office: 1,408 Days
• Field of Search: 324/326, 324/207.26, 324/244, 324/226, 324/67, 324/327, 324/328, 324/329, 175/45
• US Class Current: 324/326
• CPC Class Codes: E21B 47/0228 using electromagnetic energy or detectors therefor
• CPC Class Codes: E21B 7/04 Directional drilling
• 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

Abstract

A monitoring device defines a boundary for movement of an underground object such as a booring tool. The underground object generates a magnetic field which is detected by the monitoring device. The monitoring device then determines the position of the underground object relative to itself, and hence to the boundary. The movement of the underground object can then be controlled so that it does not cross the boundary. The monitoring device may therefore define a protection zone so that a buried object within that protection zone will not be contacted by the moveable underground object.

Claims

1. A method of detecting the movement of an underground object comprising:

storing, in a monitoring device, data defining a boundary extending in space, the boundary extending at a position relative to said monitoring device;

generating a magnetic field using generating means on or in the object, said generating means comprising a solenoid coil, said solenoid coil defining a dipole axis; and

detecting the magnetic field at the monitoring device and determining the position of the object relative to the monitoring device, and hence the boundary, said monitoring device being spaced laterally from a vertical plane containing said dipole axis.

2. A method according to claim 1 further including detecting the direction of movement of the object so as to determine when the object approaches the boundary.

3. A method according to claim 1, wherein the monitoring device has two antennas, for detecting the magnetic field, said magnetic field having an axial component and a radial component at the monitoring device, said axial component and said radial component having a ratio there between, the monitoring device measures the axial and radial component of the field, determines said ratio of those components, and compares said ratio with stored information relating to the ratio of the axial and radial components.

4. A method according to claim 1, wherein said magnetic field has vertical components and horizontal components having further ratios there between, the monitoring device measures the vertical and the horizontal components of the magnetic field, predicts a value for the further ratio of said horizontal and vertical components vertically above the generating means, and compares that prediction with a predicted value of said further ratio at the boundary, thereby to determine when said ratios coincide and thus when the object reaches the boundary.

5. A method according to claim 1, wherein the boundary is a vertical plane.

6. A method according to claim 1, wherein the boundary defines a horizontal plane.

7. A method according to claim 1, wherein the boundary defines a volume of space.

8. A method of controlling the movement of an underground object, comprising:

storing, in a monitoring device, data defining a boundary extending in space, the boundary extending at a position relative to said monitoring device;

generating a magnetic field using generating means on or in the object said generating means comprising a solenoid coil, said solenoid coil defining a dipole axis; and

detecting the magnetic field at the monitoring device and determining the position of the object relative to the monitoring device, and hence the boundary, and controlling the movement of the object to prevent the object crossing the boundary, said monitoring device being spaced laterally from a vertical plane containing said dipole axis.

9. A method according to claim 8, wherein the monitoring device has two antennas, for detecting the magnetic field, said magnetic field having an axial component and a radial component at the monitoring device, said axial component and said radial component having a ratio there between the monitoring device measures the axial and radial component of the field, determines said, ratio and compares said ratio with stored information relating to the ratio of the axial and radial components.

10. A method according to claim 8, wherein said magnetic field has vertical components and horizontal components, said vertical components and said horizontal components having further ratios there between, the monitoring device measures the vertical and the horizontal components of the magnetic field, predicts a value for the further ratio of those components vertically above the generating means, and compares that prediction with a predicted value of said further ratio at the boundary, thereby to determine when said values coincide and thus when the object reaches the boundary.