Electronic guidance system and method for locating a discrete in-ground boring device

• US 5,585,726 A
• Filed: 05/26/1995
• Issued: 12/17/1996
• Est. Priority Date: 05/26/1995
• Status: Expired due to Term

• Current Assignee: UtilX Corporation (Novinium, Inc.)
• Original Assignee: UtilX Corporation (Novinium, Inc.)
• Inventors: Chau, Albert W.
• Primary Examiner(s): STRECKER, GERARD R
• Application Number:
  US08/451,302
• Time in Patent Office: 571 Days
• Field of Search: 324/207.22, 324/207.26, 324/326, 324/345, 324/346, 33/304, 73/151, 340/853.4, 340/853.5, 340/853.6, 340/853.8, 175/26, 175/40, 175/45, 175/61, 175/62, 364/444, 364/449
• US Class Current: 324/326
• 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: G01V 3/26 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

Abstract

A guidance system for a drill tool (60) comprising a primary navigation package (80) and a secondary navigation package (74). The primary navigation package contains a triaxial magnetometer and a triaxial accelerometer. The set of signals produced by the triaxial magnetometer and triaxial accelerometer are manipulated to determine the orientation of the drill tool and, by integration over the distance the drill tool has traveled, the approximate position of the drill tool during a directional drilling operation. The secondary navigation package contains a magnetic dipole antenna for emitting an electromagnetic dipole field. Using a locator (100), an operator can periodically determine the actual drill tool position by detecting the electromagnetic dipole field. The actual position of the drill tool as determined by the secondary navigation package is used to correct for an integration error that is introduced into the drill tool position by the navigation technique used by the primary navigation package.

Claims

1. A navigation system for determining a position of a boring device within the ground, the navigation system comprising:

(a) a navigation computer located at a distance from said boring device;

(b) a primary navigation package coupled to said boring device and comprising means for generating a first set of signals indicative of the position of the boring device and a transmitter for transmitting the signals to the navigation computer, wherein the navigation computer can calculate a first position of the boring device from the first set of signals generated by the first navigation package; and

(c) a secondary navigation package coupled to said boring device and comprising means for generating a second set of signals indicative of the position of the boring device and a transmitter for transmitting the signals to the navigation computer, wherein the navigation computer can calculate a second position of the boring device from the second set of signals generated by the second navigation package, the navigation computer further periodically setting the first position equal to the second position to correct any error present in the first position.

2. The navigation system of claim 1, wherein the primary navigation package comprises:

(a) a triaxial accelerometer located in said boring device and producing a first set of data signals representative of a rotation of said boring device; and

(b) a triaxial magnetometer located in said boring device and producing a second set of data signals representative of a strength of a magnetic field intersecting the triaxial magnetometer in said boring device.

3. The navigation system of claim 2, wherein the secondary navigation package comprises:

(a) radiating means located in said boring device for emitting an electromagnetic field having a predetermined radiation pattern; and

(b) a locator for detecting the electromagnetic field emitted from the radiating means and for determining an actual position of the radiating means by measuring the strength of the received electromagnetic field.

4. The navigation system of claim 3, wherein the radiating means is a magnetic dipole antenna.

5. The navigation system of claim 4, wherein the magnetic dipole antenna is a ferromagnetic core dipole antenna.

6. The navigation system of claim 5, wherein the ferromagnetic core dipole antenna is separated from the triaxial magnetometer by at least 6 inches.

7. The navigation system of claim 6, wherein the ferromagnetic core dipole antenna is proximate to a boring head of the boring device.

8. The navigation system of claim 7, wherein the ferromagnetic core dipole antenna is positioned between the primary navigation system and the boring head.

9. The navigation system of claim 4, wherein the magnetic dipole antenna is a loop antenna.

10. The navigation system of claim 9, wherein the loop antenna is proximate to a boring head of the boring device.

11. The navigation system of claim 10, wherein the loop antenna encircles the primary navigation package.

12. The navigation system of claim 10, wherein the loop antenna encircles the triaxial magnetometer.

13. A navigation system for determining the position of a boring device within the ground, the navigation system comprising:

(a) a navigation computer;

(b) a primary navigation package comprising;

(i) a triaxial accelerometer located in said boring device and producing a first set of data signals representative of a rotation of said boring device;

(ii) a triaxial magnetometer located in said boring device and producing a second set of data signals representative of a strength of a magnetic field intersecting the triaxial magnetometer in said boring device; and

(iii) a transmitter for transmitting the first set of data signals representative of the rotation of the boring device and the second set of data signals representative of the strength of the magnetic field intersecting the triaxial magnetometer to the navigation computer, wherein the navigation computer can manipulate the first and the second set of data signals to determine a calculated position of said boring device within the ground; and

(c) a secondary navigation package comprising;

(i) radiating means located in said boring device for emitting an electromagnetic field having a predetermined radiation pattern;

(ii) a locator for detecting the electromagnetic field emitted from the radiating means and for determining an actual position of the radiating means by measuring the strength of the received electromagnetic field; and

(iii) a transmitter for transmitting the actual position of the radiating means to the navigation computer, wherein the navigation computer periodically sets the calculated position of the boring device generated by the primary navigation package to the actual position of the radiating means generated by the secondary navigation package to correct an error that has occurred in the calculated position as determined by the primary navigation package.

14. The navigation system of claim 13, wherein the radiating means is a magnetic dipole antenna.

15. The navigation system of claim 14, wherein the magnetic dipole antenna is a ferromagnetic core dipole antenna.

16. The navigation system of claim 15, wherein the ferromagnetic core dipole antenna is separated from the triaxial magnetometer by at least 6 inches.

17. The navigation system of claim 16, wherein the ferromagnetic core dipole antenna is proximate to a boring head of the boring device.

18. The navigation system of claim 17, wherein the ferromagnetic core dipole antenna is positioned between the primary navigation system and the boring head.

19. The navigation system of claim 14, wherein the magnetic dipole antenna is a loop antenna.

20. The navigation system of claim 19, wherein the loop antenna is proximate to a boring head of the boring device.

21. The navigation system of claim 19, wherein the loop antenna encircles the primary navigation package.

22. The navigation system of claim 19, wherein the loop antenna encircles the triaxial magnetometer.

23. A method of accurately following a predetermined borehole path by monitoring the position of a boring device beneath the ground, the boring device containing a primary navigation package containing means for generating a first set of signals indicative of the position of the boring device and a secondary navigation package containing means for generating a second set of signals indicative of the position of the boring device, the method comprising the steps of:

(a) receiving the first set of signals indicative of the position of the boring device;

(b) calculating a first position of the boring device; and

(c) guiding the boring device along the predetermined borehole path based on the calculated first position, the first position being periodically cleared of accumulated error by;

(i) receiving the second set of signals indicative of the position of the boring device;

(ii) calculating a second position of the boring device; and

(iii) setting the first position of the boring device equal to the second position of the boring device to remove any error present in the first position.

24. A method of accurately following a predetermined borehole path by monitoring the position of a boring device beneath the ground, the boring device containing a primary navigation package comprising a triaxial magnetometer and a triaxial accelerometer and a secondary navigation package comprising a radiating means for emitting an electromagnetic field having a predetermined radiation pattern and a locator for determining a position of the radiating means by measuring a strength of the electromagnetic field emitted from the radiating means at a point distant from the radiating means, the method comprising the steps of:

(a) receiving a first set of signals from said triaxial magnetometer indicative of a magnetic field intersecting the triaxial magnetometer and a second set of signals from said triaxial accelerometer indicative of a rotation of said boring device;

(b) calculating a first position of the boring device from the first set of signals, and the second set of signals; and

(c) guiding the boring device based on the calculated first position, the first position being periodically corrected of an accumulated error by;

(i) determining a second position of the boring device by using the locator to determine the position of the radiating means; and

(ii) setting the first position equal to the second position.