Guidance system for drilling boreholes

• US 5,657,826 A
• Filed: 11/17/1995
• Issued: 08/19/1997
• Est. Priority Date: 11/15/1994
• 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): Tsay, Frank
• Application Number:
  US08/560,392
• Time in Patent Office: 641 Days
• Field of Search: 175/40, 175/45, 175/61.62, 175/50, 175/74
• US Class Current: 175/45
• 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: E21B 7/046 horizontal drilling drilling with mechanical conveying means E21B7/003

Abstract

A single guide wire system for use in continually directional drilling of boreholes, includes a guidewire extending generally parallel to the desired path of the borehole. The guidewire is connected at a first end to one side of a reversible source of direct current, and at a second end to ground. A second side of the DC source is also connected to ground. A known current flow in a first direction for a first period of time and in a second direction for a second period of time produces corresponding static magnetic fields in the region of the borehole. The vector components of the fields are measured in the borehole by a 3-axis magnetometer, and from these vector components the effects of the Earth'"'"'s magnetic field are canceled and the distance and direction from the borehole to the guidewire are determined. These values permit control of further drilling of the borehole along a desired path.

Claims

1. A method for guiding the drilling of a borehole along a subsurface path, comprising:

positioning an elongated electrically conductive and insulated subsurface guide cable adjacent a desired path to be followed by a subsurface borehole to be drilled, the desired path extending through a resultant magnetic field including at least the Earth'"'"'s apparent magnetic field;

connecting a first terminal of a current source to a first end of said guide cable;

connecting a second end of said guide cable to electrical ground;

connecting a second terminal of said current source to electrical ground to provide a return ground path for current flowing in the guide cable;

supplying from said source a current of known amplitude in a first direction to said first end of said guide cable to cause said current to flow to said electrical ground at said second end of said guide cable and to return to said second terminal of said source for a first period of time to produce changes in said resultant magnetic field in the region of said desired path;

measuring, at a subsurface borehole being drilled through the Earth along said path, vector components of said resultant magnetic field and;

determining, from changes in said vector components of said resultant magnetic field the distance and direction from said borehole being drilled to said guide cable.

2. The method of claim 1, further including supplying, for a second period of time, said current of known amplitude in a second direction to produce further changes in said vector components of said resultant magnetic field.

3. The method of claim 1, further including connecting a ground return wire between said second end of said guide cable and said second terminal of said current source to provide said ground return path.

4. The method of claim 1, wherein positioning said guide cable includes locating the guide cable in a subsurface borehole substantially parallel to said desired path.

5. The method of claim 1, wherein positioning said guide cable includes locating the guide cable on the Earth'"'"'s surface in a location substantially parallel to said desired path.

6. A guidance system for a subsurface borehole comprising:

an entry location for a borehole to be drilled along a desired path past an inaccessible region, said entry location being at a near side of said region;

an exit location for said borehole said exit location being at a far end of said desired path and at a far side of said inaccessible region;

a reversible electric current source having first and second terminals and located near said exit location;

an electrically insulated guide cable having first and second ends and connected at said first end to said first terminal and located along a path extending from said exit location toward said entry location;

an uninsulated ground wire connected to said second end of said guide cable, said ground wire extending generally perpendicular to said guide cable;

a second ground wire connected to said second terminal, said current source supplying a current of known amplitude for a first period of time in a first direction to said first end of said guide cable to cause current to flow to said ground wire at said second end of said guide cable and to return to said second terminal of said source to produce a first resultant magnetic field in the region of said desired path, and thereafter supplying said current of known amplitude for a second period of time in a second direction to produce a second resultant magnetic field in the region of said desired path; and

magnetic field sensor means located on a drill for drilling said borehole, said sensor means measuring vector components of said resultant magnetic fields.

7. The system of claim 6, wherein said guide cable and said uninsulated ground wire are located on the Earth'"'"'s surface.

8. The system of claim 7, wherein said guide cable extends from said inaccessible region to said exit location.

9. The system of claim 8, wherein said second guide wire is generally collinear with said desired paths.