Solenoid guide system for horizontal boreholes

• US 5,513,710 A
• Filed: 11/07/1994
• Issued: 05/07/1996
• Est. Priority Date: 11/07/1994
• Status: Expired due to Fees

• Current Assignee: Vector Magnetics, Inc.
• Original Assignee: Vector Magnetics, Inc.
• Inventors: Kuckes, Arthur F.
• Primary Examiner(s): Dang, Hoang C.
• Application Number:
  US08/337,188
• Time in Patent Office: 547 Days
• Field of Search: 175/61, 175/62, 175/45, 324/346, 324/326
• 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 7/04 Directional drilling

Abstract

A method and apparatus for drilling a borehole under an obstacle including placing a solenoid on the surface of the earth at the far side of the obstacle, near a preselected borehole exit location. A drilling assembly at an entry location on the near side of the obstacle is driven to produce a borehole which is directed under the obstacle toward the exit location. Initially, guidance of the drilling assembly is by conventional survey techniques, but when the borehole moves to within about 100 meters of the solenoid, the solenoid magnetic field is used to guide the drilling operation.

Claims

1. Apparatus for drilling a generally horizontal borehole, comprising:

a drill assembly including a drill for forming a borehole, a drill steering tool for directing the drill, an inclinometer for measuring the orientation of the drill with respect to the earth'"'"'s gravity, and a magnetometer for measuring vector components of the Earth'"'"'s apparent magnetic field in the region of the drill assembly;

a borehole entry at the earth'"'"'s surface;

drilling equipment at said borehole entry for supporting said drill assembly in a borehole being drilled by said drill;

a controller connected to receive signals from said inclinometer and said magnetometer;

a desired borehole exit in the earth'"'"'s surface at a location remote from said entry;

a solenoid at a known location with respect to said exit for said borehole;

a reversible direct current source connected to said solenoid for producing a reversible target magnetic field superimposed on the earth'"'"'s magnetic field to provide said apparent Earth'"'"'s magnetic field at said magnetometer; and

means responsive to the measured vector components of said Earth'"'"'s apparent magnetic field and to said measured orientation of said drill to determine the distance and direction from said drill assembly to said solenoid and thus to said desired borehole exit to thereby control the direction of drilling of said borehole.

2. The apparatus of claim 1, wherein said borehole entry and said desired borehole exit are on opposite sides of an obstacle.

3. The apparatus of claim 1, wherein said means responsive to said measured vector components and measured orientation is a computer.

4. The apparatus of claim 1, wherein said solenoid is transportable for location on the surface of the earth at or near said desired borehole exit.

5. The apparatus of claim 1, wherein said reversible direct current source produces a direct current in a first direction for a preselected period of time and thereafter produces a direct current in a second direction for said preselected period of time.

6. A method for drilling a generally horizontal borehole comprising:

locating drilling equipment at a borehole entry;

activating said drilling equipment to operate a drilling assembly for producing a borehole;

directing said borehole toward a preselected exit region;

locating a solenoid at a known location with respect to said preselected exit region;

periodically stopping said drilling assembly and activating said solenoid to produce a first static magnetic field in a first direction for a preselected period of time and thereafter to produce a second static magnetic field in a second direction for a preselected period of time;

measuring vector components of the Earth'"'"'s apparent magnetic field, including said first and second static magnetic fields;

measuring vector components of the inclination of said drilling assembly;

determining the orientation of the drilling assembly; and

determining from the orientation of the drilling assembly and the vector components of the apparent Earth'"'"'s magnetic field the distance and direction from said drilling assembly to said solenoid, and thereby the distance and direction to said exit region.