System and method for locating and tracking a boring tool

A horizontal directional drilling system comprising:

• a frame;
• a drill string having a first end and a second end;
• a rotary drive system attachable to the frame, operatively connectable to the first end of the drill string, and adapted to rotate and advance the drill string;
• a downhole tool assembly comprising:
• a bearing housing assembly connectable to the second end of the drill string;
• a front housing connectable to the bearing housing assembly and rotatable independently of the bearing housing assembly;
• a first beacon supported by the front housing for movement therewith and adapted to transmit signals indicative of the orientation of the front housing;
• a second beacon assembly supported by the bearing housing assembly for movement therewith and adapted to transmit signals indicative of the orientation of the bearing housing assembly;
• and
• a receiving assembly adapted to monitor the orientation of the bearing housing assembly and the front housing, the receiving assembly comprising:
• an antenna assembly adapted to detect the signals emanating from both the first beacon and the second beacon and to transmit the detected signals;
• and
• a processor assembly adapted to receive the detected signals from the antenna assembly, to process the detected signals to determine the orientation of the front housing and the orientation of the bearing housing assembly.

A downhole tool assembly for use with a rotatable drill string comprising:

• a rotatable bearing housing assembly connectable to the second end of the rotatable drill string;
• a front housing connectable to the bearing housing assembly and rotatable independently of the bearing housing assembly;
• a first beacon supported by the front housing for movement therewith and adapted to transmit signals indicative of the orientation of the front housing;
• and
• a second beacon assembly supported by the bearing housing assembly for movement therewith and adapted to transmit signals indicative of the orientation of the bearing housing assembly.

A method for drilling a borehole having a desired pitch using a downhole tool assembly attached to a drill string and a signal receiving assembly, the downhole tool assembly comprising a first beacon adapted to emit a first pitch signal indicative of the pitch orientation of the first beacon and a second beacon spatially separated from the first beacon and adapted to emit a second pitch signal indicative of the pitch orientation of the second beacon, the method comprising:

• sensing the first pitch signal and the second pitch signal using the signal receiving assembly;
• processing the first pitch signal and the second pitch signal substantially simultaneously to determine the pitch orientation of the first beacon and the pitch orientation of the second beacon;
• and
• comparing the pitch of the first beacon and the pitch of the second beacon to the desired pitch.