Our Crossings and Intersects (with ParaTrack)

Prime Horizontal’s success was initially based on the development in 1998 -1999 and successive improvements of the ParaTrack system of horizontal guidance. Originally developed by Vector Magnetics as an underground parallel-drilling location system, the ParaTrack system was co-developed and continues to be improved by Prime Horizontal and Vector Magnetics for specific application to the HDD market.

Steering of the drill bit is performed by first measuring the location of the drill bit relative to its planned track using magnetometers and accelerometers in the ParaTrack steering tool. The magnetic field from an external magnetic source, typically a large coil of wire through which is passed an AC electric current (ParaTrack-2) or a DC electric current (ParaTrack-1), is measured at the steering tool with the magnetometers in the tool and the location relative of the drill bit is computed and passed to a display unit in real time so the driller can adjust the drilling parameters to stay on track. Additionally, wireless AC sources give the necessary precision of plus or minus a few centimeters to complete intersect crossings underground, and ParaTrack-2 is the only steering system today capable of measuring and analyzing AC magnetic fields.

Magnetic sources include both wire-based coils and non-wire based magnetic sources with the ParaTrack-2 system, including the Axial Magnet sub, the Rotating Magnet (RM) Sub, the AC Beacon, and the AC Benchmark making possible many new steering applications, especially for the completion of intersect crossings requiring maximum precision where the crossing is completed entirely underground with the intersection of two drill bits, one drilling from the entry side and the other drilling from the exit side.

With the addition of the Pressure While Drilling (PWD) Sub to the drill string, ParaTrack-2 also measures pilot-hole annulus and internal pipe pressure at the steering tool.

We have used ParaTrack-2 in the freeze drilling of tunnels. Freeze drilling is a technique used in the tunnelling industry when the tunnel must be bored in soft, unconsolidated sediments which collapse as the boring operation takes place. To prevent this collapse, many small, parallel bore holes are made through which is circulated a slurry of freezing brine. After the surrounding formations are frozen solid, the boring operation can continues to completion. The tolerances are very small for the brine holes and the ParaTrack-2 system meets these tolerances when used with the MicroCoil magnetic source (the Naples Metro project} and with the Rotating Magnet source (the Hallandsås Rail Tunnel project still ongoing).