Vector Magnetics: A HDD intersect method pioneer

Jed Sheckler, director of marketing at Vector Magnetics, shared his insights on the depths of a rapidly changing and ever-evolving industry, and how the company’s ParaTrack™ HDD Guidance System has allowed it to always be at the forefront.

Rapid evolution of the civil construction sector is leading contractors to push the limits of their horizontal directional drilling (HDD) capabilities. Drill lengths continue to increase, while tolerances for planned bore paths are tightening.

Added to this, environmental regulations often limit allowable annular pressures to mitigate potential contamination of sensitive wetlands and protected waterways. These realities have spurred a renewed industry interest in the HDD pilot bore intersect technique.

Vector Magnetics pioneered the HDD intersect method in partnership with Prime Horizontal in 2000. With a portfolio of successful intersect technologies developed for the oil and gas production market, Vector Magnetics was positioned for success as they made the transition to HDD.

The ParaTrack™ HDD Guidance System was released to market in 1999, and the first successful ParaTrack™ Magnetic Intersect was completed under the Tees River, England just one year later. ParaTrack™ Magnetic Intersect technology has since guided thousands of successful intersections for customers across the globe.

Why intersect?

While the pilot bore intersect process is well established, the decision to undertake an intersection is never one to be taken lightly. The procedure adds complexity, increases required resources, and requires careful coordination between drilling operations that may be located many kilometers apart.

There are four primary situations when an HDD may require an intersect rather than a single continuously drilled pilot bore:

1. The proposed bore length is beyond the capabilities of any single available rig.
2. Geotechnical reports or expected ground conditions require the installation of conductor casing on each side of the crossing to prevent fluid loss and enable directional control.
3. Local regulations set annular pressure limits that would be exceeded under a standard drilling profile.
4. A shallower-than-normal profile is designed for geotechnical or avoidance considerations which lowers allowable annular pore pressures.

Alternatives to a pilot bore intersect in these conditions are generally microtunnelling or a direct pipe installation at significantly higher costs. The HDD intersect method is a cost-effective way of extending the capabilities of HDD to installations where it may otherwise be unsuited.

The contractor’s choice

The selection of guidance technology plays a critical role in the successful completion of an HDD intersection. The chosen guidance system must be capable of accurately tracking the relative positions of the pilot bores in 3D space as they advance toward the planned intersect point. Good survey practices, whether using a magnetic or gyro guidance system, are crucial during this first phase of an intersect program.

Calculated surveys alone will typically bring the two bores into close alignment, however completing the intersection typically requires the use of a secondary verification system capable of taking direct, independent measurements of each bore’s relative position. Those measurements are used to assist the driller in making the precise steering adjustments necessary to successfully complete an intersection.

Prime Horizontal Australasian Area Manager Gary Bowen’s testimony highlights that the ParaTrack™ Magnetic Intersect provides engineers and contractors multiple options for designing and constructing complex bores.

“Ideally, the engineering and design team will get input from contractors with experience performing a pilot intersection under similar conditions before putting a design out to bid,” he said.

“Additionally, getting input from the guidance provider will ensure not only that the design is feasible, but may also open the door for consideration of different ways of achieving the same result more efficiently.”

Magnetic Intersect is available as part of the standard ParaTrack™ HDD Guidance System and provides a variety of options for intersect guidance, without requiring any costly intersect-specific hardware.

ParaTrack2™ Intersect

When surface access along the right-of-way is readily available, standard ParaTrack™ magnetic steering supplemented with ParaTrack2™ magnetic tracking is an accurate, effective, and trusted method for intersecting quickly and at low cost.

When the intersection is performed under a tracking wire, no supplemental intersect-specific technology is required.

The two bores are referencing the same fixed tracking system, and their relative positions can be measured extremely accurately. The ParaTrack2™ Intersect method is used on hundreds of successful intersections every year.

Passive Magnetic Ranging intersect 

When an intersection is planned below a portion of the right-of-way with limited surface access, passive magnetic ranging (PMR)  is the accurate and cost-effective solution. ParaTrack™ PMR is designed to guide HDD intersections using standard ParaTrack™ guidance equipment.

Vector Magnetics President David Mohler said PMR is unique due to using the magnetic sensors present in a standard steering tool.

“This simplifies the drill string tool configuration, minimizing the number of potential failure points, while keeping operating costs low,” he said,

As the two pilot bores approach, PMR data is collected and transmitted to the surface where it is processed. RivCross™ Guidance Software analyses the data and provides precise steering information to successfully join the two pilot bores.

An intersect success

Prime Horizontal recently completed an intersection under Taichung Harbour, Taiwan using ParaTrack2™ Magnetic Intersect technology. The proposal called for 1367m of 36-inch steel pipe to be installed under the harbor at a maximum depth of 40m. A 1500m horizontal curve further complicated the installation.

Despite the relatively short crossing length, an intersect was chosen due to the presence of cobbles at both entry and exit. Drilling from the South side of the harbor was guided by a ParaTrack™ Gyro, while drilling from the North side was guided by a magnetic steering tool.

As the pilot bores entered the intersect zone, secondary tracking was conducted by referencing an underground ParaTrack2™ guide wire installed in an adjacent conduit. By referencing the same fixed tracking system, the intersect was successfully completed without the need for any intersect-specific ranging.

A guidance system’s intersect capability has become an important factor in a contractor’s ability to bid and complete modern HDD installations. ParaTrack™ Magnetic Intersect delivers a multifaceted approach that offers an array of both active and passive intersect options.

This flexibility provides options for design engineers and contractors, reduces design constraints, and expands the scope of project feasibility.

This article featured in the August edition of Trenchless Australasia.