HDD: Horizontal Directional Drilling
The directionally controlled horizontal drilling process was developed in the U.S., and has become commonly used for installing pipelines under natural or manmade obstacles, especially river crossings. This method has revolutionized complicated river crossings for pipelines which were initially done by conventional dredging methods or were rerouted through long distances and crossed over at a bridge location.
The method, an outgrowth of the oil well drilling technology, was reportedly first developed in the early 1970s by Titan Construction, of Sacramento, California. The first installation was accomplished in 1971 for Pacific Gas & Electric Co., and involved the installation of approximately 600 lf (180 m) of four-inch diameter steel pipe under the Pajaro River near Watsonville, California. Prior to 1979, the method was limited to the installation of short lengths. In 1979, the method was acquired by Reading & Bates Construction Company (Now Inarc Drilling, Inc.), Tulsa, Oklahoma. Since 1979, the method has progressed to state-of-the art where long lengths of crossing with a wide variety of pipe sizes can be accomplished.
From 1971 to 1979, only 36 crossings were made using this method, all of them in the United States. However, in the next seven years, over 175 crossings were made, with several accomplished in South America, Europe, Africa and Asia. Currently, there are several firms competing in the market, and the total number of crossings exceed well over 500.
For a time, horizontal directional drilling (HDD) was primarily used by the oil and gas industry on large-diameter, cross-country pipeline transmission lines. Increasingly, it is being approved and used for small-diameter gas distribution lines in urban and suburban areas, as well for municipal water and telecommunication cable crossings at airports, highways, and waterways.
HDD has become the preferred technique of many pipeline and utility companies by virtue of its lower costs and decreased surface disruption. Because it minimizes the negative impact of construction on the surrounding areas, HDD provides a method of installation that is unsurpassed in its ease and overall “friendly” nature. Pipeline companies have been increasingly turned to HDD over traditional, open-trench methods for underground construction projects.
Equipment and systems
Introduced in the 1970s, the first HDD rigs were considered difficult to operate. But improvements came quickly, and more manufacturers developed products as utility companies and contractors recognized the advantages offered by the technique.
A basic HDD system is highly user friendly, and includes a drill frame, power source, hydraulics, drilling fluid and guidance systems. No starting pits are needed; bores are launched from the surface and proceed downward at an angle until the necessary depth is reached. Then the path of the bore is leveled, and the bore head is steered to a designated exit point, where it is brought to the surface.
As the bore progresses, lengths of drill pipe are added. When the initial bore is complete, material to be installed is attached to the drill string, often with a backreamer, to enlarge the diameter of the borehole. The installation is made by pulling the product pipeline back through the borehole, with drill pipe sections being removed as the drillstring approaches the drill frame.
Drilling fluid is used in making the initial bore, and during pullback. For utility work, bore lengths generally range from 50 to 600 ft, but, with some systems, can extend as far as 1,800 ft. and further.
HDD equipment has evolved dramatically over the past several years. The introduction of a reliable walk-over locating system spawned the initial growth of the mini- and midi-class drills that use high drilling fluid pressure (up to 5,000 psi) and low drilling fluid volume (2-10 gpm). This method of drilling is effective in soft to medium ground conditions.
The evolution of walk-over locating systems has been almost as dramatic as that of the HDD rigs themselves. Early systems were limited to very shallow depths, and information update times were extremely slow by today’s standards. Now, not only do contractors have a choice of sondes to match their project scopes, but wireline steering tools have been simplified. Walk-over system status readouts that are broadcast back to the driller’s console enable the driller and locator to see the information simultaneously.
In 1996, about 30% of all underground work was completed with directional drilling equipment. That figure increased to close to 50% in 1999 and 2000, as demand from the telecommunications companies joined that of pipelines and utilities.
That rapid growth has slowed with the recent downturn in the telecommunications and internet-broadband industries. But demand for trenchless installation techniques from pipeline companies and utilities has remained strong, and is expected to increase in the future. This is due to advantages HDD offers in the environmental, technical, contractual and economic arenas.
Today, utilities and contractors often make HDD their first choice. In the early days, the only obvious drawback to choosing HDD was that the technology was so new, there was not a large pool of experienced personnel to draw from. This has changed as well but experience doesn’t always mean expertise. Today, there is a much larger amount of HDD operators, but contractors need to be careful who they hire.
Utility construction, particularly in the gas and telecommunications industries, ensures a growing demand for the use of directional drilling techniques into the 21st century. The potential for work spans the spectrum, from major river crossings to utility installation in congested urban areas, to various types of environmental remediation.
In addition, HDD offers unique solutions to environmental problems. For example, directional systems can install horizontal remediation wells to access contaminated soil and ground water in areas where other procedures are uneconomical. Some in the industry predict the environmental market for HDD will eventually be larger that the utility market.
Overall, HDD reduces restoration time and costs in both urban areas and residential neighborhoods. The public appreciates the reduced inconvenience made possible by the use of directional drilling equipment.
Americom is a full service utility construction company that specializes in Horizontal Directional Drilling. Americom’s state-of-the-art equipment and certified, experienced operators make it an easy choice when selecting a qualified expert in directional drilling.
Municipalities, general contractors, oil, gas, and power companies, and telecommunication organizations throughout the rocky mountain states have made Americom the right choice for over 38 years. Let us know how we can help!
Content credit: Hart Energy