Horizontal directional drilling (HDD) has always been associated with the oil and gas industry, and in comparison, is new in the construction industry. With the advent of sophisticated survey instruments, it has become possible to use HDD in the congested underbelly of cities.
|Free Download: An In-Depth Look At the Horizontal Directional Drilling Process|
When it comes to drilling under city surfaces, the drill path is likely to pass through areas conveying sewer, water, gas, oil, cables and electricity lines. The survey instruments located in the drill string helps operators to monitor the path of the drill bit and take necessary recourse in case it encounters a service line; making it a great method to install conduits under obstacles and avoid cross boring. Drilling deviations were a major obstacle in the early days of HDD. (Learn more in " The Science of Getting it Right: Locating Underground Utilities.")
The Origin of HDD
HDD is a brainchild of the oil and gas industry and can be traced back to the early 1900’s. From the time the oil industry was born, the wells only went down in the vertical direction though there was no way of telling if deep down, the well maintained the vertical path or deviated at a random angle as the drill progressed. There were no survey instruments at that time to monitor the progress of the wellbore.
During the 1920’s it was discovered that the seemingly vertical wellbores were, in fact, deviating at their own will with inclinations up to 50° from the vertical path. Since the oil wells are located very deep under the surface of the earth, the intermediate soil and rock strata with dips and faults were causing the drill bit to deviate. In addition, it was observed that the weight applied to the drill bit, and the drill strings' tendency to bend was also contributing to the deviation. (Read " Working With Drilling Deviations.")
Measuring Deviation in the 1800's
To measure inclination, a method developed in the late 1800’s for the purpose of surveying boreholes in the diamond mines was adopted. Known as the acid bottle technique, a glass bottle filled with acid was lowered into the borehole. The acid would settle in the bottle at an angle and after a while etch the glass at that angle, which would be the angle parallel to the angle of inclination. Another more accurate method developed during this time was the mechanical drift recorder which could measure inclination.
However, neither of these methods could point the direction of well drift. The urgency of finding better surveying methods and wellbore control techniques was sped up by the fact that this deviation of the wellbore was causing some parties to unknowingly trespass into oil fields of other parties by crossing lease lines. The court ordered that leaseholders could only own deposits that were within their lease lines. Since the technology to control well drift was scarce and only possessed by a few, it was not uncommon for those with the technology to exploit the oil fields of their less fortunate neighbors. (Learn more in " Easement and Contract: The Legalities of Trenchless Projects.")
1926 Sperry Corporation Gyroscope
This dilemma led to the invention of survey instruments and deviation methods designed to control wellbore deviation to the required inclination. 1926 saw the use of gyroscopes by Sperry Corporation to measure borehole inclination and azimuth.
In 1929, H. John Eastman developed the magnetic single shot and multi-shot instruments that could measure both inclination and direction. This began the era of controlled directional drilling because it was accurate and could intentionally deviate wellbores to the desired bottom hole locations. It could also help restrict vertical holes from deviating beyond a few degrees of inclination, thus limiting wellbore drift.
Deviation was achieved by using hardwood wedges to push the bit to the desired side to produce deflection and direct the borehole to the desired direction. From there, the oil industry has taken great strides in reaching multiple remote locations from a single entry point and also for harvesting oil from offshore rigs.
Introduction of HDD in Construction
In the early 1960’s, Martin Cherrington learned about guided drilling by observing another company in Los Angeles installing a gas line using a handheld air drill. This led him to design his own drill rig that was basic and lightweight. Soon, he started to work under contractors with the Sacramento Municipal Utility District (SMUD). He performed road boring for the various utility companies in that area, and since electronic tracking had not developed yet, he used the technique of the handheld air drill he learned from the LA gas company.
That was the first milestone for HDD in construction, but there was more to come. Seeing his innovative method for installing utility lines, Pacific Gas & Electric Co. asked him to install a gas line 4” in diameter and approx. 500-feet in length under the Pajaro River. It took him a month and several techniques including those used in the oil industry, but he made it. That was the beginning of using HDD for crossing environmentally sensitive areas with even bigger pipelines.
About 10-years later contractors started becoming comfortable with using HDD for installing utility lines, and today, it is a favored method for many construction projects especially for crossing environmentally sensitive areas such as estuaries and palustrine wetlands.
Technological Advancements in HDD
The evolution of HDD from the oil and gas industry to the construction industry has been noteworthy. While the concept was adopted and applied advantageously, the advancements in computer technology and surveying techniques, such as geotechnical investigation, has taken HDD to a far higher level than Cherrington could have imagined at the time.
A steering technology developed by a company called Tensor in the late 1980’s used an artificial magnetic field that enabled determining tool position relative to a source, in this case, a drill head. This opened a wide avenue for the application of HDD from medium-sized to very large projects including crossings.
With the advancements in global positioning systems (GPS) and drilling sensors, a greater amount of efficiency is obtained, all while making the project cost-effective. It waits to be seen what other technological advancements are coming, that will take HDD to even higher levels of innovation in the construction industry. (Read on in "Studies Claim the Trenchless Construction Cost Comparison is Massive.")