Horizontal directional drilling has been enjoying a resurgence over the past few years from the dramatic slowdown that occurred between 2001 and 2003. Although telecommunications installations still account for about one quarter of the work being done, the remaining sectors such as sewer, water, gas, oil/gas pipelines and electric are seeing steady work.
HDD is becoming established as a viable construction method, but one of the areas where the technology can still improve is documentation. This is especially important in light of the need to convince design and consulting engineers to specify HDD where appropriate. This is where education and properly documented information will go a long way toward assisting engineers and municipalities in justifying the use of HDD.
One of the areas where documentation could be improved is as-builts. There is an obvious benefit to contractors to clearly document their installations. Currently most, if not all, contractors use field logbooks to keep track of their installation as it is proceeding. The logbooks can be a great tool in assisting with steering decisions or when rerouting of the bore path is required. Those logs, however, may not be the most effective way of storing bore data long term, especially if the data needs to be reviewed in the future. This is where the tracking systems used in the installation come in.
Most of the currently used tracking systems have available an as-built feature, often referred to as DataLogging. By recording data such as pitch, depth and knowing the rod length of the drilling machine, a profile of the pilot bore can be plotted. Some software programs also include topographical information for better detail. If the bore was pre-planned using bore planning software (or even on a piece of graph paper), it is now easy to compare the installation to the plan.
The method by which the data is acquired differs by tracking system, but essentially they do the same thing. As the drill head is being located during the pilot bore, the tracking system is used to capture the pertinent drilling data and it is stored in the system. As the bore progresses, more data gets added. It is important to note that this should not take the place of the log books, but rather should be considered an augmentation. At the end of the pilot bore, the operator now has a well-documented description of the depth and, with some systems, topographical details. Along with the bore profile, a detailed rod by rod report is also included allowing for more analysis of the bore, if required.
Most systems have the capability to store numerous runs before they have to be downloaded to a computer. This yields a report that then becomes an easily stored and distributable permanent record of the particular installation. This has the added benefit of keeping all the bore records in the same format and also can be used in planning future bores.
In recent years, requirements for monitoring the HDD installation process in more detail have emerged. Some countries in Europe are working on mandating stricter rules when installing gas pipes. One area in particular is the tension load applied to the product pipe during installation. The drilling fluid pressure during installation is another variable that is of interest as it relates to helping prevent frac-outs. Products do exist to monitor tension load and fluid pressure, both in real time and also as a logging device whereby the installation details are downloaded after the fact. The downside to this method, especially in relation to tension loads, is that the damage may already have been done when the data is viewed after the fact.
A monitoring device is placed in-between the reamer and the product pipe being pulled in. As the pullback proceeds, load and drilling fluid measurements are continuously transmitted to a receiver. Using real time monitoring, the machine operator can take appropriate measures as soon as either the load or fluid pressure reaches values that approach established safety levels for the installation. The information being displayed can also be stored for subsequent downloading to a computer. Once this is done, a graphical representation of the tension loads and fluid pressures can be created along with a list of the individual data points.
The technology to automatically log drill data has existed for quite some time, but its use, although gaining momentum, is not too widespread. Current locating systems have made the data collection as simple as clicking a button and have integrated the data logging into the locating function. This means that there is no added time involved for the locating personnel but potentially significant returns for the contractors that choose to use the feature.
Siggi Finnsson is product manager at Digital Control Inc. All Electronic Drillmaster Reports are reviewed by the Electronic Drillmaster Advisory Board: Finnsson; John Archambeault, McLaughlin Mfg.; John Bieberdorf, Subsite Electronics; and Ed Savage, Vermeer Mfg.