The installation of a product pipe using horizontal directional drilling is a process where the drilling machine part of the solution does all the physical work, and the directional guidance is the responsibility of the other part of the solution, the locating system. Although both systems use data of various kinds, the locating systems increasingly have the capability to collect, store and document data related to the HDD process. This has become 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 field data will go a long way towards assisting engineers and municipalities in justifying the use of HDD.

One of the areas where HDD documentation has improved significantly is walk over as-builts. There is an obvious benefit to the contractor in clearly documenting their installations. Traditionally field log books have been used to keep track of their installation as they are 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.

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 walk over tracking system is used to log the pertinent drilling data and it is stored in the system. For most locating systems, this logging step does not add any time to the drilling process. As the bore progresses, more data gets added. At the end of the pilot bore the data can be wirelessly downloaded to a laptop and the operator now has a well-documented illustration of the bore profile with depth data 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.

In recent years requirements for monitoring the HDD installation process in more detail have emerged. In particular, stricter rules are being employed when installing gas pipes. One area is the monitoring of 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 help preventing of frac outs. Products do exist to monitor tension load and fluid pressure, both in real time and also as a logging device where by the installation details are downloaded after the fact. The downside to the latter method, especially as they relate 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 reach values which 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.

Another aspect of the HDD process where a new kind of information has become available is Fluid Pressure Monitoring during the pilot bore. A special battery-powered transmitter sends out continuous pressure readings while it is running. The pressure data is received a receiver and displayed in real time on the receiver’s display. Additionally, the fluid pressure information along with other pertinent drilling data is transmitted back to the remote display at the drill rig. The drill rig operator therefore has a real-time view of the down-hole fluid pressure and can take corrective action should it be required. This fluid pressure data can be recorded individually and also combined with bore log data to provide a historical data graph of pressure as it relates to the as built in time and placement.

The technology to automatically log HDD drill data has existed for quite some time, but its use although gaining momentum, it not yet very 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, engineers and municipalities that choose to use this feature.

Siggi Finnsson is product manager at Digital Control Inc. and is an Electronic Drillmaster Advisory Board member. All Electronic Drillmaster Reports are reviewed by the Advisory Board: Finnsson, John Bieberdorf, The Charles Machine Works Inc.; John Archambeault, McLaughlin Mfg.; and Tod Micheal, Vermeer Corp.

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