Borehole surveying might seem like a niche industry, and it is very specialized, but it benefits many other industries in ways you might not realize. Borehole surveying assesses the surface on which buildings are constructed, where quarries are blasted, and where further oil and gas drilling is done. Borehole surveying is also referred to as drillhole surveying or directional surveying.

A borehole survey is the process of lowering different apparatuses into a drillhole to determine the structural, physical, and mineralogical characteristics of the rock formations. This information is then recorded to create either more drilling plans, reserve planning, or financial planning. This information is important for engineering, construction, and blasting holes for tunnels and quarries because it can be used to keep crews safe and prevent equipment from being damaged by avoiding weak spots in the rock or abnormalities that will affect the quality of work.

There are many things to consider when performing borehole surveys, though, including how the borehole deviates, as well as the surveying methods and technology used to survey the borehole.

Borehole Deviations

A borehole deviation is when the hole curves or spirals away from a straight line. Depending on the length of the borehole, the width of deviation will vary. It’s important to take deviations into account because the metrics taken from different apparatuses will change depending on how much the borehole has changed directions.

There are many factors to take into account for why deviations occur in boreholes, as deviations from one borehole to the next will not be the same. The main reasons a borehole will deviate are:

  • Rock type
  • Drill rig type and power
  • Drill rod type
  • Drilling technique

The amount a borehole deviates also depends on the length of the borehole as well. For short boreholes, like blast holes for quarries that are 10 to 25 meters long, the deviation can be several meters wide. The longer the borehole, the wider the deviation is likely to be, but some borehole deviations can be wider than normal. On average, boreholes that are 150 meters long can deviate 10 to 20 meters, but some deviate up to 50 meters. For extremely long boreholes, like 1000 meters or longer, it is not uncommon for deviations to be wider than 100 meters.

It’s important to take deviations into account when doing surveys to make sure blasts happen in the right place, underground utilities are installed correctly, and further drilling is done safely and effectively.

Use Accurate Borehole Survey Instruments

When surveying boreholes, it’s important to be able to measure the deviation of the borehole as well as the characteristics of the rock that’s been drilled into. To do this, you need to use equipment that delivers reliable results and is also sturdy enough to use in a variety of harsh environments.

When you purchase or rent instruments from Bore Path Services, you will be using some of the most cutting-edge technology for borehole surveying because you’ll receive results quickly that are accurate and reliable. The composition of the instruments are rugged and reliable as well, withstanding a variety of drilling conditions. If you know what tools you need, check out our products and reserve the ones you need. For more information on which borehole survey tools to use for different environments, check out Borehole Surveying, Part 2: Tools And Equipment.