"With directional drilling, we choose a point where we enter the ground and then, using GPS and a gyro compass, drill a corridor at the desired depth and over a desired distance," says Richard van Doorn, projectmanager Drilling at Visser & Smit Hanab. "We emerge exactly at point B. We then widen the hole underground and pull a casing pipe through it. This way we can drill under any object up to a length of 2.5 km, depending on the surface and diameter."
Under the surface
That sounds simple, but there is a lot involved, explains engineering geologist Arthur ten Katen. "Before you dig into the ground, you want to know what you will encounter along the way. In the Netherlands you have three types of soil: sand, clay and peat. In the North you will encounter boulders, gravel can be a problem along the river courses, and on the coast you can you have to deal with salty groundwater, which affects the drilling fluid. And the grain distribution and grain shape also influence the drilling process. For a good design of the drilling, it is also important that you know the hardness of the soil type. In soft peat soil you will need a different bit than in hardened glacial clay. In short: before we go into the ground, we conduct thorough research using soil samples."
Working all over the world
The display cabinet in Arthur's office contains dozens of soil samples that provide a nice overview of the rocks through which we drilled. Not only from the Netherlands, but from all over the world. “Norway, Morocco, Greenland and Suriname: we carry out directional drilling all over the world,” he points out. "The most special country in terms of soil type so far is Cyprus. There we had to drill through the uplifted ocean floor. But our Dutch soil can also pose quite a few challenges. For example, clay can clump, causing the borehole to become clogged and the drill bit to become encapsulated in clay. This can lead to significant delays and therefore increasing costs. That is why I try to provide the best possible estimate in advance of the duration and complexity of the drilling work based on the soil research provided, supplemented with archives and geological maps, among other things."
“Especially now that we are increasingly conducting our drilling electrically, directional drilling is by far the most sustainable choice”
Working in the UK
One of the countries where Visser & Smit Hanab is currently carrying out directional drilling is the UK. "We are working on two projects where we are installing drinking water pipes and conduits for electrical cables in East England," says Richard van Doorn, project leader. "You come across all kinds of things in the English soil. At the same drilling location you can encounter rock, clay, lime and sand. That is why we work closely with Arthur, who provides us with tailor-made advice. All in all, a challenging job, which is very which requires specialist knowledge and equipment.
It is very busy at the English construction site where the pipes are going into the ground. Large steel sheet pile planks absorb the pushing and pulling forces associated with drilling. “Those forces amount to tens of tons,” Richard explains. "You want to prevent the rig from moving from its place. In addition, we need a lot of space for the necessary equipment. Supplying and moving equipment easily involves 10 to 15 loads. Once the hole has been drilled from A to B - the so-called pilot drilling - we connect a 'reamer' from point B, which widens the hole to the desired size. And finally, we use telescopic cranes to ensure that the pipes are already hanging in the correct arc radius, so that we can place them as quickly as possible. able to pull through the hole as smoothly as possible. This is truly a technical tour de force."