Choosing the right drilling rig
A drilling rig is a type of construction equipment used to make holes in the earth’s surface. They can vary considerably in size: they can be massive structures or light enough to be moved manually by a single person.
Drilling rigs can take samples from mineral deposits as well as test the physical properties of rocks, soil and groundwater. They can also be used for underground installations: tunnels, shafts or pipes.View drilling rigs
How to choose a drilling rig?
You could need a drilling rig for a multitude of applications, for example to drill a well to access a natural resource (water, oil, geothermal energy, etc.), to build foundations, to make blasting holes in a mine, to take samples from the ground, etc.
It is necessary to determine what the drilling rig will be used for, as well as what kind of terrain it will mainly be operating on. Depending on the terrain, you can choose between different types of drilling rigs: rotary drilling rigs, percussion drilling rigs, down-the-hole drilling rigs, top hammer drilling rigs (with high hammer), etc.
In order to make the best choice, it is important to determine whether the drilling rig will be used for your core business or for occasional operations, and in particular whether you want to take advantage of the latest innovations or whether a machine that has proven its worth over several decades might be suitable for you.
Safety, reliability and ease of use are also important elements to consider and are directly linked to each other. A machine that’s reliable and easy to operate, when used according to the manufacturer’s recommendations, increases user safety.
It is also important to define the type of mobility you will need. There are autonomous crawler drilling rigs and truck-mounted or trailer-mounted drilling rigs that need to be powered by a generator or the truck that carries them.
Once you have determined the type of machine you need, you can calculate the size required according to the diameter and depth of the borehole.
When is drilling necessary?
Many jobs require drilling, for example:
- Drilling wells: whether it’s to access groundwater or oil.
- Geothermal drilling: to access and extract the earth’s heat.
- Pile drilling to support a building on unstable ground: up to 2,000 millimeters in diameter and 70 meters deep.
- Micropile drilling, in particular for the reinforcement of existing structures: between 150 and 200 mm in diameter and up to 30 meters deep.
- Blast hole drilling for quarries.
- Continuous flight augering maintains the walls of the borehole with the drill cuttings that are driven by the auger.
Drilling is most often done vertically, but it can also be horizontal or directional, for example for the placement of anchors.
Some types of drilling:
- Well drilling
- Geothermal drilling
- Pile drilling
- Micropile drilling
- Blast hole drilling
- Continuous flight augering
What drilling technology should you choose?
|Drilling type||Soil type||Comments|
|Rotary drilling||Soft rock||Significant depths up to 5,000 meters
Possibility of inclined or horizontal drilling
|Down-the-hole drilling||Hard and cracked rock (limestone, granite, etc.)||Depth up to 4,000 meters|
|Top hammer drilling||Consolidated land||Small diameter (150 mm maximum), shallow depth
Able to do inclined drilling
|Auger drilling||Clay, clayey sand, gravel||Depth of a few dozen meters|
|Core drilling||All soil types||Drilling for soil analysis
Able to do inclined drilling
|Percussion drilling||Hard rock: sandstone, limestone, shale||Depth up to 100 meters|
|Pipe Jacking||Clay, clayey sand, gravel||Installation of horizontal or vertical pipes|
Rotary drilling: This type of drilling digs a hole by grinding the rock with a tool under the effect of weight and rotation. It is mainly used in oil production. The cuttings are brought to the surface under the pressure of a drilling fluid that is injected into the drill string. Drilling fluid also helps consolidate the walls of the borehole, so it is not necessary to case it as the operation progresses.
Down-the-hole drilling (rotary percussion drilling or rotary hammer drilling): this type of drilling uses drilling rigs that drill with a rotary cutter (drill head) and hammer the bottom of the hole with a pneumatic hammer. The excavated material rises to the surface under the pressure of the compressed air used for the hammer. These drilling rigs are powerful and have high drilling rates, especially in rock. For artesian wells (wells where water naturally rises to the surface under groundwater pressure) or geothermal drilling, an air injection at the end of the drill pipe pushes the water up the borehole, allowing the operator to immediately determine the water flow encountered. This type of drilling is used for hard and cracked ground up to 4,000 meters deep. When the drilling bit is eccentric, the drilling can be done with a casing advancement system (installation of tubes by gravity) which reinforces the hole as the drilling progresses.
Top hammer drilling: this type of drilling uses drilling rigs that also operate on a percussion system, but one that remains outside the borehole. They are mainly used for small diameter drilling, for example for mineral exploration or the installation of tie rods in rock. This system is used for shallow boreholes, as there can be significant deviation due to the structure of the ground drilled through. These drilling rigs can operate in any direction however.
Auger boring: This is a type of rotary drilling using a worm screw (the auger). This type of drilling is mainly used for unconsolidated clay or sand terrain. The excavated material is directly brought to the surface by the worm screw. For deep drilling, it may be necessary to regularly raise the auger to empty it of its excavated material.
Core drilling: Core drilling is similar to rotary drilling, but it uses a crown to extract a sample, called a core, inside the tool.
Percussion drilling: consists in breaking the rock by dropping a tool, the drill bit, by gravity. This type of drilling can only be used vertically. To prevent the borehole from collapsing, it is necessary to case it as it is drilled. The cuttings are reassembled as soon as they interfere with drilling by replacing the drill bit with a flap valve bailer. The flap valve bailer is a type of tube equipped with a tilting flap in the lower part. This tilting flap allows the tube to be filled with excavated material which is then transported to the surface.
Pipe jacking: is mainly used to install horizontal pipes. The tube is pushed progressively by percussion, the excavated material being removed at the end of the drilling operation either by water injection or with an auger. This technique is used in particular to avoid transmitting vibrations to the surrounding buildings or to avoid digging a trench.
What type of drilling rig should you choose?
There are two main types of drilling rigs: autonomous crawlers and truck or trailer-mounted.
- You will need to choose a crawler if it needs to move at a low speed over unlevel areas or on very loose ground. The stability of the drilling rig depends on the surface area of the tracks. As such, the wider the tracks, the more stable the drilling rig will be. However, wide tracks will tend to wear out more quickly and break down the ground when moving, especially when turning. The travel speed of a crawler drilling rig is about 4 km/h. They are therefore better adapted for work that requires little travel.