UNDERSTANDING THE DIFFERENT DRILLING TECHNIQUES
Aquacore Boreholes has earned its positive reputation because we go out of our way to provide truly exceptional service to each of our customers. Successful borehole drilling depends on negotiating the geology of your site, with different soil structures and subterranean conditions requiring different techniques, ranging from mud rotary drilling or air percussion drilling to odex drilling. We will recommend the best drilling method for the best chance of success in your specific terrain. Given the specific geology of the Cape Peninsula, in many instances a single borehole may require all three techniques at different stages. Read on to learn more.
OUR DRILLING RIGS
Aquacore Boreholes uses Audie Spider XXL drilling rigs, because they are a great option for accessing Cape Town’s urban environment – at just over 3 tons, they are the lightest rig that can successfully drill up to depths of 200 metres. These South African-designed and -manufactured rigs are incredibly versatile and can be manoeuvred into confined areas.
They can even be lifted over walls provided we can get a crane truck close enough.
MUD ROTATION DRILLING
Mud rotation drilling is used in soft ground formations (sand and clay layers). Water and drilling chemicals are pumped down the hollow drill rod and vented through holes in the drill bit. The pressurised drill fluid is forced back to the surface, carrying the drill cuttings and at the same time maintaining hole stability. At the surface, the fluid is channelled into a mud pit where most of the cuttings settle out. The drilling fluid is then recirculated down the hole, and the process is repeated until the drilling is complete.
AIR PERCUSSION DRILLING
Air percussion is the technique required to penetrate rock and other hard formations. (Picture a very large pneumatic drill.) Pulverised rock cuttings are transported up the hole to the surface on a conveyor of extremely high-pressure air.
When we encounter a boulder field neither mud rotation nor percussion drilling will work. Imagine I gave you a box of marbles and asked you to drill and keep open a channel through the marbles. Clearly, you would not succeed – the marbles would move and tumble back into position once you withdrew your drill bit. Odex drilling provides the solution.
This technique uses a specialised drill bit and draws a hollow steel column down behind the bit as you penetrate. The steel column keeps the hole open and prevents the borehole from collapsing. This column remains in place permanently and is extended by welding on successive sections as required. This technique is slow, expensive and requires an experienced operator, however in certain circumstances it is your only option.