Drilling in sands for Rio Tinto

Sonic drilling for Rio Tinto ’s Richards Bay Minerals sands project at the RBM site near Richards Bay. 

Geomech Africa uses the SDC 450-24 sonic drill rig from Canada to drill the required deep boreholes in mineral sands.

Why a sonic rig? Sonic drilling is most suited to softer ground formations and it is the high frequency vibrations generated in the sonic head of the drill rig, which cause the liquefaction of the ground at the drill bit and facilitate good core recoveries in ground in which conventional drilling would not succeed. Experience has taught that the required depths could not be reached in top sand dune areas using traditional sonic drilling methods. A new approach had to be investigated. There is currently no “wireline system” available on the market suitable to sandy conditions which enables the user to quickly retrieve the inner tube of the core barrel without the need to remove the rods from the ground. The sonic drilling under these conditions is therefore managed in a more conventional drilling method requiring the rods and core barrel to be removed from the borehole each time the core barrel is filled with sample. Sample quality has always been a top priority, and delivery of high recovery has been successfully achieved.

In spite of this, more time-consuming approach, Geomech Africa and its local partners have been successful in sustaining the drilling techniques suitable for successfully drilling these challenging mineral sands and is currently completing the initial two-year contract.