Another drilling method we can consider using is sonic drilling. This is similar to conventional rotary drilling but with the addition of low frequency vibration which can significantly speed up the drilling process.

A sonic drilling method utilizes essentially conventional rotary drilling equipment. The biggest difference is in the drill head and power swivel, which is larger than a conventional rotary system and contains an oscillator mechanism. The hydraulic oscillator produces a low frequency vibration simultaneous with rotary and pull-down forces which are then directed onto the drill string. Combined, these forces enable improved drilling speeds through most types of soil, groundwater and rock. The frequency of vibration is dictated by the ground conditions encountered and ranges between 50-120 hertz. The frequency applied is varied throughout the drilling process as required.

The vibration causes liquefaction of the soil particles and micro-fracturing of the rock at the bit face. This enables significantly improved drilling rates, but also allows for the bore to be drilled in some cases without the need for drilling fluids, which is a major benefit when drilling through environmentally ‘sensitive’ soil and rock. Air, bentonite, synthetic polymers and water can also be used as flush mediums as with conventional rotary drilling techniques.

The drill string also acts as the casing, with the drill bit being mounted on the lead section. This can be a particular advantage when drilling in unstable ground compared to conventional methods. The collector pipe installation and back filling are also simplified using this approach.

The Econic team will advise on whether sonic drilling is appropriate for your project.