We qualify sonic drilling as an advanced form of drilling. It employs the use of the resonant energy produced inside the sonic head. This should help a lot in advancing a casing or core barrel into whatever subsurface formations you are trying to drill into. While drilling, the resonant energy will be relayed to the drill string to the bit face in different sonic frequencies. While the drill is rotating simultaneously, the energy, together with the impact at the bit, is evenly distributed by the drill.
The sonic head comes with two counter-rotating weights and it is responsible for creating resonant energy. There is a pneumatic isolation system happening inside the sonic head and this will keep the resonant energy from being relayed to the drill rig, directing the said energy down to the drill string.
The resonant energy produced by the oscillator in the sonic head is controlled by the driller so that it can match any kind of surface formation it is encountering, helping it in the process to achieve its maximum drilling productivity. The moment that the resonant sonic energy conforms with the drill string’s natural frequency, resonance is likely to happen. This will eventually pave the way for delivering the maximum amount of energy to the face. At the same time, it also minimizes the soil friction that is adjacent to the drill string, making way for penetration rates to go faster.
Procedure for Sonic Drilling
There are several ways in which sonic technology can be used for drilling, and this may have to depend upon your project objectives and site-specific conditions. The most prevalent of which will involve advancing a core barrel. Often, a larger diameter drill overrides the drill string, encasing the open borehole. This should help in keeping it from collapsing.
STEP 1: Core Barrel Advancement
By employing sonic frequencies, the core barrel is advanced. Depending on the situation, the part of the process can be carried out even in the absence of air, fluids or mud.
STEP 2: Casing override
Soon after you set the core barrel in place, the casing can be advanced sonically over the barrel core. This helps protect the integrity of the borehole in the loose and unconsolidated ground.
STEP 3: Core retrieval
Upon retrieving the core barrel, what it is capable of producing is a relatively undisturbed sample. It would always be close to 100% core recovery.
STEP 4 – Repeat core advancement
You can repeat steps 1 through 3 to depth, and this can be anticipated to produce a continuous core sample by unconsolidated formations with 1% deviation or even less.
It may appear to most of us that the working principle behind sonic is very much complicated, but the truth of the matter is, it is very simple to operate. If you are going to work as the driller, you will only have to add vibratory energy to its rotary motion. You will need to select a frequency that you know will give you the best drilling rate, or a better core recovery, as the case may be.