22 MAY 2023 WorldWide Drilling Resource® Sonic Drilling is the Way Adapted from Information by Royal Eijkelkamp Sonic drilling is a technique that significantly reduces friction on the drill string and drill bit by using high-frequency vibration (resonance) to affect the soil structure where it contacts the drill string to advance the string and bit where surrounding particles are either liquified (in loose materials) or fractured (in hard rock). This combination makes penetrating a large range of soils much easier. It is most often used when drilling is difficult and the integrity of the core sample is extremely important. Rotation can also be added when drilling in harder geologic formations. The resonant energy is generated inside the sonic head with two counter-rotating weights called eccentrics. One turns clockwise, and one turns counterclockwise, with both weights moving up to 9000 revolutions per minute. Resonant frequencies are audible, and the drill operator controls the energy generated by the sonic head’s eccentrics to match the formation being encountered to achieve maximum drilling productivity. The high-frequency, low-amplitude mechanical vibration is combined with rotation and downpressure. When the resonant sonic energy coincides with the natural frequency of the drill string, resonance occurs. The core barrel is advanced using sonic frequencies. This causes the maximum amount of energy to be delivered to the face of the drill bit. This step can typically be performed using no fluids, air, or mud. As the sonic energy is increased, resonance occurs with the formation adjacent to the drill string, reducing sidewall friction and increasing the amount of energy placed at the face of the bit. At the same time, the friction of the soil immediately adjacent to the entire drill string is substantially minimized, resulting in faster penetration rates. Borehole advancement accelerates as a result of shearing and displacement. The high frequency eases retrieval of the drill string, even in quick-expanding clays, boulders, and difficult conditions. Once the sample is contained in the core barrel, the casing is sonically advanced over the core barrel, protecting the borehole against cave-in in softer formations. The core barrel is then retrieved, producing a relatively undisturbed sample with near 100% core recovery. These steps are repeated to depth, producing a continuous core sample even through unconsolidated formations. Whether you’re performing environmental exploration, geotechnical sampling/testing, water well development, observation well construction, mineral exploration/sampling, dewatering, groundwater exploration, remediation, or even seismic drilling, the sonic method can be a fast, clean, safe, and accurate way to get the job done. ENV
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