Borehole Drilling

Borehole drilling is carried out using different techniques depending on the geological conditions identified during a hydrogeological survey. The two most commonly used methods are mud rotary drilling and air (DTH) drilling. The selection of the drilling method is guided by hydrogeological survey results to ensure efficiency, safety, and successful water yield.

Mud rotary drilling uses a circulating drilling fluid, commonly known as drilling mud, to support the borehole during excavation. The mud is pumped down the drill string and returns to the surface carrying rock cuttings.

This method is mainly applied in soft to medium formations such as clay, sand, and loose alluvial soils where borehole walls are prone to collapse. It is also suitable for shallow to moderately deep boreholes because the drilling fluid helps stabilize the formation and ensures smooth removal of cuttings.

Air drilling, also known as Down-The-Hole (DTH) hammer drilling, uses compressed air to power a hammer located at the bottom of the drill string. The hammer breaks hard rock formations while the air lifts cuttings to the surface.

This method is best suited for hard rock terrains such as granite, basalt, and gneiss, as well as fractured rock aquifers where groundwater is stored in cracks and joints. Air drilling is particularly effective for deeper boreholes and offers fast penetration rates in consolidated formations.

In summary, mud rotary drilling is ideal for soft and unstable ground conditions, while air (DTH) drilling is more appropriate for hard rock environments. The selection of the drilling method is guided by hydrogeological survey results to ensure efficiency, safety, and successful water yield.