reversecirculationborrning
Reverse circulation drilling, or reverse circulation boring, is a drilling method used mainly in mineral exploration to obtain continuous rock samples quickly and with minimal downhole contamination. In this system, compressed air is pumped down the center of the drill string to the bit. The cuttings produced at the bit are carried up the outside of the drill string through the annulus between the drill pipe and the borehole wall and are directed to a surface sampling system, such as a cyclone or sample barrel. The sample is therefore collected in a line separate from the air path, enabling relatively continuous, representative recovery of material.
The technique typically uses a hollow drill pipe with an air line inside the string. The returned
Advantages include faster sample turnover, cleaner and more representative cuttings, and reduced reliance on drilling fluids,
Limitations include less suitable sampling for fine-grained or clay-rich intervals, potential sample contamination at the surface