Reverse Circulation Drilling (RC)

Reverse circulation drilling is a drilling technique commonly used in the mining, exploration, and water well drilling industries. It involves the use of drilling rig that uses compressed air to drive a rotating drill bit down into the ground.

In Reverse Circulation drilling, the drill string consists of a drill pipe and a dual-walled drill rod assembly. The drill bit is attached to the bottom of the drill string, and the compressed air is pumped down the annular space between the drill pipe and the dual-walled drill rods. Compressed air flows through the drill bit and enters the hole, carrying the cuttings and rock fragments (or samples) back up to the surface through the innertube of the drilling string.

The cuttings and samples then move through a specially designed Reverse Circulation head-motor onto the diffuser and are collected in a sample cyclone at the surface, where they are separated and collected for further analysis. The clean air is then discharged or recycled, depending on the specific drilling operation.

Reverse Circulation drilling is known for its ability to quickly and efficiently drill through various types of rock formations, including hard and abrasive materials. It is often used for mineral exploration, mine dump exploration and resource delineation, as well as for geotechnical investigations and well drilling.

Some advantages of RC drilling include:

Fast drilling rates

Reverse Circulation drilling can achieve higher drilling rates compared to other drilling methods, reducing the time required for project completion.


The compressed air used in Reverse Circulation drilling is typically cheaper than core drilling or other methods, resulting in cost savings.

Sample recovery

Reverse Circulation drilling provides high sample recovery rates, making it suitable for obtaining accurate geological and mineralogical information as it provides an uncontaminated sample and can be recorded at exact depths.

Minimal environmental impact

The use of air as the drilling fluid reduces the potential for contamination of groundwater or surface water.

However, Reverse Circulation drilling has some limitations, such as limited drilling depth and reduced ability to obtain consolidated samples. Therefore, the choice between RC drilling and other drilling methods depends on the specific objectives of the drilling project.