RC Drilling Introduction

Summary

This video provides an overview of how reverse circulation (RC) drill rigs work in mineral exploration. RC drilling uses a pneumatic hammer driven by compressed air to break rock and bring samples to the surface. The method ensures sample integrity by preventing contamination through reverse circulation. RC drilling is cost-effective for shallow exploration and provides accurate samples, especially in irregularly distributed deposits like gold. However, it is limited to depths of 250-400 meters, beyond which diamond drilling is used. The video also explains the sample collection process and orientation tools for hole accuracy.

Takeaways

• 😀 RC drills are a type of percussion drill, similar to a jackhammer, using compressed air to drive a pneumatic hammer for breaking rock.
• 😀 Compressed air is pumped through drill rods to power the hammer and clear rock debris from the hole.
• 😀 The method is known as reverse circulation (RC) because the airflow goes in the opposite direction, ensuring the sample stays uncontaminated.
• 😀 The air and rock debris are sent up the center tube of the dual-walled drill rods to return to the surface.
• 😀 The RC drill bit uses tungsten carbide buttons to break the rock into chips, which are then carried by the airflow.
• 😀 The rock chips are funneled into a cyclone where centrifugal force separates the samples by size.
• 😀 The cyclone’s splitter cuts a small, two-kilogram sample for assay, while the rest is kept for other analysis.
• 😀 The orientation of the drill hole is monitored with an orientation tool that measures dip and azimuth at regular intervals.
• 😀 RC drilling is cost-effective and efficient for early-stage mineral exploration and resource definition, especially for near-surface deposits.
• 😀 The main limitation of RC drilling is depth, with most rigs struggling beyond 250-400 meters, at which point diamond drilling is preferred.
• 😀 Pre-collar drilling combines RC for the first 200-300 meters to reduce cost, followed by diamond drilling to complete deeper holes.

Q & A

What is the basic principle behind RC drilling?

RC drilling is a type of percussion drilling where a pneumatic hammer, driven by compressed air, breaks away pieces of rock. The air flows in reverse direction to carry rock chips back to the surface, ensuring samples are not contaminated.

How does a percussion drill, such as an RC drill, operate?

A percussion drill uses a pneumatic hammer attached to a string of drill rods. Compressed air drives the hammer, which breaks the rock, while air and rock chips return to the surface through the center of the drill rods.

What is the function of the external compressor in RC drilling?

The external compressor supplies compressed air to the drill rig, which powers the pneumatic hammer and also helps clear broken rock from the hole, as well as cool the bit.

What distinguishes open hole percussion drilling from reverse circulation (RC) drilling?

In open hole percussion drilling, air and broken rock return to the surface outside the drill rods, potentially contaminating the sample. In RC drilling, compressed air flows in reverse through the dual walls of the drill rods, preventing contamination of the sample by keeping the rock chips separate from water and debris.

Why is reverse circulation (RC) used in drilling over open hole percussion?

RC drilling prevents contamination of the sample by keeping broken rock chips separate from potential contaminants like water or debris from the hole walls. It is also more efficient and provides cleaner samples for analysis.

What is the role of the cyclone in the RC drilling process?

The cyclone separates the rock chips from the air. It uses centrifugal force to push rock chips to the walls, allowing air and fine dust to exit through the top, while the rock chips fall to the bottom to be sampled.

How are samples collected and analyzed in RC drilling?

Samples are collected by a splitter at the bottom of the cyclone, which cuts the rock chips into a smaller sample for assay and a larger one for other analyses. The splitter ensures that the samples are consistent, even if the rock bits are larger.

What is the purpose of the orientation tool in RC drilling?

The orientation tool is used to measure the dip and azimuth of the hole. It ensures that the exact position of each sample is known in 3D, which is crucial for accurate data collection in resource evaluation.

What are the main limitations of RC drilling?

RC drilling is limited in depth. It is effective up to around 250 to 400 meters, but beyond that, it becomes difficult to lift the column of air and rock chips. Deeper holes generally require diamond drilling.

How does RC drilling contribute to early-stage mineral exploration?

RC drilling is commonly used in early-stage exploration because it is fast, cost-effective, and provides large-diameter samples that are crucial for accurate resource definition, especially in erratic gold deposits.