Downhole Hammer and Casing Advancement

What It Is:

A Downhole Hammer is a percussive drilling tool powered by compressed air. It operates by striking a drill bit rapidly while rotating, delivering high-frequency blows that fracture hard rock.

How It Works:

• Compressed air drives a piston inside the hammer body.
• The piston strikes the bit while the bit is rotated by the drill string.
• The energy is delivered directly to the bit at the bottom of the hole, unlike top-driven systems.

Key Features:

• High penetration rate in hard rock
• Straight boreholes due to minimal deviation
• Used with tungsten-carbide or button bits
• Requires an air compressor and air lines

Casing Advancement Systems

What It Is:

Casing advancement systems are used to install casing simultaneously as the borehole is advanced. This prevents borehole collapse, especially in loose or unstable ground.

Typical System: ODEX, Symmetrix, or Ring Bit Systems

How It Works:

• The drill bit drills a larger diameter hole than the casing.
• A ring bit or eccentric reamer cuts the oversized hole.
• The casing is advanced along with the bit using the DTH hammer’s energy.
• Once target depth is reached:
  • The drilling tool is removed.
  • The casing remains in place.
  • Optionally, drilling can continue inside the casing using a smaller bit.

Combined Operation: DTH with Casing Advancement

Application Steps:

1. Drill setup with DTH hammer, casing shoe, and casing.
2. Simultaneous drilling and casing insertion down to the desired depth.
3. Casing is left in place to stabilize the borehole.
4. Continue drilling with smaller tools through the casing into bedrock if needed.

When to Use:

• Overburden or boulder zones
• Unconsolidated ground (sands, gravels, tills)
• Groundwater-sensitive areas
• Pre-drilling for foundation piles, tiebacks, and anchoring

Summary

• Downhole Hammer delivers high-impact energy at the bit, ideal for drilling into hard rock.
• Casing Advancement Systems allow casing to be inserted as drilling progresses, stabilizing loose formations.
• Combined, they are highly effective for drilling in difficult, mixed, or unstable geology, particularly when borehole integrity and rapid advancement are critical.