How to Solve the Bit Jamming Caused by Poor Cuttings Removal in Deep-Hole Drilling with DTH Hammers?
2025.03.06Shandike eason
Here is a detailed solution addressing the issue of bit jamming due to inefficient cuttings removal in deep-hole drilling operations, covering equipment design, operational parameters, geological adaptability, and maintenance practices:
I. Optimization of Cuttings Removal System Design
- Ensure Adequate Air Pressure and Volume
- Air Compressor Matching: Select compressors with sufficient air volume (≥12–25 m³/min) and pressure (1.0–2.5 MPa) based on hole diameter and depth. Use multiple compressors in parallel for deep holes.
- Pipeline Sealing: Inspect drill rod joints and pipelines for leaks. Enhance sealing with O-rings or sealants.
- Air Distribution: Use dual-wall drill rods (specific to DTH hammers), where the inner pipe delivers high-pressure air and the annular space between pipes evacuates cuttings, improving debris transport efficiency.
- Improve Bit Cuttings Channel Design
- Enlarge Cuttings Channels: Select bits with wide, deep flutes (e.g., parabolic or spiral designs) to prevent debris accumulation.
- Optimized Carbide Button Layout: Adopt staggered or stepped button arrangements to minimize fine powder from repeated rock crushing.
- Central Jet Design: Install high-pressure air nozzles at the bit center to directly blast debris at the hole bottom, preventing blockages.
II. Adjustment of Operational Parameters
- Rotation Speed and Thrust Pressure Control
- Low-RPM Strategy: Reduce rotation speed (e.g., 20–40 RPM) in hard rock to avoid fine powder cohesion; increase speed moderately in soft formations.
- Thrust Pressure Matching: Dynamically adjust thrust via hydraulic systems to prevent overloading and blockage of cuttings channels.
- Intermittent Rod Lifting for Cuttings Clearing
- Lift the drill rod 10–20 cm every 0.5–1 m of penetration to allow high-pressure air to thoroughly flush the hole bottom, avoiding excessive debris buildup.
III. Geological Adaptability Measures
- Handling Complex Formations
- Water-Bearing/Clayey Layers: Inject foaming agents or polymers to reduce cuttings viscosity and enhance air transport efficiency.
- Fractured Zones: Use low air pressure (to prevent collapse) with frequent short-stroke rod lifting (e.g., every 0.3 m).
- Hole Opening Management
- Install dust collectors or cyclone separators at the hole mouth to promptly remove discharged debris and prevent re-entry blockages.
IV. Auxiliary Technologies
- Foam/Mist Water Injection
- Inject misted water or foam agents (1%–3% concentration) through drill rods to moisten cuttings, reducing dust and increasing debris weight for easier removal.
- Vibration-Assisted Cuttings Removal
- Install high-frequency vibrators (50–100 Hz) at the top of drill rods to loosen adhered debris on hole walls and promote evacuation.
V. Maintenance and Monitoring
- Bit Wear Management
- Regularly inspect carbide button wear (replace if worn beyond 1/3 of height) and repair/replace bits with deformed cuttings channels.
- Real-Time Monitoring Systems
- Equip with air pressure sensors and depth counters. Trigger alarms and auto-lift prompts when pressure spikes (>10% above set value) or penetration rates drop abruptly.
- Preventive Maintenance
- Clean drill rod interiors after each shift, and test compressor efficiency monthly to ensure unobstructed airflow.
VI. Emergency Response Protocols
- Initial Jamming: Stop drilling immediately, reverse rotation, slowly lift the rod, and increase airflow for flushing.
- Severe Jamming: Inject lubricating slurry (e.g., diesel + bentonite mixture), soak for 1–2 hours, then attempt vibration-assisted extraction.
Summary
By optimizing equipment design, refining operational parameters, adapting to geological conditions, and strengthening maintenance monitoring, systemic solutions can address cuttings removal inefficiencies. Practical applications require flexible adjustments based on hole depth (>20 m demands higher pressure), rock type (granite, shale, etc.), and combined technical approaches to minimize jamming risks and improve drilling efficiency by over 30%.
