In mineral exploration and mining, it has always been a challenge to efficiently and environmentally complete drilling operations in complex and ever-changing geological conditions. Especially in arid, water-scarce areas with fractured formations and severe loss zones, traditional drilling tools often face issues such as low core recovery, borehole collapse, and poor cuttings removal, significantly impacting project efficiency and costs. In recent years, through-passage down-the-hole hammer reverse circulation drill bits have provided a new solution for drilling in complex formations due to their unique advantages. This article explores the working principle, technical features, and application benefits of drill bits in complex geological conditions.
Technical Background and Principle
In recent years, environmental pollution and damage caused by mining operations have become increasingly prominent. Conventional air drilling methods generate dust that pollutes the atmosphere and severely harms the health of workers. While diamond drilling avoids dust pollution, the heavy metals in the drilling slurry can leach into the ground, causing long-term harm to water sources and soil. Furthermore, drilling in complex formations is difficult, and conventional methods often fail to ensure drilling efficiency and core recovery.
The through-passage down-the-hole hammer reverse circulation drilling technology was developed in this context. This technology merges the efficiency of pneumatic down-the-hole hammers with the benefits of reverse circulation for effective cutting removal. Compressed air generated by the air compressor drives the down-the-hole hammer, and the broken rock and cuttings are continuously discharged to the surface via the center passage of the drill bit, achieving full-hole reverse circulation. This process reduces dust pollution at the borehole entrance and significantly improves drilling efficiency and core recovery.
Technical Features of Through-Passage Down-the-Hole Hammer Reverse Circulation Drill Bits
High Drilling Efficiency: The drilling efficiency of the through-passage down-the-hole hammer reverse circulation drill bit in hard rock formations is over five times greater than conventional diamond drilling methods. Its efficient rock-breaking capability is due to the transmission and release of stress wave energy, allowing the drill bit to break rocks quickly and enhance drilling speed.
Environmentally Friendly and Energy-Efficient: This technology uses compressed air as its power source, eliminating the need for slurry, which avoids groundwater and soil contamination. Additionally, the absence of dust at the borehole entrance significantly improves the construction environment and protects the health of workers and the surrounding ecosystem.
Strong Adaptability: The through-passage down-the-hole hammer reverse circulation drill bit performs well in complex formations prone to collapse, loss, falling blocks, and fractures. Its full-hole reverse circulation design effectively reduces the risk of borehole collapse and enhances borehole stability.
High Core Recovery: The continuous cuttings removal through the center passage of the reverse circulation drill bit ensures that the broken rock and cuttings are rapidly transported to the surface, guaranteeing high core recovery rates and providing accurate geological data for exploration.
Advantages of Through-Passage Down-the-Hole Hammer Reverse Circulation Drill Bits in Complex Formations
Solving Drilling Challenges: In complex formations with fractures, faults, and weak layers, the through-passage down-the-hole hammer reverse circulation drill bit, with its efficient drilling ability and good adaptability, can complete drilling operations and significantly increase the drilling success rate.
Cost Reduction: Compared with conventional diamond drilling methods, the through-passage down-the-hole hammer reverse circulation drilling technology does not require slurry for wall protection, simplifying the construction process and reducing material consumption and labor costs. Moreover, high drilling efficiency shortens the construction period, lowering overall costs.
Environmental Protection: The technology does not use slurry, preventing environmental contamination. With no dust pollution at the borehole entrance, it contributes to protecting the ecological environment of the construction area, in line with the development trend of green mining.
Enhanced Safety: The technology eliminates the need for slurry circulation, reducing the risk of slurry leakage and borehole collapse, thus enhancing construction safety. Furthermore, the clean borehole entrance with no dust is beneficial for safeguarding workers’ health.
Application Case
In a field trial at a mining site, the through-passage down-the-hole hammer reverse circulation drill bit demonstrated excellent performance. The geological conditions of this mining area are complicated, with the development of folds and fracture structures, rock joints and fissures, and poor stability of the hole wall, which makes the drilling operation extremely difficult. Traditional diamond core drilling methods often faced issues, like collapses and falling blocks, resulting in reduced drilling efficiency.
When the through-passage down-the-hole hammer reverse circulation drill bit was used, the situation improved significantly. The trial used the RC-400 air reverse circulation sampling drill rig and the XHP1070 screw-type air compressor to provide strong power support for the drill bit. Two new types of reverse circulation drill bits—double-row internal spray hole drill bits and spline internal spray hole drill bits—performed well in forming reverse circulation and rock-breaking drilling effects.
The trial results indicated that the average mechanical drilling speed for both types of drill bits reached approximately 10.59 meters per hour, which greatly exceeded the speeds achieved with traditional diamond drilling methods. Additionally, the borehole entrance remained clean and free of dust pollution, and the core recovery rate showed significant improvement. Notably, the double-row internal spray hole drill bit performed exceptionally well, with only minor wear on the buttons, while other parts remained intact without visible cracks. Although the spline internal spray hole drill bit also demonstrated high drilling efficiency, occasional breakage occurred, which may be related to the drill bit’s structural design.
Conclusion
Using through-passage down-the-hole hammer reverse circulation drill bits in complex formations offers significant advantages. This technology not only improves drilling efficiency and reduces energy consumption but also enhances adaptability in challenging geological conditions, including varying hardness, fragility, and water content. With ongoing technological advancements and developments in material science, the design of these drill bits will continue to improve, and their performance will become even more exceptional. They will provide more reliable and efficient technical support for geological exploration, infrastructure construction, and other fields, advancing related industries to new heights. In the future, the broad application prospects of this technology will bring more efficient, environmentally friendly, and safer drilling operations.
