Innovation and Application of Cluster Edge Buttons of DTH Hammer Drill Bit in Large-Diameter Geothermal Well with High-Strength Rock

Abstract

Down-the-hole (DTH) hammer drilling has high rock-breaking efficiency and a decisive advantage in hard rock drilling, which can reduce the cost of geothermal drilling. However, when the drill bit rotation speed and the DTH percussion frequency do not match properly, especially when the drill bit diameter is large and the ball button diameter is small, while drilling a high-strength formation, the edge buttons of the drill bit are prone to fracture and break, leading to the failure of the drill bit and a significant reduction in its lifespan. This paper investigates the failure modes firstly, then analyzes the failure mechanism of the large-diameter DTH bit, and finally proposes a novel method of cluster edge buttons of the DTH hammer drill bit in a large-diameter geothermal well with high-strength rock. The drill bit has been tested in a high-compressive-strength formation, and we will continue to do more testing and research in various geological conditions. Field application shows that this technology significantly improves the bit life and drilling efficiency and reduces the drilling costs.

Keywords

• DTH hammer drill bit
• large-diameter geothermal well
• high-strength rock
• failure of edge bit buttons
• cluster edge bit buttons