Unveiling Rock-Breaking Tools: How PDC Drill Bits Conquer Complex Formations?

In the extraction of mineral resources such as coal, oil, and natural gas, as well as various geotechnical engineering projects, rock-breaking drill bits, as an important rock-breaking tool, are widely used. With the continuous growth of energy demand and the gradual depletion of shallow mineral resources, drilling and extraction activities have gradually shifted toward deeper, more complex, and harder-to-drill formations. This shift places higher demands on the performance of rock-breaking drill bits.

According to the classification of cutting tooth materials, rock-breaking drill bits mainly fall into two categories: carbide bits and PDC (Polycrystalline Diamond Compact) drill bits. Carbide bits have played an important role in past extractions, but with the increasing difficulty of extraction, their performance gradually fails to meet the needs. In contrast, PDC Drill Bits stand out with their excellent rock-breaking capabilities, and their market size has been increasing year by year.

PDC Drill Bits and Their Working Principle

PDC Drill Bits are mainly composed of the bit body, cutting teeth (PDC inserts), hydraulic structure, gauge surface, and connector. The cutting teeth are the core of PDC Drill Bits, made of PDC inserts. PDC inserts are a new type of composite super-hard material that is sintered from diamond micropowder, a binder, and a carbide substrate under high temperature and ultra-high pressure conditions, possessing extremely high hardness and good toughness. 

During the drilling process, the PDC drill bit uses the torque applied by the drilling machine to make the cutting edges of the teeth cut into the formation. Due to the high hardness and toughness of the PDC inserts, PDC Drill Bits can easily cut into the rock and maintain sharp cutting edges over long periods of rock-breaking operations, continuously and efficiently working. Depending on the manufacturing process and materials, PDC Drill Bits can be divided into matrix body and steel body types. Matrix body bits are sintered from tungsten carbide powder, offering high rigidity and hardness, less prone to damage, and better gauge retention, though the manufacturing process is relatively complex. Steel body bits are made from medium to low carbon alloy steel through machining, ensuring processing quality, but the strength and durability of the bit are generally lower.

Rock-Breaking Mechanism of PDC Drill Bits

The rock-breaking mechanism of PDC Drill Bits primarily includes the following forms:

Cutting action

Mainly occurs in softer formations. The cutting teeth of the PDC drill bit penetrate the formation under drilling pressure, producing shear force on the formation as the bit rotates, thus cutting the formation and forming rock debris.

Fracturing action

Mainly occurs in brittle rock formations and is unique to PDC Drill Bits with alternating configurations of pointed and round teeth. Pointed teeth create stress fractures in the formation upon contact, followed by round teeth cutting the already stressed formation, thereby improving rock-breaking efficiency.

Plowing action

When the round teeth of the PDC drill bit cut the rock, drilling pressure causes the round cutting teeth to form cracks within the rock, which expand as the teeth penetrate further, ultimately causing the rock to break.

Abrasion action

Predominantly occurs in high-hardness, high-abrasiveness formations. Due to the high density and difficulty of breaking the formation rock, the cutting teeth of the PDC drill bit repeatedly cut the formation under drilling pressure, grinding it into fine particulate debris. However, this method accelerates the wear of cutting teeth.

Impact crushing action

Mainly reflected in PDC composite bits. During drilling, the rotation and revolution of the roller bit produce vibrations, and the uneven formation rock at the bottom of the well also generates vibrations, causing the bit's cutting teeth to crush the rock under the combined action of drilling pressure and vibration. This mechanism offers higher drilling efficiency and longer service life compared to ordinary PDC Drill Bits.