Since the introduction of PDC cutting blocks by General Electric Company in 1973 and the development of the first PDC bit, the PDC bit has been widely used in oil drilling due to its advantages of fast drilling speed, long life and high footage.
The PDC bit consists of the bit body, PDC cutters, and nozzles.
According to the difference in structure and manufacturing process, it is divided into two series: steel body and carcass.
The entire drill body of the rigid body PDC drill is made of medium carbon steel and formed by a mechanical manufacturing process. Drill holes on the drill face and secure the PDC cutters to the drill crown with a press fit.
The crown of the drill bit is treated with a surface hardening process (spraying tungsten carbide wear-resistant layer, carburizing, etc.) to enhance its erosion resistance. The main advantage of this drill is that the manufacturing process is simple; the disadvantage is that the body of the drill is not resistant to erosion, and the cutting teeth are difficult to fasten, so it is rarely used at present.
The upper part of the drill body of the matrix PDC bit is a steel body, and the lower part is a tungsten carbide wear-resistant alloy matrix, which is manufactured by a powder metallurgy sintering process.
The PDC cutting teeth are welded to the reserved grooves of the carcass with low-temperature solder. Tungsten carbide carcass has high hardness and erosion resistance, so the carcass PDC bit has a long service life and high footage and is currently widely used.
2) The working principle of PDC bit
PDC bits break rock by cutting.
The self-sharpening cutting teeth can easily cut into the formation under the action of WOB and move forward to shear the rock under the action of torque.
With multiple PDC cutters working at the same time, there are many free surfaces in the bottom hole rock, and the rock is easily broken under shearing action, so the rock-breaking efficiency is high and the drilling speed is fast.
3) Correct use of PDC drill bits
●PDC bits work best in large sections of homogeneous soft to medium hard formations.
Not suitable for drilling gravel layer and soft and hard interlaced formation.
●It adopts low drilling pressure, high speed, and large displacement for drilling, and the drill bit has a good effect.
●Before the drill bit goes into the well, the bottom of the well should be cleaned to ensure that there are no metal falling objects.
●When the drill bit just goes into the well, it is necessary to use a small WOB and low rotational speed to run in harmony, and resume normal drilling after the bottom hole is formed.
●PDC drill bits are integral drill bits without any moving parts and are suitable for high-speed turbine drilling.
