PDC bit is the abbreviation of Polycrystalline diamond compact bit, also known as Polycrystalline diamond cutting block bit or composite chip bit. Because of its advantages of fast drilling speed, long service life and high footage PDC bit is widely used in oil drilling.
PDC bit is composed of bit body, PDC cutting teeth and nozzle. According to different structure and manufacturing process, PDC bit is divided into two series: steel body and matrix body.
The whole bit body of rigid PDC bit is made of medium carbon steel and formed by machine manufacturing process. Drill holes on the working face of the bit, and fix PDC cutting teeth on the bit crown by pressing in and tight fitting. The crown of a drill bit is treated by surface hardening process (spraying tungsten carbide wear-resistant layer, carburizing, etc.) to enhance its erosion resistance. The main advantage of this kind of bit is simple manufacturing process, but the disadvantage is that the bit body is not erosion resistant and the cutting teeth are difficult to be fixed, so it is seldom used at present.
The upper part of PDC bit is made of steel and the lower part is made of WC wear-resistant alloy. The PDC bit is made by powder metallurgy sintering process. The PDC cutting teeth are welded on the preformed groove of the carcass with low-temperature solder. Tungsten carbide matrix has high hardness and erosion resistance, so the matrix PDC bit has long service life and high footage, which is widely used at present.
PDC bit breaks rocks by cutting. The self-sharpening cutting teeth can easily cut into the formation under the action of WOB and move the shear rock forward under the action of torque. Many PDC cutting teeth work at the same time, there are many free faces of the bottom rock, and the rock is easy to be broken under the shear action, so the rock breaking efficiency is high and the drilling speed is fast.
PDC bit has the best effect in large homogeneous soft to medium-hard formation. It is not suitable for drilling gravel layer and soft hard cross formation.
Drilling with low WOB, high rotation speed and large displacement has a good effect.
Before the bit is put into the well, the bottom of the well shall be clean to ensure no metal falling.
When the bit is just put into the well, it should adopt small bit pressure and low rotation speed to run and resume normal drilling after the bottom of the well is formed.
PDC bit is an integral bit, without any moving parts, suitable for high-speed turbo drilling.