PDC drill bits are made of polycrystalline diamond cutting blocks, and a certain number of cutting blocks are then embedded (or sintered) onto the drill body.
The cutting block is composed of a thin layer of artificial polycrystalline diamond (about 0.6-2.5mm) and a bottom layer of tungsten carbide sintered into a whole, forming a flat cylindrical shape, and is called polycrystalline diamond composite sheet (referred to as composite sheet). Weld the composite sheet and cylindrical body together to form a cutting element.
The structure of PDC drill bits is divided into two series based on different materials and manufacturing processes: steel body and matrix body.
Parabolic type: It has a larger drill surface and can be fitted with more cutting blocks to improve the wear resistance and footage of the drill. Its shape can concentrate the lateral thrust towards the center, reduce the deviation of wellbore direction, and is conducive to overcoming wellbore deviation.
Double cone type: It has an inner cone and an outer cone, which can maintain the stability of the drill bit. The outer cone surface is longer and can be embedded with more cutting blocks. When drilling hard interlayer or hard formation, the top cutting block is easily damaged under impact.
Short cone: It is beneficial for drilling through hard interlayers, and the surface area of the drill bit is small, so the hydraulic power is relatively concentrated and the cleaning is better.
Rock breaking mechanism of PDC drill bits
The PDC drill bit cutting block is used to break rocks by scraping and shearing. The self sharpening cutting block can cut into the formation under the action of drilling pressure, and then move forward to shear the rock under the action of torque. Fully utilize the low shear strength of rocks. When PDC drill bits break rock, there is no repeated cutting caused by the "pressure difference" caused by the cone bit teeth, similar to the pressure difference when breaking rock.
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