The core bit is used to break the rock at the bottom of the hole with the annular structure to drill the core.The size of core harvest rate and the speed of drilling are all related to the quality and selection of bit.The structure design of the coring bit should be conducive to improving the core yield, the drill bit drilling should be stable, so as to avoid vibration, damage to the core, the edge of the bit and the hole center should be concentric, the position of the bit water hole should not direct jet to the core and reduce turbulence erosion of the core.The cavity of the drill bit should allow the core claw to be as close as possible to the core inlet, so that the core can be protected by entering the core barrel through the claw soon after formation, and the core can be cut as close as possible to the core root, reducing residual core at the bottom of the hole.
Coring bits commonly used in well drilling are classified into steel coring bits, drag coring bits and diamond coring bits, etc.
1. Steel coring bit
The steel coring bit crushes the rock by grinding, which is one of the most commonly used drill bit forms in the construction of water well drilling rig, and is also the most commonly used drilling method in the construction of water well at present, which is often used in the construction of large diameter pipe well.
2. Scraper coring bit
The scraper core bit is cut to break the rock, it is the same as the full drilling scraper bit, the edge is set with cemented carbide, the scraper blade is evenly distributed on the annular area of a concentric circle symmetrically, the drill bit is made into a ladder shape to improve the drilling efficiency of the well drill.
3. Diamond coring bit
Diamond coring bits have various structures and are suitable for a wide range of strata, including natural diamond coring bits, artificial diamond coring bits and polycrystalline composite coring bits.
