July 29, 2021
1) PDC bit, flat polycrystalline diamond bit and surface mounted bit are generally used for soft, medium hard and complete homogeneous rocks.
2) Impregnated bits are generally used for hard, hard, broken, fractured and highly abrasive rocks.
3) Hard matrix diamond bit is selected for soft rock with strong abrasiveness, coarse grain and broken.
4) The soft matrix diamond bit is selected for hard, weak abrasive, fine-grained and intact rock ("sliding" formation).
5) If there is a contradiction between abrasivity and hardness, it is subject to abrasivity. For example, in case of rocks with strong abrasivity and high hardness, extra hard matrix should be selected. Otherwise, the matrix will be quickly worn by the rocks and the bit will lose its working ability.
6) High grade and fine-grained diamond should be selected because of the complex rock formation and stronger abrasiveness.
7) The rock has strong abrasiveness, relatively broken and coarse particles. The matrix with high diamond concentration is selected.
8) If the rock is soft, broken, abrasive and hard, the impregnated diamond bit with multi nozzle and large nozzle should be selected, otherwise, the bit with multi nozzle and small nozzle should be selected.
9) The application scope of typical diamond bit lip shape is as follows
① Flat bottomed. There is a running in process after the hole is lowered, and the normal footage can only be achieved after the hole is ground into a micro arc. Poor stability, easy to cause borehole bending, commonly used in drilling hard and medium abrasive rock.
② The lip is circular. It can shorten the initial grinding time, and is often used in medium hard and medium abrasive rocks.
③ Semicircular lip. The inner and outer edge of the lip is reinforced, suitable for hard and abrasive rock.
④ Stepped lip (single or multiple steps). It is commonly used in wire line coring and other thick wall drills to produce broken free surface. It has good drilling stability and certain anti deviation effect. It is suitable for medium hard weak abrasive rock stratum.
⑤ Conical lip surface (inner cone, outer cone, biconical). At the bottom of the hole, it has good stability and guidance, which is conducive to deviation prevention. It is often used in wire line coring bit.
⑥ Bottom spray lip. The hole bottom is washed clean, which can improve the recovery rate in broken rock, but the processing is complex.
⑦ Concentric serrated lip. The results show that there are many free surfaces at the bottom of the hole, and the coarse rock powder is helpful to diamond cutting; The required axial pressure is small, and it also has the function of anti deviation; It is suitable for hard, dense and weak abrasive rocks.
⑧ Right angled trapezoid lip. The contact area with the rock at the bottom of the hole is small, the specific pressure is large, and the nozzle is large. It is suitable for the formation and has a certain broad spectrum, but it is not suitable for the broken formation.
⑨ The selection of the lip of the inclining bit. A bit with small curvature outside the bottom lip should be selected for branch point deflecting, so as to take rock laterally and make new holes; In order to improve the service life and quality of the inclining bit, a bit with larger curvature outside the bottom lip can be selected for hole bottom inclining. The lip center of inclining bit should avoid the "dead point" of zero speed.