In the work of tapered drilling tools, correctly analyzing the wear and deformation of the drill bit is an important part to ensure normal drilling, prolong the life of the drill bit and improve the technical level of the drilling operation. Through the analysis of the causes of tapered bit damage during drilling construction, several common types of abnormal wear of tapered bits in the field are summarized, in order to achieve the role of attracting new ideas.

1. Burning drill deformation

During drilling, the flushing fluid was suddenly interrupted due to blocked water or poor water supply, and the drill bit continued to drill at the bottom of the hole without being cooled in time, and the temperature rose sharply, which burned the drill bit. The degree of burn-in can be divided into mild burn-in and severe burn-in. When the drill burning accident is discovered earlier, the drill should be lifted in time. The damage of the drill bit is manifested by the blackening of the lip surface, some of which have been graphitized, and the lower part of the steel body of the drill bit is gray-black, which is obviously different from the bright steel body at the upper part. There is no significant deformation of the lip surface of the drill bit, and no serious consequences have been caused. When mild drill burning is not found in time and continues to rotate at high speed, the temperature of the drill bit continues to rise, causing the matrix to melt and cement with the bottom rock and core, resulting in a serious drill burning accident.

2. Lip groove deformation

This kind of wear and deformation is common in artificially impregnated tapered bits and accounts for more than 1/2 of all damaged drill bits in the drilling of the Baoding mining area. The main reasons are:

1) Since the artificial impregnated tapered bit has been used for a long time when the impregnated layer is nearly worn out, the concentration of the lip surface gradually decreases, and the wear of the lip accelerates. However, the inner and outer sides of the drill bit are reinforced by polycrystals, which are not easy to wear, and the lip surface of the drill bit The shape gradually grinds from arc to flat.

2) Due to the thick lip surface of the impregnated tapered bit, the inner and outer edges of the drill bit are cooled better due to the circulation of flushing fluid when drilling into highly abrasive rock, and the heat generated by the lip surface cannot be transferred in time during high-speed rotation because it is close to the rock. As the temperature rises, the physical properties of some parts change at high temperatures, which makes the hardness of the middle part of the lip surface lower. During continuous drilling, the inner and outer edges are gradually worn out to form grooves.

3. Carcass grinding and deformation

After the groove deformation on the lip surface of the drill bit, the drill has not been lifted in time, and when drilling continues, due to the weak strength of the remaining carcass, insufficient cooling of the flushing fluid, and the impact of the rotary vibration of the drill, the outer edge of the groove is under a greater force , falls off quickly.

4. Deformation of inner and outer steps

Because there are many residual cores left in the hole, and the drilled rocks are hard and broken, or the cores are too thick, it is easy to cause deformation of the inner steps when sweeping the residual cores (or falling cores). When the aperture becomes smaller, it is easy to cause the deformation of the outer step when entering a new drill bit for reaming. Sometimes inner and outer steps occur at the same time.

5. Trumpet-shaped deformation

If the core is blocked during drilling and drilling continues, the broken core will easily cause early wear on the inner side of the drill bit, forming a trumpet-shaped deformation. In addition, when the core is left in the casing sweep hole or the core falls off, it is also easy to cause horn-shaped wear and often causes the carcass to collapse.

6. Carcass collapse

When starting to use a new drill bit, due to negligence in operation, when lifting and lowering the drilling tool, the drill bit is subjected to violent bumping and impact, or the pressure is too high when sweeping the core and live rock, often causing large pieces of the carcass to collapse and cause serious damage. Sometimes after the carcass comes off, it is not found in time, and if it continues to rotate, it often causes all the carcass to come off.

7. Carcass cracks

Due to the strong vibration of the drilling tool during drilling, a large impact load is generated, or the drill bit in the lifting drilling tool is collided, which often causes cracks in the bit matrix. In addition, due to the use of pliers to unscrew the drill bit, the drill bit is often cracked, and sometimes the crack extends to the steel body and causes elliptical deformation).

8. Erosion deformation

When drilling into rocks with strong friction or using mud as flushing fluid, due to the large amount of fine sand and rock powder in the mud and a large amount of flushing fluid, the speed of flushing fluid flowing through the drill bit is very high, which is harmful to the drill bit. The carcass produces strong erosion.

9. The inner diameter of the drill bit is severely worn

If the core is blocked and the drill is not lifted in time, the inner diameter of the drill bit will be severely worn. The inner tube of rope coring gets loose, and the upper part of the inner tube hangs out of order, which will easily cause the core to be blocked and damage the inner diameter of the drill bit. It should be noted that core plugging is often the cause of drill burning or sticking.

In short, tapered drilling tools manufacturers need to correctly judge the working condition of the tapered bit in the hole, analyze the causes of some abnormal wear and tear, and take targeted measures on this basis in order to improve operation and technology, thereby reducing production cost, and promote greater improvement in the economic and social benefits of drilling.