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Method for rational use of diamond bit
Jul 12, 2017

Method for rational use of diamond bit

The diamond is constituted by carbon, carbon is crystallized under high temperature and high pressure, it was listed as the highest hardness Mohs hardness in grade 10. Diamond is not only high hardness, high strength, high thermal conductivity, but also easy to absorb heat, but also can quickly dissipate heat. Small diameter diamond drilling is one of the main methods of rock drilling in water conservancy project. In recent years, I have carried out the exploration and reinforcement of a large number of small and medium reservoirs, due to the lack of awareness of diamond bit performance, burning drill and abnormal wear occurs frequently in drilling process, affecting the normal drilling. In order to improve the drilling efficiency, reduce the cost of diamond drilling, need to raise awareness, on the performance of diamond bit to master the correct use, to reduce the abnormal wear of drill bit, improve the life of diamond bit.

1. diamond bit characteristics

1.1 Strength and thermal stability of diamond bit

Diamond has the characteristics of high hardness, high strength and high thermal conductivity, but it has the defects of brittle and poor thermal stability. It is easy to break under impact and easy to oxidize and graphitized under high temperature. The temperature has a great influence on the diamond strength, and the diamond decreases with the increase of temperature. The initial oxidation of diamond bit is heated to 300 DEG C in the air, to 800 DEG weight starting to reduce the crystal color change; when the temperature reached 900 degrees, the diamond quality changed obviously, performance is loose, easily broken; at 1000 DEG C diamond burn clean, formed after combustion of carbon dioxide. The adaptability of the 1.2 diamond bit is very strong for the formation of the diamond bit. As long as the corresponding bit is selected according to different strata, the long life and high efficiency of the diamond bit can be achieved. When the rock is in the 8 - 9 stage, the hardness of the matrix is HRC34 - 42, and the diamond particle size is 60 - 100. The purpose of the impregnated or electroplated bit is more suitable. But when the hard granite vein and quartz vein, this bit is not suitable, the matrix hardness is relatively soft, thin steel grit drill.

2.Main problems in diamond bit drilling

2.1 Diamond bit burning

Burning diamond is the most serious problem in diamond bit drilling. Severe burns can make the drill bit matrix all burned, even the drill steel body, reamer, inner tube or short tube all burned or burned part, or the core drill and burn together, caused by the accident, treatment is very difficult. After a severe burn drill, the entire drill will be scrapped. Some diamond bit has played only a few centimeters or meters will cause burning accident drilling footage, the great loss. The use of drill bit is still mild burning, but the strength of the drill will sharply decline in each footage in diamond drill wear, several dozen silk, bit life will fall about 60%.

2.2 Abnormal wear of diamond bit

Abnormal wear is mainly caused by foreign matter or hard rock particles in the hole, partly due to light burning. The diamond bit drilling center matrix poor cooling conditions, diamond poor cooling, easy to cause the local light burned, resulting in the diamond strength decreased, increased wear, resulting in kerve. Once the groove is formed, the rock powder in the groove is not easy to discharge, and the diamond cooling is difficult, and the graphitization phenomenon is intensified, resulting in the scrapping of the drill bit. In recent years, the slotting phenomenon often occurs in impregnated diamond bit. The groove often appears on the bit matrix, which shortens the service life of the drill bit.

3.Cause analysis of diamond bit burning and abnormal wear

3.1 Why diamond bit drilling methods generally require at a higher speed to full effect. If the vertical shaft speed is too high, the pump quantity can not meet the requirements, the supply of washing fluid is insufficient, it will cause the drill to burn lightly and intensify the drill wear. In addition to the weak or broken formation, too much pressure, so that the diamond rock cut too deep, blocking the water cycle, the rock powder can not be excluded, the water cycle condition, the bit can not get effective cooling, there will be fire drill.

3.2. the reason of the circulating water is that the washing fluid plays the role of excluding rock powder and cooling bit in drilling, and keeping the water unobstructed is very important to the exertion of drill bit efficiency. If the diamond bit diameter too much wear bit nozzle becomes small, the cooling effect will impact on the drill bit; sometimes the diameter is too large, too small core diameter, or outer diameter of the drill bit and the hole wall of an annular gap becomes smaller, will affect the cooling effect of the drill flushing liquid. In addition the drill pipe or double pipe joint waterway is blocked or drill wear lax lead buckle connection will cause the bottom hole flushing fluid supply, caused by bit light burning. How will drill bit, rock powder was blocked in the role of the whereabouts of the impact force of the bit nozzle, not back to the water hole to drill bit, will lead to poor cooling and burning. 

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