The BHA which includes GREAT Tricone bit drilled the interval of 2840-3325 m. Drilling time for this interval – 72 hours, ROP – 6,74 m/h. The reason for the lifting – the geophysical surveys. This type of bit showed a very good result in ROP and durability. According to the Tricone bit program, the planned ROP-5,0 m/h. Very stratified rocks were drilled with a bit, mainly dense clay up to 30%, abrasive sandstones up to 45% and hard siltstones up to 25%. While drilling and lifting the tools, no complications were observed. On the surface, a visual inspection of the BHA elements did not reveal any damage. The condition of the bit is classed as – 0-1-DL, CT-S-X-IN-RR-TD. Bit has not lost the diameter. Jetting nozzles – clean, no blockages. Depressurization of supports – no. A visual inspection of the thread revealed no damage. 

Total footage of the bit:  512 m. The bit was used to drill a shoe in the other two wells;

• Total drill time: 79 h.

• The bit has worked over 650,000 revolutions with very good technical performance. 

• Bit is suitable for further use. 

Recommendations:

1. To increase the ROP, it is required to increase the working WOB to 9-10 tons;

2. Do not use bits without hydraulic nozzles;

3. The WOB should be fed smoothly and continuously. Automatic feeding (auto boring) of the WOB is recommended.

Roller bit Core barrel