The drill manufacturers will help you understand the cause of the drill pipe failure.

 

Drilling assembly and drilling technology

 

As a rotating slender elastic rod, drill pipe has its natural vibration frequency, which is determined by the combination of drill tools. When the drill pipe rotates, it also generates longitudinal, transverse and torsional vibration, and resonance occurs when their frequencies coincide with the natural frequencies. The result of resonance will add an additional fatigue stress to the original fatigue stress of the drill pipe to accelerate the failure of the drill pipe. The rotary bending fatigue of drill pipe can be reduced by using long-acting screw drill pipe instead of rotary disc drilling in directional wells and horizontal wells.

 

Two. Basic mechanical condition of drill pipe

 

Drill pipes work in long and narrow boreholes filled with drilling fluids inside and outside, usually under pressure, bending, torsion, hydraulic and other loads. If the stress on the drill pipe is less than 206.8 Newton per square metre, the drill pipe will not produce fatigue cracks even though it has undergone numerous bends. When drilling, the composite stress of bending, torsion and tensile stress is very large, especially in extended-reach directional wells and horizontal wells. When the number of bending times of drilling pipe is far less than 1 million, fatigue micro-cracks will occur. When micro-cracks occur, they will continue to expand and extend. At this time, if high-pressure drilling with corrosive effect. When the drilling fluid enters the micro-crack, the crack propagation will be accelerated, which will eventually lead to the failure of drilling fluid penetrating the drill pipe. As a result of piercing development, the effective cross section of drill pipe is shrinking continuously. When the total length of piercing plus crack exceeds its critical crack size, the drill pipe will break. Besides rotary downward movement, there are various vibrations and whirling of drill pipes.

 

With the continuous depletion of shallow resources, more and more deep and ultra-deep wells will be drilled in the future, and the safety and reliability of drill pipe will become a very prominent problem. Do a good job of drill pipe failure analysis enough, I believe that the use of better help!