Drilling advances ///

It starts unexpectedly and robs the drilling operation of efficiency. Penetration rates drop, new bits are seriously worn in mere hours, drillstring components like MWD/LWD tools and pulsers cease to function and it all occurs during “normal” operations. Often, it can't be identified on the surface easily, or its effects are masked by mechanical systems. No, it's not a computer virus. These symptoms are caused by a more insidious thief—stick-slip. Stick-slip is defined as energy storage in a moving system that, when released, results in some system component lunging forward at high velocity only to stop again shortly thereafter. Energy is stored again until it is released in another forward lurch. The process repeats itself in a cyclic pattern. In stick-slip drilling, the bit stops rotating in the hole, usually because of excessive friction at the rock face or on some BHA component. As the rotating equipment on the surface continues to turn, the drillstring “twists up” . . .

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