Stuck Pipe and Bent Kelly Hazards: 3 things to know

On a drilling rig, mechanical packing, differential pressure, or shifting formations can pin the tubulars in place. This is stuck pipe.

When drillers pull up hard to jar or yank the string free, that extra tension above the string's normal weight is overpull. Because steel stretches under high tension, pulling beyond structural limits turns thousands of feet of pipe into a loaded mechanical spring.  If the string parts under high load, that stored energy snaps back to the surface at acoustic speed unleashing an upward shockwave straight into the hoisting system. 1. What Happens When a Drillstring Gets Stuck?

Sometimes, drill pipe gets stuck in the well because of pressure differences, shifting formations, or buildup around the pipe. This is known as stuck pipe.

To free it, drillers may pull the drillstring upward. The extra pulling force beyond the string's normal weight is called overpull.

But if too much force is applied, the pipe can break. When this happens, the tension stored in the stretched pipe is suddenly released, potentially causing equipment to move violently.

2. How Can a Broken Drillstring Cause Equipment to Fall?

When a drillstring breaks under high tension, the sudden release of force can cause equipment at the surface to move unexpectedly.

• Equipment can move upward suddenly. The release of stored energy can cause a rapid rebound.

• The Kelly can come loose. In some circumstances, the Kelly or connected equipment may come out of position if its connections or restraints fail.

• Heavy equipment can fall. If the equipment becomes disconnected from its support, it can fall onto the rig floor or nearby areas, putting workers at risk.

This is why personnel must stay clear of hazardous areas during high-tension operations.

3. Why is it Important to know the Drillstring's limits?

Not all drill pipe can withstand the same pulling force. Its strength depends on factors such as its grade, wall thickness, wear, corrosion, and previous use.

Using the strength listed for new pipe without accounting for its actual condition can lead to incorrect pull limits.

Before applying overpull, the crew must consider the condition and strength of the drillstring, identify its weakest component, and follow the approved operating limits and safety procedures.

Drillstring failures can happen suddenly, but understanding the risks can help crews make safer decisions. Knowing equipment limits, following proper procedures, and keeping personnel clear of hazardous areas can help prevent serious incidents.

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