What Stuck Pipe Is and What It Costs

A definition the whole crew can use

The drill string is stuck when it cannot be pulled out of the hole with the maximum load the crew is allowed to apply, and it cannot be freed by normal working of the pipe. Many operators add a time element: if the string cannot be freed within a short period of normal effort, the event is recorded as a stuck pipe incident.

Before that point there is usually a warning stage. The pipe becomes tight: it still moves, but only with extra pull, extra weight or extra torque. A tight hole is not yet stuck pipe. It is the best chance the crew will get to stop a stuck pipe event from happening.

Stuck pipe can happen with any string in the hole: drill pipe and bottomhole assembly (BHA) while drilling or tripping, casing or liner while running it, a logging tool string on wireline, or a completion string. The principles in this course apply to all of them. The examples mostly use the drill string, because that is where most events happen.

Where the money goes

Stuck pipe is one of the largest sources of non-productive time (NPT) in drilling. NPT is rig time that does not make progress on the well plan. The direct cost is the full daily spread rate of the rig and all its services for every hour spent working the pipe, jarring, fishing or sidetracking.

The indirect costs are often larger:

• equipment left in the hole, which may include expensive directional and logging tools, sometimes with a radioactive source that must be recovered or abandoned under strict rules;
• a sidetrack — drilling a new hole past the lost section — which repeats days of drilling;
• a well that cannot reach its target, or a section that must be cased early;
• delays to the next wells in the campaign, and lost production for the operator.

Stuck pipe also brings safety risk. Heavy jarring, high overpull and high trapped torque put the derrick, the top drive and people on the rig floor under unusual loads.

A worked example

On a land well in a desert field, a drilling crew pulled out of an 8½ in hole after a long reaming run. They saw extra drag at three depths but kept pulling, because each time the pipe came free with more pull. At the fourth tight spot the string stuck hard. Two days of jarring failed. The string was backed off above the BHA, and the section was sidetracked.

The incident review found that the shakers had shown very few cuttings for several hours, and that the drag had been rising on every stand. Nobody connected the two facts. The cost was about six days of rig time and a lost directional assembly — for an event that gave clear warnings over many hours.