Snubbing

Due to the large rigup, it is only used for the most demanding of operations when lighter intervention techniques do not offer the strength and durability.

Unlike conventional drilling and completions operations, snubbing can be performed with the well still under pressure (not killed).

It consists of a hydraulically powered snubbing unit, which provides the force on a pipe, above a string of multi-layered pressure control components.

Another popular method of stripping tubulars in/out of a wellbore is with the use of an "Annular" Blow Out Preventer (BOP).

An Annular BOP consists of a natural or synthetic rubber element with encased metal reinforcement sections.

The upset or larger diameter section of a pipe connection can be pulled or pushed through a closed annular element without damage and while still maintaining a gas tight seal.

At this point, the snubbing mechanism is changed over to the one which provides upward force to hold the pipe and lower it controllably into the well.

The more complex method of pressure control, as compared to coiled tubing and wireline, naturally invites more opportunity for things to go wrong.

The excessive force applied to the pipe caused it to break apart, dropping the string below the failure into the well.

In the case above, adequate supervision could have prevented this dramatic consequence of operator error by limiting the hydraulic force allowable to be an applied to a level below what was required to part the pipe string.

In the Canadian oilfield many companies use small "Stand Alone" snubbing units which can be broken down and rigged up in less than 3hrs.

These units are set up in such a fashion so as to be able to cope with the harsh roads and remote locations required in the Canadian winter.