Historically classification of ships was introduced for the maritime industry. This was back in the 18th. Century when all ships had very similar tasks. The diversity today is something completely different and workover units are one of the latest add-ons to the wide variety of ships and offshore units. So how do the shelf states, flag states and classification societies address this situation?

The term workover is used to refer to any kind of oil well intervention involving invasive techniques, such as wireline, coiled tubing or snubbing. What are the accident scenarios following workover/well intervention? Many shelf state authorities consider any unit that connects to a live hydrocarbon well to be an offshore unit. Are the vessels involved in workover suited for the task? The current situation is very complex due to the fact that the different types of workover techniques and operations have a very different risk profile. Today there are very few international requirements associated with the vessels or equipment used during well intervention. With the Macondo disaster fresh in mind it is also prudent to ask if the systems and safeguards in use during well intervention and workover are sufficient. Also in this growing industry new operators are rapidly entering into this market; with or without relevant experience. Practically any offshore supply vessel can swiftly be converted into a well intervention unit without any assessment or approval of the modification of the vessel.

At the same time the number of subsea wells used in the offshore industry is rapidly increasing. Any subsea well in any deepwater development will need well intervention sooner or later to varying extent. And the vessels used can undertake heavy or light well intervention with minor modifications to the vessels.

To a big extent the well intervention industry is self regulating. In this paper DNV will present their view on the regulatory challenges in this booming industry and the risks involved in these activities.


Before discussing the subject of this paper further I will need to clarify the subject. What is workover? And what is Well Intervention? There are different understandings amongst different parties in the oil industry what these terms really mean. There is no reason to argue whether one view is more correct than the other, but for the sake of this paper it is important to clarify what is being addressed In the Schlumberger Oilfield glossary Well Workover and Intervention is defined as follows:

" The process of performing major maintenance or remedial treatments on an oil or gas well. In many cases, workover implies the removal and replacement of the production tubing string after the well has been killed and a workover rig has been placed on location. Through-tubing workover operations, using coiled tubing, snubbing or slickline equipment, are routinely conducted to complete treatments or well service activities that avoid a full workover where the tubing is removed. This operation saves considerable time and expense.??

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