In a continuous effort to reduce cost and improve efficiency, the Oil and Gas industry has been trying for the last 10 years to develop methods to perform subsea Coiled Tubing (CT) operations from a vessel and without a riser.

In September 2020 a large campaign of Riserless Coiled Tubing (RLCT) coring was successfully executed in the Norwegian Sea, on the Mohns Ridge, approximately 330 nautical miles from the coast.

The campaign was performed from a small Anchor Handler Tug Supply vessel, the Island Valiant.

A total of 14 open water gravity-fed RLCT runs were executed in water depths between 2780 and 3085 m.

The system performed extremely well and proved to be very robust, efficient and effective for these innovative operations. This was the first time that RLCT coring operations were completed without the use of a subsea injector, in the so-called gravity-fed mode, and in such ultra-deep water.

This paper describes the project in detail, including the system setup used, a summary of the operations and the actual results achieved, before discussing future improvements and applications of the RLCT technology.

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