Statoil said production drilling has started on the massive Mariner field on the East Shetland Platform of the UK North Sea about 95 miles east of the Shetland Isles.

Statoil said the field will provide a long term cash flow over a 30 year field life.

Mariner is one of the largest projects currently under development in the UK Continental Shelf (UKCS).

First oil is expected to be produced from Mariner in 2018.

Statoil (U.K.) is the operator of Mariner with 65.11% of the equity — and co-venturers are J.X. Nippon Exploration & Production (UK) with 20%, Siccar Point Energy with 8.89% and Dyas Mariner with 6%.

The heavy oil field has reserves estimated at more than 250 million barrels with an average plateau production of around 55,000 barrels per day.

Hedda Felin, managing director, Statoil Production UK said: “This is an exciting period for us as a UKCS operator as we transition from the planning phase to active offshore operations.

“Predrilling enables production to reach plateau levels more quickly after the start of operations on Mariner A.

“It will also be an important learning period for us in terms of understanding the reservoir and identifying potential efficiencies for future wells, with safety and the protection of the environment being our fundamental priorities.”

Statoil said contracts worth over £1 billion have been awarded so far to the UK supply chain by the project.

Statoil said it made its investment decision for the Mariner project in 2012 — which entailed a gross investment of more than $7 billion.