OSLO (Reuters) - Statoil (>> Statoil ASA) confirmed on Tuesday its cost estimate for developing Norway's Johan Sverdrup oilfield, the largest North Sea discovery in decades, and announced contract awards for the second and final construction phase.

The overall field development investment is now seen at 137 billion-152 billion Norwegian crowns ($16.2 billion-$18 billion), in line with a Feb. 7 forecast and down from a previous range of 140 billion to 170 billion seen in August.

At an earlier stage Statoil had said it could cost up to 220 billion crowns to develop the field, which is expected to have peak production of 660,000 barrels of oil per day.

Germany's Siemens (>> Siemens AG) and Norwegian engineering firms Kvaerner (>> Kvaerner ASA) and Aker Solutions (>> Aker Solutions ASA) won contracts for the second phase on Tuesday, although a formal investment decision will not be made until the second half of 2018, Statoil said.

Statoil's partners in the field are Lundin Petroleum (>> Lundin Petroleum AB), A.P. Moeller-Maersk (>> AP Moeller Maersk A/S) and Aker BP (>> Aker BP ASA).

(This story corrects headline and text to show estimate was cut on Feb. 7, not on Tuesday)

(Reporting by Terje Solsvik and Stine Jacobsen, editing by Gwladys Fouche)