Sea1’s first offshore energy support vessel launches at Chinese yard

July 22, 2026, by Nadja Skopljak

The first of four 120-meter-long offshore energy support vessels (OESVs) being built in China for Norwegian offshore services provider Sea1 Offshore has been launched at the yard.

Sea1 Offshore placed the order for the first two OESVs with Cosco Shipping in November 2024, revealing at the time that negotiations were ongoing for the delivery of more vessels. The contract for the construction of two additional vessels was announced in March 2025.

The construction of the first vessel, named Sea1 Diamond, began in September 2025, with the second, named Sea1 Citrine, following in December.

Sea1 Offshore reported yesterday, July 21, that Sea1 Diamond was launched at the yard, marking an important step forward in the newbuild program.

Based on the ST-245 design, the OESVs will have a cargo deck of 1,400 square meters, and each will be equipped with a 250-ton deck crane, two remotely operated vehicle (ROV) hangars, and a moonpool. They will provide accommodation for up to 120 personnel.

The vessels will be methanol-ready, with generators that can operate on 100% biofuel, and will be capable of serving both the oil & gas sector and the renewable energy market. Kongsberg Maritime will deliver comprehensive equipment packages.

They are scheduled for delivery during 2027 and the first half of 2028.