The subsea installation of three kilometer-class deep-water suction piles for Phase II of Deep Sea No. 1 project has been independently completed by COOEC in the Lingshui waters of Hainan.

Phase II of Deep Sea No. 1 project involves the first deep-water high-pressure gas field independently explored and developed by China.

The suction piles prefabricated at the COOEC’s special equipment manufacturing field are 19.68 meters in height, 8 meters in diameter, 12.5 meters in designed penetration depth. A single suction pile weighs up to 94 tons, and is composed of a pile body and a pile cap. The upper part of the pile cap is equipped with high-precision components such as a guide docking device, a drainage hatch and a penetration suction pump interface. China’s first independently-developed deep-water bubble level “bull eye” is adopted here to accurately monitor the verticality of suction piles during subsea installation.

The difference between the required penetration pressure of suction piles and the allowable pressure of the pile structures was only 20%, and the required installation position, direction and horizontal accuracy were 60%, 50% and 40% higher than those of suction anchors of the mooring system respectively, thereby bringing unprecedented difficulties to the installation operation.

The Hai Yang Shi You 285 Deep Water Engineering Ship that demonstrates DP3-level dynamic positioning and reaches as deep as 3,000 m was used for the offshore installation work. Three lifting slings were customized according to the gravity center of the suction piles to ensure that the suction piles were perpendicular to the sea level during lifting. In the process of penetration, ROVs (subsea robots) assisted in the operation with the ship crane to keep accurate control of the hook head load and the penetration pressure, ensuring slow and stable settlement of suction piles. Finally, three suction piles were penetrated with high precision in one operation successfully.