H2SY278 entering jacket slot
The installation of CNOOC’s HZ25-8 DPP (Drilling Product Platform) topside was successfully completed in the eastern waters of the South China Sea for the Enping Oilfields.
“The success of HZ25-8 DPP topside DP floatover installation is a perfect realisation of applying world-class offshore structure installation technology in the South China Sea area. Our cooperation with international leading technical service provider DNV GL has enabled the new breakthrough of our technology and competence in offshore installation,” said Ruhua Yuan, vice general manager of China Offshore Oil Engineering Corporation (COOEC).
“As a result of the merger between DNV and GL, we can now help customers to reduce operational risk even further by partnering with a single global marine advisor. The Noble Denton Marine Assurance and Advisory section in DNV GL has unique and extensive experience of floatover operations onto both floating hulls and fixed platforms. Our experts were able to help CNOOC perform the floatover installation safely, while saving time, manpower and material resources,” said Wolfgang Wu, regional manager of DNV GL Oil & Gas in China.
Transverse load-out and dynamic positioning
DNV GL’s Noble Denton Marine Assurance and Advisory experts provided technical support to CNOOC with two challenges in particular: transverse load-out and dynamic positioning (DP) of the floatover installation. To ensure the safety and success of the load-out and floatover operations, DNV GL applied expertise and operational experience gained from its worldwide involvement in large topside transverse load-out operations and conducted thorough testing of the ballast and DP systems on HYSY278. Based on the test results and taking into account the tide level in the quay and the characteristics of the ballast air compressors, DNV GL was able to optimise the loadout operational procedures and ballast sequences.
The project first started in 2013 when DNV GL Shanghai and Singapore was invited by COOEC to cooperate on the verification of the HZ25-8 DPP topside DP floatover installation, detail design and joint installation design. With the load-out weight exceeding 13,000WT, this project is the largest transverse load-out operation in China to date.
During the design stage, DNV GL performed DP capability analysis, time domain analysis, docking, undocking and mating analysis, in order to assess the capabilities of the DP system under different sea states and the limited weather conditions for floatover installation operation. This analysis helped the site operation. In addition, DNV GL engineers, DP operators and field engineers participated in the simulation test organised by COOEC in Netherlands. It simulated the docking and undocking operation under several virtual environments, enabling the team to make contingency plans in case of failure of one thruster.