On May 13th, in the eastern waters of the South China Sea, the installation of the upper module and jacket of the Enping 20-4 drilling and production platform weighing over 15000 tons was completed, setting a new record for the installation weight of dynamic positioning floats on domestic offshore oil and gas platforms, filling the gap in China's independent design and installation technology for dynamic positioning floats, which is of great significance for ensuring national security and building a maritime power.
According to Liu Huaxiang, General Manager of the Deepwater Engineering Construction Center of China National Offshore Oil Corporation Shenzhen Branch, the Enping 20-4 platform is independently designed, constructed, and installed in China. It can achieve multiple functions such as drilling and repair, intelligent oil production, comprehensive treatment of oil, gas, and water, and associated gas recovery and utilization. The platform is composed of topside and jacket. The single deck area of topside is equivalent to 9 Basketball court and weighs 15463 tons. The jacket has a height of 104 meters and a weight of nearly 12000 tons, and has been installed in advance at a depth of nearly 100 meters on the seabed. In order to fix the jacket on the seabed, the project team drove 12 steel piles with a length of nearly 145 meters and a diameter of 2.4 meters into the seabed 120 meters deep, so as to ensure that the steel giant with a total weight of more than 27000 tons can be as stable as Mount Tai under the Super Typhoon.

▲ Completion of docking between the upper module of China's largest dynamic positioning floating platform and the jacket
Due to the weight of the topside components exceeding the capacity limit of domestic offshore floating cranes, dynamic floating technology was adopted for offshore installation. The float installation cleverly utilizes the natural forces of the ocean tides and the precise load adjustment of the ship to complete the installation in a manner similar to that of a weightlifter's "clean and jerk". Dynamic positioning float is a new installation technology. Taking the installation of the Enping 20-4 platform as an example, this method can double the transportation speed of the platform, shorten the climate window required for offshore installation operations from 48 hours to 24 hours, greatly improve work efficiency, and accelerate the construction speed of offshore oil fields.

At the moment of docking between the upper part of the platform and the jacket
It is understood that the installation process of the dynamic positioning float is equivalent to driving a super truck with a length of over 220 meters, a width of over 40 meters, and a load of 10000 cars, "reversing and entering" on the rough sea, with a gap of only 10 centimeters on both sides. The precision of the docking between the module tip and the conduit is required to reach the millimeter level, posing great challenges to the accuracy of design calculations, the reliability of the dynamic positioning system, and the technical level of operators.
According to Sheng Xiangming, the general contracting project manager of Enping oilfield group development of COOEC, the project team independently tackled technical problems, successfully broke through multiple key technologies such as dynamic positioning floatation design, analysis and calculation, 3D simulation, precise positioning operation, and carried out a large number of virtual model training and key operation rehearsals, fully identified Operational risk and formulated countermeasures. In order to ensure safety, technicians have installed two independent positioning systems on the main operating vessel "Offshore Oil 278" to provide stable and accurate "reverse collision radar" for the float, and independently designed a new type of guard string system and pile leg coupling buffer device to prevent damage caused by accidental collisions.

▲ Aerial photography of offshore installation of China's largest dynamic positioning floating platform
During the float installation period, the sea conditions were relatively harsh, which added difficulties to the implementation of the installation work. During the construction, the project team conducted real-time monitoring of wind, waves and ship movement. When the ship was about to enter the jacket notch, the ship control mode was adjusted from "automatic gear" to "manual gear". The experienced dynamic positioning operator accurately controlled the ship to "reverse", with the maximum error of only 5mm, and the accuracy control reached the international advanced level.
It is reported that Enping 20-4 drilling and production platform is the highest production platform of Enping 15-1 oilfield group of CNOOC. After the oilfield group is fully put into production, the peak annual crude oil output will exceed 3.6 million tons, injecting new impetus into the economic and social development of Guangdong–Hong Kong–Macao Greater Bay Area.