How Did Engineers Install the Heaviest Offshore Structure Ever Built in the Bohai Sea?
On 8th June 2026, engineers completed one of the most demanding offshore installation operations in recent history. The central processing platform for Phase I of the Kenli 10-2 oilfield development project — the largest and heaviest offshore oil and gas platform ever installed in China’s Bohai Sea — was successfully positioned onto its subsea jacket in a single, precise manoeuvre. The platform weighs over 20,000 metric tonnes. Its deck area covers the equivalent of fifteen standard basketball courts. It stands 22.8 metres tall.
The engineering challenge was considerable. No available crane in the region could lift a structure of this scale. Therefore, engineers turned to a technique that uses the forces of nature itself to do the heavy lifting — float-over installation.
What Float-Over Installation Actually Is
Float-over technology is one of offshore engineering’s most demanding installation methods. Rather than lifting a platform topside into position using a crane vessel, engineers load the entire structure onto a barge or pontoon. They then manoeuvre that vessel directly over the pre-installed subsea jacket — the steel framework already fixed to the seabed. As the tide rises and falls, the platform’s own buoyancy and the tidal movement work together. The upper structure settles precisely onto the jacket connection points. Engineers then secure and weld the connection to create a single, integrated offshore structure.
The concept is straightforward in principle. In practice, it demands extraordinary precision. The platform must align within millimetres of the jacket connection points in open water, under the influence of waves, currents and tidal movement — with no margin for error. Furthermore, any contact between the barge and the jacket during the installation window risks catastrophic structural damage to both.
How CNOOc Solved the Precision Problem
The engineering team at CNOOC’s Tianjin Branch developed a multi-layered precision control strategy for the Kenli 10-2 installation. Three BeiDou satellite positioning systems — China’s equivalent of GPS — with AI algorithms operated simultaneously on the main installation vessel. Multiple tugboats worked in coordinated formation around the structure, each responding to real-time positioning data to maintain precise alignment throughout the operation.
Before a single vessel moved into position, engineers completed the entire installation virtually. Digital twin technology modelled the operation in three dimensions — simulating tidal conditions, vessel responses, mooring behaviour and structural loads throughout the installation sequence. CNOOC’s team independently developed software for multi-pontoon catenary calculations and a dynamic mooring coordination system. Key operations were simulated repeatedly. Risk mitigation measures were formulated and tested virtually before any physical work began.
Consequently, when the installation took place, it completed in a single attempt. That outcome reflects not simply good execution — but the engineering rigour of a programme that resolved every critical variable before committing to the operation.
The Scale of the Engineering Achievement
The Kenli 10-2 platform is a three-deck, eight-leg multifunctional offshore facility. It integrates oil and gas production equipment, chemical treatment systems, pipeline infrastructure and living quarters for operational personnel into a single structure. Moreover, it incorporates integrated smart production, management and safety systems — establishing what CNOOC describes as a new approach to building low-carbon intelligent offshore platforms.
To put the scale in context: CNOOC has now completed 50 large-scale offshore platform float-over installations. The cumulative float-over weight across those 50 projects exceeds 600,000 tonnes. The maximum single float-over capacity the company has achieved is 32,000 tonnes. The Kenli 10-2 installation, at over 20,000 tonnes, therefore represents one of the most demanding operations in that extensive portfolio.
Why Offshore Engineering Matters
The Bohai Sea is China’s largest crude oil production base. The Kenli 10-2 oilfield hosts the largest lithologic oilfield discovered offshore in China — with proven geological crude oil reserves exceeding 100 million tonnes. Therefore, the engineering work to bring this resource into production carries significant economic and energy security implications for China.
Furthermore, the engineering capability demonstrated at Kenli 10-2 has broader significance. Developing increasingly large and complex offshore structures in increasingly challenging environments is a defining trend in offshore energy engineering worldwide. The techniques, tools and digital engineering methods developed for projects like this advance the entire discipline — not just a single installation.
Precision Engineering at Every Scale
The Kenli 10-2 project illustrates a principle that applies across engineering at every scale. Precision is not simply about small components and tight tolerances. It is about the rigour of engineering thinking — the quality of analysis, planning and risk management that determines whether a complex operation succeeds or fails.
Digital twin modelling, AI-assisted positioning, coordinated systems control and thorough pre-installation simulation are all expressions of the same engineering discipline that underpins precision mechanical design, test rig development and bespoke system engineering across every sector.
At CNR, that same discipline — rigorous analysis, intelligent design and thorough validation — sits at the heart of every engineering project, whatever its scale or sector.
Note: This article is for general information only
