The recovered and installed gas tree has a volume of about 5 cubic meters and a weight of about 70 tons in the air. The operation depends on a stable and reliable marine crane, sufficient deck area and accurate underwater underwater positioning system. The installation of gas production trees in deep water areas of 1,500 meters or less is currently the mainstream practice in the world by using drilling platforms or floating cranes. CNOOC's single-ship operation is the first time in the industry, and the daily rate is much lower than the drilling platform.
In this operation, the CNOOC service ship lifted a damaged gas tree from the wellhead, transported it to the wellhead 4.5 km away in the floating state, and then installed a new gas tree at the original wellhead. Finally, the damaged gas tree is salvaged to the deck, and the workload is equivalent to installing and recycling the deep water gas tree twice. Due to the water depth of the working area of ​​1500 meters, the installation accuracy is high, and the state investigation and cleaning of the subsea wellhead is required, and the technical requirements are extremely strict.
The operation team took less than 72 hours from the simulated lifting heavy block drill, to the investigation of the current status of the gas tree to the completion of the entire underwater facility, and maintained a safe and high quality construction record.
The 3,000-meter deep-water engineering survey vessel, which integrates drilling, water engineering and exploration functions, has DP2 dynamic positioning capability, and the ship is equipped with a 150-ton crane with a heave compensation function. In the past one year since the ship was commissioned, on the basis of the safeguard engineering survey business, CNOOC Limited has entered the oil and gas field underwater facility life cycle management market and gradually established equipment, talents, management and systems to meet the needs of the installation of underwater facilities in deep water and oil fields.
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