On Oct 30, China National Offshore Oil Corporation (CNOOC) completed the drilling operation of Liwan 22-1-1 well in the approximately 2,600-meter deep-water area in South China Sea.
The well creates a new record in drilling depth in not just China but also the Western Pacific, indicating that China's independent exploration of ultra-deep water oil and gas resources has entered the world-class level.
This year, China's external dependence for crude oil has exceeded 68 percent, and natural gas dependence has risen to 40 percent. CNOOC, in order to fulfill its mission and expand the scale of deep-water oil and gas reserves, has increased domestic oil and gas exploration and challenged deep-water and ultra-deep water areas.
The ultra-deep water area refers to the area that is more than 1,500 meters in depth. Before that, only a few developed countries such as the United States and Norway independently mastered the ultra-deep water exploration technology.
The Liwan 22-1-1 well, a deep water drilling platform independently designed and constructed by China, has an operational effectiveness of up to 99.57 percent. With 25.36 days of construction period, and only 16.92 days of drilling, the well created a new record in the ultra-deep well construction cycle and drilling cycle in China.
Compared to the conventional deep-water wells, there are lower seafloor temperatures, higher seawater pressure, and extremely narrow formation pressure in the drilling operation of Liwan 22-1-1 well. The well location is farther offshore than conventional operating points, and logistics replenishment and emergency management are therefore more difficult.
The drilling team of CNOOC has overcome many technical problems such as ultra-deep water formation pressure prediction, mechanical analysis of ultra-deep water pipe inserting, and stability analysis of ultra-deep water submerged wellhead. In view of the safety and environmental protection issues, CNOOC developed risk emergency plans, optimized well control procedures under different conditions, and achieved safe, environmentally friendly, high-quality and efficient operations.
The oil and gas resources of the South China Sea account for about one-third of China's total, of which 70 percent are in deep water and ultra-deep water areas. Since CNOOC started its own deep-water exploration in May 2012, it has completed 46 deep-water exploration wells in the South China Sea, with a total footage of nearly 110,000 m, and found a batch of deep-water oil and gas fields including Lingshui 17-2, Lingshui 18-1, and Liuhua 20-2, promoting the effective development of deep-water oil and gas resources in China.
CNOOC has independently established China's deep-water drilling engineering standards and a set of key technologies, independently researched and developed deep-water drilling core devices, tool materials, and realized industrial applications.
The deep-water high-speed drilling mode pioneered by CNOOC greatly reduced the economic and technical threshold of ultra-deep water drilling in China, and provided a more solid technical guarantee for deep-water oil and gas exploration in the South China Sea.