CNOOC Announces High-Productivity Volcanic Well at a Depth of 5,770 Metres in Bohai
Key Facts
CNOOC announced on 12 November 2026 the discovery of a high-productivity volcanic oil and gas well in ultra-deep layers of the Bohai Sea, describing the step as a breakthrough in ultra-deep offshore gas exploration. The well is located in the central sea, alongside the Bozhong Sag, which the company describes as Bohai’s largest hydrocarbon-rich sag. The company said drilling penetrated more than 120 metres of gas-bearing layers within volcanic formations before reaching a total depth of 5,770 metres. The well test provides an initial indication of its productivity, while the company has not announced discovered reserves or a date for the start of commercial production. CNOOC said the discovery opens a new area for gas exploration in ultra-deep offshore layers.
The announcement is significant for expanding exploration in Bohai toward deep formations, with the company saying the well’s success widened the scope for deep oil and gas exploration in the basin. CNOOC quoted its chief scientist and chief geologist, Xu Changgui, as saying that the drilling success “opened a new area for ultra-deep offshore gas exploration and widened the scope for deep oil and gas exploration in Bohai.” This assessment places the discovery in the context of regional exploration, rather than as an announcement of the well’s reserve size or a specific production plan. The company did not specify the volume of recoverable gas from the well or when test results might be converted into commercial production. The announced test remains evidence of gas-bearing layers, while determining commercial viability would require evaluation and development steps for which no details were provided in the announcement.
The company said target identification relied on the 3D, multi-source, wide-azimuth marine seismic survey techniques it developed to explore deep layers. It added that it had devised methods to predict high-quality reservoirs in ultra-deep buried hills, geological formations beneath sedimentary layers. CNOOC said these techniques helped it identify areas of gas accumulation in the Bozhong Sag. The company thus links the development of seismic imaging tools with improving the selection of drilling targets in a deep and complex geological environment. Its description of the well as volcanic reflects the nature of the formations that contained the gas-bearing layers penetrated by drilling.
The discovery is part of the company’s broader exploration activity in Bohai, which it describes as China’s largest crude oil production base and its most important oil-producing region. During 2025, CNOOC said it made 3 new discoveries in Bohai and successfully evaluated 10 oil- and gas-bearing structures. Its data also showed that a geological assessment of the Qinhuangdao 29-6 field in the area estimated in-place volume at about 100 million tonnes, a separate indication of exploration potential in shallow stratigraphic reservoirs. These figures provide background on the breadth of exploration activity in the basin, but do not represent reserves for the new well and cannot be combined with its test results. The new well announcement adds an ultra-deep exploration track to the company’s record in the region.
CNOOC said the discovery could support faster ultra-deep exploration in Bohai, linking this effort to its ambition to build a major gas region in the basin with a scale of 1 trillion cubic metres. The company provided no timeline for achieving this ambition and did not describe it as proven reserves or as a result specific to the well it announced. In the context of developing gas resources in the region, the company’s mid-2026 review said the second-phase development project for the Bozhong 19-6 field had completed construction of its main structure. This phase provides context on the progress of another gas project in Bohai, but does not set a start date for production from the newly discovered well. The company gave no date for commercial production or details of its development plan in the announcement.