CNOOC Drills Ultra-Deep Gas Well in Bohai Sea with Daily Production of 800,000 Cubic Meters

en.Wedoany.com Reported - On November 12, CNOOC announced that it had drilled a high-yield oil and gas well in ultra-deep volcanic rock in the central waters of the Bohai Sea. The well has a total depth of 5,770 meters and encountered a cumulative natural gas layer of more than 120 meters in volcanic rock formations. Testing yielded approximately 800,000 cubic meters of natural gas per day. The well is adjacent to the Bozhong Sag, the largest hydrocarbon-rich sag in the Bohai Sea, and represents another important discovery in China's offshore ultra-deep volcanic rock natural gas exploration.

The main challenge of this exploration lies in the complex geological conditions of volcanic rock reservoirs. The ultra-deep volcanic rocks in the Bohai Sea have undergone multiple phases of volcanic activity and tectonic reworking, resulting in significant lithological variation, strong reservoir heterogeneity, and complex distribution of natural gas storage spaces. Conventional seismic data struggle to accurately identify high-quality reservoirs, and drilling operations also face challenges such as hard rock formations, high formation pressure, and wellbore stability control.

To identify natural gas enrichment zones, CNOOC independently developed offshore deep multi-source broadband three-dimensional seismic exploration technology and innovated a prediction method for high-quality reservoirs in ultra-deep buried hills. By integrating seismic information from different sources and frequency bands, the company improved imaging and reservoir identification capabilities in complex volcanic rock formations, thereby pinpointing favorable exploration areas in the ultra-deep volcanic rocks of the Bozhong Sag. The drilling operation encountered more than 120 meters of natural gas layers, validating the effectiveness of the reservoir prediction method in this area.

Drilling operations also had to contend with high-temperature and high-pressure conditions. According to Jiemian News, Guo Tao, project chief geologist at the Bohai Petroleum Research Institute of CNOOC Tianjin Company, stated that the reservoir temperature of the well is approximately 150 degrees Celsius and the formation pressure exceeds 80 megapascals. The combination of high temperature, high pressure, and the complexity of volcanic rock formations placed high demands on drilling fluid performance, wellbore stability, downhole pressure control, and coordination of drilling and completion operations. The project team completed the drilling through multidisciplinary collaborative efforts and obtained a high-yield natural gas flow.

There remains substantial exploration potential for deep to ultra-deep oil and gas resources in the Bohai Sea. Volcanic buried hill reservoirs differ from conventional sandstone reservoirs in terms of lithology, pore structure, and natural gas occurrence conditions, requiring comprehensive evaluation integrating seismic imaging, geological interpretation, and drilling data. This discovery provides new drilling evidence for the evaluation of ultra-deep volcanic rock reservoirs in the Bozhong Sag and expands the scope of deep natural gas exploration in the Bohai Sea area.

The Bohai Sea is an important offshore oil and gas production area in China, and its natural gas resources supply part of the natural gas demand for the Beijing-Tianjin-Hebei region and the Bohai Rim area. CNOOC has proposed the exploration goal of building a trillion-cubic-meter-level large gas province in the Bohai Sea, and this discovery provides a new target area for subsequent ultra-deep exploration deployment.