China's first offshore natural gas development project with high temperature, high pressure, and low permeability has been successfully put into operation

On July 29th, CNOOC announced that China's first offshore high-temperature, high-pressure, and low-permeability natural gas development project, the Dongfang 1-1 gas field 13-3 area development project, has been successfully put into operation, with test production exceeding expectations.

The reservoir temperature of this project is nearly 150 degrees Celsius, with a maximum pressure coefficient of over 1.8 and an average permeability of only 0.8 millidarcies, making it a typical high-temperature, high-pressure, and low-permeability gas reservoir. Developing such gas reservoirs requires high technical requirements, high operational risks, and limited natural gas resources, making it difficult to achieve economic development. The successful operation of this project provides a reference for the development of more complex oil and gas resources in China's offshore areas, and is of great significance for ensuring China's energy security.

After the discovery of the gas reservoir, CNOOC conducted in-depth research and demonstrated the development plan, and decided to adopt the strategy of "long horizontal wells+simple platforms+relying on surrounding facilities" to comprehensively innovate and tackle challenges, and reduce costs throughout the entire process. Deploy 6 horizontal wells with a length of 800-1200 meters in the project, to penetrate the gas layer to the maximum extent and release production capacity; Build a new four legged simple platform, lay two submarine pipelines with a total length of about 22 kilometers and one submarine cable with a length of about 6.9 kilometers. The electricity required for the new platform is supplied by nearby platforms, and the oil and gas produced are connected to the production system of the gas field for processing.

In September 2024, the construction of the lower pipeline rack for the new platform of the project was initiated in Zhuhai. The pipeline rack is about 75 meters high and weighs about 1850 tons. China National Offshore Oil Corporation (CNOOC) adopts the method of "vertical construction on land and lifting and launching at sea" for construction, achieving efficiency improvement and cost reduction. At the end of the same year, the upper module of the platform was built in Tianjin, and CNOOC accelerated the construction by adopting the "integrated prefabrication, integrated coating, and space assembly" method, saving nearly two months in time compared to other similar platforms; The project innovatively applies multiple intelligent technologies such as intelligent lighting and intelligent injection of chemical agents. Compared with conventional platforms in offshore gas fields, this platform has a higher degree of integration and automation.

Submarine pipelines are also being laid at the fastest speed possible. On the early morning of February 19th, with the termination of the last section of the submarine pipeline and mud settling on the seabed, the two 22 kilometer long submarine pipelines were fully laid, and the construction period was ahead of schedule.

In terms of drilling and completion operations, due to the fact that the upper strata in the sea area where the project is located are similar to an "eggshell", with a hard upper part and a soft lower part, CNOOC has selected a "large pile boot" self elevating drilling platform and innovatively adopted a 10 level grouping and loading method to allow the platform pile legs to safely penetrate the "eggshell" and achieve "precise positioning" of the platform.

On June 10th, drilling and completion operations began. Prior to drilling operations, CNOOC aimed at the three core challenges of "sweet spot identification - whole process reservoir protection - production capacity release", systematically carried out research and development, and formed targeted technologies; During drilling operations, on-site personnel carried out precise construction, achieving precise targeting of sweet spot reservoirs and maximizing reservoir protection. The footage of the high-temperature and high-pressure horizontal section exceeded 1230 meters, breaking the record for the longest horizontal section of a high-temperature and high-pressure well by CNOOC.

Recently, the first well operation of the project was efficiently completed, encountering a gas reservoir of 756 meters and achieving high production through testing. The entire project started running and was successfully put into operation.