By Ran Yongping, Ding Yiting, People’s Daily
China’s first offshore carbon storage project was operated on June 1 in the South China Sea.
With an annual capacity of 300,000 tons, the project is designed to store more than 1.5 million tons of carbon dioxide(CO2), equivalent to planting nearly 14 million trees.
The project’s operation signifies China’s achievement in acquiring a complete set of technologies and equipment for capturing, processing, injecting, storing, and monitoring (CO2) at sea.
The project, serving the Enping 15-1 oil platform 200 km southwest of Shenzhen, south China’s Guangdong province, captures and processes CO2 from oilfields and then injects CO2 into a “dome” geological structure at a depth of around 800 meters under the seabed and about 3 km from the platform.
What needs to be done to inject CO2 into the seabed strata?
Firstly, a location appropriate for storage shall be found. The “dome” geological structure discovered by Chinese experts, which resembles a massive bowl, is a natural “can” that can hold CO2 stably and perpetually.
After the location is decided, a 900-meter-deep extended-reach well with a displacement of over 3,000 meters must be drilled so that CO2 can be transmitted to the “dome” geological structure.
Given such a vast displacement, the friction on the sidewall of the well is expected to multiply, so the drill would probably get stuck inside the well. In addition, the well is prone to collapse and drilling fluid loss because of the loose soil under the seabed.
To cope with these challenges, drilling experts tailored anti-corrosion drilling fluid that can support the sidewall and moisture of the well, which makes the injection of CO2 unimpeded.
Besides, a fiber optic monitoring system has been installed in the CO2 injection tube, with a monitoring point every one meter along it. Thousands of monitoring points are there to see if the line is leaked.
China’s sea areas boast a wide distribution of sedimentary basins, thick strata, and many structural traps, which creates a sound environment for the storage of CO2.
The potential CO2 storage capacity in the country’s sea area is estimated to be 2.58 trillion tons, offering the necessary support for the government to reach its “dual carbon” goal of peaking carbon dioxide emissions by 2030 and achieving carbon neutrality by 2060.