Shuttle system beats the pipe
Researchers in Japan have published a study on shipping CO2 to offshore storage sites, which could offer an attractive solution to industrialised nations which lack the appropriate geology, skills or infrastructure necessary to bury emissions.
The work from Chiyoda Corporation, led by Professor Masahiko Ozaki of Japan's Department of Ocean Technology, Policy, and Environment, offers a technical prefeasibility study of CO2 transportation by ship, the design of ship equipment and injection methods suitable for offshore operations and their regulatory considerations.
The argument is that offshore burial will bring into the fold those nations that do not have suitable local geology or the skills and infrastructure that come from having a domestic oil and gas industry, necessary to bury emissions. An offshore option could help accelerate the development and deployment of CCS and provide an economical alternative to lengthy seabed pipeline transportation.
The only major offshore CCS project currently operating is Norway's Sleipner project which removes CO2 from natural gas and sequesters it in a sandstone repository at least 800 m below the sea bed. The Gorgon Gas project in Western Australia plans to also strip CO2 from the gas stream and bury it in a repository via a facility on Barrow Island, between the field and the mainland.
Ozaki's model supports systems to store liquefied CO2 at ports for offloading to shuttle ships equipped to inject it into geological storage via floating terminals and wellheads on the seafloor. Advantages include flexibility of access to suitable geological storage formations and cost savings in establishing and potentially reusing infrastructure.
The study considered CO2 being transported in liquid phase at -10oC and 2.65 MPa in shiploads of around 3000m3 in two tanks to be offloaded into offshore reservoirs in a 24-hour period. Before injection it would be heated to 5oC to avoid freezing seawater around the injection pipe and wellhead.
Frequent transport and injection by small to medium ships would be effective, said Ozaki, particularly when facilities for CO2 buffer storage are difficult to build "for technical, economical, or social reasons".
In its conclusion, the study calls for more detailed analysis to optimise the suggested engineering systems.
Source: tce today