RRS James Cook Cruise 77, 02 -28 Sep 2012. Investigating carbon capture and storage at the Sleipner Field

Abstract

The NOC lead cruise, JC077 represents the main cruise activity as part of the UK’s input to the EC funded ECO2 project. The project aims to develop a “Best environmental practice” for the carbon capture and storage (CCS) industry. CCS has been proposed as a means of mitigating climate change by storing CO2 in geological reservoirs. The UK has identified sub-seabed storage as the most likely CCS process to be used. Other countries such as the US and Germany are pursuing land based CCS geological storage. Two types of reservoirs have been identified, saline aquifers such as Slepiner or depleted hydrocarbon reservoirs (oil and gas fields). The storage process require a monitoring strategy to ensure that any storage site is effectively monitored to ensure no leakage, or if there is leakage, to detect and monitor the effect of that leakage on the marine environment.

The Sleipner site in the Norwegian sector of the North Sea is one of the longest operated CCS sites in Europe. It uses CO2 that has been separated from the natural gas from the Sleipner West Field and injects it into a saline aquifer in a permeable sand body called the Utsira sand. The aquifer is capped by a seal of shale and is thought to be impermeable. The depth of the aquifer is 900 m below the seafloor with 80m of water. This storage site has been in operation since 1996 and contains more than 14 million m3 of CO2 with more being continually added. The site has been monitored mainly though the use of seismic on regular intervals to produce “4D” maps of the distribution of the CO2 though the reservoir. These models show a migration of the plume of CO2 to the north west.

JC077 takes a multidisciplinary approach to assess the Sleipner area for signs of leakage from the existing CCS reservoir. We will use a combination of AUV technology with a suite of sensors to determine if leakage is already occurring from the Sleipner field and if so to examine the effects of such leakage. The use of the AUV Autosub allows us to survey areas of the seabed at a resolution that is simply not possible by other means over a comparable time frame. The newly developed pH, pCO2 and Eh sensors attached to Autosub allow us to detect sites of leakage if it is occurring. Chirp and sidescan sonar mounted on Autosub would also allow the identification of sub-seabed and seabed features of interest. In conjunction with this we will use ship based multibeam and EK60 to look for leakage sites, and use water and sediment sampling systems to examine the state of the environment at present, and examine any areas of leakage detected.

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