In the discussion of climate change the capture and storage of CO2 (known as CCS - carbon capture and storage) is seen as a key factor. This is one option in a broad pallet of measures necessary to abate climate change in a period of transition to sustainable forms of energy. The oil and gas sector will be able to facilitate this by CO2 storage. Decision-making on this is currently with the government.
CO2 is the carbon containing gas that is given off when combusting (fossil) fuels. To store CO2 it first has to be separated from the other gases emitted. Thought is firstly being given to collecting CO2 from large industrial complexes and power plants. The separated CO2 would be transported by pipeline or ship to depleted oil and gas fields in which it would then be stored. Both on and offshore in the Netherlands there are large gas fields which in principle could safely store large quantities of CO2.
Internationally it has been accepted that CO2 storage in empty oil and gas fields is basically safe provided good locations are selected. The International Panel on Climate Change (IPCC) states that over 99% of the stored CO2 should still be safely in place after 1,000 years (see IPCC special report on CCS). In practice relatively little experience has been gained in CO2 capture and storage. In the Netherlands, CO2 has been stored since 2005 in a gas reservoir in North Sea block K12-B. This is a relatively small scale project. For the last ten years CO2 has been successfully stored in Norway at the Sleipner platform.
Over recent years NOGEPA has been involved in various research projects to identify the possibilities of storing CO2 in the Netherlands.
The possibilities and risks of CO2 storage deep underground in the Netherlands have been researched in the project AMESCO - Algemene Milieu Effect Studie CO2-Opslag (General Evaluation of Environmental Effects of CO2 Storage). This is the initiative of a group from the energy sector and government. It is not clear yet which gas fields in the Netherlands would be most suited for the purpose. More information on results obtained is available from the AMESCO Report.
To study the possibilities of CO2 storage in depleted gas fields in the Dutch part of the North Sea NOGEPA has undertaken three studies.
1) The storage capacity of the Dutch sector of the continental shelf
The first study evaluated the potential of old gas reservoirs on the Dutch continental shelf for CO2 storage. The research addressed field capacity, availability and suitability of the existing infrastructure (platforms, pipelines etc.). The researchers came to the conclusion that the depleted fields on the Dutch sector of the continental shelf would offer storage for some 900 million tons. The 21 largest fields would represent over half of this.
Because building new platforms and drilling new wells in depleted fields is expensive and technically complex there is a strong preference for using existing pipelines and infrastructure wherever possible.
More information: Potential for CO2 storage in depleted gas fields on the Dutch Continental Shelf; Phase 1: Technical assessment.
2) Estimated costs for transport and storage.
After publication of the first investigation, NOGEPA gave instruction for a second study addressing the costs involved with large scale storage of CO2 in empty gas fields in the North Sea. The investigation described the investments and operational costs necessary over a period of 30 years to store 30 million tons of CO2 per year at sea. This study assumed the construction of two new pipelines and various gas platform modifications. Based on a number of such assumptions, the first estimates suggested a cost of 8 Euro per ton of CO2 for its transport and storage. The costs of capture and compression on land were not included in the research. These costs will be significantly higher than those shown above.
More information: Potential for CO2 storage in depleted gas fields on the Dutch Continental Shelf; Phase 2: Costs of transport and storage.
3) Storage capacity in aquifers related to oil production
The third investigation of the Carbon Capture and Storage (CCS) working group addressed the possibility of storing CO2 in empty oil fields and in the water containing layers below them (aquifers).
The total oil reserves under the Dutch continental shelf are but modest. The volume of oil produced in the past thus suggests a restricted capacity for CO2 storage. Further capacity restriction is suggested by the fact that in the oil production process, seawater is injected to keep up the field pressure, in turn reducing future storage capacity. The storage capacity in empty oil reservoirs is estimated at some 200 million tons. This could be raised appreciably if the CO2 could be stored in the aquifers under the oil reservoirs. In that case water would have to be forced out of the aquifer to create space for the CO2. Much research is still necessary to accurately quantify the CO2 capacity of aquifers.
Conditions for CO2 storage
CO2 storage will require legislative underpinning and broad social consensus. It will be important that an effective organisation structure of companies storing the CO2 be in place when it is needed. Clarity will be essential as to all the financial obligations, responsibilities and liabilities and their various moments of applicability. The EU Directive on CCS and related guidelines will be important guides to national legislation.
Finally it will all depend on the cost of CO2 emissions. Developments in among other things emissions trading will make clear whether CO2 storage will be an economically attractive activity.
Good timing will be important in CO2 storage. Where will fields become available for storage? What infrastructure will have to be retained to facilitate CO2 storage? How much time lies between the stopping of production and the moment that the storage location can actually be taken into use?