It is neither straightforward nor simple to estimate the capacity of a geological formation to store CO 2 . In a recent attempt to list the various estimates of CO 2 storage capacity for the world and regions of the world (Bradshaw et al., 2006), the estimates are often merely given as "very large", with ranges in the order of 100s to 10,000s Gt CO 2 . It is clear that there is a general lack of definitions, rules and general procedures for calculating storage potentials.Having conducted studies in the past, TNO is convinced that we now need a more uniform and standard method to calculate the storage potential of any subsurface location -be it a gas or oil field (whether totally or partially depleted) or an aquifer. In any calculation of storage capacity, TNO prefers to include the concept of total affected space i.e. the entire space whose state or qualities change during the total storage time as a result of the storage operation. Furthermore, in the storage calculations we consider the injectivity of the selected injection location, and the pressure and fluid conductivity of the total affected storage space.. The intended free CO 2 storage location must have enough storage space or enough sealing capacity to contain the CO 2 for at least 10,000 years and prevent it from migrating to the surface. And finally, it must be taken into account that as a result of gravity segregation, the heavier CO 2 -saturated formation water will sink to deeper parts of the affected space.We describe a standard method we have devised to be used for any storage location to calculate the maximum storage volume based on affected space and maximum pressurization, the storage potential based on injectivity, and finally the storage efficiency of the geological trap.

As part of the Dutch Climate Policy on the implementation of the Kyoto protocol, the Netherlands government is currently investigating to what extent CO2 sequestration in the deep subsurface could help reduce CO2 emissions. On 7 February 2002 the Dutch Minister of Economic Affairs introduced a new policy to promote feasibility studies into CO2 storage in the subsurface (The CRUST program). Gaz de France Production Netherlands B.V. (GPN) is currently producing natural gas from the Dutch North Sea continental shelf. As one of the players in the Dutch gas supply market, GPN supports the idea of injecting CO2 into depleted gas fields in order to reduce CO2 emissions into the atmosphere. The gas produced at one of GPN's platforms, the K12-B platform, contains a relatively high proportion of CO2. This CO2 is at present separated from the produced natural gas and released into the atmosphere. Preliminary assessment shows that it may be relatively easy to re-inject this CO2 into the Rotliegend gas reservoir. The reservoir is located at a depth of some 3800 meters; with a hydrostatic pressure regime and a formation temperature of 132 °C. Hence GPN's K12-B platform offers a good opportunity to study the technical conditions of CO2 injection at greater depths including the behavior of the gas reservoir itself. Developing the CO2-injection demonstration facility at the K12-B platform will increase our understanding of the benefits and drawbacks of this technique. This paper reports on the results of the phase 1 and 2 studies of the ORC project - Offshore Re-injection of CO2. Phase 1 included a desk feasibility study into the possibility of underground CO2 injection at the K12-B platform. Phase 2 comprises of actual demonstration of the concept of underground storage. Some results of the early CO2 injection tests ar1 reported. Introduction The Netherlands has very actively contributed to research into the possibility of subsurface CO2 storage. This was highlighted by the fact that the first Greenhouse Gas Mitigation conference was held in Amsterdam, in 1992[1]. During the past 12 years, the Dutch tried to find a suitable field-scale test site in the Netherlands. However, in the meantime, storage plans and objectives changed and the project suffered greatly from financial constraints. However, the key question remained: "can underground storage of CO2 be achieved, and can CO2 that has been stored underground be recovered and re-used". The Offshore Re-injection of CO2 (ORC) project by GPN is subsidized by the CRUST subsidy arrangement. The ORC project aims to investigate the feasibility of CO2 injection and storage in depleted natural gas fields with the objective to realize a permanent CO2 injection facility on short terms. The nearly depleted K12-B gas reservoir produced via the K12-B platform in the North Sea was chosen as demonstration site for the ORC project. The ORC project consists of three phases:Phase 1: Feasibility study, a desk top study to investigating the feasibility of underground CO2 injection at K12-B by optimum use of existing installations, equipment and techniques;Phase 2: The actual demonstration of offshore underground CO2 re-injection by means of a small scale operational test facility. During the demonstration phase about 30,000 Nm3 CO2 per day will be re-injected, this is about 20 kton per year.Phase 3: Scale-up to a full scale CO2 injection unit including the investigation of possibilities for future re-use of the injected CO2. During the full-scale phase about 20,000 to 30,000 Nm3 CO2 per hour will be injected, this is about 310–475 kton per year.

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractAs part of the Dutch Climate Policy on the implementation of the Kyoto protocol, the Netherlands government is currently investigating to what extent CO 2 sequestration in the deep subsurface could help reduce CO 2 emissions. On 7 February 2002 the Dutch Minister of Economic Affairs introduced a new policy to promote feasibility studies into CO 2 storage in the subsurface (The CRUST program).Gaz de France Production Netherlands B.V. (GPN) is currently producing natural gas from the Dutch North Sea continental shelf. As one of the players in the Dutch gas supply market, GPN supports the idea of injecting CO 2 into depleted gas fields in order to reduce CO 2 emissions into the atmosphere.The gas produced at one of GPN's platforms, the K12-B platform, contains a relatively high proportion of CO 2 . This CO 2 is at present separated from the produced natural gas and released into the atmosphere. Preliminary assessment shows that it may be relatively easy to re-inject this CO 2 into the Rotliegend gas reservoir. The reservoir is located at a depth of some 3800 meters; with a hydrostatic pressure regime and a formation temperature of 132 °C. Hence GPN's K12-B platform offers a good opportunity to study the technical conditions of CO 2 injection at greater depths including the behavior of the gas reservoir itself. Developing the CO 2injection demonstration facility at the K12-B platform will increase our understanding of the benefits and drawbacks of this technique. This paper reports on the results of the phase 1 and 2 studies of the ORC project -Offshore Re-injection of CO 2 . Phase 1 included a desk feasibility study into the possibility of underground CO 2 injection at the K12-B platform. Phase 2 comprises of actual demonstration of the concept of underground storage. Some results of the early CO 2 injection tests ar1 reported.

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