Nearshore CO 2 storage – description

Relevant geological structures have been mapped with, often older, 2D seismic and the use of analogue wells.

Further maturation of the nearshore storage potential will therefore involve 3D seismic and drilling of one or several appraisal wells, some of which potentially can be reused for injection or observation. See also discussion about maturation in section 1.3.

Hanstholm structure (2753 Mt):

This very large structure was mapped by Japsen and Langtofte (1991) and has not been evaluated by a well inside the closure. However, the Felicia-1 oil exploration well tested the Gassum Formation sandstone in a fault block adjacent to the Hanstholm structure. Detailed geological and numerical modelling was carried out by Frykman in Lothe et al., 2015: Updated estimate of storage capacity and evaluation of Seal for selected Aquifers, NORDICCS Technical Report. These studies indicate good permeability ranging between 200 and 650 mD and a theoretical storage capacity of at least 250 Mt. (see Figure 3-5 below). The expected injection site is located some 30-50 km offshore from the Port of Hanstholm. Water depth at the injection site is 30-40 m.

Import of CO2 is expected to take place by ship to an intermediate storage located at an existing seaport.

Figure 0-21: Geological map of the Hanstholm Structure [19]

A similar type of near-shore storage option may exist in the southern part of the North Sea, off the coast of Esbjerg, with the geological structure located some 100 km offshore. This immature option has not been spec-ified in any detail and is considered to be included in the generic case. See the map in Figure 2.7.

Røsnæs structure (227 Mt):

This structure is located under the Great Belt with a smaller part below the tip of Røsnæs. This means that wells could potentially be drilled from land whereas marine 3D seismic surveys could still be acquired by ship. See the map in Figure 0-17.

Due to the nature of the structure with a large fault, at least two additional appraisal wells will be required.

Potential CO2sources are located in the Kalundborg area (0.5 Mt/Y) requiring a 10-15 km pipeline. Other CO2

sources could be urban areas such as the Copenhagen area, i.e. capture of CO2 from e.g. Amager Bakke, Amager Værket, HC Ørsted power plant, Avedøre power plant, Roskilde waste incineration and others, a total of 3 to 5 Mt/y or maybe up to 7-8 Mt/y. This would either require a pipeline across Zealand or import to the nearby Kalundborg port.

Generic nearshore case

The generic case assumes some local CO2 capture in a port area, which can also be used for import of CO2 by ship. The port facilities will include an intermediate storage and CO2 injection plant from where the CO2 is trans-ferred to the injection plant through a 40 km pipeline to the nearshore injection site.

Wells will be drilled from a minimum facilities wellhead platform. Initial studies have shown that the costs of a minimum facilities wellhead platform and subsea injection development are comparable even for a few wells, and if additional wells are required, the wellhead platform option is the optimal solution.

Figure 0-22: Nearshore storage facility 1.2.1 1 Mt/year nearshore CO² storage

CO2 is expected to be supplied to the port by shuttle tanker and stored in a 20,000 tonnes intermediate storage close to the port. The storage will consist of a number of well-insulated pressurised tanks where the CO2 is stored under the same conditions as in shuttle tankers (between -50˚C at 6 barg and -30˚C at 14 barg). A recov-ery unit will capture and liquefy the CO2, which evaporates in the storage.

The CO2 is pumped from the storage tanks and heated with sea water before high-pressure pumps increase the pressure to the required injection pressure to allow injection into the reservoir. The CO2 is transferred in a high-pressure pipeline to the wellhead platform where the CO2 can be injected directly into the reservoir.

It is expected that the 1 Mt/y CO2 will require a minimum of two injection wells: one to provide redundancy and one for observation.

1.2.2 3 Mt/year nearshore CO2 storage

CO2 is expected to be supplied to the port by shuttle tankers and stored in a 30,000 tonnes intermediate stor-age. The CO2 is heated and then pumped to the minimum facilities wellhead platform for injection.

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It is expected that the 3 Mt/y CO2 will require a minimum of six injection wells, one to provide redundancy and one for observation.

1.2.3 5 Mt/year nearshore CO2 storage

CO2 is expected to be supplied to the port by shuttle tankers and stored in a 50,000 tonnes intermediate stor-age. The CO2 is heated and then pumped to the minimum facilities wellhead platform for injection.

It is expected that the 5 Mt/y CO2 will require a minimum of ten injection wells, two additional wells to provide redundancy and one for observation.

1.2.4 Typical timeline for a nearshore CO² storage

Year Activity

1-2 Additional 3D seismic surveys Appraisal well

Conceptual studies for facilities

3 Environmental impact assessment, public hearings and approvals FEED studies

Construction and installation of wellhead platform Drilling of first injection wells

6-7 Commence Injection CO2

Evaluation of reservoir behaviour

Investment decision for additional injection wells 8-9 Drilling of additional injection wells

10-35 Injection at nominal capacity

Continuous observation and seismic surveys , say every 5 years 36 Decommissioning of surface facilities, plug and abandonment of wells Up to next

20 years Continuous observation of seabed and seismic surveys Transfer of responsibility

Release of financial security Table 0-3: Typical timeline for a nearshore CO2 storage

It may be possible to accelerate the timeline shown above depending on priority. Based on experience from other projects in terms of the permitting process, involvement of stakeholders and internal company approval to pass Final Investment Decision, the timeline presented here may seem shorter than what is realistic. But in view of the urgency of solving the climate problem and the need for reduction of CO2 content in the atmos-phere, the timeline presented here is an estimation based on the assumption that the required political support will be available to realise it.

1.2.5 Sensitivity case – Subsea wells

Instead of drilling the wells from a minimum facilities wellhead platform, the wells can be drilled from a subsea template, which is a heavy steel structure that protects the valve assemblies on top of the wells, the manifold and the controls.

An umbilical with control signals and hydraulic fluid is routed from the subsea template to the host platform, which in this case will be onshore and 40 km away.

Figure 0-23: Nearshore storage facility with subsea wells

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