Scope of the case study

The case study includes the 18 biggest CO2 emission sources in the UK and 10 largest sinks in the Southern North Sea and the East Irish Sea. The aim of this scenario is to illustrate the development of a CCS network from 2010 (i.e. the beginning of this PhD programme) until 2050 over four 10 year time periods. The condi- tions or parameters under which the network functions i.e. costs, inflation rates, capture targets etc are assumed to remain constant throughout each phase. The driver behind the expansion of the network is a capture target that begins with 15% for the first time period and linearly increases to 60% mitigation of the total emission during the last time period.

3.7.1.1 CO2 emitters

A full list of the selected CO2 emission sources can be found in Appendix A. The eighteen sources include thirteen coal power plants, three CHP and CCGT plants and two Iron and steel manufacturers. The sources’ annual CO2 emissions range from 22.4Mt CO2 per year from the Drax coal power plant down to annual emissions of around 3MtCO2 per year. A total emission of 112 Mt per year is considered for capture and storage.

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Figure 3.3 Selected source‘ shares of total emission by asset class

The sources have been selected from a list of UK emitters obtained from the data published by the EU ETS [102]. The selection process was based on the most CO2 intensive sources in the UK regardless of their geo- graphical locations. The case study aims to produce a picture of a UK wide CCS network through the geo- graphical diversity of the selected sources and sinks. If required, the generic nature of the model easily allows for developing scenarios, which include a larger number of the UK emitters or potential storage sites.

3.7.1.2 CO2 storage sites

The UK’s potential storage capacity in hydrocarbon fields and saline aquifers is significant. The British Geo- logical Survey estimates a capacity of 14,880 MtCO2 in the saline aquifers of the Southern North Sea and the East Irish Sea, however the estimated saline aquifer capacity is associated with more uncertainty than the hydrocarbon reservoirs. The BGS also reported an EOR capacity of 1,175Mt CO2 in the Central and Northern sea basin and in the Southern North sea, the gas fields’ capacity is estimated to store 5,140MtCO2 [83, 103]. On the other hand, the East Irish Sea oil and gas fields have considerable potential to store CO2. The East Irish Sea is well placed to receive CO2 from power plants and other industrial sources in North Wales and North West England. The best storage potential is likely to be in the larger gas fields such as Morecambe South and Morecambe North. The calculated CO2 storage capacity in the oil and gas fields of the East Irish Sea basin is approximately 1,047 Mt [104].

Southern North Sea Rotliegend gas fields are selected as the potential candidates for the storage sites of the UK CCS scenario. This is because these sinks are placed close to many of the UK’s emission intensive sources. Also the availability of seismic data for hydrocarbon fields and their cap-rock integrity makes them

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attractive candidate for storing CO2. The Triassic East Irish sea basin sinks, Morecambe North and South are also selected to explore if an optimal CCS network in fact chooses to transport and store CO2 in this location and how that affects the layout of the network.

Eight of the largest depleted gas fields in the Southern North Sea were selected. A total capacity of 3.43Gt is assumed for the selected Southern North Sea and the East Irish Sea sinks. A complete list of the selected fields and their storage capacities has been included in Appendix C. Appendix C also contains the assump- tions regarding the number of platforms, the number of wells, the maximum injection rates and the capital and operational cost figures for both the Southern North Sea and the East Irish Sea sinks.

3.7.1.3 A CCS transport infrastructure that follows the existing gas lines

For the UK scenario, a cost incentive is introduced in the model to encourage the new CO2 pipelines to fol- low the routes of the existing gas infrastructure. Concerns regarding adverse environmental impacts such as crossing and interrupting certain ecosystems, route surveys, issues with the landowners in the path of the pipeline, obtaining rights of way etc will have already been resolved, if the existing gas lines are fol- lowed.

In the CC supply chain model, these potential benefits are introduced through a constraint, which applies a cost reduction factor if a route is built between the nodes, which represent the UK’s current gas infrastruc- ture. Either the nodes are at the locations of gas terminals or they are dummy nodes. If connected they represent a layout very similar to parts of the existing gas lines. The dotted lines of figure 3.4 indicate the routes of the gas lines as fed to the GAMS model. This can be compared with parts of the actual UK gas infrastructure shown in figure 3.5.

The scenario of this chapter was tested for several cost incentives and it was concluded that cost incentives less than 50% do not result in a notable portion of the CCS pipeline infrastructure following the existing gas lines. Tests indicated that as expected increasing the cost incentive encourages the CCS network to follow the existing lines extensively. However considering some of the potential benefits listed above for following the existing infrastructure, costs savings above 50% may not be realistic. Therefore, in the scenario pre- sented here, a cost reduction factor of 50% was applied if the model selects to connect two nodes between which a gas pipe has already been built.

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Figure 3.4 Sources and sinks of the UK CCS scenario and the assumed gas lines

Figure 3.5 The UK’s gas infrastructure (National grid) 3.7.1.4 Elevation or depth of the supply chain nodes

An elevation or depth parameter is introduced for every node. The model considers extra costs associated with taking into account the actual distances. The elevations of the sources range between 0-69m with majority only as high as 10m. The water depth values at the location of the sinks are taken as depth values ranging from -25m to -40m. The depth and elevation data can be found in appendix A.

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