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1| Introduction
This document reports the results and recommendations of a study of the key issues bearing on the development and deployment of Carbon Capture and Storage ( CCS) technology in Scotland. It was funded by the Scottish Government and industry, and was conducted by the Scottish Centre for Carbon Storage in cooperation with key industry participants.
The key issues are:
- identifying and assessing potential carbon storage sites in Scotland
- appraising Scottish infrastructure and the costs of developing it to enable CCS projects
- understanding the regulatory environment for CCS
- understanding the economics of CCS projects.
This study has:
- identified the principal sources of carbon dioxide (CO 2) that could be captured and stored (that is, power generation and major fixed industrial plants) throughout Scotland and NE England and modelled their likely future emissions
- screened potential CO 2 storage sites to identify those that are likely to be safe and commercially and technically viable
- examined the economics and practicality of enhanced oil recovery using CO 2 in North Sea oil fields
- developed a high-level model for a transport network capable of taking CO 2 from these sources to offshore CO 2 storage sites
- examined current and future regulations that may affect CCS
- identified gaps between the current commercial/fiscal conditions and those required to make CCS commercially viable
- created the evidence base and economic models required to support informed decisions regarding the early development of CCS infrastructure in Scotland
- established the further steps necessary to make large scale CCS in Scotland a reality.
The results of this strategic study have been derived from scientific literature, data from a variety of governmental organisations, and calculations and conclusions generated within the study itself.
It is now established that man-made emissions of carbon dioxide (CO 2) are a major contributor to climate change. Carbon Capture and Storage ( CCS) has the potential to enable very large reductions in CO 2 emissions arising from major industrial sources such as the generation of electricity. CCS is one of several possible options for reducing the rate of build-up of CO 2 in the atmosphere and should be seen as forming part of an overall CO 2 mitigation strategy.
This can be illustrated using stabilisation 'wedges' where each wedge represents a strategy to reduce CO 2 emissions (Figure 1). The thickening of each wedge reflects take up of the particular CO 2 reducing initiative.
Figure 1
Wedge diagram illustrating proportions of different initiatives required to reduce CO 2 concentration in the atmosphere.
CCS comprises a set of technologies that together enable CO 2 to be captured from industrial point sources, be processed, transported via pipelines (or ships in certain cases) and injected into deep rock formations at 1000 to 2500 m below the Earth's surface (Figure 2). At present, a small number of CCS projects have been initiated within the UK and the EU but as yet there are none within UK waters of the North Sea. For instance, there are two projects operating within Norwegian waters, one at the Sleipner Field in the Norwegian sector of the northern North Sea, the other at the Snøhvit Field offshore northern Norway which transports CO 2 via a 150 km pipeline to a subsea injection location. There is also a small scale injection test being undertaken at the K12B Gas field offshore Netherlands.
Figure 2
Schematic showing elements of CCS infrastructure and relationship with geological structure.
Although a gas at the Earth's surface, carbon dioxide takes a very different physical form under only slightly changed conditions. Most people are familiar with the cold, solid form known as 'dry ice' that CO 2 takes when frozen. By contrast, when placed under moderate pressure (73.7 bar or greater), and warmed (to greater than 31.1°C), it becomes a dense fluid with properties of both a liquid (density) and a gas (viscosity). In this form, CO 2 occupies one hundredth of the volume it does as a gas. Nevertheless, liquid CO 2 (density 0.7 g/cm 3) is less dense than water (1.0 g/cm 3) and like oil will float upon water. Thus some form of physical containment is needed to prevent upward migration and leakage in a subsurface store, and the physics of liquid CO 2 therefore place depth and temperature, as well as geological, constraints on any potential storage reservoir (Figure 2). In this dense state, CO 2 is readily and efficiently transported by pipeline, as it flows like gas.
Choice of study area
The extent of the study area is shown by the limits of the Scottish Renewable Energy Zone which spans onshore Scotland and extends to offshore areas and is defined in The Renewable Energy Zone (Designation of Area) (Scottish Ministers) Order 2005, ISBN 0110736176 (see map facing Contents page). Although this limit excludes a large number of potential carbon dioxide storage sites it defines an area covered by Scottish environmental statutes and as such lies within a legally defined area. Competition and/or co-operation with other potential carbon dioxide storage sites outwith the area defined in this study is possible but was not considered in detail in this study. The study focussed on the offshore area to the east of Scotland as this is closest to the major Scottish and northern English CO 2 sources. The geological formations with the greatest potential for storage of CO 2 are located offshore and include a large number of hydrocarbon fields and saline aquifers and the data to enable meaningful assessment.
Part of the Sleipner Field CCS infrastructure, offshore Norway. Courtesy of StatoilHydro.
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