The project newsletter

"Bridging to the future" is the Vattenfall newsletter on work and progess within Vattenfall's project on CCS. The newsletter is distributed three times a year.

Bridging to the future No.9 December 2007

Below you will find the online version of the project newsletter - Bridging to the future. A choice of shorter articles from December 2007 are presented below.
The Altmark gas field
CO₂ storage in natural gas reservoirs
Lars Strömberg takes up new position...
... and Göran Lindgren takes over
New power plant in Hamburg with commitment for CCS
Choice of technology and logistics for Vattenfall CCS applications
Building and updating knowledge on HSE issues
PhD thesis on Oxyfuel completed
Investigating CO₂ quality requirements for CCS projects
On the other side of the bridge
Construction progress at Schwarze Pumpe

The Altmark gas field

Mature or almost depleted natural gas fields provide great storage potential for CO₂ Capture and Storage Projects. The combination of CO₂ storage with enhanced gas recovery makes such fields an attractive option for natural gas producers as well. The joint CO₂ injection project in the Altmark gas field is the result of this positive synergy and the first step in investigating the possibility of the Altmark gas field for future large-scale CO₂ storage.

Major potential for CO2 storage

The natural gas fields of northern Germany provide major storage potential for CO₂ emissions from coal-fired power plants. The total storage potential in depleted gas fields in Germany amounts to more than 2,500 million tonnes of CO₂. The Altmark gas field is the second largest onshore gas field in Europe. Its subsurface storage capacity has been estimated to a maximum of approximately 500 million tonnes of CO₂. The Altmark gas field is thus a promising possible candidate for storing all the CO₂ emitted from a large-scale power plant throughout its entire life cycle.

The Altmark gas field is part of a suite of gas reservoirs stretching from the Netherlands, with the large Groningen gas field in the west, to the Altmark gas field in Germany to the east. The Altmark gas field was discovered in 1968 and has been in production ever since. With its peak in 1984, it has been declining steadily since 1996.

The present cumulative production amounts to 206 billion m3 of gas, which means that 78% of the original gas on site has been recovered up to now and economically viable gas production is coming to an end. A recovery rate of 70–80% is expected for gas fields. A gas field like Altmark that is at the end of its production period needs to look at alternative options to increase production beyond the 80% recovery point. The present alternative to extending the field’s life and hence reserves is to inject CO₂ into the gas-bearing layers of the reservoir, thereby displacing the remaining gas towards the production wells.

Favourable geology

The natural gas reservoirs of the Altmark region are located in the federal state of Sachsen-Anhalt, approximately 120 km southeast of Hamburg. The gas field is licensed to Erdgas Erdöl GmbH (EEG), a subsidiary of Gaz de France. Geologically speaking the Altmark belongs to the North German Basin, part of the Mid-European Basin. Sandstone and siltstone of the Permian Rotliegend make up the main reservoir unit of the structure. The Permian period occurred 299–251 million years ago.

During the Permian, almost all the Earth’s major landmasses were collected into a single supercontinent known as Pangaea. Large continental landmasses create climates with extreme weather conditions. Much of the interior of Pangaea was probably arid, with great seasonal fluctuations (wet and dry seasons). Deserts seem to have been widespread on Pangaea.

The geological remnants of this period making up the reservoir rocks in the Altmark region are red sandstone and siltstone intercalated with shale layers. Porosity and permeability are thus highly variable in these stratified terrestrial sediments. The intense compartmentalisation of the field is mainly the result of tectonic faulting.

The reservoir rocks are located at a depth of 3.5 km. They are overlain by several hundred metre thick massive Zechstein salt. This rock type is characterised by a very low permeability, forming an effective barrier to fluid migration, and thus constitutes an excellent cap rock.

The Altmark gas field consists of nine sub-reservoirs in total, the largest being Salzwedel-Peckensen, which is currently being investigated as part of the German geoscientific R&D programme CSEGR (see www.geotechnologien.de). Simplified numerical simulations of CSEGR suggest that the Salzwedel-Peckensen reservoir could be suitable for CO₂ storage.

The selected sub-reservoir for the pilot phase is Altensalzwedel, which is a depleted natural gas reservoir with a limited area. It is isolated from other compartments and has good reservoir quality. The infrastructure is already in place and there are wells for injection, observation and production. Experience of the pilot phase at Altensalzwedel will be of great value in the future, as this small field is representative for Altmark conditions in general.

The total injection volume of the pilot phase amounts to 100,000 tons of CO₂ transported from the Schwarze Pumpe pilot plant by trucks to the Altmark gas field. This transport solution will be specific to the pilot phase, and will require seven or eight CO₂ trailers running in shuttle traffic almost round the clock once the pilot plant is running at full capacity. For a future full-scale power plant operation, it would be necessary to transport the CO₂ in pipelines. The main target for the future is to ensure the suitability of the entire Altmark gas field for large-scale CO₂ storage with the help of this injection pilot project.
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CO2 storage in natural gas reservoirs

A number of CO₂ projects are currently ongoing or being studied from a global perspective. Some of them are using depleted gas reservoirs for storage purposes only, but several projects involving CO₂ storage combined with Enhanced Gas Recovery (EGR) are emerging, the Altmark gas field being one of them. Some storage projects are presented below.

Sleipner: Almost 10 million tonnes of CO₂ have been successfully stored in the sandstone aquifer called the Utsira Formation off the coast of Norway, 1,000 meters below the sea floor. Natural gas from the Sleipner field contains up to 9% CO₂. This level is too high and the CO₂ is therefore separated from the gas produced. The Sleipner project commenced in 1996 when Statoil decided to inject the CO₂ back below the sea floor in an aquifer located above the gas field. The site has been well monitored and after ten years of operation, no leakage of CO₂ from the sandstone formation has been observed.

Snøhvit: The Snøhvit field is located offshore to the north of Norway. Statoil has received approval to inject the CO₂ separated from the gas produced in the Snøhvit field into an aquifer called the Tubåen Formation located below the gas reservoir, in the same manner as has proven successfully for Sleipner. The operation is planned to last for more than 20 years.

K12B: The K12B gas field is located off the coast of the Netherlands. The reservoir is in the Rotliegend, the same stratigraphic level as the Altmark but at a slightly deeper level (3,500–4,000 metres beneath the sea floor). Gaz de France has undertaken a feasibility study for EGR, and since 2004 it has been successfully injecting CO₂ that is separated from the gas produced on site. The operation is planned to last 20 years in total.

Atzbach-Schwanenstadt: The Atzbach-Schwanenstadt gas field is located in north-central Austria and has been investigated as part of the CASTOR project. It is an almost depleted gas field at a depth of 1,400–1,600 metres. The option of turning the gas field into a CO₂ storage site with the possibility of enhanced gas recovery was investigated during the CASTOR project but up until now, no decision has been made by the operator about how to continue.

In Salah: The gas field of In Salah in central Algeria naturally contains up to 10% CO₂. This amount has to be reduced to 3% for commercial reasons. The CO₂ is therefore separated on site and re-injected into an aquifer that is 2,000 meters below the surface. The chosen carboniferous aquifer is characterised by a low permeability. To facilitate injection of the CO₂, the injection well was drilled partially horizontally in the reservoir horizon. There are three injection wells and four producing wells. So far, the operation has been successfully and no CO₂ has yet been observed in the methane produced.
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Lars Strömberg takes up new position...

Lars Strömberg, who has managed Vattenfall’s project on CCS, has a new job. He has been appointed Vice President Research and Development at the Vattenfall Group.

This means that he is now in charge of the entire R&D performed within the Vattenfall Group, of which the project on CCS is one part. He will however chair the project’s steering committee and therefore still have a close connection to the project.

He says: “I have been living with this vision for seven years now, and although new forces are taking over, my heart will always be in this project. But I now need to move away from the operative issues.”
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... and Göran Lindgren takes over

Göran Lindgren will take over as project manager. He has been heavily involved in the project for several years and was formerly group manager at Vattenfall Research and Development AB.

Lars Strömberg wishes Göran Lindgren a warm welcome to his new job and is very happy that the project has been able to get such competent person to take over the leadership. “The project is progressing with increasing speed and ever-increasing complexity, which is described in this newsletter. It now has a new leadership, but with the same intentions and vision and with the skillful and professional team within Vattenfall growing larger all the time,” says Strömberg.

New deputy project manager is Sascha Lüdge.
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New power plant in Hamburg with commitment for CCS

On November 14, the City of Hamburg and Vattenfall reached an agreement to start the construction work at the planned coalfired power station at Moorburg. The power station itself will reduce the regional emissions by 2.3 million tonnes of CO₂ annually, when older power stations are taken out of operation.

Hans-Jürgen Cramer, spokesperson for the board of Vattenfall Europe, explained: “There has never been such a highly efficient coalfired power station in a metropolitan region that can produce district heating and power at the same time. With flag-bearing power-generating efficiency and up to 62% fuel efficiency in the case of the power-heat coupling, the Moorburg power station forces older, less efficient power stations out of the market and thereby reduces CO₂ emissions from the power station stock overall.”

Commitment for CCS

Vattenfall is committed to build a CO₂ capture plant with the exact date being agreed on by a commission of the state and Vattenfall in 2013. Vattenfall has already obtained an option on the land required to build the capture plant.
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Choice of technology and logistics for Vattenfall CCS applications

Ship transport is the logical choice for offshore storage sites, but it might also be a sustainable alternative to pipeline transport, or a temporary and more flexible solution while a pipeline infrastructure is being built, or a complement in logistic chains involving both pipelines and ships.

Recently Vattenfall has initiated a study of the transport of CO₂ by ship, with consultancy support from Norwegian TelTek-GassTek. The purpose of this study is to further clarify ship transport technology for CO₂ captured in power plants in coastal locations. Possible logistic solutions for these Carbon Capture and Storage (CCS) applications with CO₂ transport to local storage sites or sites in the North Sea will also be studied.

Large volumes

Ship transport of very large amounts of gas is currently used for liquid petroleum and natural gas (LPG and LNG), with a typical payload of up to 100,000 m3 liquefied gas or more. For the transport of industrial grade CO₂ there are four small ships with a payload of about 1,000 m3. The CO₂ is today transported in its liquid phase at about -28°C and 15 bar.

Because of the large volumes, transport of CO₂ from power plants would require larger ships, which in turn would need to be developed technically due to the different physical behaviour of CO₂ compared to LNG and LPG. The lowest possible pressure for CO₂ would be about 7 bar at -50°C. In 2003 Statoil and partners put forward a proposal for a ship concept for the transport of CO₂ with an estimated payload of 20,000 m3, which they regard as a good compromise in terms of size for CCS and EOR logistics.

Other options

Another Norwegian ship concept was presented in 2006, where the idea is to transport compressed CO₂ at considerably higher pressure, about 70 bar. In this “floating pipeline” solution, the CO₂ would be contained in packages made of standard pipeline pieces. The idea is to avoid energy loss in the processing of CO₂ by changing the pressure and physical state. In spite of the lower amount of CO₂ transported per ship, the full logistic chain may prove advantageous.

An additional option has recently been presented by a shipping company which is big in the field of transporting other liquefied gases such as ethylene. Six of their existing ethylene ships were originally designed to also carry CO₂, providing an alternative for large scale, low pressure transport of liquified CO₂. These ships can carry up to 10,000 m3 each.

No standard solution

No optimal, standard solution for the logistics of CO₂ in the CCS chain can currently be identified, and will probably not be identified at a later stage either. The logistics to be preferred depend on a number of parameters such as the geographical prerequisites, power plant and storage site locations, amounts to be transported, timing, choice of technology, ship sizes, etc. Sets of logistic cases need to be formulated and studied in greater depth to improve understanding of the technical and economic characteristics of possible ship transports of CO₂ for Vattenfall.
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Building and updating knowledge on HSE issues

Vattenfall is continuously following the results and progress of the research community with respect to environmental aspects of capture, transport and storage of CO₂. Vattenfall also cooperates with external partners and participates in international projects to build knowledge. The work focuses on identifying and assessing potential risks to health, safety and environment (HSE), how to address these and how to communicate them clearly. Most environmental risks can be eliminated or minimised by gaining knowledge of the issues and implementing preventative measures.

Potential critical areas have previously been identified (as published in Bridging to the Future no. 5, Sept 2006). What the areas designated as critical have in common is that they are difficult to manage due to a lack of knowledge, standards, guidelines and regulations. The risks have since then been analysed with respect to the magnitude of potential environmental consequences and how likely they are to occur. The potential for launching preventative measures or neutralising risks by gathering background information and knowledge has been taken into account in the evaluation.

The most critical HSE risks relate to the consequences of a potential leakage of CO₂ from a geological storage reservoir, or from a pipeline used for transporting CO₂, as illustrated in the figure below. The probabilities are in some cases estimated to be medium to high, but the resulting consequences are still expected to be limited (little or very localised impact). The sizes of the circles in the diagram illustrate the spread of uncertainty in the evaluation. Environmental work is focused on decreasing the uncertainty, but in order to eliminate unknown factors, a site-specific investigation will in many cases be required.

The success of a CO₂ capture, transport and storage project depends on us making the right choices regarding aspects such as proper site selection methods and criteria, use of best available technology, thorough monitoring and plans for mitigation and remediation. When the work moves on to site-specific evaluations and the realisation of a CO₂ capture, transport and storage project, uncertainties associated with potential risks will be addressed through thorough investigations and studies, and measures will be taken to minimise risks.

It is Vattenfall’s conviction that capture, transport and storage of CO₂ can be undertaken in a safe and acceptable way with good environmental performance. The dominating environmental effect of the technology will be significant reductions of CO₂ emissions to air.
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PhD thesis on Oxyfuel completed

Research into Oxyfuel combustion has been carried out at Chalmers University of Technology for several years, and the first PhD thesis is now available. Klas Andersson, who we have previously written about here in Bridging to the Future, has completed his work at Chalmers.

The work presented includes the design and construction of a 100 kW Oxyfuel test unit, at which extensive test campaigns have been carried out using both gaseous and solid fuels. Among other results, a detailed description of Oxyfuel flames with emphasis on their composition and radiative heat transfer characteristics has been presented. The Oxyfuel research group at Chalmers will continue their work at the test unit to increase knowledge on combustion fundamentals. The aim is to develop both descriptive and predictive modelling tools to be used in the design of Oxyfuel combustion systems.
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Investigating CO2 quality requirements for CCS projects

An important aspect in the analysis of a system with CO₂ capture, transport and storage is the quality requirements for the captured CO₂, that is, the limits set for the concentration of the non-CO₂ components present in the stream sent to the storage site.

The quality requirements may have a significant impact on the cost of CO₂ capture, transport and storage. CO₂ capture combined with other emission reductions may provide a cost- and energy-efficient solution for overall emission control in power plants. However, the co-capture of other components into the CO₂ stream may increase the risk of negative impact on capture, transport and storage systems. This will eventually increase the overall costs of power generation and should be avoided as much as possible.

Requirements on the quality of the CO₂ stream should be based on scientific and technical knowledge of CO₂ mixture properties, impurity behaviours and their interactions with the main components of the systems and the environment. The objective should be, as is the case with other industry applications, to reach an acceptable balance between minimising the potential for increased costs and environmental impact. An initial article on this topic was presented in newsletter no. 6, 2006.

CCS is not EOR

Vattenfall started looking into the CO₂ quality issue in 2003 and has since then worked to increase knowledge in the field to avoid arbitrary limits being introduced. The CO₂ specifications considered range from CO₂ mixtures of about 95% CO₂ content to up to 99.9% CO₂. Existing specifications from projects related to EOR (Enhanced Oil Recovery) operations provide a good knowledge base; however, they are not directly transferable to CCS projects for several reasons.

One important difference is that most EOR projects are located in remote areas with pipeline transport of CO₂ through vast unpopulated areas, which makes it easier to handle risks related to the unlikely event of a pipeline rupture and release of CO₂ and the other components. In addition, CO₂ injection for EOR is part of an industrial operation, while CCS is related to environmental control, with the main aspects linked to the long-term safe storage of CO₂.

Experimental data is lacking

During the work it has been identified as important that the thermo-physical properties of the CO₂ gas mixture can be accurately predicted, so that the fluid behaviour regarding storage capacity estimations related to phase equilibrium, density and solubility properties can be estimated. Today, experimental data in this field is to some extent lacking.

In addition, the interaction between brine and rock in the CO₂ storage reservoir in relation to the redox potential of the mixture and the presence of acidic or basic components needs to be accounted for. Geochemical experimental data is needed to calibrate geochemical numerical simulations. Aspects related to the corrosion of equipment in the CO₂ capture plant, pipeline and injection equipment also need to be considered when determining a suitable standard for CO₂ quality and may require experimental qualification of materials.

These aspects and others are investigated by Vattenfall and also by several universities and institutes such as the Royal Institute of Technology in Stockholm, TU Hamburg-Harburg, BGR in Germany, SINTEF in Norway, BRGM in France, and EU projects such as ENCAP, DYNAMIS and CO₂ReMoVe.
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On the other side of the bridge

Vattenfall’s strategy for fighting climate change is made up of three prongs, of which capture and storage technology is one. The other two are the optimisation of existing technology and the increased use of energy sources without emissions of fossil-fuel carbon dioxide.

Hydropower — premier renewable energy

Hydropower plays a very important role in electricity generation in the Nordic countries, representing about 50 per cent of the total supply in the region. In Sweden, Vattenfall has about 100 hydropower plants, about 50 of which are small-scale, while in Finland Vattenfall operates ten hydropower plants, also mostly small-scale. During a year with normal rain and snowfall, the plants in Sweden and Finland provide about 33 TWh. In Germany, Vattenfall operates six hydropower plants and eight pumped storage power plants. The latter constitute a very useful tool, for example, for the integration of wind energy into the system by storing energy when the wind is blowing and generating power when there is no wind.

Major investments

Vattenfall is currently engaged in a major re-investment programme in its hydropower plants to the tune of around € 675 million. The investments will secure long-term production, improve dam safety and environmental performance, decrease maintenance costs and increase generation. As a result of the upgrade, an additional 300 GWh will be produced per year by 2013, without any CO₂ emissions whatsoever.

For years and generations to come, hydropower will definitely continue to play an increasingly important role in renewable energy generation.
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Construction progress at Schwarze Pumpe

On 20 september Vattenfall successfully installed the furnace at the construction site for the Oxyfuel pilot plant. The combustion chamber, which weighs 230 tonnes, was lifted into the boiler house by a 500-tonne crane. The Oxyfuel boiler has an overall height of 25 metres, which made the process a logistical challenge. The whole process took about two hours and 30 people were involved. On the same day, the two CO₂ storage tanks were installed.

A couple of weeks later, parts of the air separation unit (ASU) also arrived at the pilot plant site in Schwarze Pumpe.

With these two events, Vattenfall has reached another important milestone in the construction phase, and the project is therefore in keeping with the construction schedule.
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