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carbon capture and storage

New study of natural CO2 reservoirs: Carbon dioxide emissions can be safely buried underground for climate change mitigation

New study of natural CO2 reservoirs: Carbon dioxide emissions can be safely buried underground for climate change mitigation

New research shows that natural accumulations of carbon dioxide (CO2) that have been trapped underground for around 100,000 years have not significantly corroded the rocks above, suggesting that storing CO2 in reservoirs deep underground is much safer and more predictable over long periods of time than previously thought, explains Suzanne Hangx a postdoctoral researcher at the University of Utrecht.

The findings, published today in the journal Nature Communications, demonstrate the viability of a process called carbon capture and storage (CCS) as a solution to reducing carbon emissions from coal and gas-fired power stations, say researchers.

About 80% of the global carbon emissions emitted by the energy sector come from the burning of fossil fuels, which releases large volumes of CO2 into the atmosphere, contributing to climate change. With the growing global energy demand, fossil fuels are likely to continue to remain part of the energy mix. To mitigate CO2 emissions, one possible solution is to capture the carbon dioxide produced at power stations, compress it, and pump it into reservoirs in the rock more than a kilometer underground. This process is called carbon capture and storage (CCS). The CO2 must remain buried for at least 10,000 years to help alleviate the impacts of climate change.

The key component in the safety of geological storage of CO2 is an impermeable rock barrier (the ‘lid’ or caprock) over the porous rock layer (the ‘container’ or reservoir) in which the CO2 is stored in the pores – see Figure X. Although the CO2 will be injected as a dense fluid, it is still less dense than the brines originally filling the pores in the reservoir sandstones, and will rise until trapped by the relatively impermeable caprocks. One of the main concerns is that the CO2 will then slowly dissolve in the reservoir pore water, forming a slightly acidic, carbonated solution, which can only enter the caprock by diffusion through the pore water, a very slow process.

Some earlier studies, using computer simulations and laboratory experiments, have suggested that caprocks might be progressively corroded as these acidic, carbonated solutions diffuse upwards, creating weaker and more permeable layers of rock several meters thick and, in turn, jeopardizing the secure retention of the CO2.  Therefore, for the safe implementation of carbon capture and storage, it is important to accurately determine how long the CO2 pumped underground will remain securely buried. This has important implications for regulating, maintaining, and insuring future CO2 storage sites.

Schematic diagram of a storage site showing the injection of CO2 (in yellow) at a depth of more than one kilometer into a layer of porous rock (the ‘container’ or reservoir), and kept from moving upwards by a sealing layer (the ‘lid’ or caprock). Via Global CCS Institute

Schematic diagram of a storage site showing the injection of CO2 (in yellow) at a depth of more than one kilometer into a layer of porous rock (the ‘container’ or reservoir), and kept from moving upwards by a sealing layer (the ‘lid’ or caprock). Via Global CCS Institute

To understand what will happen in complex, natural systems, on much longer time-scales than can be achieved in a laboratory, a team of international researchers and industry experts traveled to the Colorado Plateau in the USA, where large natural pockets of CO2 have been safely buried underground in sedimentary rocks for over 100,000 years. The team drilled deep below the surface into one of the natural CO2 reservoirs in a drilling project sponsored by Shell, to recover samples of these rock layers and the fluids confined in the rock pores.

The team studied the corrosion of the rock by the acidic carbonated water, and how this has affected the ability of the caprock to act as an effective trap over long periods of time (thousands to millions of years). Their analysis studied the mineralogy and geochemistry of the caprock and included bombarding samples of the rock with neutrons at a facility in Germany to better understand any changes that may have occurred in the pore structure and permeability of the caprock.

They found that the CO2 had very little impact on corrosion of the caprock, with corrosion limited to a layer only 7cm thick. This is considerably less than the amount of corrosion predicted in some earlier studies, which suggested that this layer might be many metres thick. The researchers also used computer simulations, calibrated with data collected from the rock samples, to show that this layer took at least 100,000 years to form, an age consistent with how long the site is known to have contained CO2. The research demonstrates that the natural resistance of the caprock minerals to the acidic carbonated waters makes burying CO2 underground a far more predictable and secure process than previously estimated. With careful evaluation, burying carbon dioxide underground will prove safer than emitting CO2 directly to the atmosphere.

By Suzanne Hangx, Post Doctoral Researcher at the University of Utrecht

 

Reference:
Kampman, N.; Busch, A.; Bertier, P.; Snippe, J.; Hangx, S.; Pipich, V.; Di, Z.; Rother, G.; Harrington, J. F.; Evans, J. P.; Maskell, A.; Chapman, H. J.; Bickle, M. J., Observational evidence confirms modelling of the long-term integrity of CO2-reservoir caprocks. Nat Commun 2016, 7.

The research was conducted by an international consortium led by Cambridge University together with universities in Aachen (Germany) and Utrecht (Netherlands), the Jülich Centre for Neutron Science (Germany), Oak Ridge National Laboratory (USA), the British Geological Survey (UK) and Shell Global Solutions International (Netherlands). The Cambridge research into the CO2 reservoirs in Utah was funded by the Natural Environment Research Council (CRIUS consortium of Cambridge, Manchester and Leeds universities and the British Geological Survey) and the UK Department of Energy and Climate Change.

GeoCinema Online: The Geological Storage of CO2

 Welcome to week two of GeoCinema Screenings!

In a time when we can’t escape the fact that anthropogenic emissions are contributing to the warming of the Earth, we must explore all the options to reduce the impact of releasing greenhouse gases into the atmosphere. The three films this week tackle the challenge of separating CO2 from other emissions and then storing it in geological formations deep underground (Carbon Capture and Storage, CCS).

Infografics of the CO2 Storage at the pilot site in Ketzin (modified after: Martin Schmidt, www.starteins.de) Credit: http://www.co2ketzin.de/nc/en/home.html

Infografics of the CO2 Storage at the pilot site in Ketzin (modified after: Martin Schmidt, www.starteins.de) Credit: http://www.co2ketzin.de/nc/en/home.html

Geological Conditions and Capacities

Porous rocks with good permeability have, in Germany and world-wide, the highest potential for geological CO2 storage. Where do these rocks occur? And which further criteria do potential CO2 storage sites need to meet?

Ketzin Pilot Site

At the Ketzin pilot site in Brandenburg, Germany, CO2 has been injected into an underground storage formation since June, 2008. …”. The monitoring methods used at the pilot site Ketzin are among the most comprehensive in the field of CO2 storage worldwide. Of importance is the combination of different monitoring methods, each with different temporal and spatial resolutions. Which methods are used? And what has already been learned?

Scientific Drilling at the Pilot Site Ketzin

Well Ktzi203 offers, for the first time, the unique opportunity to gain samples ) from a storage reservoir that have been exposed to CO2 for more than four years. The film follows how the samples were collected and studied.

 

You can view all three films and journey through the exploration of CCS here.

Have you enjoyed the films? Why not take a look the first posts in this series: Saturn and its icy moon or some of the films in last year’s series?

Stay tuned to the next post of Geo Cinema Online for more exciting science videos!

Credits

All three films are developed as part of the Forshungsprojekt, COMPLETE, Pilotstandort Ketzin. (Source).

‘Coaland’ – fossil fuel addiction, renewables envy and Poland’s energy future

The Emerging Leaders in Environmental and Energy Policy (ELEEP) Network brings together young professionals from Europe and North America with the aim of fostering transatlantic relations. As Warsaw prepared to host last month’s UN climate convention (COP19), ELEEP members, including former EGU Science Communications Fellow Edvard Glücksman, sat down for coffee with one of the early pioneers of Poland’s green movement.

Last month, Poland hosted the COP19 UN climate talks amidst a flurry of controversy. One of the EU’s least energy-efficient countries, Poland remains staunchly committed to a future powered by coal and shale gas, presently deriving over 90% of its electricity from the most carbon-intensive of fuels. Polish politicians almost unanimously agree that coal, their ‘black gold’, is critical for the country’s future energy needs – and independence – as well as for the increasingly industrial developing world. They therefore believe that, rather than shifting to renewables, the most sensible next step is to focus on developing greener coal technology, including carbon capture and storage (CCS) and flue gas separation.

However, not everyone shares the coal-centric view held by Poland’s political leadership. According to veteran green campaigner Andrzej Kassenberg, president of the Institute for Sustainable Development, continuing to rely on coal would be a big mistake. Yet, in a bustling coffee shop at the heart of Warsaw, Kassenberg speaks with cautious optimism about his country’s future and the prospect of significantly lowering emissions, even within neighbour Germany’s ambitious 2050-timeframe. To that end, his recently published evidence-based report, 2050.pl – the journey to the low-emission future, thoroughly demonstrates how Poland can continue growing whilst also shedding its addiction to coal.

Andrzej Kassenberg, known to many as the ‘father of Poland’s green movement’. (Credit: Edvard Glücksman)

Andrzej Kassenberg, known to many as the ‘father of Poland’s green movement’. (Credit: Edvard Glücksman)

Time to decarbonise

Recounting his country’s energy story, Kassenberg describes the slow weathering of Polish infrastructure and its ageing fleet of power stations, neglected by generations of narrow-minded politicians keen to promote coal and nuclear quick-fixes. He fears that, should Poland continue to embrace fossil fuels, they too, like Spain, Portugal, and Greece, would fall into a “middle income trap”, their development grinding to a halt without the modern infrastructure needed to support growth. Other nations, he explains, like South Korea and Finland, avoided such a fate because they “decarbonised” before it was too late.

When asked to summarise how Poland’s low-emissions future could work, Kassenberg is quick to suggest that a commitment to drastically overhauling the country’s energy portfolio, mirroring Germany’s ongoing energy transition, would improve almost every sector of Polish society, not least the population’s health. According to the European Environment Agency, Poland experiences the second highest levels of air pollution in Europe; citizens of major cities breathe in the pollution-equivalent to 2,500 cigarettes per year.

Waiting for COP19 to begin, ELEEP members debate the prospect of a greener energy future on the streets of Warsaw. (Credit: Edvard Glücksman)

Waiting for COP19 to begin, ELEEP members debate the prospect of a greener energy future on the streets of Warsaw. (Credit: Edvard Glücksman)

Shale gas as a transition fuel

Kassenberg maintains a discernible realism when he speaks about the future. He sees shale gas as a potentially effective transition fuel and one that could best be used on the local level by small-scale power stations, complemented by locally harvested renewables. However, he notes that shale has until now been largely neglected in Poland; at present, it gets no mention in the national energy policy agenda, perhaps because reserves lie deeper – and under a denser population – than in the United States.

With such strong political support for coal, how, then, could one go about convincing members of the population to push politicians to go back on their word? According to Kassenberg, much of the challenge lies in understanding how power works in the old East. Democracy, he explains, does not work in Poland as it does in western Europe or North America, primarily because of a lack of basic knowledge and overly short-term planning.

An expensive addiction

To that end, Kassenberg is convinced that policymakers overlook long-term challenges in favour of short-term, local issues and popular grievances, such as unemployment. Voters, in turn, think that energy from renewables would be expensive, failing to understand the high costs associated with a coal portfolio. Polish coal is naturally expensive to exploit, with reserves lying deep underground, making the mining process relatively costly and often more expensive than importing from mining areas that are further afield, such as South Africa. Furthermore, other hidden costs associated with deep-lying coal burden the taxpayer, not least in their subsidising of miners’ health benefits.

In spite of vehement opposition from coal lobbyists, Kassenberg’s arguments provide at the very least a guiding framework through which Poland can cut back on its coal consumption. However, only time will tell whether two rollercoaster weeks in the international climate change spotlight will have compelled the nation’s leadership to reconsider their defiant approach and take action.

ELEEPers at the COP19 UN climate convention, held inside Warsaw’s national football stadium. (Credit: Edvard Glücksman)

ELEEPers at the COP19 UN climate convention, held inside Warsaw’s national football stadium. (Credit: Edvard Glücksman)

By Edvard Glücksman, Postdoctoral Research Fellow, University of Duisburg-Essen

ELEEP is a collaborative venture between two non-partisan think tanks, the Atlantic Council and Ecologic Institute, seeking to develop innovative transatlantic policy partnerships. Funding was initially acquired from the European Union’s I-CITE Project and subsequently from the European Union and the Robert Bosch Stiftung. ELEEP has no policy agenda and no political affiliation.

GeoTalk: Suzanne Hangx on Carbon Capture & Storage

Today in GeoTalk, we’re talking to Suzanne Hangx, who explains the great potential of carbon capture and storage and the challenges emerging technologies, like CCS, face.

First, could you introduce yourself and let us know what drew you to geomechanics?

Let’s start with the introduction: I’m Suzanne Hangx and I currently work as a researcher on geomechanics for subsurface storage containment technologies at Shell Global Solutions in the Netherlands. Actually, I hadn’t planned, or even thought of, becoming a geomechanist at first. In high school, I was mainly interested in chemistry and I was thinking of studying Chemical Technology. It wasn’t until I read a book about volcanoes for Geography class that I thought: “maybe I want to become a volcanologist!” To me it nicely combined chemistry, travelling and Earth processes, which I also found interesting. So I enrolled for my geology studies at Utrecht University. As it turned out, volcanoes were not my cup of tea, but I did meet a great professor that introduced me to geomechanics. All of a sudden I had found it: breaking rocks (for scientific purposes of course… and also a bit for fun) was my ‘thing’.

After finishing my Master’s in 2004, I continued working with Professor Chris Spiers at the High Pressure and Temperature Laboratory at Utrecht University. I started a PhD project on CO2 storage and the effect of chemical CO2-rock interactions on the mechanical properties of rocks. To me that was a nice combination of putting science in a socially-relevant context, as CO2 storage is considered to be a potential solution to reduce greenhouse gas emissions. When I finished my PhD in 2009, I got the opportunity to continue this work at Shell Global Solutions.

Last year, you received a Division Outstanding Young Scientists Award for your work on Carbon Capture and Storage (CCS). Could you tell us about your research in this area?

Suzanne Hangx

Suzanne Hangx

One way to get rid of large quantities of greenhouse gasses, like CO2, is to inject them into the subsurface, reducing their effect on climate change. Suitable locations are depleted oil or gas reservoirs, or aquifers, at several kilometres depth. However, it is key to ensure that after injection the CO2 also stays there – not just today or tomorrow, but for thousands of years. Once a potential injection site is identified, it is important to see if the reservoir (the ‘container’) and the seal keeping the CO2 in place (the ‘lid’), are up for the job, so to speak. I investigate if the injected CO2 does anything to the rocks to alter their mechanical behaviour, i.e. how they break, under which force they break and if they get weaker. Once I have this data, I will give it to the people that make the long term (thousands of years) numerical modelling predictions of the behaviour of the reservoir-seal system. This way, we all work together to determine whether or not a potential site is suitable for geological storage of CO2.

How does carbon dioxide affect the chemical and mechanical properties of rocks?

When you inject CO2 into a depleted oil or gas reservoir, part of it will start to dissolve into the water that is present in that reservoir, while the rest will stay in a dense liquid or supercritical phase. When CO2 dissolves in water, the water will become acidic. This acidic fluid can chemically interact with the surrounding rocks – like in fizzy drinks, where CO2 is injected to make them fizz, but they also become acidic and corrode your teeth if you drink too much of them. As a result, certain minerals may dissolve and new ones may be formed, also the way cracks propagate through the rock may be affected, changing their strength and the way they break. If a rock gets sufficiently weakened by the chemical interaction with CO2 it may compact or break. As a result, a fracture may be created through the seal and CO2 could leak out of the reservoir. This is something we absolutely do not want, and therefore, for every new, potential site we look at how CO2 can affect the rocks of that specific location in great detail.

At the same time, chemical interactions may occur on different timescales. Processes that happen in days, weeks or months can still be dealt with in a laboratory setting. However, to be able to predict what will happen on the timescale of thousands of years, we are currently trying to learn as much as we can from naturally occurring CO2 fields, such as those in Utah (USA), Australia and Europe. These fields can contain over 90% pure CO2 and have mostly done so for millions of years. At Shell, we have recently set up a research consortium with international universities and research institutes to investigate the chemical, mechanical and transport properties of a natural CO2 field in Green River, Utah. The results from this program can help us understand better how anthropogenic CO2 injection into the subsurface will evolve over time.

In some areas in Utah (USA), subsurface rock formations of the Entrada Sandstone have held natural CO2 accumulations for millions of years. (Credit: Suzanne Hangx)

In some areas in Utah (USA), subsurface rock formations of the Entrada Sandstone have held natural CO2 accumulations for millions of years. (Credit: Suzanne Hangx)

Under what conditions can caprock integrity be compromised, and how can we avoid this?

Loss of caprock integrity, i.e. a leaking ‘lid’, can occur if you try to inject too much CO2 into a reservoir. As a result, the pressure in the reservoir may get too high and will try to escape, usually along the path of least resistance. To avoid overpressuring of the injection site, strict regulations are set to injection volumes and pressure. It is not allowed to inject CO2 at a higher pressure than the original oil or gas pressure in the reservoir, before production started. We strive to stay well below this value to make sure we do not induce failure of the seal.

Integrity can also be compromised by chemical weakening of the seal by the injected CO2. Here, laboratory experiments and studying the seals of natural CO2 field helps to understand what processes we need to look at and pay attention to, before we can say that a seal is good enough.

What technical challenges face CCS and how do you think we can overcome them?

The CCS chain consists of CO2 capture at source, followed by transport to the site, and then injection into the reservoir for storage. For storage, we already understand the larger part of the processes that are of importance. Key challenge is still to investigate every new site in great detail, which is very time consuming and could take several years. In addition, it is also about getting the general public to accept this technology as a way to battle climate change.

Finally, what do you hope to work on next?

I’m mainly driven by my curiosity about the physical and chemical processes that control rock material behaviour in the subsurface, along with the direct relevance of this field to socially relevant issues. With energy and water demand rapidly increasing globally, while availability continues to diminish, densely populated areas are becoming increasingly targeted for exploitation. We already notice that in some areas oil, gas and ground water pumping leads to surface subsidence and induced seismicity. In addition, hydraulic fracturing (‘fracking’) of subsurface reservoirs for shale gas and geothermal exploitation meets with strong public opposition, due to the risk of induced ground motion, seismicity, and health and safety hazards, some of which are miscommunicated. I would like to contribute to such geo-energy problems, by investigating and quantifying these risks and coming up with socially acceptable solutions or technologies.

If you’d like to suggest a scientist for an interview, please contact Sara Mynott.