Greenpeace International  [Printer-friendly version]
July 16, 2009

LEAKAGE IN THE UTSIRA FORMATION AND ITS CONSEQUENCES FOR CCS POLICY

By Emily Rochon and others

The Sleipner CO2 project in the North Sea is one of only three large-
scale CO2 storage projects worldwide. The oldest in operation,
Sleipner has been injecting about 1 million metric tonnes of CO2 into
a sub-seabed saline aquifer since 1996. Carbon capture and storage
(CCS) proponents point to Sleipner as proof that CO2 can be stored
safely and permanently while heralding the Utsira formation, that it
is a part of, as large enough to hold Europe's emissions for years to
come. However, recent developments in the North Sea indicate
otherwise:

** A StatoilHydro-operated project was abandoned in the spring of
2008 after leaked process-water from the Utsira formation revealed an
incomplete understanding of the geology of the storage site.

** A study by the Norwegian Petroleum Directorate has reversed
previous estimates of CO2 storage capacity in the Utsira formation
from "able to store all European emissions for hundreds of years" to
"not very suitable".

While neither of the above issues received much international
attention, they call into question the presumption that Sleipner is
flawless and the storage space in Utsira infinite. This briefing
provides information on developments related to leakage from Utsira
injections and revised storage capacity estimates.

Utsira leakage from Tordis-processed water injection

In May 2008, workers on the Gullfaks platform in the North Sea outside
Norway happened to notice oily water at the sea surface near their
platform.

The produced water[1] originated from the Tordis field and had been
injected into the Utsira formation by StatoilHydro. An internal
investigation[2] conducted by the company revealed that injection
activities had caused cracking in the seabed above the reservoir,
thereby allowing a stream of processed water to escape back into the
sea.

The project utilised an injection method that created cracks in the
reservoir in order to increase permeability. When several unexpected
pressure drops occurred in the process, injection was stopped and the
cause for the drop investigated. The exact reason for the pressure
drops was not ascertained, but each time the injection process was
allowed to begin again.

StatoilHydro claims that the technology used has functioned very well.

"The problem is the injection well. [...] It's probably located in the
wrong place of the formation," said Gisle Johansen, a spokesperson for
StatoilHydro.[3]

Even though the Norwegian Petroleum Directorate requires monitoring
and warning systems to discover possible leakages, there was no such
system near the location of the leakage, 300 meters away from the
installation and the monitoring system. As a result, no one is able to
determine how long the leakage had existed before its fortuitous
discovery in May 2008. Once the source of the oily water was
identified, injection operations ceased. StatoilHydro estimates that
48-175 m3 [cubic meters] of oil leaked from the storage formation.

The leakage from this formation is particularly significant as it was
previously believed to be an ideal storage site, completely sealed,
and with a seemingly limitless storage capacity for almost
anything.[4]

StatoilHydro is an experienced operator claiming to know the Utsira
formation better than anyone. However, if these so-called experts in
the field cannot reliably inject processed water into a single
underground formation, how can we assume that gigatonnes of CO2 from
thousands of coal-fired power plants can be safely disposed of in
prospective geological reservoirs across the globe?

The Tordis leakage illustrates StatoilHydro's practice of making
invalid assumptions and operating a site without proper monitoring.
But most importantly, it proves how difficult it is to inject and
store anything in underground reservoirs, even in the Utsira formation
which is considered to be one of the best studied geological
formations on Earth.

Similar problems in other injection projects in Utsira

Today 20-30 projects are in operation involving injection of processed
water, sand and liquid refuse into the Utsira formation. In addition
to the Tordis leakage, there have been at least two other accidents
related to injection projects since 2004 -- one at the ExxonMobil-
operated Ringhorne site and another at the StatoilHydro-operated
Visund site.

The Ringhorne field started production in 2001, injecting well
cuttings, slop and fluids into the Utsira formation. In February 2004,
oily water was observed on the sea surface near the platform. The
leaked oil was found to be coming from the injection well.

Approximately 100-1,000 litres of base oil leaked into the sea.[5]

The Visund field started production in 1999, injecting gas, well
cuttings, slop and fluids into the Utsira formation. In 2007, there
was unexplained activity in the seabed, which was probably related to
the injections, in the form of cracking or other damage to the
formation.[6,7,8] Other smaller irregularities have also taken place.

Utsira and CO2 storage

The leakages from Tordis, Visund and Ringhorne all occurred in the
Utsira formation, the same geological structure where the Sleipner
field is located. The CO2 storage project at Sleipner has been used by
the Norwegian government, as well as the EU, IEA and numerous others,
as proof that CO2 can be safely and permanently stored.

For years now, the Utsira formation has been heralded in scientific
journals, by industry, NGOs and the media as a geological structure
that can store 'endless amounts' of CO2:

** The storage potential for CO2 in the Utsira formation has been
claimed to be "practically unlimited",[9] or "capable of storing up to
600Gt of CO2, e.g. all CO2 emissions from all power stations in Europe
for the next 600 years."[10]

** Another study described the Utsira formation as "one of the most
promising aquifers for CO2 storage in Europe. It is estimated that the
Utsira Formation, below 800 m depth, has a pore volume of 918 km3, a
storage capacity in traps of 847 Mt (megatonnes) CO2, and that the
storage capacity of the entire aquifer is 42,356 Mt CO2".[11]

In global assessments of future CO2 storage capacity, CCS proponents
point to saline aquifers[12] like the Sleipner as the structures with
the greatest storage potential.[13]

However, a recent study conducted by the Norwegian Petroleum
Directorate to evaluate possible storage sites for CO2 from the
planned Mongstad and Kårsto CCS gas-fired pilot plants. It concluded
that " [...] it remains uncertain whether Utsira is suitable for
large-scale storage of Europe's carbon emissions".[14]

The main reason for this is the depth of the formation, which is too
shallow to provide the pressure required to ensure that the CO2 stays
in a fluid phase. The evaluation instead recommends the Johansen
formation as a better option. The Johansen formation is said to
provide a deep, sealed structure where "carbon storage will almost
certainly be possible without leakage to the surface". However, this
formation has never been used for injection purposes.

The Sleipner CO2 injection project

The introduction of a Norwegian CO2 offshore tax prompted StatoilHydro
to begin removing CO2 from natural gas streams in 1990 and allowed the
company to save money and simultaneously conduct research into CO2
storage. About 12 million tons of CO2 have been separated from natural
gas and injected back into the formation since 1996.[15]15 As far as
StatoilHydro and the Norwegian government have reported, there have
been no major leaks from the Sleipner injection. However, several
scientists claim that the current technological limitations make this
impossible to guarantee.

"It's not possible to prove that all injected CO2 is still there.
There's no way of measuring the amount of CO2 in the formation with
sufficient accuracy using seismic mapping," said Peter Haugan, the
leader of the Institute of Geophysics at the University of Bergen.[16]

What's more, unpredicted movement of injected CO2 has been observed in
the reservoir and so far has not been satisfactorily explained by any
reservoir geologist.

When the Sleipner project began in 1996, CO2 was expected to rise
gradually through the layers of the formation once it was injected
underground. However, seismic imaging has shown that the CO2 is
instead flowing almost immediately to the top of the formation --
moving up by more than a hundred meters per year.

As described in a recent article, this demonstrates that the mudstones
present in the formation were not serving as a barrier to the vertical
CO2 movement, as scientists had originally expected. Additionally, it
indicates that the geological characteristics of the formation may
have been altered by the injected CO2.[17] A more disturbing
possibility is that much less CO2 is being stored in the formation
than estimated, meaning that CO2 is leaking at an unknown rate.[18,19]
While this is currently speculative, leakage rates at any level are of
interest. Even very low annual leakage rates, as low as 0.1 percent,
could undermine potential climatic benefits of geological storage on a
time scale of a few centuries.[20] As mentioned, it is currently not
possible to detect CO2 leakages in these small volumes. While
StatoilHydro acknowledges this, they argue that the above ceiling
structures are nevertheless safe enough to prevent leakage into the
external environment.

However, the relevant issue for decision-makers is that the current
scientific ability to accurately map and interpret geological
structures, such as the Utsira formation, for the purpose of ensuring
safe, permanent CO2 storage, may not be possible.

Summary

Greenpeace believes that the Utsira events regarding unpredicted
leakages, unpredicted CO2 movements inside the geological formation
and dramatically reduced storage estimates, underline how each field,
each injection rate and each storage location is unique and would
require detailed characterisation, management and monitoring. The
occurrences described above show that CCS is neither a simple process
nor a one-sizefits-all solution to CO2 pollution. It should give pause
to policymakers as they deliberate what role, if any, CCS should play
in mitigating climate change emissions.

In general, Greenpeace does not support CCS given the substantial
risks and uncertainties surrounding the effectiveness, safety, energy
penalties, liability and environmental impacts of the technology.
Alternative energy strategies, namely ones based on renewable energy
and energy efficiency, are already available to deliver emission
reductions. These technologies do not carry similar risks to those
posed by CCS, nor do they leave open the possibility of transferring
the burden of today's climate pollution to future generations. In
light of all of the above, we urge the EU and other governments to
reconsider attempts to encourage CCS and, instead, to redouble their
efforts to fully support the development of truly sustainable energy
solutions.

For more information:

You can find the Greenpeace report on CCS "False Hope: Why carbon
capture and storage won't save the climate" (May 2008) on 
www.greenpeace.org/ccs. Or here.

Emily Rochon, CCS Policy Coordinator, Greenpeace International, +31
(0)6 4618 4250 or emily.rochon@greenpeace.org

Truls Gulowsen, Programme Manager for Greenpeace in Norway, +47 90 10
79 04 or Truls.Gulowsen@greenpeace.org

Joris den Blanken, Climate and Energy Policy Director, Greenpeace
European Unit, +32 (0)2 274 1919 or joris.den.blanken@greenpeace.org

==============

[1] Produced water is oil-polluted water that often comes up with oil
extraction. In the past, this had often been released to sea, but now
it is often re-injected to avoid pollution.

[2] StatoilHydro internal investigation of the event: "EPN OWE
SNO/Tordis: Utslipp av oljeholdig vann og tap av injeksjonsbronn"
(11.08.2008) (Available only in Norwegian so far. Available in full
from Greenpeace.)

[3] Stavanger Aftenblad: 
http://aftenbladet.no/energi/olje/article652315.ece (Norwegian news)

[4] There are more than 20 injection projects in Utsira. See for
example Statoil 1998. (Norwegian only)

[5] ExxonMobil: Annual report: "Arsrapport SFT 2004 -- Balder og
Ringhorne.doc /ISk/28/02/05" (Norwegian only)

[6] StatoilHydro internal investigation of the Tordis event: "EPN OWE
SNO/Tordis: Utslipp av oljeholdig vann og tap av injeksjonsbronn»
(11.08.2008)" (Norwegian only so far; available in full from
Greenpeace).

[7] SFT: Nullutslipp til sjo fra petroleumsvirksomheten: Status og
anbefalinger 2003 (Norwegian).

[8] Norwegian Petroleum Directorate: "Development and operations -
northern North Sea"

[9] Statoil 1998 (in Norwegian)

[10] ZEP (2006), or indirectly

[11] CO2 point sources and subsurface storage capacities for CO2 in
aquifers in Norway

[12] Saline formations are sedimentary rocks saturated with formation
waters and dissolved salts.

[13] See for example http://www.ieagreen.org.uk/putcback.pdf. The
IPCC special report on CCS estimates the total global technical
storage potential at 2000 Gt [gigatonnes] CO2 in geological
formations.

[14] Carbon containment in the spotlight:

[15] See StatoilHydros description here.

[16] Newspaper article in Norwegian: "No guarantee against CO2-
leakage" (22.10.2008)

[17] CO2 Flow in the Utsira Formation: Inferences made from 4D
seismic analyses of the Sleipner area

[18] Modelling carbon dioxide accumulation at Sleipner: Implications
for underground carbon storage, M. Bickle et al, Earth and Planetary
Science Letters 255 (2007) 164-176, Editor: C.P. Jaupart.

[19] Effects of CO2 capture and storage on ocean, Haugan, P. M.,
Geophysical Institute, University of Bergen, Bergen Marine Research
Cluster in Monaco, October 2008.

[20] "Metrics to assess the mitigation of global warming by carbon
capture and storage in the ocean and in geological reservoirs,"
Haugan, P. M., Joos, F., Geophysical research letters, vol. 31, L18202
doi:10.1029/2004GL020295, 2004.