NATURAL ANALOGUES OF CO2 LEAKAGE IN FLORINA AREA, N. GREECE

NATURAL ANALOGUES OF CO2 LEAKAGE
IN FLORINA AREA, N. GREECE
George Hatziyannis and Apostolos Arvanitis
October 17-19, 2011
Maria Laach, Germany
2nd
CGS Europe Knowledge Sharing Workshop
Natural Analogues

Natural analogues of CO2 leakage in Florina area,
N. Greece
Natural analogues of CO2 leakages in Greece are located
in:
- various geothermal fields all over the country
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- Florina basin (Macedonia, Northern Greece)
Low enthalpy
geothermal
field of
Therma
Nigrita
(T=40-64oC,
3.5-4,7 kg
CO2/t H2O)
(Macedonia,
Northern
Greece)
Low enthalpy
geothermal
field of
Akropotamos,
Kavala
(T=83-90oC,
large amounts
of CO2)
(Macedonia,
Northern
Greece)

LOCATION of STUDY AREA
Geographical location
Access by plane either up to Thessaloniki, then by car (150
km) or up to Kozani and then by car (85 km)
Easy access to area for field work and to wells for sampling
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N. Greece
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The basin of Florina
3D representation of a satellite image of the basins of Florina county (Enhanced
Landsat image of bands R:4,G:5,B:3,Intensity:Panchromatic & SRTM DEM)
The Florina basin represents a good natural analogue for the
study of the impact of geologic carbon storage.

In the wider area of the
Florina sedimentary
basin, CO2 leakage
creates mineral springs
in some places and/or
gas bubbles in shallow
wells where the
geological structure
(fractures, permeable
cap rock, etc) allowed
this slow migration.
GEOTECTONIC
POSITION:
The Florina area
belongs to the
Pelagonian tectonic
zone.
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The Florina CO2 field lies
in the northern part of a
NNW-SSE oriented
graben from Monastiri
(FYROM) to Kozani
(Greece) with a total
length of about 150 km.
The middle Tertiary
graben formed in
metamorphic rocks of
the Pelagonian zone of
the internal Hellenides
during extensional
stresses following the
Alpine orogenesis.
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The basement is
characterized by
metamorphic
rocks and
carbonate rocks at
the eastern
margins of the
basin.
The studied basin
has been filled up
by Neogene and
Quaternary
sediments.
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Metamorphic rocks,
intruded by granites,
flank the west margin
of the Florina Basin.
The fault zone that
created this basin
runs along this
western margin,
where rapid filling
with coarse clastic
sediments took place.
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Mesozoic crystalline limestones, schists and gneisses occur in
the east where a slower rate of sedimentation deposited
finer clastics on the basement limestones.

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The Neogene sediments, overlying the Mesozoic crystalline
limestones, comprise fluvial, coarse to fine siliciclastics
with clayey tops to the sequence (conglomerates, sands,
clays).
Neogene sediments distinguished in the lower part (Base
formation, up to 300 m thick), the middle part (Vevi
formation, thickness 50-130 m) and the upper part
(Lophon formation, up to 200 m thick). These three parts
are characterized by the continuous sedimentation from
Late Miocene to Pleistocene.
Quaternary deposits are mostly terrestrial and were
characterized by fluviolacustrine, fluvial and alluvial fan
environments that developed during early Pleistocene.
Lignite seams are developed mainly from the eastern
margin, starting at the contact with the basement, and
extending westwards to the basin centre.
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Stratigraphy of the Florina basin,
based on the drill core analysis
(m=mud, s=sand and
c=conglomerates). Numbers and
letters in each part show cycles
and sequences respectively.
Drill core analyses
showed a lot of (>40)
sedimentary cycles in
the Florina Basin from
Neogene to Quaternary,
with a total thickness
>600 m.

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Correlation
among three
stratigraphic
sections in
the Florina
basin

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There are many mineral
springs and wells in the
wider basin area, resulting
from a slow upward
movement of CO2 along rock
discontinuities.
The gas composition is very
pure, with CO2 content
between 90 and >99.5%
plus traces of CH4 (22 ppm-
1.3%) and other gases (e.g.
He: 0.3-66 ppm).
Carbonated springs are also
common throughout the
area.
Local cap rocks consist of
clayey sediments (clays and
silts).

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CO2 leakage at the surface in the Florina basin occurs as
CO2-rich springs throughout the area and, where basement
limestones are exposed, as surface gas seeps.
Surface CO2 seeps occur in areas where Tertiary clays and
silt cover do not exist.
CO2 gas vents
(damaged pasture
from natural CO2
seeps) in the
Florina area

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Carbon dioxide occurs at various levels in the Mesozoic
limestones and in overlying Neogene sandstones.
As CO2 source could be considered the thermal
decomposition of carbonates.

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According to D’Alessandro et al
(2008, 2011a,b), carbon isotopic
composition ranging from -2.3 to
0.3‰ (vs. V-PDB) indicates a
deep (magmatic / hydrothermal)
origin of CO2 and also He isotopic
composition (0.24-0.82 R/Ra)
reveals a small (2-10%) but
significant mantle contribution.
According to D’Alessandro et al.
(2011a,b), CO2 originates mainly
from crustal sources (carbonate
rocks) but has also a minor
(~10%) mantle contribution
probably associated with the
volcanic activity in the Almopia
area (Voras Mountain).

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CO2 storage sites mostly referred to fluvial and alluvial fan
environments. Moreover, the internal change of stratigraphy
in the same environment of sedimentation does not allow the
escape of CO2.

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The Florina basin is a
seismically active
area with maximum
magnitudes of
around 5 on the
Richter scale.
The potential
relationship between
fluid migration (CO2
leakage) and
seismicity can be
investigated.
Seismicity of Florina and
surrounding area before
1995. In 1995 an
earthquake of Ms=6.6
struck the Kozani-Grevena
area (south of Florina)

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A cored well, 574,70 m
deep, was drilled close to
the village of Messokampos
penetrating the full
sequence of sediments
down to the crystalline
basement.
This borehole was drilled in
the framework of the
European Union Fifth
Framework Project
NASCENT (2001-2004)

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Temperature,
gamma - ray,
fluid conductivity
and density
(both LSD and
HRD) logs were
carried out into
this borehole.
The water
temperature
ranges from
14.5°C at the
surface to 43°C
at the bottom of
the CO2
reservoir (560 m
depth).

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Finally, the well has been cleaned using the air lift method
that gave formation water and CO2 gas.
A number of
CO2 shows
were
detected at
depths of:
128 m
300-310 m
320-330 m
380-390 m
400-410 m
457-465 m
490-500 m
550 m

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SAMPLING IN THE FLORINA AREA
A total of 18 fresh samples (some of them were loose
sand and silt) were collected for moisture, porosity,
permeability, uniaxial compressive and point load tests.

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PETROPHYSICAL MEASUREMENTS AND FLUID TRANSPORT
EXPERIMENTS ON SAMPLES FROM FLORINA AREA
(NASCENT Report, 2005) (i)
17 samples were collected from well
M-1 in the Messokampos area.
Hg-injection porosimetry was
performed successfully on 4 of these
samples. Although their absolute
porosity values are similar, these 4
samples exhibited significant
differences in their pore-size
distributions.
One (1) sample was selected for permeability tests and CO2
diffusion experiments. This sample appeared to be very clay-
rich and the pore-size distribution indicated a considerable
amount of microporosity.

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(NASCENT Report, 2005) (ii)
Permeability coefficients perpendicular to the bedding plane
were initially in the 5-10 nDarcy (5 – 10x10-21 m2) range.
After the first two CO2 diffusion experiments, a significant
increase in permeability coefficients, up to >300 nDarcy, was
noticed.
The last permeability test yielded a coefficient of 76 nDarcy.
The effective diffusion coefficients (Deff) measured in the
experiments are in the range of 10-10 m2/s.
Within the first 3 measurements they show an increase from
0.84x10-10 to 1.5x10-10 m2/s, while the final value is lower
again, thus following the permeability trend. Chemical reactions
of CO2 with the mineral matrix of the sample might be one
explanation, but mechanical damage of this very brittle and
poorly consolidated sample during the fluid pressure changes
between the individual experiments cannot be excluded.

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(NASCENT Report, 2005) (iii)
The results of permeability and CO2 diffusion tests, conducted
with the plug parallel to the bedding plane, showed a slight
increase in permeability after the first two CO2 diffusion
experiments.
The final diffusion experiment yielded a diffusion coefficient of
1.7x10-10 m2/s, i.e. slightly higher that the perpendicular plug.
The observations indicate that clay/silt content in poorly
compacted lithotypes could play a significant role in the
retention or storage of CO2.
Future studies should focus on clay content and cation
exchange capacity as parameters controlling sealing efficiency
for CO2.

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A hydrogeological and hydrogeochemical study of the
Florina basin has been carried out to determine possible
changes in water quality that could be attributed to CO2
springs. The survey included the following tasks:
• Recording all the wells and springs in the basin using
available references (about 400 points).
• Sampling for general chemical analysis (a total of 132
samples were collected).
• Analysis of all the above samples for: SiO2, B, CO2, O2,
Cl, CO3, HCO3, SO4, NO3, NO2, K, Na, Ca, Mg, NH4, Fe, and
for T.D.S., pH, conductivity and water hardness (total,
permanent, temporary).
• Analysis of some of the samples (17) for the trace
elements: I, Br, Fe, Al, Cr, Mn, Ni, Cu, Zn, As, Sr, Li, V, Mo,
Cd, Sb, Ba, Pb, Rb.
HYDROGEOLOGICAL AND HYDROCHEMICAL STUDY

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Two aquifers exist in the Florina basin:
A confined or artesian aquifer, which hosts the CO2, occurs
throughout the basin in clastic sedimentary Miocene rocks
that are capped by silts and clays.
The second aquifer occurs in karstic carbonate rocks of the
eastern and southern margins of the basin. A few mineral
springs also exist in this aquifer.

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MAP OF
ISOPIEZOMETRIC
CURVES compiled from
deep well data:
The higher point of the
isopiezometric surface
lies in the southern part
of the Florina basin with
a ENE-WSW axis and
highest value of 680 m
(a.s.l.). It decreases at
both sides of this axis
and reaches a value of
580 m in the northern
part and 540 m at the
SSE edge of the basin.

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WATER
TEMPERATURE MAP:
There is no any
significant thermal
anomaly in the basin.
The values range
between 12 and 20oC
(at wellheads).

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MAP OF pH VALUES :
pH values range
between 5.70 and
8.40.
In the northern part of
the basin, the water
has an acid
composition.
In the center of the
Florina basin and in the
southern part of the
Ptolemais basin,
groundwater has an
alkaline composition.

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MAP OF T.D.S. VALUES:
T.D.S. values range from
150 up to 4,230 mg/l.
In the large part of the
basin T.D.S. values are
close to 800 mg/l.
Highest values are
encountered in the central
axis of the basin and in
the northern part.

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MAP of TOTAL
HARDNESS :
Values of Total Ƭardness
of the Florina water
range from 70 to 1,950
mg/l.
The most part of the
basin shows values of
400 mg/l and some
extreme values are
observed along the
central axis and in the
northern part of the
area, as in the case of
T.D.S. values.

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Waters from shallow wells and springs are of Ca-HCO3 type
with a small concentration of Mg. Waters from deep
boreholes are rich in magnesium and bicarbonate with a
small Ca content.
Based on the ratio Mg/Ca the deep waters are fed by
limestones.

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Throughout the basin, waters are of a good quality with some
increased content of some elements in a few of those samples.
The water quality close to the CO2 field is poorer due to the
increased content of Ca, Mg, Fe, ƬCO3 and high total hardness.
CO2 dissolution and subsequent acidification (lowering of pH) of
the water caused increased water-rock interaction (the mobility
of some trace elements increases) and the subsequent
modification of the chemical composition of shallow groundwater.
The most altered groundwater was only located in close vicinity
of the actual CO2 gas vents and that it can still be considered
potable.
Petrographic evidence indicates that dissolution of some
mineralogical components within the sediments, caused by
interactions with CO2-rich ground waters could account for these
changes.
There is not any significant pollution of groundwater from NO2
and NH4. In the northern part of the basin, some increased NO3
concentrations occur.

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KARSTIC WATER
The east border of Florina basin consists of marbles that
continue under the Miocene sediments filling the basin
(below 600 m).
From P.P.C. drilled in the east part of the basin the
surface of the karstic aquifer lies at 610 m. In contrast the
Ptolemais basin hosts the karstic aquifer at a depth of 510
m.
pH of this aquifer ranges between 5.6 and 7.7.
In the most part of the basin, this water is acid with the
exception of north and south parts where it is alkaline.
T.D.S. values range from 400 mg/l (north) to 1,300 mg/l
(south).

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BOREHOLE FAILURE ASSOCIATED WITH CO2 LEAKAGE (i)
In the summer of 1990, the Department of Hydrogeology of
I.G.M.E. drilled an exploration well for the location of mineral
water in the Florina basin, since the existence of CO2-rich
water in the wider area had been known since the early
1960’s.
The well was completed after drilling to a depth of 559 m.
The borehole was cased throughout with a steel tube with an
external diameter of 70 mm. Well completion included the
installation of a wellhead with a valve.
CO2 occurred along the well from a depth of 97 m to a final
depth of 559 m. The pressure, as measured at the wellhead,
was 30 atm and the flow rate of water 30 m3 per hour. The
calculated pressure at the bottom of the well was about 50
atm.

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BOREHOLE FAILURE ASSOCIATED WITH CO2 LEAKAGE (ii)
After the well completion and while the valve of the wellhead
was closed, CO2 leakage was observed at a distance of 100
m from the well. Later, the CO2 leakage advanced towards
the well and created a hole around it having an area of more
than 25 m2 (5x5 m) and a depth of 50 m. The cement base
used for the drill rig collapsed and a small lake was created.
Access to the hole, for people and animals, was restricted by
the installation of a fence.
In early 1993, I.G.M.E. tried to control CO2 leakage by
drilling a new borehole about 150 m away from the first one
in order to reduce the pressure, without any result.
After some months it was decided to fill the pool with about
900 m3 of loose soil and waste rock material, leaving only a
small quantity of water and flowing CO2.

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Small lake created as a result of the upwards migration of
naturally occurring CO2 outside the casing of a mineral water
exploration well drilled in the Florina area.
BOREHOLE FAILURE ASSOCIATED WITH CO2 LEAKAGE (iii)

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BOREHOLE FAILURE ASSOCIATED WITH CO2 LEAKAGE
(iv)
The local authorities created a circular pool with a diameter
of 4-5 m with a cement lining, around the leaking well.
The pool was used by local people as a heath cure, by
immersion of their feet only in the pool whilst keeping their
face about 1.5 m above the water surface. This continued
for some years until a fatal accident when a man was
asphyxiated when
swimming in the pool
due to the concentrated
CO2 layer lying above
the water surface.
At this point the local
authority prohibited the
use of this pool.

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BOREHOLE FAILURE ASSOCIATED WITH CO2 LEAKAGE
(v)
In 2000, water and CO2 were still flowing from the pool with
the flowing water causing a red-brown Fe-rich deposit on
the banks of small streams created by the flowing water.
In 2002, CO2 and water flow finally ceased, probably
through self-sealing.
During field work for the NASCENT project in 2003, the pool
and the well were found to be dry. No water or gas was
flowing.
From a CO2 storage
prospective, this event
illustrates that in relatively
poorly consolidated
successions CO2 leakage can
be induced by drilling wells.

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In the Florina area, CO2 storage sites mostly referred to
fluvial and alluvial fan environments (sands) and a detailed
study (i.e. porosity) could be relating these environments
with future storages of CO2.
Moreover, the internal change of stratigraphy in the same
environment of sedimentation (presence of clays) does not
allow the escape of CO2.
However, it should be a connection between the presence
of CO2 with aquifers and the height of column of water and
how much the hydrostatic pressure increases the trapping
of gases in the sediments.

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Siderite developed following breakdown of biotite and dolomite
with the later siderite generation having higher Mg
concentrations, suggesting possible formation following the
extensive dolomite dissolution seen at certain intervals.
A detailed diagenetic study indicated that the latest diagenetic
events – calcite corrosion, siderite breakdown and replacement
(pseudomorphing) by iron oxide, and precipitation of gibbsite are
only recognized at depths below 390 m from the surface. These
events may be attributable to the
Messokampos: Typical example of FeOx
after siderite - note location within
expanded micas, subsequently being
replaced by poikilotopic calcite. CO2 zone 8,
FL34, 393.38-393.48 m (Q=quartz,
F=feldspar, D=dolomite, k=kaolinite,
Fe=Fe oxyhydroxides, S=siderite, M=mica)
reaction of low-pH CO2-charged
waters, since both calcite and
siderite could be unstable in low
pH waters.

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LONG-TERM GEOCHEMICAL INTERACTIONS AT THE
NATURAL CO2-ANALOGUE IN THE FLORINA AREA –
MODELLING (Gaus et al., 2004) (i)
In the Florina area: replacement of one mineral (siderite)
with another (Fe oxide, probable goethite)
The impact of long-term CO2 accumulation has been
assessed in the shallow, low-temperature (max.43ǎC) &
low-pressure (1 MPa at the bottom & 0.25 MPa at the top
of well) reservoir at Messokampos (Florina Basin).
Petrographic characterization of the reservoir enabled the
identification of both the effects of CO2-induced
geochemical interactions as well as their impact on
reservoir lithology.
Subsequently, geochemical modelling (using PHREEQC)
was applied to reproduce the observed effects, identify
their driving parameters and to assess their impact in
terms of potential mineral trapping and porosity changes.

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Modelling Data (I)
-Temperature and pressure conditions: The highest T & P of the
system (43°C, 1 MPa) were selected for the modelling in order
to study a highest impact scenario.
-Mineralogical composition of the reservoir before CO2 loading.
It was based on a sample representing an average composition
located in the area which was thought to be unaffected by CO2
flow (initial simplified mineralogy).
LONG-TERM GEOCHEMICAL INTERACTIONS AT THE NATURAL
CO2-ANALOGUE IN THE FLORINA AREA (Gaus et al., 2004) (ii)

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Modelling Data (II)
- Composition of the formation water in the reservoir at the
moment CO2 is injected. Based on the saturation indices of
the minerals in the samples taken from the reservoir, two
types of water were distinguished: subsurface groundwater
above the CO2 reservoir (0-140 m depth) and deep water
(250-560 m depth).
The water composition resulting from the equilibrium
modelling between the deep groundwater and the initial
simplified mineralogy was used as initial water for the
modelling. A similar water composition was obtained when
allowing equilibrium between the shallow groundwater and
this mineralogy.
CO2-ANALOGUE IN THE FLORINA AREA (Gaus et al., 2004) (iii)

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CO2-ANALOGUE IN THE FLORINA AREA (Gaus et al., 2004) (iv)
Messokampos: batch kinetic modelling of the impact of CO2 loading of the formation
water (1 MPa, 43oC): precipitating (left) and dissolving (right) minerals due to CO2
interactions.
Modelling of the Messokampos site - batch kinetic simulation

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The batch kinetic simulation was run for 800 years.
At the end of the simulation, equilibrium was still not attained.
Little CO2 is sequestered (2.4x10-6 mole per REV representing
12.7 dm3 of reservoir rock).
Sequestration occurs only through dissolution in the liquid
phase as no carbonate precipitation occurs.
A slight dissolution (8.0x10-3 mole) of dolomite is modelled due
to the initial buffering effect of the carbonate system when the
CO2 comes in contact with the reservoir rock.
Fe oxide and gibbsite precipitation are reproduced but the
calculated amounts are very small (the amount of Fe oxide is
too small to have any significance).
Slight dissolution of albite and K-feldspar is modelled.
4.2x10-2 mole of chalcedony and 5x10-3 mole of muscovite
precipitate (no petrographic observations).
CO2-ANALOGUE IN THE FLORINA AREA (Gaus et al., 2004) (v)
Batch kinetic modelling for the Messokampos site (A)

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The reactions involving Fe oxide and gibbsite precipitation,
dissolution of albite and K-feldspar as well as chalcedony and
muscovite precipitation have very little impact on the
mineralogy to affect the porosity in the reservoir.
The formation water at the beginning of the simulation is
compositionally equal to the sampled water from the reservoir,
so very little change occurs during the course of the modelling.
A significant increase in Ca, Fe and Mg concentration (an order
of magnitude approximately) is modelled due to the initial
dissolution of carbonate minerals.
The lack of reactivity is attributed to the fact that no obvious
donor minerals are present in the rock which need to provide
the necessary cations and which react with CO2 leading to the
precipitation of carbonates.
Batch kinetic modelling for the Messokampos site (B)
CO2-ANALOGUE IN THE FLORINA AREA (Gaus et al., 2004) (vi)

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Some general results:
(1) Potential reactions involving CO2 include siderite dissolution,
the precipitation of iron oxides and gibbsite, triggered by the
dissolution of feldspars.
(2) The impact of these reactions does not seem to influence the
porosity of the sediment.
(3) Thermodynamic equilibrium conditions seem not to be
established.
(4) The reservoir’s temperature and pressure conditions
determine the impact of CO2 interactions, with elevated
temperatures significantly increasing the reaction rates of
mineral-trapping reactions. This is of great importance for the
selection of future CO2-storage sites.
(5) Mineral trapping does not occur. Dawsonite was not identified
during the petrographic analysis.
CO2-ANALOGUE IN THE FLORINA AREA (Gaus et al., 2004) (vi)

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GEOMECHANICAL MODELLING OF THE FLORINA SITE
(NASCENT Report, 2005) (i)
The geomechanical modelling of the behavior of the reservoir
and cap rocks and of the existing faults bounding the reservoir
to the east and west in Florina area contributes to the
understanding of the prediction of the effects of CO2 leakage
from storage sites.
The results of geomechanical numerical modelling of the Florina
field provide fundamental insight into the causes of human-
induced geohazards related to CO2 extraction and injection.
The model assured the observations made during production
history, i.e. there was no geohazard induced by the CO2
production.
Up to now, no increase in the seismicity of the area has been
observed and surface subsidence is not noticeable.

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(NASCENT Report, 2005) (ii)
Maximum predicted subsidence during reservoir depletion
amounts to about 7 cm, while CO2 injection up to the initial
reservoir pressure leads to a full recovery of the subsidence
profile. Further CO2 injection above the initial reservoir
pressure will cause minimum uplift of the surface (prediction of
subsidence during reservoir depletion and uplift due to injection
was based on the assumption of the elastic behavior of rock
mass and on non-calibrated elastic rock properties).
Very important for the shallow reservoir in the Florina area is
the prediction of the potential for fault reactivation and
differential movement during depletion and reinjection.
CO2 injection into the depleted reservoir results in a stress path
which is anti-parallel (i.e. has the opposite gradient) with the
stress path for depletion. Due to elastic response of the fault
when injecting up to the virgin revervoir pressure, the stress
path for depletion and the stress path for injection overlap.

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(NASCENT Report, 2005) (iii)
Injection above the virgin reservoir pressure shows a critical
stress development. The stress path is converging towards and
reaches the Mohr-Coulomb failure line, when plastic slip on the
fault surface occurs.
CO2 injection above the original reservoir pressure generally
deteriorates the fault stability leading to its reactivation and an
upwards movement of some cm on the downthrown sides.
Graphical representation of the
Mohr-Coulomb failure criteria

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CONCLUSIONS (I)
In the wider area of the Florina sedimentary basin, CO2
leakage creates mineral springs in some places and/or gas
bubbles in shallow wells where the geological structure
(fractures, permeable cap rock, etc) allowed this slow
migration.
In the Florina area, CO2 storage sites mostly referred to
fluvial and alluvial fan environments (sands) and a detailed
study could be relating these environments with future
storages of CO2.
The internal change of stratigraphy in the same environment
of sedimentation (presence of silts and clays) does not allow
the escape of CO2. Clay content and cation exchange capacity
are parameters controlling sealing efficiency for CO2.
CO2 is dissolved in the groundwater of an existing aquifer and
this is what will happen in the case of a leak from geological
storage.

October 17-19, 2011
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CONCLUSIONS (II)
The evaluation of the geohazards from CO2 extraction and
subsequent injection in the shallow reservoir of the Florina
area simulates the case of slow leakage (through fractures) of
the gas from a geological storage site and accumulation at
shallow depth below surface.
The formation of a “sinkhole” at a Florina site after the drilling
of a borehole shows that if site characteristics are favorable,
gas migration, dissolution and mineral reactions can occur
over relatively short periods of time.
From a CO2 storage perspective, in relatively poorly
consolidated successions CO2 leakage can be induced by
drilling wells. Wells may provide leakage pathways to the
ground surface from natural CO2 fields.
Before exploration drilling took place, there was no indication
for leakage at the surface and the pressure of the CO2-rich
groundwater exceeded 50 bars (at a depth of 300-600 m).

October 17-19, 2011
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CONCLUSIONS (III)
Geochemical modelling indicates that the system is far from
equilibrium and, as observed in petrographic examination of
cores, CO2 is not being precipitated as a carbonate mineral.
The study of analogous natural CO2-rich reservoirs is crucial
for the assessment of the long-term geochemical impacts of
CO2 storage and accumulation.
The geomechanical modelling of the behavior of the reservoir
and cap rocks and of the existing faults bounding the reservoir
in the Florina area contributes to the understanding of the
prediction of the effects of CO2 leakage from storage sites.
The increased CO2 contents have a negative impact on
groundwater quality. Due to CO2, the groundwaters become
acidic and consequently strongly aggressive with respect to
the host rocks resulting in elements release to the water
solution (increased concentrations of Ca, Mg, Fe, ƬCO3 and
trace elements, increased total hardness).

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NOTE:
Most of the pre-mentioned works (drilling and completion of well,
574,7 m deep, petrophysical measurements and fluid transport
experiments on samples, hydrogeological and hydrogeochemical
study of the Florina basin, geochemical modelling, geomechanical
modelling etc) were carried out in the framework of the
European Union Fifth Framework Project NASCENT (2001-2004)

October 17-19, 2011
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Natural Analogues
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REFERENCES (I)
1. Gaus I., Le Guern C., Pauwels H., Girard J.-P., Pearce J., Shepherd T.,
Hatziyannis G. & Metaxas A. (2004), “Comparison of long term
geochemical interactions at two natural CO2-analogues: Montmiral
(Southeast Basin, France) and Messokampos (Florina Basin, Greece) case
studies”, GHGT7-7th International Conference on Greenhouse Gas
Control Technologies, Vancouver, Canada, 5-9 September 2004, 9 pp.
2. Beaubien S.E., Lombardi S., Ciotoli G., Annunziatellis A., Hatziyannis G.,
Metaxas A. & Pearce, J.M. (2005), “Potential hazards of CO2 leakage in
storage systems - Learning from natural systems, Proceedings of the 7th
International Conference on Greenhouse Gas Control Technologies
(Vancouver, Canada, 5-9 September 2004), vol.1: Peer-Reviewed Papers
and Plenary Presentations. Rubin, E.S., Keith, D.W., and Gilboy, C.F.
(eds.). Elsevier, Oxford, UK, pp. 551-560.
3. Pearce J. (2011), “What is the worst-case? Understanding potential
impacts from leakage: current European research”, 3rd technical
workshop CAGS (China Australia Geological Storage of CO2 Project): CO2
Storage and Enhanced Oil Recovery, Changchun, China,11-14 July 2011.

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REFERENCES (II)
4. http://www.bgs.ac.uk/nascent/
5. NASCENT, “Natural Analogues for the Geological Storage of CO2”,
NASCENT Report Number 2005/6, March, IEA Greenhouse Gas R&D
Programme, 92 pp.
6. D’Alessandro W., Brusca L., Kyriakopoulos K. & Karakazanis S. (2008),
“Groundwater quality issues in the Florina area (N. Greece)” 26th
European Conference – SEGH 2008 “Health Implications of
Environmental Contamination”, Athens, Hellas, March 31st-April 2nd
2008, Poster presentation.
7. Holloway S., Pearce J.M., Ohsumi T. & Hards V.L. (2005), “A Review of
Natural Occurrences and their Relevance to CO2 Storage”, British
Geological Survey External Report, CR/05/104, 117 pp.
8. Lewicki J.L., Birkholzer J. & Tsang C-F (2006), “Natural and Industrial
Analogues for Release of CO2 from Storage Reservoirs: Identification of
Features, Events, and Processes and Lessons Learned”, Earth Sciences
Division, Earnest Orlando Lawrence Berkeley National Laboratory,
Berkeley, California 94720, 57 pp.

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REFERENCES (III)
9. Stevens S. H., Pearce J. M. & Rigg A. J. (2001), “Natural Analogs for
Geologic Storage of CO2: An Integrated Global Research Program”, First
National Conference on Carbon Sequestration, U.S. Department of
Energy, National Energy Technology Laboratory, May 15-17, 2001,
Washington D.C., pp. 6.
10. Karakatsanis S., Koukouzas N., Pagonas M. & Zelilidis A. (2007),
“Preliminary sedimentological results indicate a new detailed
stratigraphy for the Florina sedimentary basin and relate them with CO2
presence”, Bulletin of the Geological Society of Greece, vol. XXXX,
Proceedings of the 11th International Congress, Athens, May 2007, pp.
78-84.
11. D’ Alessandro W., Bellomo S. & Brusca L. (2011a), “Elevated trace
metals and REE contents in the CO2-rich groundwaters of Florina (N.
Greece) - A natural analogue of Carbon Storage Systems”, Abstract,
GeoMed2011 - 4th International Conference on Medical Geology,
September 2011, Bari, Italy.

October 17-19, 2011
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REFERENCES (IV)
12. D’ Alessandro W., Bellomo S., Brusca L., Karakazanis S., Kyriakopoulos
K. & Liotta M. (2011b), “The impact on water quality of the high carbon
dioxide contents of the groundwater in the area of Florina (N. Greece)”,
In: Advances in the Research of Aquatic Environment (Proceedings of
the 9th International Congress of Hydrogeology and 4th MEM Workshop
on Fissured Rocks Hydrology), Editors: Nicolaos Lambrakis, George
Stournaras & Konstantina Katsanou, Volume 2, ISBN: 978-3-642-
24075-1, Springer, p. 135-143.

October 17-19, 2011
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Natural Analogues
THANK YOY VERY MUCH
FOR YOUR ATTENTION!

NATURAL ANALOGUES OF CO2 LEAKAGE IN FLORINA AREA, N. GREECE

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