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

    George Hatziyannis and Apostolos Arvanitis

    October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural 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

    October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    - Florina basin (Macedonia, Northern Greece)

    Low enthalpy geothermal

    field of ThermaNigrita

    (T=40-64oC,3.5-4,7 kg CO2/t H2O)

    (Macedonia,NorthernGreece)

    Low enthalpy geothermalfield of Akropotamos,Kavala(T=83-90oC,large amounts of CO2)(Macedonia,NorthernGreece)

  • LOCATION of STUDY AREAGeographical locationAccess 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

    October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

  • Natural analogues of CO2 leakage in Florina area, N. Greece

    October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    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.

    October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

  • 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 Hellenidesduring extensional stresses following the Alpine orogenesis.

    October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

  • 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.

    October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

  • 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 clasticsediments took place.

    October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    Mesozoic crystalline limestones, schists and gneisses occur in the east where a slower rate of sedimentation deposited finer clastics on the basement limestones.

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

  • The Neogene sediments, overlying the Mesozoic crystalline limestones, comprise fluvial, coarse to fine siliciclasticswith 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 (Veviformation, 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.

    October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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.

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    Correlationamong three stratigraphic sections in the Florina

    basin

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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).

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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 CO2seeps) in the Florina area

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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.

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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 Almopiaarea (Voras Mountain).

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

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

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    The Florina basin is a seismically active area with maximum magnitudes of around 5 on the Richter scale.The potential relationship between fluid migration (CO2leakage) 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)

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    A cored well, 574,70 m deep, was drilled close to the village of Messokampospenetrating 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)

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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 CO2reservoir (560 m depth).

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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 m300-310 m 320-330 m380-390 m400-410 m 457-465 m490-500 m

    550 m

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    SAMPLING IN THE FLORINA AREAA 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.

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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 CO2diffusion experiments. This sample appeared to be very clay-rich and the pore-size distribution indicated a considerable amount of microporosity.

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    PETROPHYSICAL MEASUREMENTS AND FLUID TRANSPORT EXPERIMENTS ON SAMPLES FROM FLORINA AREA (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.

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    PETROPHYSICAL MEASUREMENTS AND FLUID TRANSPORT EXPERIMENTS ON SAMPLES FROM FLORINA AREA (NASCENT Report, 2005) (iii)

    The results of permeability and CO2 diffusion tests, conductedwith 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 cationexchange capacity as parameters controlling sealing efficiency for CO2.

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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 CO2springs. 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

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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.

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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.

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

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

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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.

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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.

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    MAP of TOTAL HARDNESS : Values of Total �ardnessof 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.

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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.

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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, �CO3 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 NO2and NH4. In the northern part of the basin, some increased NO3concentrations occur.

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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).

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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 mineralwater 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.

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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.

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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)

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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 whenswimming 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.

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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.

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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.

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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 diageneticevents – 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.

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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.43�C) & 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.

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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 CO2flow (initial simplified mineralogy).

    LONG-TERM GEOCHEMICAL INTERACTIONS AT THE NATURAL CO2-ANALOGUE IN THE FLORINA AREA (Gaus et al., 2004) (ii)

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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.

    LONG-TERM GEOCHEMICAL INTERACTIONS AT THE NATURAL CO2-ANALOGUE IN THE FLORINA AREA (Gaus et al., 2004) (iii)

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    LONG-TERM GEOCHEMICAL INTERACTIONS AT THE NATURAL 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 CO2interactions.

    Modelling of the Messokampos site - batch kinetic simulation

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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 theCO2 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).

    LONG-TERM GEOCHEMICAL INTERACTIONS AT THE NATURAL CO2-ANALOGUE IN THE FLORINA AREA (Gaus et al., 2004) (v)

    Batch kinetic modelling for the Messokampos site (A)

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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 obviousdonor 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)

    LONG-TERM GEOCHEMICAL INTERACTIONS AT THE NATURAL CO2-ANALOGUE IN THE FLORINA AREA (Gaus et al., 2004) (vi)

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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.

    LONG-TERM GEOCHEMICAL INTERACTIONS AT THE NATURAL CO2-ANALOGUE IN THE FLORINA AREA (Gaus et al., 2004) (vi)

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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 Florinafield 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 CO2production.Up to now, no increase in the seismicity of the area has been observed and surface subsidence is not noticeable.

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    GEOMECHANICAL MODELLING OF THE FLORINA SITE (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 ofsubsidence 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.

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    GEOMECHANICAL MODELLING OF THE FLORINA SITE (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

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    CONCLUSIONS (I) In the wider area of the Florina sedimentary basin, CO2leakage 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, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    CONCLUSIONS (II)The evaluation of the geohazards from CO2 extraction and subsequent injection in the shallow reservoir of the Florinaarea 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, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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, �CO3 and trace elements, increased total hardness).

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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 hydrogeochemicalstudy of the Florina basin, geochemical modelling, geomechanicalmodelling etc) were carried out in the framework of the European Union Fifth Framework Project NASCENT (2001-2004)

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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): CO2Storage and Enhanced Oil Recovery, Changchun, China,11-14 July 2011.

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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.

  • October 17-19, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    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 CO2presence”, 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, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    Natural analogues of CO2 leakage in Florina area, N. Greece

    REFERENCES (IV)

    12. D’ Alessandro W., Bellomo S., Brusca L., Karakazanis S., KyriakopoulosK. & 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, 2011Maria Laach, Germany

    2nd CGS Europe Knowledge Sharing WorkshopNatural Analogues

    THANK YOY VERY MUCH FOR YOUR ATTENTION!


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