The study on coals in Slovenia and their potential as geological medium for sequestration of CO2 was a part of the national project entitled Possibilities of geological storage of CO2 in Slovenia. The whole project, carried out by coordination between 4 organisation (see "Objavljeno v") was written in 8 books - from presenting theoretical background, through evaluation of CO2 storage potential in deep saline aquifers, in deep coal seams and in depleted oil and gas fields, to presentation of a programme for real injection and storage of CO2 in different media - especially in depleted oil and gas fields. Previous investigations on characteristics of our coals (geological structures of coal deposits, reserves, coal quality, rank, petrography, porosity, rock-mechanics, geochemistry etc) and especially preliminary tests of gas sorption capacity, which were done in the past only for the Velenje lignite, were the only realistic data for estimation of CO2 storage potential in coals of Slovenia. As a final result it was concluded, that only deep ()800 m underground) coals of NE Slovenia in the Mura formation (see Chap. 7.1 of this report) might be potentially suitable for CO2 sequestration. This potential was theoretically - based on volume and porosity - estimated to 35-100 Mt CO2. However, real potential, due to realistically expected low permeability and swelling effect by injected CO2, is most probably considerably lower.
F.02 Acquisition of new scientific knowledge
COBISS.SI-ID: 1948757Main results of the project entitled "Possibilities for CO2 sequestration in Slovenia, and outside Slovenia" were presented at the 3th International "EnRe - Energy technology and Climate changes" conference.The mentioned project was carried out for more than one year (8 books) by the following organisations: Geological Survey of Slovenia (GeoZS), Institute for ecology (ERICo-Velenje), Faculty of natural Sciences and Technology- University Ljubljana (NTF-UL), Nafta Geoterm Lendava and a private company HGEM. All three main geological media potentially suitable as the media for CO2 sequestration were considered in the study: saline aquifers, depleted oil and gas fields, and coal seams, all in depths more than 800 m. Like in the world, also in Slovenia deep saline aquifers represent the greatest potential, but are well explored only to depths of about 1000 m in the sites of previous hydrogeological and thermalwater explorations. Aquifers of potable, mineral, thermal, thermomineral waters should not be interrupted by activities which would negatively affect the quality and quantity of the natural waters. CO2 is forbiden to be introduced in such aquifers. Potential for CO2 sequestration in deep saline aquifers therefore still remains quite an open question. The most reasonable potential for eventual CO2 sequestration represent depleted oil and gas fields in the Petišovci area. Knowledge on these fields is at a high level and the infrastructure is already established. A simbolic production of oil and gas is still going on and could be maybe increased by injection of CO2 to enhance recovery of the remaining gas and oil (EOGR technology). NE Slovenia (Pannonian Basin) is not known only by its underground water, geothermal and oil and gas potential but also by deep (down to 1000 m) coal layers (metalignite rank), very well explored in the Lendava Petišovci area and detected in almost all oil and gas, and geothermal wells across the Slovenian part of the Pannonian Basin. Problem of coals is their low permeability (low gas-flow potential) in spite of their often high porosity. To get some data what quantities of gas caould be adsorbed into the coal is one of the main reasons why we study adsorption of CO2 in laboratory conditions on coal samples available to us. Tectonic structure of the Pannonian Basin coals is expected to be simple but the seams are most probably thin (in Lendava three seams ( 2m, but very widely extending). Coal layers - their thickness, structure, petrology, spatial distribution - should be chequed by core drilling, because data from existing wells (not cored) do not give reliable answers to these questions.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 2181205The aim of the thesis was to study the mineralogical, petrological and geochemical composition of sediments from Velenje lignite basement layers. Forthis purpose, 32 samples from core hole P-9k/92 was collected and analyzed for: dry sieve analysis, sieve analysis using a laser granulometry, optical microscopy in plane-polarized light, X-ray powder diffraction and geochemical analysis. Results showed that basement layers represent very heterogeneous and rapidly changing bedding sediments that occurred in a relatively calm fresh water environment where redox conditions prevail. Studied profile is dominated by silts and coal-rich sediments, among which the sandstones and breccia-conglomerates stands out. Thicker fine-grained sediments reflect intense events and increased intake of terigeneous material from the north by rivers to the sedimentary basin. Within the layers of sediments siderite lenses and coarse siderite-rich sediments was found. Based on negative cerium anomaly we found out that these sediments resulting in more oxidizing conditions. Geochemical analysis showed that the samples dominated by the following major oxides: SiO2, AI2O3, Fe2O3, K2O, CaO and Na2O. The samples differ only in the amount and ratio of major oxides. Siltstones are composed mainly of quartz, kaolinite and illite/muscovite. The amount of clay minerals in the coarse grain sediments is significantly lower than in fine grain sediments. Some feldspar is also present in these sediments. In a good lithify sandstones marcasite, siderite and calcite cement occurs. Correlations between major oxides and rare earths elements have shovvn that light -are earth elements (LREE) are bound on clay minerals, while concentration of heavy rare earth elements (HREE) are bound to carbonates mainly on siderite.
D.10 Educational activities
COBISS.SI-ID: 1086558The paper entitled "Oil shales - in the World and in Slovenia" was written for Proteus, a Slovenian popular natural-sciences journal (founded in 1933). In 2005 a similar paper was written for coal and years ago for oil. All those papers represent in brief economic significance of the mentioned geo-energy sources and focus then especially in their genesis (initial geologic conditions, tipology of source organic components, biogeochemical processes of early diagenesis and further physico-chemical processes of coalification/maturation), and in their present day occurence and composition. Oil shales, which can in average produce by pyrolisis ca 100 l of oil per tonne of shale, are today very far from to be an economically important energy source, except for some states and regions as in e.g. Estonia, China, and Brazil. However, interesting is their petrology and chemistry. Oil shales are rocks with subordinated organic matter content (less than 50 %) and represent transition between sapropelic coals and "true" rocks, which are almost free of organic matter and have no commercial potential for industrial oil production. Oil shales are mostly mudstones, siliciclastic or carbonate, and might represent in geological history source rocks for natural generation of oil and/or gas. Source rocks may contain very low organic matter, as low as only ca. 2 % of organic carbon (Corg). Oil shales in many cases occur together with coals, especially when peat (terrestrial vegetation) forming paleo-environments transited to sea-influenced environments. In Slovenia, similar examples exist in the roof strata with algeae and spicules of sponges (so called "black roof", eventhough not sea- but fresh-water influenced) above the Zasavje coal seam and in connection with bituminous coal layers and organic-rich limestones in the Kras (Karst) and Istria regions. Oil shales of economic significance are not known to exist in Slovenia (up to date).
D.11 Other
COBISS.SI-ID: 2217045This was an invited lecture/presentation about unconventional geoenergy resources in Slovenia, in the frame of EU. The presentation was organised (and financed) by the SMi Conference, London. In fact, in Slovenia, we partially know for unconventional geoenergy resources, and both classical (conventional) and potential, at present still unconventional energy resources were presented at the meeting. Likely in EU countries in general, deep geoenergy data are quite scarce in Slovenia. A sincere call for further multidisciplinary exploration comes from us.
B.04 Guest lecture
COBISS.SI-ID: 2032725