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SHALE GAS RESEARCH GROUP
(SGRG)
SGRG is oriented towards multidisciplinary expert exploration and appraisal of gas shales in Bulgaria. The members of the group are scientists from the Geological Institute, Institute of Organic Chemistry and the Department of Fossil Fuels, Sofia University. They are experts in regional geology, stratigraphy, sedimentology, petroleum geology, organic geochemistry and geology of the fossil fuels.
The SGRG databases support the opportunity assessment of uncovered potential shale gas in Bulgaria. The potential shale gas source formations are significant in their mineral content, thickness, TOC, fracturing, geographic distribution, overburden, etc. Multiple methods and sources of information are used as general screening criteria for shale gas reservoirs and potential production, i.e. influence of clay mineralogy, TOC, thickness, thermal maturity.
We are focused on: - Compilation of Bulgarian black shale databases – potential source rocks for natural and shale gas; - Basic analytical research in regional geology and stratigraphy, sedimentology, organic geochemistry and the hydrocarbon potential of Bulgaria.
A. Regional geological knowledge on the main tectonic units and orogenic phases and databases of the main source rocks in Bulgaria - Tectonic map of Bulgaria – main tectonic zones and units (after Zagorchev et al., 2010) The main Alpine tectonic zones in Bulgaria are the Moesian Platform, the Balkan Zone, Srednogorie Zone and Morava-Rhodope Zone. Thick sedimentary successions, including black shales, occur extensively in the Moesian Platform and the Balkan Zone. SGRG gives assessment on the distribution of prospective shales related to the specific tectonic units and their basinal evolution and further orogenic phases, responsible for shale gas formation. - Databases of the main source rocks (black shales) in the Palaeozoic, Mesozoic and Cenozoic sedimentary succession, stratigraphy (age), thickness, depth. Black shale formations are widely distributed in all tectonic zones of Bulgaria, covering stratigraphic ages from Silurian to Neogene. SGRG is focused to deliver comprehensive databases on black shales, e.g. from drillings in the Moesian Platform, and Black Sea offshore, compiled from the huge existing sources on the lithostratigraphy, geophysical logs, age assignment, thicknesses, depths, etc. - Palaeoenvironmental interpretation of the depositional settings In the case of shale gas, the reservoir rock in the source rock. The depositional environment is anoxic, favorable for the organic-rich material to settle without oxidation before its burial and hydrocarbon generation. Good depositional systems for the gas shale are the continental slope and silted basins.
B. Analytical facilities Laboratory of Fuel chemistry (Institute of Organic Chemistry, BAS) The Laboratory of Fuel Chemistry has a long-term experience and suitable equipment for characterization of oil shales, organic matter and products of their destruction by chemical and thermal methods. The main Bulgarian oil shale deposits, namely Krasava, Borov dol, Mandra, Nikolaevo, Gurkovo, Kosacha, Pirin, Kosharevo, Koprinka deposits, etc. have been considered and investigated during the period 1970-1985. They are characterized in order to explore their structure and possibility for utilization as fuels, chemical products and grow stimulators: - ultimate, proximate analysis, oxygen and sulphur distribution; - calorific values; - solubility in organic solvents and bitumen study by spectral methods (IR, NMR); - oxidative destruction by HNO3, KMnO4 in alkaline media and O2; - standard pyrolysis with semicoke, tar/char and gas determinations; - group composition of products of pyrolysis, i.e. oils, phenols, acids, basic components, asphaltenes, etc.; - chemical composition of oils were determined by GC and GC/MS; Later on, with economical changes in the country, the interest towards the oil shale declined a bit, but has been renovated recently. Bulgarian oil shales were characterized by modern chemical and spectral methods: - steam pyrolysis of Bulgarian oil shales (Razvigorova et al. 2008, Oil shales, 25, 27-37); - oil shale chemical compositions (Razvigorova et al. 2008, Int. J. Coal Geol., 76, 243-249); - shale oxidative degradation (Budinova et al. 2008, Chemie der Erde, v.69, 235-245). The competence of the scientific staff of the Laboratory as well as the modern equipment offer excellent opportunities in the field of oil shale organic matter characterization.
Department of Paleontology, Stratigraphy and Sedimentology (Geological Institute, BAS) Maturity of the organic matter – vitrinite reflectance, Color Alteration Indices (CAI), Thermal Alteration Indices (TAI); The vitrinite reflectance values typically ranging from 0% Ro to 3% Ro can help in determining whether or not the source rock was buried enough to produce hydrocarbons. The CAI method studies the natural colour alterations in conodonts connected with paleotemperatures in the host rocks. Organic matter is a sensitive recorder of the thermal stress experienced by the host rocks. Since organic maturation is irreversible, it provides information that helps in the reconstruction of some aspects of the lost geological record and can be focused on the paleotemperature records of the sediments.
Contact SGRG: sgrg@geology.bas.bg
Tel: (+3592) 9792213 Fax: (+3592) 8724638 Address: Geological Institute BAS,
24 G. Bonchev str., 1113 Sofia, Bulgaria
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