Results of geological and geophysical investigations of the Siljan Ring impact structure (central Sweden) revealed complicated relationships between Paleozoic sedimentary succession and the Precambrian basement. Tectonic and depositional evolution caused complex geology. Studies of a new drill core from the C-C-1 well provide information necessary for the reconstruction of the geological setting in the southwestern part of Siljan Ring. The whole interval of the core section is from 32.60 to 634.90 m with almost no breaks. The sedimentary cover is 373.55 m thick in total. The sedimentary sequences are predominantly composed of wackestones, mudstones, and shales. In the lower part of the sedimentary section, limestone layers intercalate with black shales. In a result of the investigations, it has been suggested that sedimentary layers represent Late Ordovician and Silurian deposits and have disturbed stratigraphic relations. The basement section is composed of Precambrian meta-volcanic and meta-sedimentary rocks. The contact between the basement and the sedimentary cover is tectonic, not normal sedimentary, in origin. Tectonic processes caused intensive rock fracturing. Four generations of fractures were identified with analysis of fracture relations and mineralization sequence. Only two of them occur in sedimentary rocks that probably belong to the latest stages of tectonic activity. Highly fractured basement rocks in some cases contain open vugs developed along the fractures. Rock matrix is tight either in sedimentary and basement rocks and only micro-porosity space is recognized in cataclastic zones. Single evidence of bituminous filling of micro-porosity zone and partly cemented vug is established in limestone from the lower part of the sedimentary section. These findings are particularly valuable for stratigraphy refinement and tectonic setting reconstructions as well as oil and gas reservoir forecasts.
SUMMARYThe Pre-Caucasian Oil and Gas Province is one of the oldest provinces in Russia, the main hydrocarbon reserves are associated with the Meso-Cenozoic sedimentary complex. Unlike the Mesozoic sedimentary complex, which is mainly represented by fractured-porous and porous reservoirs in terrigenous and carbonate rocks, the prospects of the Cenozoic sedimentary complex are associated with clayey porousfractured Paleogene reservoirs, including reservoirs in the deposits of the Khadum suite of the Early Paleogene. Since the fractured component has a key role in the structure of the reservoir and in the filtration of fluids, it is necessary to develop a technique for developing of decompaction zones which are perspective to have a fractured reservoirs in the deposits of the Khadum suite, based on the complex of geological, geophysical and remote methods.
SUMMARYRecently North Caucasian Oil and Gas Province is one of the perspective areas for hydrocarbon reserves replenishment. As regards, unconventional perspective objects in Khadum and Batalpashinskiy deposits are new targets for exploration and development. That is why lateral heterogeneity of deposits and reservoir model are crucial work issues. In this purpose, a series of lithological and sedimentological investigations carried out. Based on obtained results lithological characterization of Khadum formation sections was build. In addition, there was conducted a comparison for two structural zones -East Stavropol Depression and Prikuma Uplifting Zone
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