Porosity-Permeability and Textural Parameters of the Palaeogene Forearc Sedimentary Fill on Lemnos Island, NE Greece

Authors: ANGELOS MARAVELIS, AVRAAM ZELILIDIS

Abstract: The Palaeogene forearc sedimentary fill on Lemnos Island, NE Greece, was examined to determine reservoir characteristics and textural parameters. During this time interval the studied area was the site of accumulation of submarine fans that underlie shelf deposits, with tectonic activity responsible for the shallowing upward trend. Turbidites were deposited in both inner (slope fan facies) and outer parts (basin floor fan facies) of the submarine fan system and consist of alternating sandstone and mudstone beds. Sandstones occur in both complete and incomplete Bouma sequences while shelf deposits have been interpreted as storm-surge deposits on the deeper parts of shelves. The 'Mercury Porosimetry Technique' was carried out on 20 sandstone samples, while 30 sandstone samples were examined under a polarizing microscope for grain-size analysis. This porosity-permeability study suggests that these rocks can be considered as both oil and gas reservoirs. 'Slope' fan facies generally reveal the most efficient values, making them the most promising sub-environment for further hydrocarbon research. Most samples display two pore-size distributions suggesting major textural heterogeneity. Textural parameter analysis reveals that sorting was of great importance during sedimentation. Rocks are generally well to very well-sorted while samples with moderate sorting are also present. This fact can be both attributed to the restricted grain-size range and their possible great distance from the source area. This generally well-sorted sequence argues well for further hydrocarbon research in the Northeast Aegean Sea, since the higher the sorting the higher the porosity. Selected samples are generally very fine to fine grained, whereas medium-grained sandstones are extremely rare and mostly seen on 'slope' fan facies. The finest grained sandstones are the best sorted.

Keywords: porosity, permeability, textural parameters, grain-size, Lemnos Island, NE Greece

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