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The anticline of the Divjaka gas field as unique focus of compelled data is an integral part of the Southern Adriatic Depression, which is composed of Middle Miocene to Pliocene deposits. There were discovered two levels of natural gas: the first level located in the Pliocene deposits, while the second one belongs to the Tortonian and Messinian san...
Context in source publication
Context 1
... palaeotectonic development. The structure of the Divjaka anticline has a regular shape of 15 x 5 km size according to the base of the Pliocene deposits. It is dissected by a longitudinal reverse fault of some hundred meters range along its western flank, as well as of some back thrusts of some tenths meters range along its eastern flank (Fig. ...
Citations
The Periadriatic Foredeep onshore Albania is the only Foredeep basin located in the frontal part of the Albanides orogeny bordering eastward the Adriatic Foreland. The recent neotectonic investigations and previously published ones prove the formation of Periadriatic Foredeep as a dextral pull-apart basin in the Middle Miocene (Serravallian), subsequently to the main folding and thrusting of the Ionian Zone, through the strike-slip faulting mechanism. The two elements that commonly lead to the formation of the Periadriatic Foredeep Pull-apart Basin are the cross-basin strike-slip faults of Drini Bay-Lezha and Vlora-Bishqemi, and the oblique normal faults of Durresi-Frakulla and Preza-Rova-Bishqemi. The infill consists of the Serravallian to Pliocene molasses succession up to 6 km in thickness. The Periadriatic Foredeep Basin is located between the South Adriatic and Tirana Marginal Basins. The development of the Periadriatic Foredeep finally led to the different evolution of both the Periadriatic and Tirana depressions with different structures and mineral resources. The Periadriatic Depression structure is built by an NNW trending narrow anticline and wide syncline lines. From southwest to the northeast, these lines are distinguished: Frakulla-Durresi anticlinal line, Myzeqe syncline, Lushnja-Golem Kavaja anticlinal line, Erzeni i poshtem syncline, and Preza monocline. The Myzeqe and Erzeni i poshtem depocenters are separated by the intrabasinal Mliku-Shkoza high. The Divjaka gas field and Patosi, Marinza, and Kuçova oil fields are well known in the Periadriatic Depression. The Tirana Depression is developed from the Tirana marginal basin eastward bordering the Periadriatic Foredeep. It is characterized by the prevailing continental and shallow-marine Miocene sediments (with coal-bearing fields in Tortonian and Messinian deposits) that formed a wide northeast verging asymmetrical syncline due to the Preza-Rova-Bishqemi backthrust. The Tirana Depression overlies the Kruja Zone substratum to the north of Tirana, and partly, the Ionian Zone substratum to the south of Tirana along its western limb to the east of the Rova anticline backthrust. Deformation of orogenic crust at the Albanides-Adria collision zone during Tertiary occurred and occurs into both levels: i) a basal fold-and-thrust system in the Ionian Zone, that accommodated an increasing amount of SW directed shortening, and ii) a structurally higher system of thrust faulting affecting the overlying structure of the Periadriatic Depression, that underwent a strong structural rearrangement.
Oil accumulations occur in the Ionian zone limestone section and in the Adriatic Basin sandstone reservoirs of Tortonian and Messinian age, respectively. A large set of geochemical compositional data of Albanian oils have been analysed. Oil entrapment occurred during two main phases: 1) during the Early Miocene, when the main part of source rocks were in the oil maturity window; 2) during the Pliocene, when the source rocks were in a more advanced stage of oil genesis. The multiphase genesis has resulted in hydrocarbon accumulations with a broad range of geochemical characteristics. Both individual fields and in field complexes, biodegraded and non-biodegraded heavy oils, light oils, condensates, wet and dry gas may occur. In general, oil density and sulphur content decrease with depth. Oil grouping is evident from the data set, although stable carbon isotope values suggest that the Berat Belt oils and the Adriatic Basin oils are slightly different from the majority of oils in the Kurveleshi Belt. No exact correlations between the oils and the individual carbonate source rock levels could be established. The Tertiary humid source rock has been matured probably in the early stage, and has generated dry gas and some immature con-densates. The gas accumulations in the Adriatic Basin consist mostly in pure biogenic and mixed thermogenic/ biogenic gases. The deeper classic reservoirs contain relatively less dry gas.
