AAPG Europe Regional Conference, Global Analogues of the Atlantic Margin

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Oligocene sedimentological model for the Sub-Carpathian Basin: hypotheses and analogue models from the Parathetys .

Abstract

The Getic Basin is situated south of Southern Carpathians (Romania) and is one of the most prolific hydrocarbon provinces of Eastern Central Europe. Oil Production started in 1857 and since then 139 fields have been discovered. The cumulative oil production in 2017 was about 2.8 billion bbl, where the gas production exceeded 1.5 TCF. Sedimentation in the Getic Basin is strongly related to the development of the Carpathian Orogen; the Carpathian had been drifting and rotating from latest Cretaceous-Paleogene to the present day time, suffering an uplift associated with a roll-back subduction. All these uplifted terranes have been eroded generating 2-4 Kilometers of sediments, that have been transported and deposited within the Getic Basin. South of the Basin, as a consequence of the rotation and collision with the Carpathians, the Moesian Platform suffered an very early uplift that allowed it to operate as another source of sediment for the Getic Basin at the first stages. All these large load of sediments generated a perfect condition for a deep-water turbiditic deposits in the basin. Poor knowledge in facies distribution for the Oligocene turbidites in the Southern Carpathian basin has an impact on reservoir risk, a crucial factor for exploration decisions. The purpose of this study is to provide a coherent depositional model for these turbiditic complex in the entire Getic Basin (Fig.1). The new stratigraphic model supports a better prediction of reservoir distribution, identifying facies and depositional environments. To accomplish this model, an important compilation of data has been conducted, analyzing and QC the information of 93 key wells and 8 outcrops. Also 16 well correlation panels based upon TST calculations and facies interpretation, were produced using sequence stratigraphy principles, allowing more accurate stratigraphic correlations to better predict reservoir presence. Finally a palinspastic map have been generated restoring the shortening of some regional structural sections. The result of this study consists mainly in a set of CRS Reservoir maps showing the evolution of the turbidites in time and space (Fig.2). These summary maps show 6 turbidite complexes in which channels, lobes, thin beds, hemipelagic, shelf and continental facies have been identified. From these maps we are able to visualize where higher probability of finding lobes facies and therefore the best reservoirs, also 3 main sources of sediment are proposed. The geological model suggests that significant exploration potential is still left from the Oligocene reservoirs in Romania. The Atlantic margin has several fields producing hydrocarbons from Oligocene turbiditic reservoirs, the properties and performance have been used as an analogs in this study.