Preliminary results of XRF and XRD analyzes for lithofacial characteristics of the Doirentsi Formation reservoir carbonates in the south-central part of the Moesian Platform

The main objective of the study is to determine the lithofacial characteristics of the Doirentsi Formation reservoir carbonates in the range of the south-central part of the Moesian platform by XRD and XRF analyzes. The obtained results demonstrate the chemical and phase composition and supplement the field description of the Middle Triassic limestones and dolomites. This will allow the creation of realistic 3-D reservoir models for gas condensate fields Pisarovo and Devetaki in the future.

Strain partitioning around an indenter during oroclinal bending: kinematics of the Circum-Moesian fault system of the Carpatho-Balkanides

<p>The Carpatho-Balkanides of south-eastern Europe is a double 180° curved orogenic system. It is comprised of a foreland-convex orocline, situated in the north and east and a backarc-convex orocline situated in the south and west. The southern orocline of the Carpatho-Balkanides orogen formed during the Cretaceous closure of the Alpine Tethys Ocean and collision of the Dacia mega-unit with the Moesian Platform. Following the main orogen-building processes, the Carpathians subduction and Miocene slab retreat in the West and East Carpathians have driven the formation of the backarc-convex oroclinal bending in the south and west. The orocline formed during clockwise rotation of the Dacia mega-unit and coeval docking against the Moesian indenter. This oroclinal bending was associated with a Paleocene-Eocene orogen-parallel extension that exhumed the Danubian nappes of the South Carpathians and with a large late Oligocene – middle Miocene Circum-Moesian fault system that affected the orogenic system surrounding the Moesian Platform along its southern, western and northern margins. This fault system is composed of various segments that have different and contrasting types of kinematics, which often formed coevally, indicating a large degree of strain partitioning during oroclinal bending. It includes the curved Cerna and Timok faults that cumulate up to 100 km of dextral offset, the lower offset Sokobanja-Zvonce and Rtanj-Pirot dextral strike-slip faults, associated with orogen parallel extension that controls numerous intra-montane basins and thrusting of the western Balkans units over the Moesian Platform. We have performed a field structural study in order to understand the mechanisms of deformation transfer and strain partitioning around the Moesian indenter during oroclinal bending by focusing on kinematics and geometry of large-scale faults within the Circum-Moesian fault system.</p><p>Our structural analysis shows that the major strike-slip faults are composed of multi-strand geometries associated with significant strain partitioning within tens to hundreds of metres wide deformation zones. Kinematics of the Circum-Moesian fault system changes from transtensional in the north, where the formation of numerous basins is controlled by the Cerna or Timok faults, to strike-slip and transpression in the south, where transcurrent offsets are gradually transferred to thrusting in the Balkanides. The characteristic feature of the whole system is splaying of major faults to facilitate movements around the Moesian indenter. Splaying towards the east connects the Circum-Moesian fault system with deformation observed in the Getic Depression in front of the South Carpathians, while in the south-west the Sokobanja-Zvonce and Rtanj-Pirot faults splay off the Timok Fault. These two faults are connected by coeval E-W oriented normal faults that control several intra-montane basins and accommodate orogen-parallel extension. We infer that all these deformations are driven by the roll-back of the Carpathians slab that exerts a northward pull on the upper Dacia plate in the Serbian Carpathians. However, the variability in deformation styles is controlled by geometry of the Moesian indenter and the distance to Moesia, as the rotation and northward displacements increase gradually to the north and west.</p>

RE-EVALUATION OF A GAS STORAGE RESERVOIR IN THE MOESIAN PLATFORM USING A MULTI-CRITERIA INTEGRATED ANALYSIS

An integrated approach was used to analyse the quality of a Miocene reservoir in the Moesian Platform, Romania. While this paper goes through all the main components of an integrated study (seismic, petrophysics, reservoir engineering), the main focus was on well data. This research focused on modelling the structure using mainly well data. The reservoir is associated with an alluvial cone structure and a canal system NNW-SSE, with the lithological traps in the southern part [1]. The reservoir pressure and the behaviour during production indicates a gas expansion is the main displacement mechanism, alongside a low influx of water. The results of this paper show that the performance of the reservoir is influenced not only by the available energy (the elastic gas expansion and a low influx of water), but also by the spatial distribution of different facies in relation to the well locations. Gas production started in 1962 and continues to this day. However, the Miocene reservoir was chosen for gas storage (UGS-Underground Gas Storage) due to its relatively large thickness, good porosity and large surface area [2]. The purpose of a reservoir characterisation is to incorporate existing data from petrophysics, geophysics, geological and reservoir engineering, so that the results obtained by the multidisciplinary team can be used to create a reservoir model which will improve economic results.

A new concept for the Paleogene lithostratigraphy in the onshore part of the Dolna Kamchiya Basin (eastern Bulgaria) on the basis of 3D modeling

This study is based on primary lithological data from 96 boreholes and lithostratigraphic interpretation of 17 seismic profiles from the onshore part of the Dolna Kamchiya Basin, which belongs to the onshore sector of the Moesian Platform and comprises the south-easternmost part of the Southern platform zone. Nine formal Paleogene lithostratigraphic units were recognized (the Byala, Komarevo, Dvoynitsa, Beloslav, Dikilitash, Aladan, Avren formations, the Dolni Chiflik Member of the Avren Formation, and the Ruslar Formation). For visualization of their spatial relationships and revealing the deep structure of the basin, a 3D lithological model was created. In addition, new data on the lithology, thicknesses and ages of the units were provided.

Palaeoenvironments of northwestern Bulgaria and northeastern Serbia during the Jurassic

Jurassic rocks in the Danube Region of northwestern Bulgaria and northeastern Serbia have been the subject of numerous earlier studies that have shown notable similarities between their sedimentary facies and depositional environments. In terms of regional palaeotectonic zonation, this area represents the westernmost parts of the Vidin Early–Middle Jurassic Complex Horst and the Mihaylovgrad Early–Middle Jurassic Graben in NW Bulgaria, as well as the easternmost part of the Lower Danubicum in NE Serbia, which collectively take part of the Jurassic Moesian Platform. For compiling an overall conception of the palaeoenvironments that existed during the Jurassic, nine palaeoenvironmental sketch maps, from the Aalenian to the late Tithonian, have been composed in this study, based on reinterpretation of the data borrowed from previous literature. It became evident that the Middle Jurassic sedimentary successions of the Danube Region record an evolution from an initially isolated lacustrine-palustrine depositional setting (Aalenian) to rapidly expanding shallow to moderately deeper-marine sandy-calcareous setting (late Bajocian–early Callovian). From the middle Callovian and onwards, during the Late Jurassic, the region became an area of laterally extensive pelagic and platform carbonate deposition. This interpretation is consistent with the available earlier data, but it links the facies and their respective settings from NW Bulgaria to NE Serbia, which has not been made to date and will be of benefit for future regional correlations.