Hydrocarbon prospects in the Western Black Sea of Ukraine

Abstract

Th is paper presents the author's integrated regional studies during the last decade. Th e main purpose is to present an overall understanding of the geological structure, sedimentary basins and hydrocarbon systems of the whole Western Black Sea Zone (WBSZ). Th is study is based on original data from boreholes, seismic and gravity-magnetic surveys and hydrocarbon accumulations.Many geophysical borehole data obtained for WBSZ during the last 3-4 decades were interpreted mostly at a national level using diff erent approaches, terminology and nomenclature for the same or similar lithostratigraphic and tectonic units. Th erefore, a unifi ed approach to interpretation of borehole-seismic data and correlation of stratigraphic, sedimentological and tectonic units has a key importance for overall clarifi cation of the deep geological structure and the hydrocarbon challenges.A set of regional geological cross-sections along good quality basic seismic lines and basic boreholes was constructed. A detailed tectonic map of the WBSZ has been compiled by integrated interpretation of seismic borehole and gravitymagnetic data. Th e defi nition of hydrocarbon systems and promising exploration trends is made by source rock assessment, Oil-Oil and Oil-Source rock correlations, analyses of the reservoir/seal pairs and the hydrocarbon migration and accumulation. Genetic correlations are based on many Rock-Eval, Gas Chromatography/Mass Spectrometry (GC-MS) and carbon isotope analyses.Th e complex geological structure of the WBSZ is defi ned by four groups of tectonic units: (1) Western Black Sea basin (WBSB) -its western zone with the Kamchia and the Histria westward wedging branches (sub-basins); (2) portions of the Moesian, Scythian and East European platforms; (3) fragments of the North Dobrogea, Eastern Balkan, Eastern Srednogorie and Strandzha orogens; (4) Burgas and Babadag basins.Four diff erent oil genetic types have been identifi ed. Th ree main hydrocarbon systems with economic potential are defi ned, they relate to: WBSB and its Histria and Kamchia branches, the East-Varna trough and the Bourgas basin. Conceptual models for hydrocarbon systems and their prospect exploration trends are constructed.

Kinematics of back‐arc inversion of the Western Black Sea Basin

“…[10] The major contraction taking place at the southern margin of the Black Sea led to the onset of inversion recorded in the extensional basins and to the formation of other foreland and thrust-sheet top basins [e.g., Finetti et al, 1988;Robinson et al, 1996;Sunal and Tüysüz, 2002;Nikishin et al, 2003]. In contrast with the large-scale structures observed in the south, inversion along the NE part of the Western Black Sea led to the formation of OligoceneMiocene reverse faults and associated folds with N-ward vergence and offsets in the order of tens to few hundreds of meters [Afanasenkov et al, 2007;Khriachtchevskaia et al, 2009]. Along this northern margin, the structural grain changes rapidly east of the Odessa-West Crimea fault system (Figure 1), where the Crimean Orogen is thrusted S-wards over the Black Sea domain from Oligocene to recent times [e.g., Stovba et al, 2009].…”

“…The Odessa-West Crimean fault system has been defined on the basis of potential field geophysics, wells and older seismic reflection profiles to accommodate a dextral displacement of the Odessa Shelf units, such as the Karkinit Trough, the Shtormavaya Graben and the Kalamit Ridge (Figure 1) [e.g., Garkalenko, 1970;Tugolesov et al, 1985;Robinson et al, 1996] (or their counterparts in Romanian nomenclature [see Dinu et al, 2005]), when compared with their equivalent units located in Crimea and East Black Sea Basin. More recent interpretations have demonstrated that this dextral structure is characterized in seismic lines by a large zone of deformation made up by high-angle reverse faults with small vertical offsets [Afanasenkov et al, 2007;Khriachtchevskaia et al, 2009].…”

“…This regional integration of inversional structures has Figure 1. Tectonic map of the Black Sea and adjacent areas (compiled from Finetti et al [1988], Doglioni et al [1996], Robinson and Kerusov [1997], Mikhailov et al [1999], Dinu et al [2005], Okay et al [2006], Saintot et al [2006], Afanasenkov et al [2007], Khriachtchevskaia et al [2009], and Nikishin et al [2010]). The inset is the location of Figure 8.…”

Heterogeneous structure of the lithosphere in the Black Sea from a multidisciplinary analysis of geophysical fields

“…Seismic data from the Black Sea are briefly presented in this paper because the most essential results are described in full detail by [Starostenko et al, 2004a,b]. Here results are updated because new seismic information has been obtained since that time [Slishinsky et al, 2007;Khriachtchevskaia et al, 2009;Scott et al, 2009;Scott, 2009;Yegorova et al, , 2013Piip, Ermakov, 2011;Stovba et al, 2013;Graham et al, 2013]. All these data were used to constrain parameters of the sedimentary cover in gravity modeling.…”

“…In the deep-water part magnetic susceptibility information is not available. In another way, values of magnetic susceptibility of samples can be used from the adjacent onshore because marine seismic stratigraphy is similar to that exposed on land [see for example, Rangin et al, 2002;Khriachtchevskaia et al, 2009;Hippolyte et al, 2010;Georgiev, 2012]. They do not exceed mostly (30-40) 10 5 SI on the conjugate margins of the Black Sea in the Pon and Cr [Kaymakci et al, 2003;Guzhikov et al, 2012].…”