AN UPDATE ON THE STRATIGRAPHIC LIMITS OF UPPER CRETACEOUS FROM LEBADA EAST STRUCTURE, ISTRIA BASIN, WESTERN BLACK SEA

Upper Cretaceous arc-related volcanic and volcanoclastic units overlying the Paleozoic sedimentary rocks of the Istanbul Zone are a key unit related to the opening of the Black Sea as a back-arc basin. They formed as a result of north dipping subduction of the Neo-Tethys Ocean beneath Laurasia. We studied the Upper Cretaceous volcanic units north of Istanbul along several stratigraphic sections, and present new geochemical data from the volcanic rocks in order to understand Cretaceous geodynamic evolution of the &#304;stanbul Zone.The Upper Cretaceous &#160;volcanic units north of Istanbul are divided into two formations. At the base there is a fore-arc turbidite succession,the &#304;shakl&#305; Formation, which is made up of volcaniclastic sandstone, shale, marl, tuff, debris flow horizons and epiclastic rocks of Turonian age. The &#304;shakl&#305; Formation is conformably overlain by the volcanoclastics, &#160;tuffs, andesite and basalt lavas and agglomerates- the Riva Formation, which represents the arc/ intra-arc series.Geochemically, basalts and basaltic andesites of the Riva Formation are low K calc-alkaline to medium-high K calc-alkaline and with magnesium numbers ranging from 32.6% to 51.5% Primitive mantle normalized spider diagram of trace elements show&#160; enrichment in LILE elements (K, Rb, Sr, Cs, Ba, Th and U) and depletion in HFS elements ( Nb,Ta and Ti) . The high ratio of LILE/ HFS and negative Nb-Ta anomalies indicate that the volcanism evolved in subduction setting. Chondirite-normalized REE pattern display slight negative Eu anomalies and the La/Yb ratios of the samples range between 2,76 and 4,89. Our new geochemical, stratigraphical and the regional geological data suggest that north of Istanbul there was a transition from fore-arc deposition to arc volcanism during the Late Cretaceous opening of the Western Black Sea.&#160; Considering the whole Pontide &#8211; Sredna-Gora Upper Cretaceous magmatic arc, it can be stated that calc-alkaline volcanism developed in relation to northward subduction of the Neo-Tethys oceanic lithosphere during the Turonian, and may have passed into high-K calc alkaline and shoshonitic magmatism as a result of the progressive extentional tectonism during the Campanian.

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Development of Tight Upper Cretaceous Reservoir in Offshore Black Sea Adds Life to a Mature Asset

10.2118/207428-ms ◽

2021 ◽

Author(s):

I. Mitrea ◽

R. Cataraiani ◽

M. Banu ◽

S. Shirzadi ◽

W. Renkema ◽

...

Keyword(s):

Black Sea ◽

Upper Cretaceous ◽

Rock Physics ◽

Oil Production ◽

Economic Life ◽

Production Performance ◽

Single Fracture ◽

Well Performance ◽

Acoustic Image ◽

The Impact

Abstract This Upper Cretaceous reservoir, a tight reservoir dominated by silt, marl, argillaceous limestone and conglomerates in Black Sea Histria block, is the dominant of three oil-producing reservoirs in Histria Block. The other two, Albian and Eocene, are depleted, and not the focus of field re-development. This paper addresses the challenges and opportunities that were faced during the re-development process in this reservoir such as depletion, low productivity areas, lithology, seismic resolution, and stimulation effectiveness. Historically, production from Upper Cretaceous wells could not justify the economic life of the asset. As new fracturing technology evolved in recent years, the re-development focused on replacing old, vertical/deviated one-stage stimulations low producing wells with horizontal, multi-stage hydraulic fractured wells. The project team integrated various disciplines and approaches by re-processing old seismic to improve resolution and signal, integrating sedimentology studies using cores, XRF, XRD and thin section analysis with petrophysical evaluation and quantitative geophysical analyses, which then will provide properties for geological and geomechanical models to optimize well planning and fracture placement. Seven wells drilled since end of 2017 to mid-2021 have demonstrated the value of integration and proper planning in development of a mature field with existing depletion. Optimizing the well and fracture placement with respect to depletion in existing wells resulted in accessing areas with original reservoir pressure, not effectively drained by old wells. Integrating the well production performance with tracer results from each fractured stage, and NMR/Acoustic images from logs enhanced the understanding of the impact of lithofacies on stimulation. This has allowed better assessment and prediction of well performance, ultimately improving well placement and stimulation design. The example from this paper highlights the value of the integrating seismic reprocessing, attribute analysis, production technology, sedimentology, cuttings analysis and quantitative rock physics in characterizing the heterogeneity of the reservoir, which ultimately contributed to "sweet spot" targeting in a depleted reservoir with existing producers and deeper understanding of the development potential in Upper Cretaceous. The 2017-2021 wells contribute to more than 30 percent of the total oil production in the asset and reverse the decline in oil production. In addition, these wells have two to four times higher initial rates because of larger effective drainage area than a single fracture well. Three areas of novelty are highlighted in this paper. The application of acoustic image/NMR logging to identify lithofacies and optimize fracturing strategy in horizontal laterals. The tracers analysis of hydraulic fracture performance and integration with seismic and petrophysical analysis to categorize the productivity with rock types. The optimization of fracture placement considering the changes of fluid and proppant volumes without compromising fracture geometries and avoiding negative fracture driven interactions by customized pumping approach.

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Striking Variation in the Provenance of the Lower and Upper Cretaceous Turbidites in the Central Pontides (Northern Turkey) Related to the Opening of the Black Sea

Tectonics ◽

10.1029/2018tc005119 ◽

2019 ◽

Vol 38 (3) ◽

pp. 1050-1069 ◽

Cited By ~ 2

Author(s):

R. Akdoğan ◽

A. I. Okay ◽

I. Dunkl

Keyword(s):

Black Sea ◽

Upper Cretaceous ◽

The Black Sea

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New objects in section of the eastern Black Sea basin from 3D seismic data

Moscow University Bulletin. Series 4. Geology ◽

10.33623/0579-9406-2020-3-138-143 ◽

2020 ◽

pp. 138-143

Author(s):

O. A. Khlebnikova ◽

Ya. E. Terekhina

Keyword(s):

Continental Slope ◽

Black Sea ◽

Seismic Data ◽

Upper Cretaceous ◽

Wave Pattern ◽

Karst Collapse ◽

3D Seismic ◽

The Caucasus ◽

Lower Miocene ◽

3D Seismic Data

In the section of the eastern Black Sea basin and the Caucasus continental slope, according to 3D seismic data, unique objects were first discovered and described — vertical failure in the Upper Cretaceous — Lower Miocene deposits. An interesting feature of these structures is a close to isometric shape in plan. About 40 objects have been identified on an area of more than 1000 m2. «Bulls-eye» («multiphase») paleo-pockmarks [Andresen, Huuse, 2011], as well as karst collapse [Zuo et al., 2009] are proposed as world analogues with a similar wave pattern on seismic data. The corresponding genesis models are considered, but none of the theories allows drawing a conclusion. The discovered objects are unique and require further investigation.

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On the Duality of Marine Geoheritage: Evidence from the Abrau Area of the Russian Black Sea Coast

Journal of Marine Science and Engineering ◽

10.3390/jmse9090921 ◽

2021 ◽

Vol 9 (9) ◽

pp. 921

Author(s):

Dmitry A. Ruban

Keyword(s):

Black Sea ◽

Late Cretaceous ◽

Upper Cretaceous ◽

The Black Sea ◽

Field Investigations ◽

Black Sea Coast ◽

Technical Properties ◽

Krasnodar Region ◽

Sea Coast

Marine geoheritage is an important but still underdeveloped concept. Field investigations in the Abrau area (Krasnodar Region, southwestern Russia) and subsequent interpretations allow for the characterization of its geoheritage. Two geosites, namely Abrau and Limanchik, are delineated and assessed semi-qualitatively. Their high heritage value, complexity, and appropriate “technical” properties are appraised. The Abrau geosite features Abrau Lake with its enigmatic origin and the outcrops of deformed Upper Cretaceous carbonate flysch deposits. The Limanchik geosite represents an outstanding example of coastal abrasion, Paleocene siliciclastic flysch with trace fossils, and a coastal lagoon separated from the sea by a bar. The heritage aspects of the study areas are related to the development of the Late Cretaceous, Paleocene, and Pliocene seas, as well as to the active dynamics of the Black Sea coastal zone. The duality of marine geoheritage is linked to its relation to both ancient and modern marine environments.

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Upper Cretaceous and Eocene litho- and biostratigraphy of the Istria Basin (NW Black Sea)

10.5194/egusphere-egu2020-5033 ◽

2020 ◽

Author(s):

Madalina Eliza Anton ◽

Ioan Munteanu ◽

Corneliu Dinu ◽

Mihaela C. Melinte-Dobrinescu

Keyword(s):

Black Sea ◽

Large Scale ◽

Upper Cretaceous ◽

Middle Eocene ◽

Structural Characteristics ◽

Normal Fault ◽

Hydrocarbon Exploration ◽

Thickness Variation ◽

Foot Wall ◽

Early Eocene

The Istria basin, situated in the NW Black Sea, is composed of Mesozoic to Cenozoic successions. The opening of the Western Black Sea, including the Istria basin, initiated in the late Early Cretaceous. Rifting and expansion continued in the Late Cretaceous, while in the Late Paleogene a compressional regime settled. In the Middle Eocene, the Western Black Sea basin margin inverted, due to the collision of Pontides and Taurides belts (Okay and T&#252;ys&#252;z, 1999; Dinu et al., 2005). The continuing compression shaped this basin until the Middle Miocene (Ionescu et al., 2002).&#160;Tens of wells for hydrocarbon exploration were drilled in the Istria basin (Romanian offshore) since the 70&#8217;s. In this study, we have interpreted the acquired core reports containing litho- and biostratigraphic data. Based on identified calcareous nannofossil biozones, a continuous deposition was found in the Cenomanian-Maastrichtian interval. Lithologically, the Upper Cretaceous is composed of carbonatic rocks, such as limestones and marlstones, with intercalations of calcareous sandstones. The Eocene deposits are unconformably lying on Upper Cretaceous ones. Lithologically, the Eocene is characterized by alternating calcareous and siliciclastic sandstones. Biostratigraphy on planktonic and benthic foraminifers, as well as calcareous nannofossils, indicate a late Early Eocene to Middle Eocene age (i.e., late Ypresian to Bartonian).&#160;The observed large thickness variation, from W towards E in the Istria Basin, is a consequence of various tectonic settings. The western part (i.e., the Sinoe area) is situated in the hanging-wall of an inverted normal fault filled with Early Eocene deposits and was inverted by high angle thrust fault during the Late Eocene-Oligocene interval. In the E (i.e., the Leb&#462;da area), there is an uplifted normal fault foot-wall, showing a reduced thickness in comparison with the W (Munteanu et al., 2011). The erosion level increased eastward, removing the entire Upper Eocene and the top of the Middle Eocene. This feature may be linked to a large sea level drop towards the Eocene top, with subaerial erosion and development of large-scale canyons system at the self to slope transition, like the Plio-Quaternary Viteaz Canyon of the NW Black Sea.&#160;The financial support for this paper was provided by the Romanian Ministry of Research and Innovation, through the Programme Development of the National System of Research &#8211; Institutional Performance, Project of Excellence for Rivers-Deltas-Sea Systems No. 8PFE/2018.&#160;ReferencesDinu, C., Wong, H.K., &#538;ambrea, D., Ma&#539;enco, L., 2005. Stratigraphic and structural characteristics of the Romanian Black Sea shelf. Tectonophysics, 410, 417-435.Ionescu,&#160;G.,&#160;Sisman,&#160;M., Cataraiani,&#160;R.,&#160;2002.&#160;Source and reservoir rocks and trapping mechanism on the Romanian Black Sea shelf.&#160;In:&#160;Dinu,&#160;C.,&#160;Mocanu,&#160;V.&#160;(Eds.)&#160;Geology and Tectonics of the Romanian Black Sea Shelf and its Hydrocarbon Potential.&#160;BGF Special Volume,&#160;2,&#160;67&#8211;83.Munteanu,&#160;I.,&#160;Ma&#355;enco,&#160;L.,&#160;Dinu,&#160;C., Cloetingh,&#160;S.,&#160;2011.&#160;Kinematics of back-arc inversion of the western Black Sea basin.&#160;Tectonics,&#160;30,&#160;TC5004.Okay, A.I., T&#252;ys&#252;z, O., 1999. Tethyan sutures of northern Turkey. Geological Society, London, Special Publications, 156, 475-515.

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