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IDENTIFICATION DEEP-WATER FAN WITH 2.1 TCM OGIP WITHIN THE ULTRA-DEEPWATER AND CONTINENTAL SLOPE OF THE BLACK SEA

North-Western Part of the Black Sea,
Ukraine, 2007

 

 



Figure 1. Exxon Mobil & Shell Skifska licence block with location of predicted deep-water fan

GEOLOGICAL PROBLEM

The Black Sea is one of the last immature but closest to the European market hydrocarbon exploration frontiers with a rather high assessment of its petroleum potential. In spite of over 60 years of
exploration, only 8 gas condensate fields and one Subbotino oil field were discovered within the Ukrainian shelf of the Black Sea. To date, a total of 25 deep-water wells have been drilled in water depths over 400 m, 11 of which were ultra-deep (water depth > 1500 m). In spite of multiple commercial discoveries in the shelf of Romania and Bulgaria, many new wells fail to discover quality reservoirs or do not encounter commercial hydrocarbon accumulations.

The sole deep-water discovery in the Black Sea is the Sakaraya gas field, which is the second largest worldwide discovery of 2020. Well Tuna-1 discovered reservoir rocks associated with paleo-delta of Danube River.

Given that all Black Sea deep-water prospects discovered to date had all of the elements of an oil system, such as source rocks & reservoirs, seals and hydrocarbon movement channels, the negative drilling results suggest the need to revise current geological concepts and implement new methods of hydrocarbon exploration.

Figure 1. Multi-zonal HC prospects, including Cretaceous deep-water fan, extracted in the form of local bodies from the 3D density model by the results of 3D inversion of gravity, seismic and well data


GEOLOGICAL RESULTS

3D joint inversion results gave the possibility to validate and refine the basin model from the surface to the Moho interface, to delineate deep mantle plumes and associated with them sedimentary basins, to delineate tectonic sutures between major tectonic units and to outline the boundaries of sub-basins.

In sedimentary cover, 3D density model allowed to locate a set of multi-zone low-density areas in Neogen-Cretaceous and associated with them hydrocarbon accumulations. Some of them corresponded to known gas fields within Odessa shelf (for example Shmidt and Golitsina fields, Figure 1) others, indicated the location of new promising prospects.
 



The major target was mapped in Cretaceous sediments within ultra-deepwater and continental slope (Figure 1, 2).  It is represented by clastic fan, Albian or Valanginian in age, with a total area of 2,745sq.km. For the most promising sweet spot area of 2,000 sq.km the gross reserves estimation was 2.1 TCM OGIP (P50).

The new prospect mapped in 2007 within the continental slope and deep part of the Black Sea is a geological analog of the prospects discovered by the Tuna-1 well in 2020, and can be associated with the delta of a paleo-river.

In 2012 – 2014 the Skifska block enclosing mapped deep-water prospect was licensed for PSA by consortium of Exхon Mobile & Shell (Figure 2).
3D GTAVITY INVERSION WORKFLOW

Structural framework for the initial 3D density model was built using the Neogene-Cretaceous structural surfaces, a result of a 2D regional seismic data interpretation, bathymetry and Moho interface from a deep seismic survey. Generalized  petrophysical data was used to define initial density properties of sedimentary cover. Interval seismic velocities were used to calculate  density of pre-Cretaceous basement. The constructed 3D density model’s dimensions were 250 km x 372 km laterally and 70 km vertically. Individual cell size of 2kmx2kmx5m resulted in the total of over 32.5 million 3D cells.
Standard deviation between the observed and the calculated gravity for the initial 3D density model was 19 mGal.
 
Depth of the Moho interface was refined by means of a 3D structural non-linear inversion of the gravity data. 3D property model was refined by 3D joint linear inversion of gravity with seismic and log data. Standard deviation between observed gravity and gravity calculated for resulting 3D density model by inversion results was 1.3 mGal (relative to the gravity field, the initial 3D density model was improved by 15 times).

PUBLICATIONS

1. Габлевский Б.Б., Ганженко Н.С., Федченко Т.А., Кольцов С.В., Чуприна И.С. Региональная пространственная сейсмогравита-ционная модель глубинного строения северо-западного шельфа черного моря в связи с перспективами его нефтегазо-носности. Вопросы теории и практики геологической интерпретации гравитационных, магнитных и электрических полей. (Материалы XXXVI сессии международного семинара им. Д.Г.Успенского) Казань, 26-31 января 2009г.. -С. 89-92.

2. Петровський О.П., Габлевський Б.Б., Ганженко Н.С., Федченко Т.О. Обґрунтування можливості картування нафтогазо-перспективних об’єктів в умовах Північно-Західної частини шельфу Чорного моря на основі сейсмогравітаційного моде-лювання. Науковий вісник Івано-Франківського національного технічного університету нафти і газу. № 3(21), 2009р. -с. 26-33

3. Petrovskyy O.P., Krupskyy B.L., Gladun V.V., Chepil P.M., Melnichuk P.M., Fedchenko T.O., Gablevskyy B.B., Kitchka O.A., Tsiokha O.G., Gerasimov M.E., Koltsov S.V., Chupryna I.S. New Insight at Oil and Gas Prospects and Geological Structure of the NW Black Sea Shelf by Integral Seismic and Gravimetric 3D Geo-Modelling. AAPG European Region Annual Conference "Exploration in the Black Sea and Caspian Regions" at Ukrainian House, Kiev, on 17-19 October 2010

4. Gablevskyy B., Fedchenko T., Petrovskyy O., Gangenko N., Sujatinov V. Theoretical bases for mapping oil-&-gas fields within Black Sea North-Western shelf by means of seismic-and-gravity modeling. AAPG European Region Annual Conference "Exploration in the Black Sea and Caspian Regions" at Ukrainian House, Kiev, on 17-19 October 2010

5. Габльовський Б.Б., Федченко Т.О. Прогноз нафтогазоносності відкладів осадового чохла північно-західного шельфу Чорного моря. Науковий вісник. – В-во ІФНТУНГ, 2010. - №4 (26) – С. 12-20.

6. Петровский О.П., Федченко Т.А., Габльовский Б.Б., Суятинов В.Н. Перспективы нефтегазоносности и геологическое строение северо-западного шельфа Черного моря по результатам интегрального 3D сейсмо-гравитационного моделирования. Вопросы теории и практики геологической интерпретации геофизических полей. (Материалы XXXVIІІ сессии международного семинара имени Д.Г.Успенского). – Пермь, 24-28 января 2011г. – С. 227-228.

 

 

7. Габльовський Б.Б., Федченко Т.О., Герасимов М.Є., Кольцов С.В. Новий погляд на геологічну будову та перспективи нафтогазоносності північно-західного шельфу Чрного моря за результатами інтегрального геолого-геофізичного моде-лювання. Матеріали міжнародної науково-практичної конференції «Нафтогазова геофізика – інноваційні технології». – Ів.-Франківськ, 2011. – C.°43-47

8. Петровський О.П., Крупський Б.Л., Зейкан О.Ю., Гладун В.В., Чепіль П.М., Мельничук П.М., Федченко Т.О., Габльовський Б.Б., Кічка О.А., Цьоха О.Г., Герасімов М.Є., Кольцов С.В., Чуприна І.С. Новий погляд на перспективи нафтогазоносності та геологічну будову північно-західного шельфу Чорного моря. К.: "Нафтова і газова промисловість", 2011, №2 - С. 7-16

9. Габльовський Б.Б., Петровський О.П., Федченко Т.О., Суятінов В.Н. Просторова інтегральна геолого-геофізична модель північно-західної частини шельфу Чорного моря для уточнення особливостей геологічної будови та перспектив нафтогазоносності. Геодинаміка. – В-во Львівської політехніки, 2011. - №2 (11) – С. 52-54.

10. Petrovskyy O., Fedchenko T. New Prospective Plays Offshore Ukraine as result of 3D Geo-modeling & Geophysical Inversion. SEG Technical Program Expanded Abstracts 2012: doi: 10.1190/segam2012-1545.1

11. Petrovskyy O.P., Kitchka O.A., Fedchenko T.O., Gladun V.V. Kambala Prospect - An Application of 3D Geomodelling and Inversion to Hydrocarbon Exploration in the Black Sea Basin. 75th EAGE Conference & Exhibition incorporating SPE EUROPEC 2013 Deep Water Sedimentary Systems 10 June 2013 DOI: 10.3997/2214-4609.20130779

12. Fedchenko T.O., Petrovskyy O.P., Ganzhenko N.S., Zhuchenko G.O. Gladun V.V., Chepil P.M., Melnichuk P.M., Kitchka A.A., Tsiokha O.G., Koltsov S.V. An Integral 3D Geo-modeling Helps to Reveal New Exploration Trends - Case Study for the NW Black Sea Basin, Ukraine. 71st EAGE Conference & Exhibition — Amsterdam, The Netherlands, 8 - 11 June 2009.

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