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Back in Black: Total returns to Bulgarian Deepwater


On 22nd September 2017, the Noble Globetrotter II left the Bulgarian port of Varna, in the Western Black Sea. The drillship is on a single well contract to Total and is expected to spud the Rubin 1 NFW on the 1-21 Han Asparuh licence before the end of the month.

Han Aspuruh Licence
Figure 1. 1-21 Han Asparuh licence

Rubin 1, the second well on the block, is to be drilled in 1,300-1,600 m of water 90km SE of Cape Kaliakra and 14km NE of the 2016 Polshkov 1 wildcat which drilled in 1,900m of water, and operator Total later announced as an oil discovery. It is understood that Polshkov was drilled to 5,500m, short of its 7,000m PTD, and targeted syn- and post-rift Cenozoic plays, overlying Mesozoic carbonate fault blocks. Rubin will likely have similar PTD and objectives and is expected to take 90 days to drill. The Polshkov and Rubin locations were selected based on 3,000km of 2D and 7,740 sq km of 3D seismic acquired during 2013. The 1-21 Han Asparuh licence covers 14,220 sq km and was awarded in August 2012 to OMV (30% equity and operator), Total (40%) and Repsol (30%), with Total taking operatorship on 1 April 2014 ahead of the drilling programme. On 12 April 2017 the licence was extended by 135 days to allow for the drilling of Rubin and is now valid until January 2018.

40 years of exploration

Offshore exploration in the Western Black Sea started in the mid 1970’s in Romanian waters where over 90 wells have been drilled to date. The first offshore wells in Bulgaria were drilled in the mid 1980’s with 30 spudded since. In Turkish waters, north and west of the Bosphorus Strait, 10 exploration wells are known to have been drilled. Romania has seen most of the discoveries made with the first commercial oil production commencing from Petrom’s Lebada East field in 1987. On the Bulgarian shelf Texaco discovered the Galata gas field in 1993 which came onstream in 2006. West of the Galata Field, Melrose Resources (later acquired by Petroceltic) discovered the Kaliakra and Kavarna gas fields in 2007 & 2008, followed by Kavarna East in 2010. The first, and only, western Black Sea success in Turkish waters was the Istranca gas discovery made by Turkish Petroleum Corp (TPAO) on the shelf in 2012.

Western Black Sea Fields
Figure 2 Western Black Sea fields, discoveries & exploration drilling

Deepwater exploration drilling started with Arco’s Limankoy 1 and 2 wildcats offshore Turkey in 1999. However, it was in Romania that ExxonMobil, in a joint venture with OMV Petrom, made the first deepwater gas discovery on the XIX Neptun Deep block with the 2012 Domino 1 wildcat. Through 2014 and 2015 the JV drilled two appraisal wells plus four further wildcats that included the Pelican South and Califar gas discoveries. Also during 2015 Lukoil drilled two wildcats NE of Neptun Deep on the E X-30 Trident block with Daria 1 coming up dry but Lira 1 adding to the discovery list. In the same year Shell and TPAO drilled the Sile 1 wildcat on Turkish block D23 but were less successful abandoning the well after technical problems and two mechanical sidetracks. In 2016 Polshkov 1 brought the total number of deepwater discoveries in the basin to five and was the first to encounter oil.

Western Black Sea exploration drilling timeline, by country
Figure 3 Western Black Sea exploration drilling timeline, by country

Looking ahead

Bulgaria and Turkey both rely heavily on oil and gas imports; coal also currently accounts for over 40% of energy consumed in both countries. Romania is a net exporter of natural gas and gas products, with established connectivity to European markets, and imports about twice as much oil as the country produces to satisfy local consumption. Consequently the regional demand for new hydrocarbon sources is well established, as is the necessary infrastructure connecting markets further afield.
A commercial discovery at Rubin would open up the western Black Sea for further development, following on from the Romanian successes 120km to the NE where Pelican South and Domino are thought to contain 3.5 Tcfg. A final investment decision is anticipated in 2018, with the project expected to be worth up to US$ 2 billion.
Technical success at Rubin would derisk nearby exploration; ExxonMobil and OMV Petrom have delineated at least nine further deepwater prospects on Neptun Deep licence, mainly in Late Miocene sands, whilst Lukoil has also identified the Flora prospect on E X-30 Trident. TPAO has an exploration well planned for 2018 on Turkish block D24, 120km SE of Rubin and Shell was awarded the 1-14 Han Kubrat licence south of Han Asparuh in 2016 completing a 5,125 sq km3D seismic survey in February 2017.

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Bruce Walker

Bruce Walker, European Manager, DI International. He worked as a geoscientist in the oil and gas, mining and environmental sectors before joining Drillinginfo. He has extensive industry experience working in locations such as Trinidad & Tobago, Mongolia, Sierra Leone, Australia and Uganda. Bruce holds a B.A. in Geology from Trinity College Dublin and M.Sc. in Land Management from Cranfield University.

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