Durresi Block

The Durresi Block covers an area of 4 200 sq. km on the Albanian side of the Apulian shelf edge hydrocarbon trend which extends across into Italian waters. Within both the Albanian and Italian territories, more than a dozen exploration wells have been drilled along the shelf margin resulting in the discovery of five oil fields and two biogenic gas accumulations. The majority are in Italy; Aquila, Rovesti, Giove, Medusa and Falco, while one well in the Albanian waters penetrated a hydrocarbon accumulation (A4-1X well), see figure 1.

Figure 1

Figure 1 – Late Cretaceous facies map with oil fields highlighted along the Apulian shelf margin

The multiple phases of basin development, which define the geological history of the Periadriatic region, exerted significant influence over the deposition/quality of potential source rocks. Hydrocarbon samples, taken from key stratigraphic levels in the A4-1X discovery well, are consistent with an Upper Triassic (earliest Jurassic?) source interval, suggested to have also been the source for the analogue Giove and Medusa fields.

With young top seals, hydrocarbon expulsion from the source is likely to have been quite recent. Given the loci of the main source rock levels, relative to the known fields - figure 2, the main hydrocarbon migration is likely to have exploited Mesozoic age normal faulting and, at least locally, a karstified upper section resulting from the exposure to millions of years of erosion. This is also the supported mechanism by which many of the known hydrocarbon accumulations along the Apulian shelf margin were filled.

Figure 2

Figure 2 – SW-NE oriented 2D seismic traverse through Giove and Aquila fields indicating source rock position and potential migration pathways.

The analogue fields nearby generally indicate hydrocarbon accumulations to be focused within Oligocene and Miocene age carbonate build-ups, deposited on the Mesozoic carbonate platform margin, and in Cretaceous age reworked gravity fed carbonates which interfinger with the pelagic carbonates deposited on the base of the slope – figure 3.

Figure 3

Figure 3 – 3D block diagram showing the platform margin to pelagic basin depositional environments.

The A4-1X discovery was drilled 30km off the southern coast of Albania (see figure 4), in approximately 750m of water by AGIP and Chevron between 21st September and the 15th November 1993. The primarily objective was to test the hydrocarbon potential of Mesozoic to Middle Miocene carbonate reservoirs in a buried seamount on the margin of the Apulian carbonate platform – see figure 5. Secondary targets were the Upper Messinian clastics (already proven reservoirs in Albania – Kucova and Patosi fields). The prospect was essentially a horst-like structure, trending NW-SE, with an areal extent of 24 km2 and a maximum vertical closure of roughly 400m. After drilling, the discovery was deemed uneconomic and the well was plugged and abandoned.

Figure 4

Figure 4 – location of the A4-1X discovery in relation to the Albanian coastline

Figure 5

Figure 5 – SW-NE seismic traverse showing the recent edge of the Apulian margin (left side) and the former edge of the carbonate platform (the A4-1X seamount) with the A4-1X discovery well highlighted.

In 2011, San Leon acquired 840 km2 of 3D seismic over the Apulian carbonate shelf margin oil play covering the A4-1X discovery well and other prospects identified on the vintage 2D seismic dataset. Combined with the well information, these data permitted a comprehensive analysis of the area’s hydrocarbon potential during the exploration phases of the licence. San Leon is currently negotiating the entry from the third exploration phase (TEP) of the Production Sharing Contract to the appraisal period with an appropriate work programme already submitted to the Albanian government. Based on the high quality seismic, and the knowns and unknowns determined from the wells, San Leon believes the A4-1X discovery, together with the near field add on prospectivity, has development potential and the company is seeking a partner for this appraisal project.



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