• vecchiap

Shpirag success and why not all “fractured carbonate reservoirs” are created equal…

(download our short paper here)

More good news for exploration in the Adriatic area!

Shell have just announced the results of the successful Shpirag-4 appraisal well in Albania, with a well test that flowed “several thousand barrels of oil per day”, and follow up plans that include a long term production test and full development of the field, if appraisal results are positive (Fig 1). See more details at:

https://www.shell.al/media/2019/shell-confirms-potential-of-significant-oil-discovery-in-albania-en.html

Fig. 1: Geological cross section across the Shpirag oil discovery in Albania, showing the wells targeting U Cretaceous & Tertiary carbonates in a faulted compressional structure at approximately 5,000m bmsl (Source: Petromanas, Annual general meeting presentation, May 2015).


As carbonate specialists, one aspect of the comment in the industry press on the Shpirag discovery that leaves us a little uncomfortable is the analogy with the Val d’Agri field in Italy on the basis that both are “fractured carbonate reservoirs”. Sure both fields are developed in compressional structures related to the Alpine thrust belts that encircle the Adriatic, and to this extent there are some clear similarities in overall geological context and trap type (Fig. 2). But what about the reservoir? The reservoir in the Val d’Agri consists of karstified and fractured shallow marine limestones and dolomites with reservoir quality controlled by a complex combination of depositional process, dolomitization, karstification and fracturing as described by Bertello et al (2010) and Shiner et al (2004). Does the “fractured carbonate reservoir” of the Shpirag discovery bear any similarities to this type of reservoir?


Fig. 2: Regional map of the Adriatic and Ionian region, showing the main hydrocarbon fields. Field colours refer to the main reservoir type within the hydrocarbon field as described in Strata GeoResearch’s CarbMed-GIS database.

Fig.3 shows the data over Shpirag extracted from Strata GeoResearch’s proprietary CarbMed GIS database. In contrast to the Val d’Agri, which is located within the shallow marine carbonate domain of the Apulian Platform, Shpirag is located within the deepwater Ionian basin sequence, several 10s of kilometres to the northeast of the platform margin. Given this location, the Shpirag reservoir is likely to consist of calciturbidites derived from the shallow marine platform to the south-east and redeposited in deepwater interbedded with pelagic limestones, resulting in very different stratigraphic architecture and reservoir properties to the Val d’Agri reservoir. Tectonic fracturing is likely to be important in creating permeability but dolomitization and karstification are likely to be absent or of minor importance. As the database highlights, much more appropriate reservoir analogues are present elsewhere onshore in Albania and in the Scaglia fields of the Italian Central Adriatic (See Strata’s post on Katakolon and the Scaglia reservoirs of the Adriatic for a more detailed description: https://www.stratageoresearch.com/blog/katakolon-a-small-but-perfectly-formed-oil-field-in-western-greece ).

We would suggest that much more effective resource exploitation strategies for the Ionian sequences in the Dinaride-Albanide-Hellenide thrust belts can be developed based on these analogues, rather than on the assumption of similar reservoir to the Val d’Agri. Furthermore, Strata’s CarbMed-GIS database is a powerful tool facilitating the quick selection of appropriate analogues and then collating the available information on these analogues, both for exploration and field appraisal/ development projects.


Fig. 3: Geological map of Albania and the S Adriatic-Ionian produced using Strata GeoResearch’s CarbMed-GIS database, putting Shell’s Shpirag discovery in regional context and showing the data available in the database. Distribution of facies and gross depositional environments is for the Late Cretaceous (Turonian-Maastrichtian), corresponding to the lower part of the reservoir in Shpirag. produced by Strata GeoResearch srl. Data is drawn from a wide variety of sources but particularly Le Goff (2015), Le Goff et al (2015), Fantoni (2017) and Van Hinsbergen et al (2012).

References

  • Bertello, F., Fantoni, R., Franciosi, R., Gatti, V., Ghielmi, M., & Pugliese, A. (2010, January). From thrust-and-fold belt to foreland: hydrocarbon occurrences in Italy. In Geological Society, London, Petroleum Geology Conference series (Vol. 7, No. 1, pp. 113-126). Geological Society of London.

  • Fantoni, R., 2017. Mesozoic petroleum system of the Adriatic foreland. Journal of Mediterranean Earth Sciences 9, 151–156.

  • Le Goff, J., 2015. Evolution tectono-sédimentaire du système carbonaté ”Plateforme Apulienne - Bassin Ionien” au Crétacé supérieur dans le sud de l’Albanie : faciès, géométries, diagénèse et propriétés réservoirs associées. Sciences de la Terre. Université Michel de Montaigne - Bordeaux III, 2015. Français

  • Le Goff, J., Cerepi, A., Swennen, R., Loisy, C., Caron, M., Muska, K., El Desouky, H., 2015. Contribution to the understanding of the Ionian Basin sedimentary evolution along the eastern edge of Apulia during the Late Cretaceous in Albania. Sedimentary Geology 317, 87–101.

  • Shiner, P., Beccacini, A., & Mazzoli, S. (2004). Thin-skinned versus thick-skinned structural models for Apulian carbonate reservoirs: constraints from the Val d'Agri Fields, S Apennines, Italy. Marine and Petroleum Geology, 21(7), 805-827.

  • Van Hinsbergen, D.J.J., Schmid, S.M., 2012. Map view restoration of Aegean-West Anatolian accretion and extension since the Eocene. Tectonics 31, 1-40.