When Adriatic offshore acreage first was opened for exploration, only part of it was known geologically. The northern part of the sea was known to be an extension of the prolific gas producing Po basin. The central and southern parts were known only as the transition between the Apennine and the Dinarids orogenic belts. Seismic reconnaissance in the Northern Adriatic revealed structural and stratigraphic features similar to the onshore portion of the Po basin. These structures are, in fact, now producing gas from 5 new offshore fields.

The geology of the central-southern part of the Adriatic revealed a more complicated geologic pattern. The Tertiary clastic cover had good seismic response and a very prominent seismic horizon, C, indicated several large structures on top of the Eocene-Cretaceous limestone. The reflections below the C horizons were very poor and affected by multiples. All the wells located on the horizon C features were dry, despite the presence of good oil and gas shows.

The second stage of exploration was begun in 1971. Improved seismic techniques showed disharmonic behavior in the structures below horizon C, which is a morphologic paleorelief horizon below the Miocene transgressive deposits. New structures located in the Mesozoic section show convergence of the pre-Miocene horizons. Also, it appears that alongside the Triassic evaporitic basin, younger Yugoslav evaporitic basins of Jurassic and Cretaceous age undergo a facies change in Italian waters. In Italy the sediments are basinal or biostromal with indications of reef development in the transitional belt and porous, prolifically gas-bearing calcarenite along the coast. This new understanding of the geology leads to highly encouraging possibilities for large accumulations in the Eocene and Meso oic carbonates.

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