Exploration in the Italian Adriatic
Italian exploration for oil and gas has been very successful in the past 50 years both onshore and offshore, with a number of large oil and gas discoveries being made. However, more recently Italy has been thought of as a mature region in terms of hydrocarbon potential with perceived limited remaining prospectivity. This has resulted in the region being overlooked by exploration companies and a significant lack of new investment as they have been lured to other parts of the world. Italy has a large and rapidly growing domestic gas and oil market, and a good pipeline and hydrocarbon infrastructure in place. Despite this there has been a gradual decline in domestic production over the last 15 years, meaning that Italy now imports much of its gas from North Africa. The country continues to have one of the best fiscal and tax regimes in the world for exploration companies, so it is surprising that more companies are not exploring for oil and gas in Italy. One of the reasons for this reduction in interest is the lack of modern regional seismic data and difficulty in accessing available older vintage regional data which together have made it difficult for interested exploration companies to make a regional evaluation. In order to help address these issues, Spectrum and S.D. Exploration Services (S.D.E.S), specialists in offshore Italian exploration, have undertaken a significant project involving the reprocessing, interpretation and evaluation of a unique regional dataset covering the Italian Adriatic Sea.
High exploration potential Offshore Italy
The Italian Adriatic Sea is the most successful exploration area offshore Italy. Numerous gas discoveries have been made in the shallow Pliocene and Tertiary section. This is particularly evident in the prolific Zone A region in the northern part of the Adriatic, where numerous gas fields have been in production for many years, providing Italy with a modest amount of domestic gas, but new production is needed to help fill the increasing gap in gas supply. In the more southerly regions of the Adriatic Sea, especially south-east of the Gargano peninsula, the geology changes and exploration has been more focused on the deeper oil plays in the Cretaceous and Jurassic carbonate section with some success, while the shallower Tertiary gas plays have been largely overlooked.
There is a modest amount of current exploration activity in the Italian offshore Adriatic but there is still a huge amount of the region (approximately 70-80%) remaining unlicensed and lying fallow. Seismic data, however, implies that the open acreage still contains many more oil and gas deposits waiting to be discovered. There are structures observed on the reprocessed seismic which remain undrilled, many of which have associated DHI’s. One of the reasons for the open acreage is that it has not been very easy for interested exploration companies to access large volumes of regional 2D data. Consequently companies have not been able to properly review the excellent opportunities that exist in the Italian Adriatic Sea.
The only regional seismic database was acquired 35 to 45 years ago. This data has never been reprocessed, until Spectrum recently reprocessed approximately 8,500 kms of this old regional dataset using modern seismic data processing techniques. The enhanced dataset, which is available to interested parties, ties numerous wells in the region to provide valuable regional stratigraphic control. SDES will compile an interpretation & evaluation report including local well control, which will be available to purchasers of the reprocessed seismic data. The study area contains both structural and stratigraphic play styles that vary significantly from the northern to the southern Adriatic. A number of very interesting play types and leads can be observed on the seismic section on pages 58 – 60.
Extrapolating new plays
The main structural elements of interest are traditionally associated with the Apennine over thrust front and the structures and play types that surround the over thrust in the basin. There are a wide variety of proven gas and oil plays associated with the thrust front and its related structuring varying from reservoir sands within the over thrust units to sands around/over/pinching out around the thrusts. There are also ripple fold plays in front of the thrusts and stratigraphic plays similar to the discoveries at Barbara, Anna-Maria and Andreina gas fields. There are a number of large multi TCF gas fields in the northern Adriatic gas province, such as the Porto Garibaldi-D’Agostino and Barbara fields, with the biogenic gas found in Pliocene turbidite reservoirs having been sourced from Pliocene-Pleistocene clays, together with deeper plays in the lower Tertiary section as well down to Miocene age.
In the central and southern part of the Italian Adriatic there are a number of oil fields that are sourced from the Burano Formation. This Upper Triassic oil source is a type II kerogen source rock with TOCs ranging from 0.1 to 0.6% and low API gravity. For example, the southern Adriatic Aquila oil field lies in a paleo-high located near the margin of the Apulian platform and produces from Cretaceous and Jurassic pelagic packstones and dolomitised mudstones sourced from the Burano Formation.
By applying modern seismic processing techniques many of the existing successful oil and gas play types can now be extrapolated into the large expanse of open acreage in the Italian Adriatic region. This availability of modern regional seismic data will hopefully stimulate hydrocarbon exploration in this forgotten petroliferous region.
