Greece is a net energy importer. Hellenic Petroleum (HP), a partially state-owned company, conducts oil exploration, imports crude and products, operates two large refineries, and distributes and markets oil products. Oil is the major import with an estimated 429,000 b/d imported in 2003. In 2004, Regal Petroleum (RP), which is the only producer in Greece, produced 2,761 bbl/d of oil, all from the Prinos area in the Aegean Sea off the coast of Kavala. Figure 1 illustrates major drilling activity in Greece and neighboring countries.
With natural gas reserves of only 35 Bcf, Greece produces negligible amounts of natural gas. Consumption, however, has taken off in the last few years and is expected to increase dramatically in the coming decade. Many analysts believe that there is potential for further oil discoveries in Greece, but extensive oil exploration activity has not yet occurred and would require significant foreign investment.
Exploration history
Herodotus (484 to 424 BC) first mentioned an oil show on Zakynthos Island, western Greece, which is still active (at Keri). Oil shows, however, did not attract attention until the beginning of the 20th century.
The first exploration for hydrocarbon (HC) sources in Greece began in 1903 with the concession of the island of Zakynthos to the London Oil Development Co. Ltd.
In 1938, Chellis began exploration in West Thrace and then in northwest Peloponnesos (NWP) and Zakynthos.
In 1940 to 1945, Italian and German armies started drilling exploration wells in the Ioannina region without any success.
In 1960, oil companies such as BP, Esso, Rapilios and Safor held concessions for similar explorations in other regions of Greece, such as the Ionian Islands, Peloponnesos, Dodecanesos, Aitoloakarnania, Thrace, etc. BP undertook systematic exploration activity from 1961 to 1964 and drilled two wells, Astakos-1 and Aitolikon-1, in the center of the area which was proposed for further exploration in late ’90s .
Only 28 bbl of oil were produced from the Aitolikon well. However, thickness of the pay (9.8 ft or 3 m) and the low productivity of the yellow-orange high-gravity oil forced abandonment.
In 1969, exploration was extended to the maritime area, with concessions to foreign companies such as Texaco, Chevron, C&K Petroleum, DA Oil, Ancar Oil, LVO, Calvin and Oceanic. Likewise, a concession was granted for exploration to the Anshutz Co. in the Thessaloniki-Epanomi region, where it drilled two wells from 1971 to 1974, but without any results.
In 1973 to 1974, maritime exploration led to the discovery of the first exploitable oil deposit in the region of Thasos (Prinos and South Kavala).
In 1975, DEP (present HP) was established, after the successful discovery of the Prinos and South Kavala deposits, with the purpose of developing the oil industry in Greece throughout all its phases. DEP initiated oil exploration in 1976 employing land and marine seismic surveys followed by drilling.
Exploration targets were limited to the Neogene clastic sediments. Generally speaking the targets were not deep reservoirs. However, the Prinos fields, which began production in 1976, were operated by the US-Greek-Canadian North Aegean Petroleum Co. (NAPC) consortium.
As a result of HP’s exploratory campaign, an oil field was discovered in 1980 offshore western Peloponnesos nearby Katakolon. The reservoir rock in Katakolon is eroded Cretaceous carbonates covered by Plio-pleistocene clastics.
In 1997, the government signed four contracts with an Anglo-American consortium for oil exploration and exploitation in four stretches in western Greece near Ioannina, the NWP, in Aitoloakarnania and Gulf of Patraikos.
The contracts for Ioannina and NWP were granted to a consortium comprising the companies Enterprise Oil Ltd, Union Texas Ltd, Mol Ltd and HP. The other contracts, i.e. for Aitolokarnania and Gulf of Patraikos, were granted to Triton Ltd and HP. Enterpise drilled two wells in NWP, the Artemis-1 and Apollo-1, and one in Ioannina area, the Demetra-1. Triton Ltd drilled two wells in the Aitoloakarnania area, the Evinos-1 and Trifos South-1. The wells were plugged and abandoned and classified as dry with oil shows.
The Greek firm Kavala Oil, which took over production from NAPC in February 2001, managed to extract 3,000 b/d. In January 2004, a UK-based exploration company with a majority stake in Kavala Oil, Regal Petroleum, found “considerable potential” for reserves to exceed estimates of 227 million bbl.
Regal made plans to raise the oilfield’s production up to 15,000 b/d as a result of the discovery. In September 2004, Regal announced that the Greater Kallirachi field holds up to 1 billion bbl of light crude. Third-party reserve auditors confirmed the findings. RP drilled the Kallirachi-1 and Kallirachi-2 and pierced four prospective Miocene zones.
The company spent US $60 million in the past 2 years, $20 million to upgrade existing wells and facilities and $20 million each on the two dry holes, according to the June 19, 2005, Financial Times. After these disappointing findings RP lowered reserve estimates to 24 million bbl.
Exploration targets
The majority of the wells drilled before the 1980s were selected solely on the basis of surface geology without advanced geophysical support. After that time, drilling activity was controlled solely by HP.
Joint ventures between HP and experienced oil companies were not encouraged till 1995. Geological surveys, although locally controlled by some rather deep wells, have not yet been capable of providing a comprehensive and reliable picture of relatively deep geological structures.
However, in western Greece there are basins with significant hydrocarbon potential, and three of these are located in a continuous sedimentary belt trending north-south along the western margin of the country.
In this area, there is more geological data available than in any other locality, although the Thessaloniki and Thrace basins have also experienced concentrated exploration activity in the early 1980s.
Production has been established in South Italy and Albania in a similar geological setting.
Western Greece is covered by northwest-southeast trending geotectonic units constituting the southern prolongation of the oil producing Albania. It can be safely stated that there is a great possibility for commercial production to be established in western Greece, which is an area of active oil seeps, repeated oil shows in wells, completed wildcat tests, thick dark-colored bituminous carbonate rocks and sustained (though minor) production. Geochemical and geological studies already undertaken are encouraging for further exploration activities.
The Triassic evaporitic sequence – at least 6,562 ft (2,000 m) thick – was never fully penetrated by any well, and the underlying rock, a possible reservoir, remains an unknown unit in terms of age, thickness, lithology and the type of hydrocarbons it contains (Figure 2).
As far as profitability is concerned, benefits from a successful pre-drilling investigation program are foreseen despite the intrinsic risks of such projects.
The tracing and eventual mapping of the evaporitic sequence should be the primary target in various projects before drilling. The interactive data evaluation combined with the overlapping information of the various geophysical methods involved would normally lead towards a comprehensive picture of the deep geological structure. The existing dynamic software and drilling technology can provide invaluable information in order to depict the targeted reservoir horizons in western Greece. Source
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