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Κυριακή, 13 Δεκεμβρίου 2015

The unconventional hydrocarbon resources of Greece

Anaximander Mountains with the
 main mud volcanoes (MVs) 
[ By Prof. Ananias Tsirambides]

Greece, in relation to many other countries of similar size, possesses very abundant reserves of energy mineral raw materials, such as lignite. However, the future of lignite in Greece is uncertain.

Further exploration is needed, new and improved mining methods must be applied, beneficiation methods must be implemented, and underground mining must be initiated.

The probable and proven reserves of al most all the hydrocarbon resources of Greece are unknown, as detailed investigations (e.g., boreholes, measurements, analyses, etc.) are lacking. The USGS (U.S. Geological Survey), the IODP (Integrated Ocean Drilling Project), the Geophysical Institute of France (FIGR), and the Norwegian seis mic sur vey com pa nies TGS-Nor and PGS have made in the last 40 years numerous explorations and drilled many bore holes in the international waters of the eastern Mediterranean (and hence within the Greek Exclusive Economic Zone – EEZ). 

According to their published reports, the oil reserves of Greece maybe in the order of tens of billions of barrels, and its natural gas reserves of tens of trillions of m3. The total value of the fossil fuel reserves of Greece is € 1,417 billion, of which € 268 billion be long to the lignites which were exploited for decades to produce only electricity. The estimated oil reserves are 10 billion barrels, with a current gross value of € 719 billion, and the natural gas reserves are 3.5 trillion m3 with a current gross value of € 430 billion.

Nowadays, reserves of conventional oil and gas, which can be produced cheaply, are limited. This is why many of the major oil companies invest in what we commonly call “unconventional  resources”.   Large reserves of such hydrocarbons, retained inlayered and highly-compacted deposits, exist in many countries. The main types are: tight gas, coal-bed methane, shale gas, shale oil, heavy oil/tar sands, and methane (gas) hydrates.
European shale gas resources are estimated at 16 trillion m3, compared to 20 trillion m3 for the US. However, it will take more time for exploration to find out how much can be extracted at a reasonable cost. Europe could start producing gas from shale in the next 3–4 years.

Shale gas deposits are possible in all areas where shales or other fine-grained and highly-copacted strata ex ist be low the groundwater level, with significant extent and organic matter content >1%. During their geological history, they were formed under conditions corresponding to the gas window (generally to depths over 5,000 m).

The most important Jurassic to Neogene rock formations which may contain shale gas are found in the land and off shore basins of northeast ern (e.g., Evros Delta-Orestias, Lemnos Island, Kavala-Prinos-Nestos Delta, Epanomi-Thermaikos Gulf), north-central (e.g., Mesohellenic), and western Greece (e.g., Diapondia is lands, Preveza, Zakynthos Is land, Peloponnesus basins). Gas hydrates are found in the submarine Anaximander Mountains, east of Rhodes Island. They cover an area of about 46 km2 and the volume of methane is 2.6–6.4 trillion m3.

With approximately 43 active open-cast coal mines, Greece holds the 2nd position in the EU and 11th world wide in the production of coal (only lignite). The extensive tectonics across the whole Hellenic Peninsula and the low content in gaseous hydrocarbons of the Greek lignites are the main factors which prevented large gas accumulations in the coal deposits. Additional research to evaluate the coal-bed gas potential is needed.

The unconventional hydrocarbons potential of Greece is unknown as long as detailed investigations are lacking. Exploration for conventional hydrocarbon reservoirs, through the interpretation of seismic profiles and surface geological data, will simultaneously provide the subsurface geometry of the un conventional ones. Their exploration should follow that of conventional hydrocarbons.

Today, because the interest of many of the major oil companies is directed to unconventional sources of energy, Greece needs re-evaluation of the data from all bore holes carried out,on the basis of new information, with the aim to identify possible reserves of unconventional hydrocarbons retained in highly compacted fine-grained deposits.

In addition to the large financial interest in the use of these unconventional sources of energy, there is currently no national or European Union legislative framework which deals with the mining issues and environmental impacts.