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Undiscovered Oil and Gas Resources in the Eastern Mediterranean - Sohbet Karbuz

A Comparison of the USGS Assessments in 2010 and 2021

More than 5 trillion cubic meters (tcm) of natural gas has been discovered in the Eastern Mediterranean region since the first gas discovery in Egypt’s Abu Madi gas field in 1967.[1] This is more than the total amount of gas discovered in Norway. Around half of that volume was discovered since 2009. Some of the discoveries, namely, the Tamar and Leviathan fields in 2009 and 2010 in Israel, Aphrodite in 2011 in Cyprus, and Zohr in 2015 in Egypt were among the world’s largest deep-water gas discoveries. Of these, the Zohr field is the largest gas discovery ever made in the Mediterranean Sea. Consequently, the Eastern Mediterranean has become one of the most exciting new frontiers of natural gas exploration worldwide. However, this is not the only reason why the region has sparked international interest.

The Eastern Mediterranean region is estimated to have substantial yet-to-be-discovered hydrocarbon resources. The United States Geological Survey assessments as well as the estimates by the officials in the region indicate that the region’s undiscovered potential is twice as much as the total gas discoveries made there so far. When the volume of discovered gas and undiscovered gas potential are combined, the resulting total places the Eastern Mediterranean region on par with the North Sea, whose holdings are divided among Norway, the UK, the Netherlands, and Denmark.

The USGS assessments

The United States Geological Survey (USGS) released three assessments concerning the technically recoverable undiscovered oil and gas resource potential in the Eastern Mediterranean.

Two of them were in 2010[2] – one for the Nile Delta and Mediterranean Sea sectors of Egypt and the other for the Levant Basin Province.

In March 2010, the USGS released an assessment concerning the technically recoverable undiscovered oil and gas resource potential of the Levant Basin Province which covers mainly offshore territories including the Gaza Strip, Israel, Lebanon, Syria and Cyprus. The study estimated the (mean) undiscovered potential of 4.8 billion barrels of oil (including natural gas liquids) and 3.45 tcm of natural gas in the area.

Two months later, in May 2010, the USGS issued another assessment. It was for the Nile Delta Basin province, which corresponds to the Nile Delta and Mediterranean Sea sectors of Egypt. This assessment put the (mean) undiscovered oil (including natural gas liquids) potential at 7.7 billion barrels and natural gas at 6.3 tcm.

The above-mentioned discoveries and the USGS assessments have not only significantly augmented hopes for large hydrocarbons potential in the Eastern Mediterranean but also made it a fast-rising favorite for international oil and gas companies if only because the potential prize seems too big to ignore.

Figure 1: The USGS assessments in the Eastern Mediterranean in 2010

Source: USGS

Recently, on 8 July 2021, the USGS released another estimate for the undiscovered resource potential of the Eastern Mediterranean.[3] It estimated undiscovered, technically recoverable mean resources of 3.1 billion barrels of oil (including natural gas liquids) and 8.1 tcm of conventional gas in the region.

Figure 2: The USGS assessment in the Eastern Mediterranean in 2021

Source: USGS

Interestingly enough, despite the previous USGS estimates have been references in virtually all technical articles and presentations on the Eastern Mediterranean hydrocarbons developments, the recent assessment has not yet attracted any attention in literature and in the press. This is very surprising!

What the 2021 USGS assessment tells?

At first sight it seems that, the recent USGS assessment revised downwards (compared to the assessments in 2020) the estimates for the undiscovered oil and gas resources in the Eastern Mediterranean. This is not necessarily the right conclusion for two reasons. First, the covered area in the USGS assessment in 2021 (or USGS 2021) is larger than the two USGS assessments made in 2010, as can be seen in the figure below. Second, although there have been no significant oil discoveries, around 2500 bcm of natural gas was discovered in the region since 2010. This means that undiscovered oil potential in the region is in fact revised downwards in USGS 2021 assessment, but natural gas potential is, in fact, revised upwards by 0.6 tcm. Similar is the case for the estimates for the other fractiles as shown in the Figure below.

Figure 3: USGS estimates for the undiscovered oil and gas resources by fractiles in the Eastern Mediterranean

Source: Author’s elaboration, based on USGS assessments. Note: F95 represents a 95-percent chance of at least the amount tabulated; other fractiles are defined similarly.

The USGS 2021 assessment is conducted for five basins. Of these, the Levantine Basin boundary is the same as the USGS assessment in March 2010. The boundaries of other basins are different from the Nile Delta basin assessment of the USGS in May 2010. Nevertheless, the Nile Delta basin is still estimated to have the largest undiscovered natural gas potential. Almost half of the undiscovered natural gas potential in the Eastern Mediterranean is estimated to lie in the Nile Delta basin. It is followed by the Levatine basin and Eratosthenes Platform.

Figure 4: USGS 2021 estimates for the undiscovered natural gas resources by basin in the Eastern Mediterranean

Source: Author’s elaboration, based on USGS 2021

It is important to note that the majority of the Mediterranean Ridge and the Herodotus basin has been assessed for the first time by the USGS. Despite the high hopes for the undiscovered gas potential in those areas, at least by industry and academics, the USGS estimates were rather disappointing. One of the reasons for this may be the lack of sufficient data and the risk assessment based on biogenic gas in the applied geological model. However, Egyptian government and major players in the upstream oil and gas industry seem to have a different opinion. For instance, major players, such as BP, Chevron, ExxonMobil, Shell, TotalEnergies have obtained several blocks in that area in the past two years. Similarly, Egyptian government has put three blocks in the Mediterranean Ridge to international tender on 17 February 2021. It appears that they have much more optimistic view than the USGS concerning the regions hydrocarbons potential.

Figure 5: Egypt’s concession map in the Mediterranean Sea

Parts of the Mediterranean Ridge and the Herodotus basin are also the subject of maritime boundary disputes between the governments of Greece, Egypt, Turkey and Greek Cyprus. The disappointing estimates for the undiscovered gas resources in those areas might be interpreted as if the overlapping blocks and contested areas are not worthwhile the geopolitical struggle. This kind of reasoning, however, misses the whole point – the dispute is not about the hydrocarbons resources, it is about national security and sovereign rights.

Figure 6: The USGS 2021 assessment area in the context of maritime boundary disputes and overlapping exploration blocks

Source: Author’s elaboration

In sum, there is no doubt that the Eastern Mediterranean has substantial hydrocarbons potential. However, a large part of the region still remains under- or unexplored and the speed of exploration have been uneven among the countries involved. Much needs to be done to better estimate and unlock the remaining hydrocarbons potential of the region.


[1] For a detailed analysis, see Sohbet Karbuz (2019), “Doğu Akdeniz’de Ne Kadar Doğal Gaz Var,” Bilkent Enerji Notları, No. 12 (July 2019), The estimate in that study, which covers the period until the end of 2018, was close to 4,900 bcm. Since then, 30 gas fields, some modest (such as Nour and Swan East in 2019) and some major (such as Bashrush in 2020), were discovered offshore Egypt as reported in various issues of Egypt Oil and Gas Magazine, in addition to upgrades to reserves in the Tamar, Leviathan and Karish fields in Israel as announced by their operators.

[2] “Assessment of Undiscovered Oil and Gas Resources of the Levant Province, Eastern Mediterranean: Fact Sheet 2010-2014,” U.S. Geological Survey, (March 2010),; “Assessment of Undiscovered Oil and Gas Resources of the Nile Delta Basin Province, Eastern Mediterranean: Fact Sheet 2010-2027,” U.S. Geological Survey, (May 2010),

[3] USGS (2021), “Assessment of undiscovered conventional oil and gas resources in the eastern Mediterranean area”, U.S. Geological Survey Fact Sheet 2021−3032, 8 July 2021,


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