A wealth under the sea (ABO Oil Magazine)
By Luca Bertelli, Chief Exploration Officer – Eni
The Levantine Basin, in the eastern Mediterranean, covers the territorial waters of various countries (Egypt, Israel, Lebanon, Cyprus, and Syria) and an area of approximately 80,000 km2. From a geological point of view, the basin borders to the South with the wide sedimentary Nile Cone, to the North with the underwater Eratosthenes High and the Cyprus thrench and, to the east, with the Syrian Arc and the Arabian plate. A large part of this sedimentary basin is characterized by deep water. The central area of the basin is an abyssal plain with an area of approximately 14,000 km2 with water depths exceeding 2,000 meters. The basin, which was unexplored until 2009, is currently a region rich in hydrocarbons where, over the past 6 years, many high profile gas discoveries have been made, including some “giants” gas fields. The southern part of the basin—the part of the so-called “NEMED” (North East Mediterranean Deepwater) block—has been intensively explored during the ’90s and 2000s in Egyptian waters with some sub-commercial gas discoveries. Subsequently, in January 2009, the basin revealed its great potential in Israeli waters when a joint venture operated by Noble Energy announced the discovery of the Tamar gas field, followed in December 2010 by that of the Leviathan giant gas field and then by many other fields of smaller size. In December 2011, a joint venture also operated by Noble Energy made the first gas discovery in Cypriot waters. The discovery, named Aphrodite, is located in Block 12.
All of these discoveries were made in clastic rocks (sandstones) of Miocene age, which have proven to be good “reservoir” rocks. In these clastic turbidite deposits over 40 trillion cubic meters of gas were discovered in the Tamar and Leviathan gas fields in Israeli waters. The hydrocarbon discovered in Israel and Cyprus is “lean gas”, essentially almost pure methane of biogenic origin. A small thermogenic contribution has also been identified in some fields, likely indicating the presence, in the basin, of a deeper active hydrocarbon system; however, as previously mentioned, almost the entire volume of hydrocarbons discovered is “lean gas” of biogenic origin.
The breakthrough of 2015 in the exploration of the Levantine was the discovery made by Eni of the “giant” Zohr gas field in Egyptian waters. The discovery of Zohr was considered a significant event by the oil industry (specifically referred to as a “transformational discovery”) not only due to the substantial size of the hydrocarbon accumulation and therefore its strategic importance for Egypt, but also because it marked the start of a new exploratory “play” in the Basin. Zohr, in fact, is a giant accumulation of methane contained in carbonate rocks of Miocene and Cretaceous age. Although rocks of a similar kinds had previously been identified near the coast of the borders of the Levantine Basin, no significant exploratory success had been achieved on this type of sequences, due to the difficulty in finding the basic necessary conditions for the entrapment of hydrocarbons.
The Levantine, therefore, until August 2015, was considered a basin with a great potential for hydrocarbons in clastic sequences, with approximately 35 trillion cubic feet of recoverable resources from existing fields discovered offshore Israel and Cyprus. However, to change the paradigm, in the summer of 2015 came the discovery of Zohr, a discovery “geologically” different from the others, made precisely by drilling a new exploration “play”. The well was drilled at a water depth of approximately 1,500 m in the Shorouk Block. The discovery well, Zohr 1, hit a 628 m of continuous gross gas column, 430 m net pay and with a potential of gas in place preliminary estimated at 30 TCF.
Indeed, this well has changed the existing dogmas of the basin exploration as the reservoir is provided by Miocene and Cretaceous limestones, in a carbonate reef and lagoon build-up at the southern margin of a very large carbonate platform.
Zohr definitely opened up a new play concept with material potential in the Basin and also suggests a different model for the paleogeographic evolution of the Levantine Basin. It had been assumed that, with the exception of the brief Messinian salinity crisis, north of the Nile Delta deep water conditions had prevailed across the basin during the Neogene.
However, the Zohr carbonate platform required shallow water conditions during the Miocene and the Cretaceous clearly indicating the presence of a shallow water basin north of the Nile Delta Cone. How this shallow water basin is spread out might have consequences for future exploration potential.
The exploration maturity of the basin is in fact at different stages in the various countries. Israeli waters are today the most explored, followed by Egyptian and Cyprus waters. Lebanon waters and Syrian waters are still untouched since no licenses have been assigned so far.
Zohr is a “play opener” and most likely we will see other discoveries in this new play type of the Prolific Levantine Basin. For what concerns the development of these discoveries the games have just started. So far only one field is in Production, Tamar Field in Israelian waters, producing with a subsea tie back to a new platform on Mari B Location and delivering gas to Israeli domestic market.
The PODs of Leviathan, still In Israel and of Aphrodite in Cyprus and Phase 2 of Tamar are in progress, while Zohr development plan has recently been approved by the Egyptian Authorities. All the gas of Zohr will be routed onshore near El-Gamil plant and will then enter into the Egyptian grid.
Zohr discovery once again tells us that also areas previously explored with limited success can provide great surprises when committed and
competent geologists and geophysicts, making the best use of the leading edge technology and developing new geological models and play concepts, decide to challenge new paradigms in exploration. The Exploration of the Levantine Basin will still provide in a near future further surprises and will confirm the basin as an outstanding gas reserves holder that can feed large volumes to the nearby countries and to Europe in the years to come.
From ABO Oil Magazine #31:
Gas – the Mediterranean at full throttle
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