Hydrocarbon Plays and Prospectivity of the Levantine Basin, Offshore Lebanon and Syria from Modern Seismic Data Glyn Roberts and David Peace
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GeoArabia, Vol. 12, No. 3, 2007 Levantine Basin, Lebanon and Syria Gulf PetroLink, Bahrain Hydrocarbon plays and prospectivity of the Levantine Basin, offshore Lebanon and Syria from modern seismic data Glyn Roberts and David Peace ABSTRACT The Levantine Basin is located in the easternmost region of the Mediterranean Sea between Cyprus and the Nile Delta marine cone in Egypt. Based on an analysis of more than 20,000 line-km of 2-D seismic data, the basin appears to contain up to 10,000 metres of Mesozoic and Cenozoic rocks above a rifted Triassic-Lower Jurassic terrain. Although many hydrocarbon discoveries have been made in the Nile Delta and the near-offshore areas in the southeastern Mediterranean Sea, no exploration wells have been drilled in its deep offshore or anywhere offshore Lebanon, Syria and Cyprus. Widespread occurrence of oil seeps (over 200) that closely correlate to hydrocarbon indication on seismic (e.g. bright spots and gas chimneys associated with possible migration pathways) suggest that the undrilled parts of the Levantine Basin can be prospective. Thirteen potential exploration plays are identified in this study and illustrated with seismic examples. The plays range in age from the Triassic to the Neogene-Pliocene. INTRODUCTION The Levantine Basin is situated in the eastern part of the Mediterranean Sea (Figure 1; Breman, 2006). Its northern boundary is defined by Cyprus and the Larnaca Thrust Zone, and its northwestern margin by the Eratosthenes Seamount. The Nile Delta Cone and the East Mediterranean coast define its southwestern and eastern margins. Evidence from seismic and other geophysical studies show that the Levantine Basin contains up to 10,000 metres of Mesozoic and Cenozoic sequences above a rifted Triassic-Lower Jurassic terrain. The basin is structurally complex with evidence of both compression and extension due to plate motions, salt tectonics and other gravitational processes. Along the eastern Lebanon offshore margin, there is good evidence of a NS-trending fault that runs semi-parallel to the Dead Sea Transform. The latter fault accommodates the sinistral movement between the Levant and Arabian plates further inland (Aksu et al., 2005). Apart from hydrocarbon discoveries made in the Nile Delta in Egypt, and the near-offshore areas in the southeastern Mediterranean Sea, the Levantine Basin is essentially an exploration frontier region. To date no exploration wells have been drilled in its deep offshore or anywhere offshore Lebanon, Syria and Cyprus. This paper is based on an analysis of over 20,000 line-km of 2-D seismic data from the Levantine Basin and adjacent areas acquired and processed by GGS-Spectrum and its co-venturers (Figure 2). It concentrates on describing the offshore exploration plays in Lebanon and Syria. REGIONAL TECTONIC SETTING It is generally considered that the East Mediterranean Basin formed during the tectonic break-up of the Pangea Supercontinent during the mid-Permian to Middle Jurassic times. However, the history and nature of the crustal evolution of the Levantine Basin is not generally agreed upon and falls into two models. The first model interprets the underlying crust as oceanic and the product of rifting and drifting (e.g. Garfunkel, 1998, 2005; Robertson et al., 1998), while the second considers it as a stretched continental-transitional crust (e.g. Vidal, 2000; Gardosh and Druckman, 2005). Reported geophysical estimates of the depth to the Moho (approximately 20 km versus 35–40 km for the true continental crust to the east) can be used to support either model. Our modern seismic data suggests that the crust beneath the Levantine Basin is probably transitional in nature since no evidence is seen of oceanic crust. Instead, deep seismic lines show a faulted terrain of Jurassic or possibly Triassic age. This is illustrated in Figures 3a and 3b, which are sections from the southern and central parts of the Levantine Basin, and which are approximately orthogonal to the basin margins (i.e. parallel to the assumed Mesozoic extensional direction). 99 Downloaded from http://pubs.geoscienceworld.org/geoarabia/article-pdf/12/3/99/4566900/roberts.pdf by guest on 30 September 2021 Roberts and Peace STRUCTURAL ELEMENTS OF THE EAST MEDITERRANEAN Adana 30° Isparta 31° 32° 33° 34° 35° Basin Angle TURKEY Iskenderun Basin 36° 36° N 0 100 Cilicia Basin km e ts n Aleppo rus o Animaxander s Th Trough Z -Misi st High Kyrenia ru Seamounts Latakia Th ca SYRIA 35° Larna 35° t s CYPRUS Thrust ru Th Cyprus s artu T Normal fault S Hekateus Palmyra out yprus Strike-slip fault h C T Basin re Ridge n Herodotus Basin c 34° Reverse fault h LEBANON 34° Coastal line and river Levantine Basin Eratosthenes Mediterranean Sea Seamount 33° 33° Slumps Nile Delta Cone n fshore High ) c r ARABIAN A PLATE stern of n a Slump i We Pleshet Basi r y S 32° ( 32° lt e Bardawil Line B ld Slump o F n a ri y S i- Nile Delta a in 31° S 31° rth No PLATE LEVANT Kattaniya Horst JORDAN 30° ransform 30° T a r Gindi Abu GharadiqBasin Basin EGYPT Dead Se Nile Rive 30° 31° 32° 33° 34° 35° 36° TURKEY Caspian Figure 1: Tectonic elements in the East Mediterranean Basin Sea 30 N (Breman, 2006). The main elements defining the Levantine Basin SYRIA 0 300 Med. Location IRAN include the Nile Delta Cone, Eratosthenes Seamount, the Cyprus/ Sea Map km IRAQ Larnaca Thrust Zone and the coastal margin faults along the Eastern JORDAN KUWAIT margin of the Basin. 29 39 40 41 BAHRAIN QATAR EGYPT Arabian UAE Shield OMAN SAUDI ARABIA Red SUDAN Sea YEMEN Arabian Sea ERITREA 100 Downloaded from http://pubs.geoscienceworld.org/geoarabia/article-pdf/12/3/99/4566900/roberts.pdf by guest on 30 September 2021 Levantine Basin, Lebanon and Syria GGS-SPECTRUM'S EAST MEDITERRANEAN SEISMIC SURVEYS 30°E 31° 32° 33° 34° 35° 36° 37° 38° 100 500 TURKEY 1,500 100 500 36°N 36° 2,500 1,000 0 N 100 2,000 2,000 km 2,000 35° SYRIA 35° Mediterranean CYPRUS Sea 2,000 2,000 2,500 2,000 LEBANON 34° 34° 1,000 2,000 Concession area Petroleum field 33° 100 Depth (m) 33° 1,500 30° 31° 32° 33° 34° 35° 36° 37° 38° 1,000 Figure 2: East Mediterranean area showing the GGS-Spectrum 2-D GGS-Spectrum Seismic Surveys seismic coverage available for this paper. The Emed-2000 survey was 1975 Reprocessed : 7,834 acquired with a 7,200 metre streamer and recorded to 12 seconds, GL-93 : 508 whilst the LEB-02 survey was recorded with a 6,000 m streamer to 9 Emed-2000 : 12,303 seconds. Leb-02 : 2,000 Total (km) 22,645 In addition, Figure 3b shows the ‘onlapping’ relationship of the Levantine Basin with the Eratosthenes Seamount. Further study of the seamount, and the incorporation of other geological and geophysical evidence, would be necessary to throw further light on the nature and history of this significant feature. Following the mid-Permian to Early Jurassic break-up of the Pangea Supercontinent, the lithosphere stretched and thinned (Flexer et al., 2000), and clastics, carbonates and evaporites were deposited in grabens throughout the Levantine Basin. During the Middle Jurassic to Late Cretaceous, the basin was in a passive continental-margin setting. This phase was characterised by normal faulting, sub-parallel to the present-day East Mediterranean coastline, and basin subsidence. The area was dominated by shallow to deep-marine carbonate deposition, alternating with clastics on the basin margin (May, 1991). In Late Cretaceous to Paleogene times, the region experienced compression due to the convergence of the African and Eurasian plates. This led to the inversion of the previously formed NE-trending grabens and to strike-slip faulting due to differential plate motion. At the end of the Miocene, the Mediterranean Sea became isolated from the Atlantic Ocean, which led to the deposition of up to 1,500 m of evaporites in the Levantine Basin (Gradmann et al., 2005). This event lasted about 1.5 million years, and is known as the “Messinian Salinity Crisis” (Butler et al., 1999). The crisis was followed by inundation of the basin with oceanic waters and Pliocene to Recent sedimentation. 101 Downloaded from http://pubs.geoscienceworld.org/geoarabia/article-pdf/12/3/99/4566900/roberts.pdf by guest on 30 September 2021 on 30 September 2021 by guest Downloaded from http://pubs.geoscienceworld.org/geoarabia/article-pdf/12/3/99/4566900/roberts.pdf Roberts andPeace SEISMIC DIP-LINE ACROSS THE SOUTHERN PART OF THE LEVANTINE BASIN West-Northwest East-Southeast a Mediterranean Sea 2.0 Pliocene-Recent Messinian Salt 3.0 Base Paleogene 4.0 Tw Upper Cretaceous o-way 5.0 T Lower Cretaceous ime (sec) 102 Jurassic 6.0 Permo-Triassic 7.0 8.0 9.0 0 10 km Figure 3: (a) WNW-ESE seismic line over the southern part of the Levantine Basin showing a Triassic-Jurassic rifted terrain (including a pop-up structure in the centre of the Basin) overlain by rocks of Cretaceous to Neogene age. Section width approximately 160 km. SEISMIC DIP-LINE ACROSS THE CENTRAL PART OF THE LEVANTINE BASIN West-Northwest East-Southeast b Eratosthenes Seamount Mediterranean Sea 2.0 Pliocene-Recent 3.0 Messinian Salt 4.0 Base Paleogene Tw o-way Upper Cretaceous 5.0 T ime (sec) Lower Cretaceous Jurassic 6.0 Permo-Triassic 7.0 8.0 9.0 0 10 Onlap of Cretaceous onto the Eratosthenes Seamount km Figure 3 (continued): (b) WNW-ESE seismic line over the central part of the Levantine Basin (offshore Lebanon). The western portion of the line covers the eastern margin of the Eratosthenes Seamount, where the Cretaceous is seen to onlap onto its structure (see inset).