Key geological characteristics of the Saida-Tyr Platform along the eastern margin of the Levant Basin, offshore Lebanon:implications for hydrocarbon exploration

More than 60 trillion cubic feet (Tcf) of natural gas have been recently discovered in the Levant Basin (eastern Mediterranean region) offshore Cyprus, Egypt and Israel, Palestine. Un-explored areas, such as the Lebanese offshore, may yield additional discoveries. This contribution focuses the Saida-Tyr Platform (STP), an offshore geological feature adjacent to the southern Lebanese coastline – part of the eastern margin of the Levant Basin. First, an extensive synthesis of recent published research work, tackling crustal modeling, structural geology and stratigraphy will be presented. Then, a new local crustal model and the interpretation of seismic reflection specifically on the STP are discussed and emplaced in the context of the upcoming petroleum exploration activities in this region. Characteristic structural features form the limits of the STP which is believed to be an extension of the Arabian continent into the Levant Basin. Its westernmost limit consists of the extension of the crustal interface, previously termed “hinge zone”, where major plate-scale deformations are preferentially localized. The northward extension of this “hinge zone” beyond the STP can be mapped by means of major similar deformation structures (i.e. S-N-trending anticlines) and can be associated to the Levant Fracture System (LFS) – the northwestern border of the Arabian plate. The northern limit of the STP (i.e. the Saida Fault) is a typical E-W, presently active, structure that is inherited from an older, deeply rooted regional fault system, extending eastward throughout the Palmyra Basin. The STP is characterized by a variety of potential plays for hydrocarbon exploration. Jurassic and Cretaceous clastics and carbonates are believed to include reservoir plays, which could have been charged by deeper Mesozoic source rocks, and sealed by Upper Cretaceous marly layers. The edge of the Cretaceous carbonate platforms and potential carbonate buildups are well recognizable on seismic reflection profiles. The western and northern anticlinal structures bordering the STP are excellent targets for Oligo-Miocene biogenic gas charging systems. Based on integrating geodynamics, tectono-stratigraphic interpretations and petroleum systems analyses, such plays are well constrained and the exploration risk is therefore lowered

Dynamique lithosphérique et architecture des marges du bassin du Levant : approche géophysique intégrée

Significant gas discoveries have been made recently in the Eastern Mediterranean (www.nobleenergyinc.com), which turned the attention of oil companies towards the Levant Basin. This region is considered today as a typical hydrocarbon frontier province. Hence, a considerable amount of geophysical data has been produced and a series of academic and industry-based studies have been performed. Understanding the crustal and sedimentary architecture, the actual and past thermicity of this basin, in particular on the Lebanese continental margin, has major academic and economic interests. This has important implications on understanding tectonic evolution and earthquakes generation and on assessing petroleum systems. Despite numerous old and recent geophysical studies in this region, the deep crustal configuration of the Levant Basin, known to be the site of rifting in the Late Paleozoic and Early Mesozoic, remains enigmatic. The transition from a typical thick continental crust to thinner attenuated crust offshore (possibly even oceanic crust) has been invoked, but not yet proven. Integrated geophysical approaches and modeling techniques are used in this thesis to study the deep structure of the lithosphere underlying the easternmost Mediterranean region.A 2D modeling approach was accomplished at a regional scale (1000x1000 km2) extending from the Nile delta in the south, to Turkey in the north, from the Herodotus Basin in the west to the Arabian plate in the east. The algorithm used is a trial and error method that delivers the crustal thickness and the depth of the lithosphere-asthenosphere boundary (LAB) as well as the crustal density distribution by integrating top basement heat flow data, free-air gravity anomaly, Geoid and topography data. Moho depth and crustal thickness were locally constrained by refraction data where available. Three models are presented, two in EW direction (580 and 650 km long) and one in SN direction (570 km long). The models in EW sections show a progressively attenuated crystalline crust from E to W (35 to 8 km). The SN section presents a 12 km thick crust to the south, thinning to 9-7 km towards the Lebanese offshore and reaching 20 km in the north. The crystalline crust is best interpreted as a strongly thinned continental crust under the Levant Basin, represented by two distinct components, an upper and a lower crust. The Herodotus Basin, however, shows a very thin crystalline crust, likely oceanic, with a thickness between 6 and 10 km. The Moho under the Arabian plate is 35-40 km deep and becomes shallower towards the Mediterranean coast. Within the Levant Basin, the Moho appears to be situated between 20 and 23 km, reaching 26 km in the Herodotus Basin. While depth to LAB is around 110 km under the Arabian and the Eurasian plates, it is about 150 km under the Levant Basin and plunges finally to 180 km under the Herodotus Basin.A 3D joint inversion of gravity, geoid and topography data applied on the same region confirmed the results of the 2D modeling. A total of 168 of simulations were run, among which the simulation with the minimal data misfits corresponds to a model where the Moho depth varies between 23 and 26 km in the Levant Basin and becomes deeper in the Herodotus Basin and off the African coast. The LAB is 100 to 150 km deep in the Levant Basin and deepens to more than 180 km in the Herodotus Basin.D’importantes découvertes de gaz ont été faites récemment en Méditerranée orientale (www.nobleenergyinc.com), incitant les compagnies pétrolières à s’intéresser de plus près au bassin du Levant, considéré aujourd’hui comme une véritable province pétrolière. Par conséquent, une quantité considérable de données géophysiques a été produite et une série d'études académiques et industrielles ont été réalisées. La compréhension de l’architecture crustale et sédimentaire associée à celle de la thermicité actuelle et passée des marges de ce bassin, notamment la marge continentale du Liban, présente des enjeux industriels et scientifiques majeurs. Cette question a des implications majeures pour l'évolution tectonique, les prévisions des tremblements de terre ainsi que celle des systèmes pétroliers. Malgré les différents travaux géophysiques menés sur la Méditerranée orientale ces dernières années, la configuration crustale profonde du bassin du Levant, connu pour avoir été le siège d’un rifting à la fin du Paléozoïque et au début du Mésozoïque, reste imprécise. La transition d’une croûte continentale épaisse vers une croûte atténuée en mer (peut-être même une croûte océanique) a été invoquée, mais pas encore prouvée. Des approches géophysiques intégrées ainsi qu’un travail de modélisation ont été utilisés dans cette thèse pour étudier la structure profonde de la lithosphère sous la région Est de la Méditerranée.Une modélisation crustale 2D à l’échelle régionale (du delta du Nil au sud à la Turquie au nord, et du bassin Hérodote à l’ouest à la plaque arabe à l’est) a été effectuée dans le but d’étudier l’architecture de la croûte dans cette partie de la méditerranée orientale. L’algorithme utilisé est une méthode d’essai-erreur qui fournit l’épaisseur crustale et la profondeur de la limite lithosphère- asthénosphère (LAB) ainsi que la distribution de la densité crustale par l’intégration du flux de chaleur surfacique, l’anomalie gravimétrique à l’air libre, les données du géoïde et la topographie. La profondeur du Moho et l’épaisseur de la croûte ont été contraintes localement par des données de sismique réfraction là où elles sont disponibles. Les résultats montrent une croûte cristalline progressivement atténuée dans une direction EW. Dans le bassin du Levant, la croûte est interprétée comme continentale et composée de deux croûtes distinctes, une supérieure et une inférieure, contrairement au bassin Hérodote qui repose sur une croûte mince, probablement océanique.Une inversion 3D jointe des données de gravité, du géoïde et de la topographie appliquée sur la même région a confirmé les résultats de la modélisation crustale 2D. A total of 168 simulations ont été réalisées, parmi lesquelles, la simulation avec les erreurs les moins grandes sur les données correspond à l’inversion d’un modèle dans lequel la profondeur du Moho varie entre 23 et 26 km dans le bassin du Levant et devient plus profond dans le bassin Hérodote et aux larges des côtes africaines. La profondeur de la LAB est située entre 100 et 150 km dans le bassin du Levant et atteint plus de 180 km dans le bassin Hérodotes. L’interprétation de cinq lignes de sismique réflexion 2D PSTM à 14 s TWT couvrant la partie nord du bassin du Levant a révélé un total de 10 horizons, dont le plus profond pourrait être une interface croûte-manteau. L’interprétation des paquets sismiques, leurs surfaces de raccord ainsi que l’analyse des facies ont été contraints par les interprétations sismiques 2D publiées de la partie nord de l’offshore Libanais (Hawie et al., 2013b), dans lesquelles les connaissances stratigraphiques et sédimentologiques récentes de la marge libanaise ont été extrapolées jusqu’au bassin. Un total de huit paquets sédimentaires a été identifié dans le bassin aux âges variant du Jurassique Moyen au Quaternaire

Lithosphere dynamics and architecture of the Levant basin margins : integrated geophysical approach

D’importantes découvertes de gaz ont été faites récemment en Méditerranée orientale (www.nobleenergyinc.com), incitant les compagnies pétrolières à s’intéresser de plus près au bassin du Levant, considéré aujourd’hui comme une véritable province pétrolière. Par conséquent, une quantité considérable de données géophysiques a été produite et une série d'études académiques et industrielles ont été réalisées. La compréhension de l’architecture crustale et sédimentaire associée à celle de la thermicité actuelle et passée des marges de ce bassin, notamment la marge continentale du Liban, présente des enjeux industriels et scientifiques majeurs. Cette question a des implications majeures pour l'évolution tectonique, les prévisions des tremblements de terre ainsi que celle des systèmes pétroliers. Malgré les différents travaux géophysiques menés sur la Méditerranée orientale ces dernières années, la configuration crustale profonde du bassin du Levant, connu pour avoir été le siège d’un rifting à la fin du Paléozoïque et au début du Mésozoïque, reste imprécise. La transition d’une croûte continentale épaisse vers une croûte atténuée en mer (peut-être même une croûte océanique) a été invoquée, mais pas encore prouvée. Des approches géophysiques intégrées ainsi qu’un travail de modélisation ont été utilisés dans cette thèse pour étudier la structure profonde de la lithosphère sous la région Est de la Méditerranée.Une modélisation crustale 2D à l’échelle régionale (du delta du Nil au sud à la Turquie au nord, et du bassin Hérodote à l’ouest à la plaque arabe à l’est) a été effectuée dans le but d’étudier l’architecture de la croûte dans cette partie de la méditerranée orientale. L’algorithme utilisé est une méthode d’essai-erreur qui fournit l’épaisseur crustale et la profondeur de la limite lithosphère- asthénosphère (LAB) ainsi que la distribution de la densité crustale par l’intégration du flux de chaleur surfacique, l’anomalie gravimétrique à l’air libre, les données du géoïde et la topographie. La profondeur du Moho et l’épaisseur de la croûte ont été contraintes localement par des données de sismique réfraction là où elles sont disponibles. Les résultats montrent une croûte cristalline progressivement atténuée dans une direction EW. Dans le bassin du Levant, la croûte est interprétée comme continentale et composée de deux croûtes distinctes, une supérieure et une inférieure, contrairement au bassin Hérodote qui repose sur une croûte mince, probablement océanique.Une inversion 3D jointe des données de gravité, du géoïde et de la topographie appliquée sur la même région a confirmé les résultats de la modélisation crustale 2D. A total of 168 simulations ont été réalisées, parmi lesquelles, la simulation avec les erreurs les moins grandes sur les données correspond à l’inversion d’un modèle dans lequel la profondeur du Moho varie entre 23 et 26 km dans le bassin du Levant et devient plus profond dans le bassin Hérodote et aux larges des côtes africaines. La profondeur de la LAB est située entre 100 et 150 km dans le bassin du Levant et atteint plus de 180 km dans le bassin Hérodotes. L’interprétation de cinq lignes de sismique réflexion 2D PSTM à 14 s TWT couvrant la partie nord du bassin du Levant a révélé un total de 10 horizons, dont le plus profond pourrait être une interface croûte-manteau. L’interprétation des paquets sismiques, leurs surfaces de raccord ainsi que l’analyse des facies ont été contraints par les interprétations sismiques 2D publiées de la partie nord de l’offshore Libanais (Hawie et al., 2013b), dans lesquelles les connaissances stratigraphiques et sédimentologiques récentes de la marge libanaise ont été extrapolées jusqu’au bassin. Un total de huit paquets sédimentaires a été identifié dans le bassin aux âges variant du Jurassique Moyen au Quaternaire.Significant gas discoveries have been made recently in the Eastern Mediterranean (www.nobleenergyinc.com), which turned the attention of oil companies towards the Levant Basin. This region is considered today as a typical hydrocarbon frontier province. Hence, a considerable amount of geophysical data has been produced and a series of academic and industry-based studies have been performed. Understanding the crustal and sedimentary architecture, the actual and past thermicity of this basin, in particular on the Lebanese continental margin, has major academic and economic interests. This has important implications on understanding tectonic evolution and earthquakes generation and on assessing petroleum systems. Despite numerous old and recent geophysical studies in this region, the deep crustal configuration of the Levant Basin, known to be the site of rifting in the Late Paleozoic and Early Mesozoic, remains enigmatic. The transition from a typical thick continental crust to thinner attenuated crust offshore (possibly even oceanic crust) has been invoked, but not yet proven. Integrated geophysical approaches and modeling techniques are used in this thesis to study the deep structure of the lithosphere underlying the easternmost Mediterranean region.A 2D modeling approach was accomplished at a regional scale (1000x1000 km2) extending from the Nile delta in the south, to Turkey in the north, from the Herodotus Basin in the west to the Arabian plate in the east. The algorithm used is a trial and error method that delivers the crustal thickness and the depth of the lithosphere-asthenosphere boundary (LAB) as well as the crustal density distribution by integrating top basement heat flow data, free-air gravity anomaly, Geoid and topography data. Moho depth and crustal thickness were locally constrained by refraction data where available. Three models are presented, two in EW direction (580 and 650 km long) and one in SN direction (570 km long). The models in EW sections show a progressively attenuated crystalline crust from E to W (35 to 8 km). The SN section presents a 12 km thick crust to the south, thinning to 9-7 km towards the Lebanese offshore and reaching 20 km in the north. The crystalline crust is best interpreted as a strongly thinned continental crust under the Levant Basin, represented by two distinct components, an upper and a lower crust. The Herodotus Basin, however, shows a very thin crystalline crust, likely oceanic, with a thickness between 6 and 10 km. The Moho under the Arabian plate is 35-40 km deep and becomes shallower towards the Mediterranean coast. Within the Levant Basin, the Moho appears to be situated between 20 and 23 km, reaching 26 km in the Herodotus Basin. While depth to LAB is around 110 km under the Arabian and the Eurasian plates, it is about 150 km under the Levant Basin and plunges finally to 180 km under the Herodotus Basin.A 3D joint inversion of gravity, geoid and topography data applied on the same region confirmed the results of the 2D modeling. A total of 168 of simulations were run, among which the simulation with the minimal data misfits corresponds to a model where the Moho depth varies between 23 and 26 km in the Levant Basin and becomes deeper in the Herodotus Basin and off the African coast. The LAB is 100 to 150 km deep in the Levant Basin and deepens to more than 180 km in the Herodotus Basin

Seismic characterization of Cenomanian–Turonian carbonate platform based on sedimentological and geophysical investigation of onshore analogue outcrop (northern Lebanon)

International audienceAbstract Outcrop analogues play a key role in the characterization of subsurface carbonate platforms. The lack of well data and relevant outcrop analogues can result in the misinterpretation of seismic data. To address this issue, we apply an integrated workflow based on sedimentology, geophysics and petrophysics on outcrop analogues present onshore Lebanon, to constrain the carbonate platform's properties on onshore seismic data. A thorough sedimentary description is completed for a 400‐m‐thick Cenomanian–Turonian carbonate platform located in Kfarhelda, northern Lebanon. P‐wave velocity is acquired directly on the outcrop, and the petrophysical properties are measured on 44 samples. A 1D synthetic seismogram is computed with Ricker wavelet 25 Hz resembling seismic resolution. The resulting reflectors are mainly (1) high amplitude reflectors at the limit between two facies with contrasting physical properties enhanced by diagenesis, (2) moderate amplitude reflectors corresponding to stratigraphic limits at the transition between facies and (3) very low amplitude reflectors in karstified units. The integration of outcrop and seismic data is based on the generation of the synthetic seismogram to identify the geological origin of reflectors. The best fit between the synthetic seismic and seismic profile is used to interpret a seismic facies representing bedded limestones of Sannine and Maameltain formations (Cenomanian–Turonian). Two other distinctive reflectors are identified at the boundary of the Marly Limestone Zone, and the Channel facies unit characterized by bioclastic packstone to floatstone. This study highlights the importance of using outcrop analogues to identify the seismic signal of stratigraphic sequences and improve the interpretation of onshore seismic data

Key geological characteristics of the Saida-Tyr Platform along the eastern margin of the Levant Basin, offshore Lebanon: implications for hydrocarbon exploration

More than 60 trillion cubic feet (Tcf) of natural gas have been recently discovered in the Levant Basin (eastern Mediterranean region) offshore Cyprus, Egypt and Israel, Palestine. Un-explored areas, such as the Lebanese offshore, may yield additional discoveries. This contribution focuses the Saida-Tyr Platform (STP), an offshore geological feature adjacent to the southern Lebanese coastline – part of the eastern margin of the Levant Basin. First, an extensive synthesis of recent published research work, tackling crustal modeling, structural geology and stratigraphy will be presented. Then, a new local crustal model and the interpretation of seismic reflection specifically on the STP are discussed and emplaced in the context of the upcoming petroleum exploration activities in this region. Characteristic structural features form the limits of the STP which is believed to be an extension of the Arabian continent into the Levant Basin. Its westernmost limit consists of the extension of the crustal interface, previously termed “hinge zone”, where major plate-scale deformations are preferentially localized. The northward extension of this “hinge zone” beyond the STP can be mapped by means of major similar deformation structures (i.e. S-N-trending anticlines) and can be associated to the Levant Fracture System (LFS) – the northwestern border of the Arabian plate. The northern limit of the STP (i.e. the Saida Fault) is a typical E-W, presently active, structure that is inherited from an older, deeply rooted regional fault system, extending eastward throughout the Palmyra Basin. The STP is characterized by a variety of potential plays for hydrocarbon exploration. Jurassic and Cretaceous clastics and carbonates are believed to include reservoir plays, which could have been charged by deeper Mesozoic source rocks, and sealed by Upper Cretaceous marly layers. The edge of the Cretaceous carbonate platforms and potential carbonate buildups are well recognizable on seismic reflection profiles. The western and northern anticlinal structures bordering the STP are excellent targets for Oligo-Miocene biogenic gas charging systems. Based on integrating geodynamics, tectono-stratigraphic interpretations and petroleum systems analyses, such plays are well constrained and the exploration risk is therefore lowered

Crustal configuration in the northern Levant basin based on seismic interpretation and numerical modeling

International audienceThe interpretation of five 2D PSTM seismic reflection sections (14 s TWT) covering the northern Levant Basin revealed a total of 10 horizons, among which, one is interpreted as an interface that may represent the Moho. The interpretation of seismic packages and their bounding surfaces as well as the seismic facies analysis were constrained by published 2D seismic interpretations of the northern Lebanese offshore. A total of nine seismic packages are identified in the basin with ages varying from the Mid Jurassic to the Quaternary. The filling of the basin is made up of thick Cenozoic and Mesozoic strata deposited above rifted Triassic – Early Jurassic interval. The sediments are deposited in deep water mixed-settings resulting from high-stand systems (various types of carbonate platforms) and low-stand systems (siliciclastic and carbonate deep-water turbidite complexes). Carbonate and siliciclastic systems are sealed by 1–1.5 km of evaporites, and underlie Plio-Quaternary hemipelagic and pelagic sediments intercalated by turbiditic sheets.The time horizons were converted into depth using two methods; the first one is based on stacking velocities and the second one on velocities resulting from refraction data. 2D crustal modeling was achieved by integrating free-air gravity anomaly, geoid heights and topography data on the five interpreted PSTM seismic lines. The models representing five sections across the northern Levant Basin, show a progressively attenuated crystalline crust in an EW direction (away from the basin's eastern margin). The crystalline crust is best interpreted as a strongly thinned continental crust under the Levant Basin, represented by two distinct components, an upper and a lower continental crust. The Moho appears to be situated between 20 and 23 km in the central and southern Lebanese offshore. Estimated surface heatflow in the basin is around 40 mW/m2, which is lower than reported values for the onshore and the margin. These differences in heatflow values between the offshore, the margin and the onshore have an important impact on hydrocarbon maturation and assessment of potential petroleum systems