Methane Hydrate Stability and Potential Resource in the Levant Basin, Southeastern Mediterranean Sea

Abstract

To estimate the potential inventory of natural gas hydrates (NGH) in the Levant Basin, southeastern Mediterranean Sea, we correlated the gas hydrate stability zone (GHSZ), modeled with local thermodynamic parameters, with seismic indicators of gas. A compilation of the oceanographic measurements defines the >1 km deep water temperature and salinity to 13.8 °C and 38.8‰ respectively, predicting the top GHSZ at a water depth of ~1250 m. Assuming sub-seafloor hydrostatic pore-pressure, water-body salinity, and geothermal gradients ranging between 20 to 28.5 °C/km, yields a useful first-order GHSZ approximation. Our model predicts that the entire northwestern half of the Levant seafloor lies within the GHSZ, with a median sub-seafloor thickness of ~150 m. High amplitude seismic reflectivity (HASR), correlates with the active seafloor gas seepage and is distributed across the deep-sea fan of the Nile within the Levant Basin. Trends observed in the distribution of the HASR are suggested to represent: (1) Shallow gas and possibly hydrates within buried channel-lobe systems 25 to 100 mbsf; and (2) a regionally discontinuous bottom simulating reflection (BSR) broadly matching the modeled base of GHSZ. We therefore estimate the potential methane hydrates resources within the Levant Basin at ~100 trillion cubic feet (Tcf) and its carbon content at ~1.5 gigatonnes.

A Gas Hydrate System of Heterogeneous Character in the Nile Deep-Sea Fan

“…at least twice as deep as the typical upper limits of 300-500 m in the open ocean. In the eastern Mediterranean Sea, the upper limit of the MHSZ has been estimated to lie at water depths of 1150-1350 m (Pape et al 2010;Römer et al 2014;Tayber et al 2019). The 1250 m depth contour is marked on Fig.…”

“…37.1 inset; Lykousis et al 2009;Pape et al 2010). A recent review of gas hydrates offshore Europe (Minshull et al 2020) found that, despite the wide distribution of seismic reflection data in the eastern Mediterranean Sea, evidence of a BSR was limited to a single profile across the central Nile fan offshore Egypt (Praeg et al 2008) and to scattered 3D seismic amplitude anomalies in the eastern Nile fan off Israel proposed to represent a 'pseudo-BSR' (Tayber et al 2019). However, geophysical evidence of gas hydrates has been recognized for 20 years by the Egyptian exploration industry, albeit based on seismic and well data that remain poorly documented.…”

Gas Hydrate: Environmental and Climate Impacts

“…To date, hydrate has been sampled only in several mud volcanoes of the accretionary complex, starting in the Anaximander Seamount region, i.e., [48,49]. In addition, a recent 3D dataset acquired in the Levan Basin, southeastern Mediterranean Sea, suggested that this region could be promising in regards to gas hydrate [50]. Reference [50] estimated the potential inventory of natural gas hydrate in the Levant Basin correlating the gas hydrate stability zone with seismic indicators of gas and providing a potentiality of carbon in this area.…”

“…So, References [50,54] suggest that the Mediterranean region should be investigated in order to understand the reason of the past-presence and the quite-absence of gas hydrate by using a multidisciplinary approach spanning from field data to modeling.…”

Hydrate occurrence in Europe: Risks, rewards, and legal frameworks

“… 63 See Nicholas A. Ioannides [ 30 ]; ‘Rights and Obligations of States in Undelimited Maritime Areas: The Case of the Eastern Mediterranean Sea’ in Stephen Minas and Jordan Diamond (eds), Stress Testing the Law of the Sea Dispute Resolution, Disasters and Emerging Challenges (BRILL 2018) 311–337; Recent geological studies have suggested that the Levant seafloor in the Eastern Mediterranean Sea contains approximately 100 trillion cubic feet (Tcf) of gas hydrates, see Ziv Tayber et al [ 31 ]. …”