Source rock characterization of mesozoic to cenozoic organic matter rich marls and shales of the Eratosthenes Seamount, Eastern Mediterranean Sea

Abstract

Several significant hydrocarbon accumulations were discovered over the past decade in the Levant Basin, Eastern Mediterranean Sea. Onshore studies have investigated potential source rock intervals to the east and south of the Levant Basin, whereas its offshore western margin is still relatively underexplored. Only a few cores were recovered from four boreholes offshore southern Cyprus by the Ocean Drilling Program (ODP) during the drilling campaign Leg 160 in 1995. These wells transect the Eratosthenes Seamount, a drowned bathymetric high, and recovered a thick sequence of both pre- and post-Messinian sedimentary rocks, containing mainly marine marls and shales. In this study, 122 core samples of Late Cretaceous to Messinian age were analyzed in order to identify organic-matter-rich intervals and to determine their depositional environment as well as their source rock potential and thermal maturity. Both Total Organic and Inorganic Carbon (TOC, TIC) analyses as well as Rock-Eval pyrolysis were firstly performed for the complete set of samples whereas Total Sulfur (TS) analysis was only carried out on samples containing significant amount of organic matter (>0.3 wt.% TOC). Based on the Rock-Eval results, eight samples were selected for organic petrographic investigations and twelve samples for analysis of major aliphatic hydrocarbon compounds. The organic content is highly variable in the analyzed samples (0–9.3 wt.%). TS/TOC as well as several biomarker ratios (e.g. Pr/Ph < 2) indicate a deposition under dysoxic conditions for the organic matter-rich sections, which were probably reached during sporadically active upwelling periods. Results prove potential oil prone Type II kerogen source rock intervals of fair to very good quality being present in Turonian to Coniacian (average: TOC = 0.93 wt.%, HI = 319 mg HC/g TOC) and in Bartonian to Priabonian (average: TOC = 4.8 wt.%, HI = 469 mg HC/g TOC) intervals. A precise determination of the actual source rock thickness is prevented by low core recovery rates for the respective intervals. All analyzed samples are immature to early mature. However, the presence of deeper buried, thermally mature source rocks and hydrocarbon migration is indicated by the observation of solid bitumen impregnation in one Upper Cretaceous and in one Lower Eocene sample.

Preliminary results based on geochemical sedimentary constraints on the hydrocarbon potential and depositional environment of a Messinian sub-salt mixed siliciclastic-carbonate succession onshore Crete (Plouti section, eastern Mediterranean)

“…1). Moreover, several recent large natural gas field discoveries in the offshore Levantine and Herodotus basins (Needham et al 2013;Ratner 2016;Grohmann et al 2018Grohmann et al , 2019 make the eastern Mediterranean one of the most promising frontier basins of the world. These new fields comprise mainly natural gas of biogenic origin and are located in either Miocene clastic turbidites (e.g., Tamar and Leviathan-Israel, Aphrodite-Cyprus; Montadert et al 2014;Bou Daher et al 2016) or in Mesozoic shallow marine carbonate buildups (Zohr-Egypt, Calypso-Cyprus; Schenk et al 2010;Bertello et al 2016;Esestime et al 2016) (Fig.…”

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

“…Recent research projects, focusing on the northern part of the Levant Basin, provided substantial new data and concepts for better understanding the crustal, structural, and stratigraphic characteristics of this region, as well as its key petroleum systems (e.g. Hawie et al, 2015;Bou Daher et al, 2016;Inati et al, 2016Inati et al, , 2018Ghalayini et al, 2017aGhalayini et al, , 2017bGhalayini et al, , 2018Symeou et al, 2017;Grohmann et al, 2018;Papadimitriou et al, 2018aPapadimitriou et al, , 2018b. These studies also led to the distinction between the basin and the margins of the Levant.…”

Thermal Properties and Burial Alteration of Deep-Sea Sediments: New Indicators of Oxic−Suboxic Diagenesis

“…In the selected samples, especially 3515-1 40-44 (or 2269 [25][26][27][28][29][30][31][32], an increase in crystallinity (=background decrease) with burial depth was observed, as well as an increase in the intensity of the selected peaks of new mineral phases. Full data of roasted samples, including diffractograms, are shown in Figure 8 and in Table 8.…”