Build-ups and hydrocarbon accumulation of the isolated carbonate platforms in the eastern Mediterranean

Abstract

Based on regional geology, 2D seismic and ocean drilling data, the formation of the Eratosthenes Seamount (ESM) and its surrounding isolated platforms, types of organic reefs and hydrocarbon accumulation conditions in the eastern Mediterranean were analyzed through fine tectonic interpretation and seismic facies study, and the future exploration targets were pointed out. The formation and evolution of the ESM and its peripheral isolated platforms are highly related to the open and close of the Neotethyan ocean. The precursors of the ESM and its peripheral isolated platforms are both horst-type fault blocks formed in the Middle Triassic–Early Jurassic intracontinental rift stage. The ESM and its peripheral isolated platforms underwent continued and inherited carbonate build-ups during the Middle Jurassic intercontinental rift stage, the Late Jurassic–Late Cretaceous Turonian passive drift stage, and Late Cretaceous Senonian–Miocene subduction stage, as well as medium-slight inversion transformation beginning in the Late Miocene Messinian caused by the closure of the Neotethyan ocean. Three types of isolated platforms formed controlled by variant paleo-tectonic settings: the first type is composed of a single patch-like reef controlled by a small-scale and narrow horst-type fault block, the second type consists of a single atoll controlled by a middle-scale and wide horst-type fault block, and the third type is comprised of multiple reef-beach complexes controlled by a large-scale and broad paleo-high. The first two types universally developed in the highs of the alternate sag-uplift structural zones on the south and west of Eratosthenes, and the third type only developed in the ESM. As a result of fluctuation of sea level, two sequences of reef build-ups, i.e. the Middle Jurassic Bajocian–Upper Cretaceous Turonian and the Miocene, developed in the ESM as well as the highs in the alternate sag-uplift structural zones on the south and west of Eratosthenes. Drillings have confirmed that the first two types of isolated platforms with a single patch-like reef and a single circle-like reef have good conditions for natural gas accumulations. The isolated platform of reef-beach complexes in the ESM also has accumulation potentials of natural gas and is worth prospecting.

Keywords

• eastern Mediterranean
• Eratosthenes Seamount
• isolated carbonate platforms
• organic reef
• hydrocarbon accumulation