PREHISTORIC, ANCIENT AND MEDIAEVAL OCCURRENCES AND USES OF HYDROCARBONS IN THE GREATER MIDDLE EAST REGION

Abstract

THE ARABIAN PLATE, and neighbouring parts of Egypt, Turkey, Iran and the southern Caucasus, includes within its boundaries numerous active hydrocarbon seepages. Their origin is related to the beginning of the current tectonic regime, which commenced in Oligocene‐Miocene times. The culmination of Alpine tectonics around the northern edge of this region gave rise to stress regimes that deformed the plate margins and ruptured the integrity of hydrocarbon traps and seals. This resulted in the many seepages recorded throughout the Arabian Plate and adjoining areas to the north.Extensional plate margins bound the Arabian Plate to the SW and south; transform margins are on the west and SE; and collisional margins on the north and NE. It is along these (or along splays from them) that most of the major active seepages occur.The collisional regimes along the Taurus and Zagros foldbelts in the north and NE caused considerable subsurface movement of Cretaceous and older hydrocarbons and their migration and remigration. As folding intensified, inefficient seals were ruptured, and very large volumes of hydrocarbons migrated vertically upwards until trapped close to the surface in vast carbonate reservoirs beneath the regionally‐efficient evaporite seals provided by the Miocene Lower Fars/Gachsaran Formations. Where these seals were thin, poorly‐developed or eroded, major seepages developed, and huge volumes of hydrocarbons may have escaped to the surface. Indeed, there is speculation whether the Zagros foreland basin, overprinted onto the vast NE Arabian Shelf as a result of the Arabian/Eurasian Alpine collision, has not lost more hydrocarbons than it has retained through this process (Beydoun et al., 1992).