The Hydrocarbon Potential of the Arabian Plate
The reasons for Middle East (Arabian plate) hydrocarbon abundance, particularly in the main producing basin(s) of the northeast margin (Enclosure 1), have been discussed by many workers specializing in the region. They include Henson (1951), Baker and Henson (1952), Lees (1951, 1953), Law (1957), Weeks (1958), Dunnington (1958, 1960, 1967, 1974), Kamen-Kay (1970), Halbouty et al. (1970), Kent and Warman (1972), Beydoun and Dunnington (1975), Grunau (1977), Riche and Prestat (1979), Murris (1980), Bois et al. (1982) and Beydoun (1986). I recently resummarized them and analyzed the differing views (Beydoun, 1988).
There is little doubt that one of the most important reasons is the fact that prevalent, large areas of high-quality source rocks have been preserved from different intervals of geologic time during the Phanerozoic, and especially during the Mesozoic, over much of the areally extensive northeast shelf, because of high organic productivity related to climate and oceanic circulation (Table 2). The development of juxtaposed source and reservoir facies belts was advantageous, as Dunnington (1974) indicated, because it facilitated expulsion and migration over long distances. Late Tertiary Zagros folding fractured inefficient Mesozoic cover and, aided by reversal of the gradient toward the rising fold front, also later facilitated vertical migration into better, younger, higher reservoirs beneath an excellent Miocene regional evaporitic seal.
Grunau (1977) considered that the main reasons for the petroleum richness of this region—more or less the northeast Arabian margin—lie in the extensive areas of mature source rocks, the huge volume of interconnected pore space within effective closures
Figures & Tables
Arabian Plate Hydrocarbon Geology and Potential—A Plate Tectonic Approach
Reported proven hydrocarbon reserves of the Arabian plate region at the start of 1991 totaled 663.2 billion barrels (B bbl) of oil and 1,325.4 trillion cubic feet (tcf) of gas (66.4% and 31.5% of the world's oil and gas reserves, respectively). More than 98% of these are concentrated in the northeast margin region between northwest Iraq and Central Oman and lie in reservoirs ranging in age from late Paleozoic to early Neogene. Additional reserves, however, increasingly are being established along the other Arabian plate margins and in intra-plate basins. Occurrence of reserves, age and distribution of the sediments that generated or preserved them, and the formation of the mainly large structural (and other) traps are linked intimately to differing histories of plate margin evolution. The proper understanding of these histories could lead to additional reserves being established. The Arabian plate margins evolved at different times, the first being the northeast passive margin. This permitted the almost uninterrupted accumulation of thick sediments over a vast area including areally extensive organic-rich source rock deposits as well as good reservoir and seal units. The north/northeast margin(s) became a col-lisional boundary and a new Levant margin became a transform boundary in the Neogene.
Consolidation of the Afro-Arabian craton in the latest Proterozoic and Early Cambrian created a prominent north-south basement “grain” and a northwest-southeast (Najd) shear fracture system. Rejuvenations (affecting structures/sediment patterns) occurred in later periods and have controlled major hydrocarbon occurrences.
From latest Proterozoic to late Paleozoic time, the present north/northeast Arabian plate margin region, Anatolia, central Iran and the Afghan and Indian plates formed part of the long and very wide northern passive margin of Gondwana. This region was intermittently covered by shallow epeiric seas and bordering lowland.