Home – Home – Jornals – Russian Geology and Geophysics 2001 number 11-12

main petroleum-bearing belts are confined to the passive margins of continents – recent and ancient. The recent margins form three global belts which can be considered subtypes differing in time and rifting-spreading stages: Indooceanic-Atlantic, Circum-Arctic, and Mediterranean-Persian.
Sedimentary basins of the three subtypes are characterized by a high rate of sedimentation, up to 5-10 cm/ka, but differ in recent thermal regime. One subtype has an increased thermal regime with a depth of 100 ^oC isotherm of 2-2.5 km in separate basins. The other two subtypes are characterized by a different thermal regime, with 100 ^oC isotherms established at depths of 5-7.5 km.
In the case of ancient passive margins, large fields are connected with rift massifs. The post-rifting stage of these belts can be finished by thrusting emerged near orogen and accompanied by formation of molasse foredeeps and multilayer nappe structures. The second type of petroleum belts is confined to active margins, mainly to the Circum-Pacific belt and Western Mediterranean region. Associated with different-age zones of subduction, the basins of the Caspian-Black Sea region can be distinguished as a specific subtype. Subsidence at the last stage is accompanied by an avalanche rate of sedimentation, up to 30 cm/ka. The increased thermal regime (except for the basins of the Caspian-Black Sea subtype) with 100 ^oC isotherms at depths of 1.5 to 2.5 km contributed to quick generation of organic matter and the most complete realization of petroleum potential.
The third is intraplatformal type of petroleum-bearing belts associated with continental platforms. It is subdivided into subtypes - rifting and epirifting. In the first case, thermal regime is rather high, with the depth of 100 ^oC isotherm ranging from 1.5 to 0.5 km; in the second case it is low with the depth of 100 ^oC isotherm of about 5 km.
The forth type includes basins of intermontane troughs of orogens. The basins of this type are rather small but with thick sediments and high sedimentation rate of 3-6 cm/ka at the Cenozoic stage. The thermal regime is characterized by the depth of 100 ^oC isotherm of to 5 km in intermontane basins of young orogens and to 1.5-2.5 km in rejuvenated orogens.
The sedimentary fill of active-margin basins and intraplatformal and intermontane troughs of young orogens is subject to tangential stress caused by collision of lithospheric plates and is characterized, especially along the periphery, by fold-thrust strains, often with stripping of sedimentary units off the basement or along the plastic horizons in the cover.
To estimate petroleum potential in each type of basins, it is necessary to take into account some endogenic factors: thermal regime, deep-level fluids, lateral stress, rate of sedimentation, etc.