Mamedov P.Z.

In the sedimentary cover of oil-gas basins (OGB) one can identify two uninterrupted series of hierarchically co-subordinated elementary bodies: a vertical series of the age chronostratigraphic units and lateral series of the formational-fasial lithostratigraphic units. The latter are identified by material-structural and genetic features and do not meet the demands of the boundaries synchroneity made on the stratigraphic subdivisions.

To create base models of OGB and to digitally simulate processes of sedimentation with the purpose to predict terms of generation and accumulation of hydrocarbons (HC), it is necessary to identify and to study in the section a class of bedded over-rock geological bodies with the isochronous boundaries.

The over-rock geological bodies are rather precisely identified in the sedimentary basins (SB) and studied by seismic stratigraphy. Seismic stratigraphy provides exclusively important data for the solution of some geological problems and, especially problems of stratigraphy. The specific objective of the latter is the determination of chronological and historical succession of the formation of sedimentary series.

The seismostratigraphic analysis of the SB is based on the following main principles:

a) chronostratigraphic importance of seismic reflecting boundaries. This enables to identify the age 3D bodies- the seismostratigraphic subdivisions (SSS) and b) hierarchy of the SSS.

The accordance with the hierarchy of the SSS, every large subdivision may be divided into small units. A successive series of the SSS of a different rank forms an objective scale of eventual stratigraphy and demonstrates stages of evolution of the SB.

In the process of the development of seismostratigraphy and wide application of seismostratigraphic data in the SB, there have been constructed and tested different schemes of subdivision of a section into hierarchic co-subordinated 3D chronostratigraphic units-SSS. The age criteria of the dissection of the sedimentary cover into the hierarchic SSS is the main one. Different schemes were tested in different SB in platforms and perioceanic regions, far from the mobile belts. The SB in the mobile belts are of a huge thickness(more than 18–25 km).One of the vivid representatives of the SB in the mobile belts is the South-Caspian Megabasin (SCMB).Its basement is subsided as deep as 27–30 km. In the cover of the SCMB one can identify several sedimentary complexes of a different age. Some of them are superior in thickness (more than 3–7 km) and volume to the structural stages and even to the whole plate complex in the adjacent platform areas. These thick complexes are composed of the age succession of the 3D bodies of a different scale and rank.

In the paper on the base of the case study of sections in the SCMB there have been considered the efficiency of methodics and schemes of the dissection of thick sedimentary covers and deep SB in the SSS of a different rank. The scheme includes 6 ranks (levels) hierarchic co-subordinated subdivisions. There have been also considered genesis, scale (regional or local) and level of the organization-specialization (tectonic-sedimentary and sedimentary) of each SSS, as well as role of tectonic, sedimentary and eustatic factors of their formation and physical and geological peculiarities of the surrounding boundaries.