СЕДИМЕНТАЦИОННЫЕ МОДЕЛИ И ПРОМЫСЛОВЫЕ СВОЙСТВА ВЕРХНЕТУРНЕЙСКИХ КАРБОНАТНЫХ ОТЛОЖЕНИЙ ЮЖНО-ТАТАРСКОГО СВОДА ПЛАТФОРМЕННОЙ БАШКИРИИ

Abstract

The article considers regional and local conditions for carbonate sedimentation in the tournaisian period of time within the Eastern periclinal termination of the East European platform and the South-Tatar arch. It is shown that during the time the bathymetry of the basin of sedimentation was determined by different tectonic elements: the southern-еastern slope of South-Tatar arch and the нorst-graben structures, complicating the passive continental margin of the Ural paleoocean. In tournaisian time, sedimentation occurred mainly on the plain topographic surface of the seabed in conditions of the epicontinental carbonate platform. The eastern edge of the platform had no an obvious ledge with a characteristic barrier reef, here known only a small single reef massifs. In the structure of the tournaisian basin have identified four facies megazone, including the narrow coastal in the west, a broad shelf in the east, relatively deep in the axial depressions, complicating the shelf, and intermediate in both side of the same depressions. Within the South-Tatar arch was made a structural-genetic typing of productive carbonate sediments. It was selected lithotypes, belonging to different sedimentation conditions and with different structure of the void space. It is shown that the field properties of the reservoir rocks were formed during sedimentation and subsequent postsedimentary transformations, which had the inherited nature. The main postsedimentary processes that had a profound effect on reservoir properties are leaching, and cracking. It is established that granular lithotypes composing the productive part of carbonate rocks, formed under conditions of high hydrodynamic activity of basin waters, corresponding to raised areas of the seabed. It is proposed conceptual depositional model, according to which the most favorable conditions for the accumulation of granular reservoir rocks is associated with paleoarch created by bioherm massifs of the upper frasnian-lover famennian age. It is shown that productive lithotypes on structural properties belong to three petrophysical classes with stable dependencies porosity/permeability.