The paper describes the shale oil and gas bearing systems of the South Caspian basin based on the results of basin modeling. Identification and assessment of the prospects for shale accumulations at the regional level is based largely on the results of numerical modeling with subsequent calibration of the resulting model.

The largest masses of oil are concentrated in shale strata, and OM is present there initially, and oil (light components of OM) emigrates from shale to neighboring reservoir rocks. Changes in the structure of kerogen during catagenetic maturation occur in contact areas. In dense immature kerogen, organic pores (“kerogen porosity”) begin to form, which, by the end of the main phase of oil formation, form a connected system that provides space for newly formed petroleum hydrocarbons. Organic porosity or porosity in the texture of kerogen, formed during the thermal maturation of rock OM, can affect the adsorption of the resulting oil by the porous surface of the kerogen. The results of organic porosity studies suggest that organic pores in the kerogen texture make a significant contribution to the space of newly formed reservoirs in the thickness of oil source rocks.

It is concluded that the following shale oil and gas systems were formed in the South Caspian basin: diatomaceous shale oil and gas system, Oligocene-Miocene shale oil and gas system and Eocene shale oil and gas system, which are combined unconventional oil and gas systems with hydrocarbons, partially emigrated from the oil and gas source rock and partially preserved (unrepressed).

Keywords: South Caspian depression, shale strata, hydrocarbon system, kerogen, catagenesis, organic porosity, adsorption

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