Hydrocarbon deposits of the Lower Carboniferous deposits of the Dnieper-Donets Depression (DDD) are connected with carbonate reservoir rocks of the Tournaisian-Visean reef complex (RC). The greatest amount of organic sediments (OS) is known to be developed in the Lower Visean deposits in so called Lower Visean “plate” (VP). Hydrocarbon deposits are connected with microheterogeneous silicicarbonate composite reservoir rocks with secondary porosity of different facies of organic structures. Direct connection between silicites and a rate of fracturing of reservoir rocks was established. Just to such intervals of the sections of the Visean plate the cavernous-fractured reservoirs are confined.

There are three systems of fractures in reservoirs: subvertical of shearing type, subhorizontal of strained type and stylolite junctures. For reef deposits of the Visean plate of the Sribne deep of the Dnieper-Donets Depression the following types of reservoirs were determined: fractured K p < 2.0 %; porous-fractured K p < 3.0 %; fractured-cavernous with K from 2 to 22 %, cavity space of which consists of pores and caverns of leaching, and paths of filtration are provided by fractures; porous - fractured-cavernous with K p > 5 %.

It should be noted that composite reservoirs with secondary porosity of the Visean deposits of organic buildups of the Sribne deep is one of perspective objects for searching for new deposits of oil and gas in the Ukraine. At present numerous oil manifestations are fixed in them and some hydrocarbon deposits have been already discovered.