Abstract Research is based on conception about field as not only migrating fluids trap with formed pore volume and shielding cover but as self-assembling oil-gas source system on one or another oil-gas generation stage. In order to study oil-and-gas source carbonate rocks in detail a core studying laboratory investigations complex was developed. Core samples, salt exhausted but not extracted, were studied by petrophysic, geochemical, electron microscope and physicochemical methods. Complex treatment to investigations allowed to discover regularities of carbonate oil-and-gas source deposits' catagenetic transformations. These regularities were put into created hearth-clustered algorithm for rock properties modeling. A hearth-clustered conception taking into account oil-and-gas source rocks' transformation regularities would allow to differentially estimate and classify hydrocarbons reserves and also choose directed recovery technologies in hearths' pay zones which correspond to different organic matter and rock-forming matrix catagenetic transformation stages. Geological hard-to-recover oil reserves in gas-saturated zones of gas-condensate and oil-gas-condensate fields are traditionally not considered in estimation of reserves, nor in field-development program but they represent tremendous unaccounted and not realized resource base of Russian Federation in regions and fields with wholly developed infrastructure. They should be necessarily considered in design estimates as on early so on late field development stages.