A great amount of geological-geophysical data on the giant oil- and gas-bearing zone of Ob' River Region has been analyzed in the context of the system-lithmological approach developed by the authors. Considerable oil reserves related to nonstructural, lithological pools of intricate Neocomian clinoformic complex were for the first time revealed within this zone in West Siberia. The systematic lithmological approach (which is more efficient than sequence-stratigraphic one) widely used in this work allowed to reveal previously unknown peculiarities of structure and formation of productive horizons and pools. This permitted improvement of the model of Priob' deposit and its reserves. Finally, the assessment of oil potential of Neocomian productive complex is given and prospect for further growth of the reserves in this zone and beyond it are justified. In addition to the main Neocomian productive complex, Jurassic and pre-Jurassic series within this zone whose prospect were considered in the monograph too, are also potentially oil- and gas-bearing. Considerable attention was focused on the theoretical-methodological and methodical problems of lithmology and sequence stratigraphy.