Comparative studies of reservoir formed conditions of Bohai Bay and Ordos Basin

A comparative study of Upper Paleozoic oil-gas reservoir formed conditions of the Bohai Bay and Ordos Basin shows that their patterns are very similar because there is little difference in thickness of source rocks and type of organic matter.Secondary hydrocarbon generation only occurred in the Bohai Bay Basin,while there only existed one in the Ordos Basin,NW China,due to high evolution of organic matter.Reservoirs in both basins are characterized by low porosity and low permeability,and oil and gas could be well sealed by the cap rocks,resulting in the formation of different types of oil-gas reservoirs.The oil and gas in Ordos Basin was mainly preserved in lithologic traps and the future plays of the Bohai Bay Basin should be focused on the Upper Paleozoic lithologic traps.