Mesozoic petroleum accumulation systems and play fairways in southern Ordos Basin

According to the concept of accumulation system,in combination with source rocks,source-reservoir relationship,reservoir characteristics and accumulation mechanism,we recognized two Mesozoic petroleum accumulation systems in the southern Ordos Basin,i.e.near-source system and system.The accumulation system is dominated by lithologic traps,and features in short migration distance,abnormal pressure as major driving force of migration,and implicit carrier system.Hydrocarbon accumulation in the system is mainly controlled by high-quality source rocks and reservoirs as well as favorable structural setting,and the pattern of hydrocarbon accumulation can be described as near-source and facies-control.The system is dominated structural traps and structural-lithologic traps,and is characterized by long migration distance,buoyancy as the major driving force of migration and source rock-rooted faults containing the major carrier system.Hydrocarbon accumulation in the system is mainly controlled by source rock-rooted faults,local structures and high-quality sandstone reservoirs,and the pattern of oil accumulation can be described as far-source and fault-control.The source rock-reservoir relationship in the system has a sandwich-like structure.The synchronism of peak hydrocarbon generation with hydrocarbon accumulation provides favorable conditions for widespread and large-scale hydrocarbon charging and accumulation near source rocks.The systems are the priority of future exploration,and the top-ranking play fairways in the CH9-CH8-CH7 systems are the important exploration targets for large-and medium-sized oil and gas fields.