CLASSIFICATION AND CHARACTERISTICS OF HYDROCARBON PRIMARY MIGRATION AND TRANSPORT SYSTEM IN CLASTIC ROCKS

Studies of hydrocarbon primary migration and transport system play an important role in secondary migration,even influencing final reservoir scale.According to researches of transport system during secondary migration,from microcosmic angle,based on generation and combination of different transport channels,the primary transport system in clastic rocks has been divided into 3 types: normal,secondary and terminative.The normal transport system is composed of pore throat and kerogen network.Hydrocarbon(most miscible phase and little immiscible phase) is expelled from source rock by capillary driving force formed from hydrocarbon bulging.The secondary transport system is formed by a large quantity of secondary microcracks.High excess pressure in source rocks is the main force for immiscible hydrocarbon expelling.In the secondary transport system,hydrocarbon expelling quantity is the largest and efficiency is the highest.The terminative system is composed of intergranular cracks and residual microcracks.The low excess pressure acts as the main force.The efficiency is low and the translocation is very weak,even down to vanish.Along with changes of burial history of source rocks in basins,the normal and the secondary transport system can transform reciprocally to certain extent,whereas the terminative system means the end of perpetual close of the primary transport canals and the complete finish of transport period.