A STUDY ON SECONDARY MIGRATION OF PETROLEUM IN JURASSIC SYSTEM OF THE SHAAN-GAN-NING BASIN ON THE BASIS OF CRUDE OIL PROPERTIES AND FRACTURING GRADIENTS IN RESERVOIR

The ratio curves of methane content to oil/gas can be used to distinguish the two different patterns of migration.The curve together with other available data may provide certain important evidences for the vertical migration in Mesozoic systems;while the direction and distance of lateral petroleum migration in the Jurassic oil pools is preliminarily determined from the rhombic pattern and Kasimov migrating coefficient.Furthermore,the determination of fracture types,the distinguishing of migrating patterns,and the prediction of oil (gas) pools are made on the basis of the data from fractured gradients and cores.Consequently,the results and understanding from the analysis of above-mentioned methods are helpful to study the formation and distribution of oil/gas fields with the paleogeomorphology;therefore,to guide the petroleum exploration in the Jurassic system.