Transformation of Driving Mechanism for the Second Petroleum Migration and Its Significance in Petroleum Geology——Taking the Niuzhuang Sag as an Example

A couple of petroleum dynamic systems can occur simultaneously in one petroliferous basin,and accordingly,main driving mechanism of petroleum secondary migration may differ;this paper studied the rule of energy transfer and gas-oil migration between different systems.Based on liquid pressure survey,petroleum geochemical characteristics,well drilling and logging,analysis on dynamic system of low Tertiary in the Niuzhuang depression and its southern margin of Jiyang,the study has revealed that a transformation from ultra-high pressure to buoyancy occurred in the pressure paralimbic system of anomalous fluid.During the driving mechanism transformation,miscible phase fluid derived form ultra-pressure fluid dynamic system separated firstly from the mixture of petroleum,gas and water,and then resumed to migrate by buoyancy after a short settlement and accumulation in transport layer adjacent to oil source fault,resulting in strengthening geological chromatographic effect.Studying on driving mechanism transformation helps us better understanding petroleum migration and its characteristics,which facilitates our tracing in detailed to migration path of petroleum.In addition,complicate dynamic condition reveals that paralimbic dynamic system is of complicated petroleum reservoir condition and exploration prospect.