The Characteristics Of Oil And Gas Distribution In The E_s4^s Hydrocarbon-bearing Fluid System In Dongying Depression

Both source rock deposition and the generation and migration of oil occur in the environment of formation water,and there is close connection between formation water and crude oil.By introducing the concept of‘Hydrocarbon-bearing Fluid System',fluids in Dongying Depression is devided into two hydrocarbon-bearing fluid systems as E_s3 and E^s_s4.Taking the E^s_s4 hydrocarbon-bearing fluid system as an example,the reservoir distribution patterns were summarised based on the investigations of geochemical properties,origins,identify indicators and modes of migration and accumulation.The disserataion has achieved the following conclusions.?1?Formation water in the E^s_s4 hydrocarbon-bearing fluid system are mainly CaCl₂-type,with high degree of salinity;Crude oil from E^s_s4 has high content of sulfur,and biomarker compounds have the characteristics of high cerium-paraffin and low enthalpy plant ratio.?2?In reservoir above E^s_s4,there is strong heterogeneity of fluids properties,and the abonormal peoperties are even more distinct where faults exist,which is the result of E^s_s4hydrocarbon-bearing fluid upward migrating and mixing.?3?The property changes of hydrocarbon-bearing fluids are consistent in the process of migration,including reduced salinity,Ca²⁺,Mg²⁺and increased HCO₃^-for formation water and increased viscosity for crude oil,etc.?4?The hydrocarbon-bearing fluids of E^s_s4 are distributed from the 4^thh member of Shahejie Formation to the Guantao Formation;Three types of subsystem can be identified based on the distribution position and dynamic characteristics,which are Primary Fluid System,Mixed Fluid System and Open Fluid System.?5?The oil and gas distributions of each subsystem are different:The primary fluid system is dominated by lithological reservoir;The mixed fluid system is dominated by structure and composite reservoirs with three modes inluding the“T”type,the mesh type,and the ladder type;The open fluid system mainly includes buried hill reservoirs.