Reservoir Forming Conditions and Filling Models for Chang 6 Oil Reservoir of the Yanchang Formation in Jiyuan Area,Ordos Basin

Key words: 
• Chang 6 oil reservoir /
• Jiyuan area /
• reservoir forming condition /
• accumulation mechanism /
• filling type

Abstract: Chang 6 reservoirs of different regions in the Jiyuan area have large differences in oil-bearing characteristics. Large lithologic reservoirs are developed in the west and east,but there are many wells producing water in the middle region. By studying source rocks,reservoir characteristics,transmission systems,shielding conditions,reservoir forming dynamics,accumulation period,and filling degree of the three regions,the differences between reservoir forming conditions and accumulation mechanisms are clarified. In the western region,the reservoir forming conditions,characterized by high hydrocarbon generation intensity,developed fracture networks,high excess pressure, and high filling degree,are the best. In the east,the reservoir forming conditions,characterized by thin hydrocarbon source rocks,but well-developed fractures,good reservoir properties,large pressure difference between source and reservoir,lateral migration of oil,and high degree of filling,are better. In the central region,the reservoir forming conditions,characterized by thin source rocks,undeveloped fractures,poor shielding conditions,low excess pressure,and low filling degree,are poor. The differences in reservoir forming conditions and accumulation mechanism lead to different types of filling. The western region belongs to the saturated filling type,the eastern part belongs to the under saturated filling type,and the central region belongs to the under-filled type. The research results provide guidance for petroleum exploration and development for Chang 6 reservoirs in Jiyuan.