Study On Hydrocarbon Migration In The Carbonate Successions In The Tahe Oilfield

The Tahe Oilfield is one of largest marine oilfields onland in China. The study on the oil migration pathways and migration history in the Tahe Oilfield is still the weakest research field. This thesis employed the Grains of bearing Oil Inclusions (GOI) Techniques to trace the fluid history in the carbonate successions and reconstruct the migration pathways configuration, and recognize their effectiveness and evolution in the Tahe Oilfield based on geological and experimental studies.GOI has been used tastily to study the secondary hydrocarbon migration in carbonate successions, together with conventional fluid inclusions analysis (homogeneous temperature analysis) and bitumen research result, under the background of geologic evolutional process study, the conclusions can be draw as that Tahe Oilfield undergone three hydrocarbon migration events, which happened in the early, late Hercynian and Himalayan period. During early Hercynian large scale of hydrocarbon migrated and accumulated in the middle-west part in the Tahe Oilfield, during late Hercynian hydrocarbon accumulation in some areas suffered modification again and re-distributed, accompanied by volcanic activity, while during Himalayan hydrocarbon migrated and accumulated in the east and south part of Tahe Oilfield.The hydrocarbon migrate predominantly in the lateral direction and secondly in the vertical direction. The unconformities play most important roles as conduits for lateral hydrocarbon migration, fluid inclusions correlation along layers under unconformity can be evidences. The biomarks, physical property of hydrocarbon over whole oilfield suggest the southern and eastern part of Tahe Oilfield could be place where hydrocarbon is from.Fractures are mainly vertical conduits for oil migration. Combining the inter-wells correlation, formation water parameters and oilfield development data, the fractures are believed to be effective depending on its location and activity time. During the early Hercynian fractures in the middle-west part of Tahe Oilfield is effective, the late Hercycian in the main district fractures are effective, while in the Himalayan the eastern of Tahe Oilfield fractures are effective. In contrast, the south of Tahe Oilfiled has poorly developed all along.Stylolites can be special and important hydrocarbon migration conduits. They are controlled by lithology, burden pressure, fluid movements, etc. stylolites are believed to form in the early Hercynian, well developed in the main district, and southern part of Tahe Oilfield, filled by bitumen and crude oil, and some tends to be replaced by dolomite. The wettability convoy is important mechanism of hydrocarbon migration along the stylolites. The experiments demonstrate the oil wettability of medium can make hydrocarbon migration pattern significantly different and improve its migration efficiency to 90%. The stylolites can act as the dominant pathway for its organic matter enrichment within and oil wettability.Unconformity, fractures, stylolites constitute the 3D migration conduits system, which not only control the hydrocarbon migration, but also hydrocarbon accumulation. Karst caves and fractures are main storage space, but with intensive heterogeneity, determined by unconformity and fractures, linked by stylolites.