鄂尔多斯盆地天环坳陷西缘长8油藏地球化学特征及成藏模式OA

[Objective]The Tianhuan Depression is a crucial area for increasing crude oil production and reserves in the Ordos Basin.However,due to its location on the western edge of the basin and complex structural conditions,the oil accumulation patterns have not yet been fully understood.This paper selects the Chang 8 oil reservoir in the Hongde area as the research subject,aiming to clarify the source and accumulation models of oil and gas on the western edge of the basin,thereby guiding further exploration and development.[Methods]By analyzing the geochemical characteristics of hydrocarbon inclusions and crude oil in the reservoir,and combining with relevant achievements in structural evolution,this study explores the enrichment patterns of oil reservoirs in the region.[Results]The results show that:① the maturity of crude oil in the western part of Hongde is lower than that in the eastern part,and it has the characteristics of early reservoir formation;② Compared to the slope zone,the light hydrocarbon of the original oil at the high point of the Hongde western structure is complete,indicating better preservation conditions;③ There are two temperature ranges of 90～100℃and 120～130℃for hydrocarbon inclusions,indicating at least two periods of oil and gas injection.Overall,it is believed that the Chang 8 crude oil in the Hongde area is mainly supplied by low maturity source rocks at the eastern edge of the Tianhuan Depression.[Conclusions]The structural high points in the western part of Hongde are minimally affected by later structural adjustments,and the oil reservoir has not undergone large-scale secondary adjustments.The adjacent structural traps still have good exploration prospects.