塔北西部玉东地区奥陶系油气成藏条件与勘探潜力

Analysis of the Hydrocarbon Accumulation Conditions and Exploration Potential in the Ordovician in Yudong Area of West Tabei Uplift

塔北西部玉东地区奥陶系未获得油气突破。对该区油气成藏条件认识不明确,其勘探潜力不落实。通过对玉东地区构造、成藏演化分析,明确了鹰山组碳酸盐岩岩溶储集体在晚海西期形成准层状古油藏,后期的构造抬升仅造成构造高点油藏破坏,对分布于围斜部位缝洞型油藏影响不大。通过对源岩条件、储盖组合及圈闭条件等成藏因素综合评价,估算了奥陶系碳酸盐岩的油气勘探潜力,明确玉东地区是塔里木盆地重要的油气战略接替区。

In the Ordovician there has been no discovery and break through of oil and gas in Yudong area of western Tabei.Previous studies suggested that there is no accumulation,or reservoir has been destroyed in the Yudong area,and there is no exploration potential.To further explore the hydrocarbon potential of carbonate rocks in the Karayulgun structural belt of west Tabei Uplift,according to the question in previous studies,this research carries out detailed analysis of the Ordovician oil-gas accumulation conditions in the Yudong area based on the relationship between structure and accumulation of hydrocarbon.On the basis of the analysis of fine structure interpretaion and evolution,it is clear that the Yudong structure was mainly formed in Late Hercynian.Affected by the Karayulgun fault sustained activity,the Yudong tectonic uplifted,the strata have suffered variable degrees of erosion.The analytical results of reservoir formation conditions show that the karst reservoirs in the Yingshan Formation could capture oil and gas generated in Late Hercynian,and form quasi-layered oil deposits distributing along the Ordovician reservoir.Reservoirs in the high position were eroded during the later stages of tectonic uplifting,but other lower structural positions relative to the Yudong 2were still relatively high area.They not only avoided the erosion during the later stages of tectonic uplifting,but alsowere in a favorable position during the later adjustment of the reservoir.Considering the source rock condition,structure,reservoir cap assemblage and igneous influence,the authors think Yudong has similar reservoir conditions as Yingmai 2,and both are quasi-layered reservoir controlled by fracture and cave karst reservoir with great exploration potential.