浅层油气运聚理论与渤海大油田群的发现

Shallow hydrocarbon migration and accumulation theory and discovery of giant oilfield group in Bohai Sea

渤海油区年产原油3 000×10~4t,约占中国海洋石油产量的70%。渤海油区位于渤海湾新生代陆内裂谷盆地的中东部,勘探面积约4.5×104km2。渤海油区具有鲜明的石油地质特征:著名的郯庐大断裂纵贯渤海,新近纪断裂活动强烈,促进石油的纵向运移,但不利于油藏的保存;中新世—上新世发育河湖相沉积,上部储-盖组合广泛分布,为浅层石油富集创造了条件;古近系生油岩埋藏深,新近系储-盖层较浅,石油垂向运移距离远,运移途径复杂。针对渤海复杂的石油地质条件,经过20年认识—实践—再认识的探索,提出1大断裂-砂体"中转站"模式运移能力强、2小断层及走滑断裂运移油气能力弱、3地层—断层组合关系控制油气富集部位、4临界盖层控制断裂活动带油田形成、5圈闭汇油面积大小决定油田规模、6主力油田展布可分为凸起与凹陷富集型、7小凸起上的披覆背斜利于形成大油田7项创新学术思想,构成了浅层油气运聚理论并指导勘探,渤海勘探团队在短期内高效发现了7个大油田、17个中型油田,共27×10~8 m^3地质储量,奠定了中国第二大油区的储量基础。

The annual output of crude oil reach3 000×10~4 t in the Bohai Sea,accounting for about 70% of offshore oil production in China.Bohai oildom is located at the central and eastern Cenozoic intracontinental rift basins in Bohai Bay,with an exploration area of about 4.5×104km2.Bohai oildom has distinctive petroleum geological characteristics;the famous Tan-Lu Fracture Belt pass through the Bohai Sea from north to south;Neogene fault activities are intensive,which accelerate the vertical oil migration,but is not conducive to the reservoir preservation;fluvial-lacustrine sediments are developed during the Miocene-Pliocene period,in the upper part of which reservoir-caprock assemblage is widely distributed,creating conditions for shallow petroleum accumulation;Paleogene source rocks are buried deep,and Neogene reservoirs and cover rocks are relatively shallow;the petroleum migration path is complicated with long vertical migration distance.According to the complicated geological conditions of the Bohai Sea,after 20 years of exploration in cognition-practice-recognition mode,7innovative academic ideas have been proposed as below：（1）the large fault-sandbody transfer station mode has strong migration ability;（2）the migration ability of small faults and strike slip faults is weak;（3）the formation-fault assemblage determines the place where hydrocarbon accumulates;（4）critical cover controls the formation of oil fields in the active fault belt;（5）the oil collecting area in the trap determines oil field scale;（6）the distribution of main oil fields can be divided into salient enrichment type and sag enrichment type;（7）drape anticlines on a small salient are favorable for the formation of large oil fields.These ideas constitute the shallow hydrocarbon migration and accumulation theory for guiding actual exploration.Through a comprehensive study,the Bohai exploration team found7 large oil fields and17 middle-scale oil fields in a short time,and the total geological reserves amount to 27×10~8 m^3,laying the reserve base of the second largest oil field in China.