海拉尔盆地乌尔逊-贝尔凹陷的地质特征及油气成藏规律

海拉尔盆地乌尔逊-贝尔凹陷是叠置于内蒙-大兴安岭古生代碰撞造山带的中新生代盆地。依据层序地层学原理和孢粉组合，确定下白垩统自下而上的地层层序为兴安岭群、铜钵庙组、南屯组、大磨拐河组、伊敏组。研究区主要发育4个方向的构造带，其中北东向、北东东向和南北向断层带形成较早且长期活动，控制了盆地的形成；北西向断层带形成较晚，对上述3个方向构造主要起改造作用。研究区的构造主要是在早白垩世经历了4个变形阶段形成的，不仅控制了油气运移、成藏和分布，而且晚期构造对早期形成的油气藏主要起破坏或改造作用。研究区的不整合面是重要的油气运移通道和良好的储集空间。乌尔逊－贝尔凹陷的4个方向构造带和不整合面是研究区有利的油气聚集带。

Geological Features and the Rule of Oil and Gas Accumulation of Urxun-Beier Depression in Hailaer Basin

Urxun-Beier depression in Hailaer Basin is the Mesozoic-Cenozoic basin located in the Paleozoic orogenic belt in Inner Mongolia-Daxing'anling area.Based on the sequence stratigraphic theory and sporopollen assemblages, stratigraphic sequences of the Lower Cretaceous have been recognized from bottom to up as: Xing'anling Group,Tongbomiao Formation,Nantun Formation,Damoguaihe Formation,Yimin Formation.The four structural belts with different directions are found in the area.The faults with NE,NEE and NS trends formed earlier with long-term activity,and control on the basin evolution;the faults with NW trend formed later and overprinted on the early structures.The structures of the area experienced four deformation stages in the Cretaceous period,which controlled on the migration,accumulation and distribution of oil and gas,and the later structures destroyed or reformed the earlier oil and gas accumulation.The unconformity within the area is an important migration pathway and good reservoir of oil and gas.The four structural belts with different trends and unconformities are the favorable zones for oil and gas accumulation in Urxun-Beier depression.