贝尔断陷层序建造及岩性油气藏发育特征

Development characteristics of lithologic reservoirs and sequence architecture in Beier Rift

应用三维地震、测井和岩心资料,对贝尔断陷构造层序进行分析,并研究了贝尔断陷同裂谷期层序建造、沉积体系及岩性油气藏的发育特征。认为下白垩统沉积时期可划分出5个与裂陷幕对应的超层序,在超层序二至超层序五内,识别出了10个三级层序;裂陷二幕和裂陷三幕对应于下白垩统铜钵庙组和南屯组,盆地以伸展断陷构造活动为主,发育湖泊、扇三角洲沉积体系以及受断裂坡折带控制的层序;裂陷四幕对应下白垩统大磨拐河组,盆地以走滑扭张构造活动为主,发育大型河流三角洲体系和受挠曲及断裂坡折带控制的层序;裂陷五幕对应下白垩统伊敏组,盆地断坳转换,发育河流和冲积平原沉积及平缓背景下的冲积型层序。下白垩统铜钵庙组及南屯组受同沉积断裂坡折带的控制,层序低位体系域砂体成藏条件良好,为岩性油气藏最发育的部位。

By using 3D seismic data, log curves and core data, and in the light of principle of tectonics and sequence stratigraphic analysis, this paper studied the Lower Cretaceous sequence architecture, depositional systems and development characteristics of lithologic reservoirs in Beier Rift. Five super sequences(second order sequences), corresponding to five rifting episodes respectively, and ten third-order sequences within super sequences 2 to 5 were identified. The second and third rifting episodes correspond to the Lower Cretaceous Tongbomiao Formation and Nantun Formation respectively, they are characterized by extensional tectonic movement, and fan delta depositional systems and sequences architecture in syndepositional fault slope breaks are developed. The forth rifting episode corresponds to the Lower Cretaceous Damoguaihe Formation, it is characterized by strike-slip tectonic movement, and fluvial delta systems and sequences controlled by syndepositional flexure slope break zones and fault slope break zones are developed. The fifth rifting episode corresponds to the Lower Cretaceous Yimin Formation, it is characterized by transition movement from rifting to depression, and fluvial and flood plain depositional systems and alluvial sequences are developed. Sand bodies of lowstand system tracts of sequences in syndepositional fault slope breaks of the Lower Cretaceous Tongbomiao Formation and Nantun Formation are favorable for hydrocarbon accumulation.