松辽盆地青山口组震积岩特征及油气地质意义

CHARACTER AND PETROLEUM GEOLOGICAL SIGNIFICANCE OF SEISMITES IN THE QINGSHANKOU FORMATION OF CRETACEOUS IN SONGLIAO BASIN

通过大量岩芯观察,结合构造背景研究,在松辽盆地白垩系青山口组中识别出震积岩。将震积岩变形构造划分为固结地层震积变形构造和未固结地层震积变形构造两大类。研究区所见固结地层震积变形构造主要有裂缝、微型断层、龟裂式地层破碎及内碎屑角砾岩等,未固结地层震积变形构造主要有液化砂岩脉、石香肠构造、同沉积塑性变形构造、环状层理、震积枕状及伴生构造等。总结震积岩的沉积特征并讨论了其油气地质意义:由地震活动引发三角洲前缘砂体垮塌沉积而成的滑塌浊积岩、高能波浪带形成的滨浅湖滩坝砂体都为良好的储集层;震裂缝附近发育溶孔和微裂缝。溶孔的发育程度无疑对改善储层的储集性能起到建设性作用;已固结地层中发生地震的断裂系统为油气运移提供通道;强烈的地震活动会造成固结的致密泥岩盖层的破裂,大量裂缝会导致油气的快速散失。

By observation of a large number of cores,combined with the study on tectonic setting in Songliao Basin,Cretaceous Qingshankou seismite is identified.On the basis of previous studies,seismite deformation structures are divided into two categories,consolidation stratigraphic seismite deformation structure and non-consolidation stratigraphic seismite deformation structure.Consolidation stratigraphic seismite deformation structures in the study area are mainly cracks,micro-faults,crack-type formation fracture zone,and intraclastic parabreccia,non-consolidation stratigraphic seismites deformation structures are mainly liquified sandstone veins,boudin structure,syn-sedimentary plastic deformation,loop bedding,pillow seismites and associated structures and so on.The sedimentary characteristics of seismites are summarized and petroleum geological significance are discussed:the collapse fluxoturbidite rocks sandbody triggered by earthquake activity from the delta front,shore-shallow lake dam from high-energy wave zone triggered by earthquake activity are both good reservoir;dissolution porosity and micro-cracks is developed in the vicinity of cracks.Development degree of micro-cracks and dissolution porosity will no doubt improve the performance of the reservoir constructively;fault system in consolidation earthquake stratum provides access for oil and gas migration.Strong earthquake activity in the dense consolidation cause the breakdown of mudstone caprock,a large number of cracks lead to rapid loss of oil and gas.