辽西低凸起中南段古近系东营组层序地层及地层-岩性油气藏勘探意义

陆相断陷盆地古地貌控砂研究较为成熟,但由同沉积构造的活动及其配置所产生的古地貌动态变化对沉积物砂分散体系控制的研究较少。通过对辽西低凸起中南段东营组构造-层序地层和沉积相开展整体和系统性研究,依据体系域界面和各体系域内三角洲地震反射构型的变化,有效地识别了东二层序的低位、水进和高位3个体系域,建立起研究区高精度层序地层格架。在层序地层单元精细划分对比的基础上,对层序格架内古地貌和沉积体系发育和演化规律进行了研究。研究区主要发育辫状河三角洲、曲流河三角洲、湖底扇和湖泊等沉积体系;辽西低凸起边界断层从北向南依次发育3个调节带,调节带的平面和空间差异活动控制了三角洲朵体的迁移。根据对各体系域砂体特征的描述,在东二层序识别了断层-岩性、上倾尖灭、岩性和地层超覆等4种地层-岩性圈闭类型。

Sequence stratigraphy of the Paleogene Dongying Formation and its significance for stratigraphic-lithologic reservoirs exploration in the central-south Liaoxi salient

The control of palaeotopography on the distribution of sandbodies has been well studied in continental rifted basin,while the control of palaeotopography dynamic changes caused by syndepositional structure movement on the sand distribution is less studied.Through the systematic study of tectonic-sequence stratigraphy and sedimentary facies of the Paleogene Dongying Formation in the central-south Liaoxi salient,the LST,TST and HST are recognized in the 2nd member of the Dongying Formation according to system tract boundaries and the seismic reflection features of deltas.A high resolution sequence stratigraphy framework is established.On the basis of the fine division and correlation of sequence stratigraphy unit,the paper studied the palaeotopography and the development and evolution of depositional system.The study reveals that braided river delta,meandering river delta,sublacustrine fan and lake are well developed in the study area.There are three transform belts along the boundary fault in the salient from north to south.The areal and spatial variation of activity of the transform belts is the key factor controlling the migration of delta lobes.Four types of stratigraphic-lithologic traps,including fault-lithologic trap,sandstone updip pinchout trap,lithologic trap and stratigraphic overlap trap,are recognized in the 2nd member of the Dongying Formation based on the sandbody characterization of each system tract.