渤海海域东南部构造转换带分级及其差异控藏作用

Classification and its differential reservoir control effects of structural transition zone in the southeastern Bohai sea

渤海东南部地区是渤海湾盆地油气最为富集的区域之一,受张家口—蓬莱、郯庐两组走滑断裂体系相互叠加的影响,研究区发育多种类型的构造转换带,控制了该区油气成藏与油气富集程度的差异。为弄清不同级别、不同类型构造转换带及其对油气成藏的差异控制作用,依托24个油田200余口钻井资料,结合连片三维地震资料解释结果,对渤海海域东南部的构造转换带进行了分级、分类,并探讨了其差异控藏作用。首先依据构造转换带规模及其形成动力机制,将研究区构造转换带分为4个级别,渤海海域东南部地区为中生界先存构造被后期走滑改造而成的Ⅰ级转换带,Ⅰ级转换带内部进一步识别出Ⅱ级共轭型构造转换带、Ⅲ级叠覆型构造转换带、Ⅳ级S型构造转换带与断梢型构造转换带;分析总结了不同级次构造转换带对烃源岩、圈闭、运移与保存等油气成藏要素的差异控制作用及其差异控藏模式,Ⅱ级构造转换带主要控制烃源岩和油气深层优势汇聚方向,决定规模性有利富集区;Ⅲ级构造转换带主要控制规模性圈闭形成,决定油气优势富集场所;Ⅳ级构造转换带主要控制油气运移和保存,决定油气优势富集断块。该研究成果对海域同类型地区油气勘探具有较强的借鉴意义。

The southeastern Bohai sea is one of the most abundant oil and gas areas in Bohai Bay basin.Influenced by the superposition of the Zhangjiakou-Penglai and Tanlu strike slip fault systems,various types of structural transition zones have developed in the study area,which control the difference in oil and gas accumulation and enrichment in the area.In order to clarify the different levels and types of structural transition zones and their differential control effects on oil and gas accumulation,this article relies on more than 200 well data from 24 oilfields and the interpretation results of contiguous 3D seismic data to classify the structural transition zones and explore their differential control effects on oil and gas accumulation in the southeastern Bohai sea.Based on the scale and formation mechanism,the structural transition zones in the study area are divided into four levels:the southeastern Bohai sea is a Grade I transition zone formed by the late strike slip transformation of pre-existing structures in the Mesozoic,and the GradeⅡconjugate structural transition zone,GradeⅢsuperimposed structural transition zone,Grade IV S-type structural transition zone and fault-top structural transition zone are further identified in the Grade I transition zone.The differential control effects of different levels of structural transition zones on hydrocarbon accumulation factors such as source rocks,traps,migration and preservation,as well as their differential control modes are analyzed and summarized.The Grade II structural transition zone mainly controls the dominant accumulation direction of hydrocarbon source rocks and oil and gas in deep layers,determining the favorable enrichment areas on a large scale.The Grade III structural transition zone mainly controls the formation of large scale traps,determining the location of oil and gas accumulation.The Grade IV structural transition zone mainly controls the migration and preservation of oil and gas,determining the dominant enrichment fault blocks of oil and gas.The research results have strong reference significance for oil and gas exploration in similar areas of the sea.