从前侏罗纪古地貌的角度论鄂尔多斯盆地靖边-鄂托克前旗地区油气成藏模式

摘要

Taking the number 9 oil reservoir of Yan'an Formation of Low Jurassic in Jingbiand tuokeqianqi area of Ordos Basin as an example, the palaeogeomorphic form of the pre-Jurassic was reconstructed by the mold method. The pre-Jurassic palaeogeomorphic framework is divided into upland, slope, river valley and mound. On that basis, the sedimentary fades belts distribution of the Fuxian Formation and the member 9 of the Lower Yan'an Formation and the pre-Jurassic palaeogeomorphic form control on the number 9 oil reservoirs were studied. The palaeogeomoyphic form had a certain control on the sedimentary facies belts distribution of the Fuxian Formation and the Lower Yan'an Formation of Lower Jurassic. The incision of the palaeo-valley not only decreases the distance between the Lower Yan'an Formation and the hydrocarbon source intervals, but also provides hydrocarbon migration pathways. If there exist profitable reservoirs combining with anticline and nose-up lifting structures, they can entrap hydrocarbons and form hydrocarbon reservoir. Two palaeogeornorphic reservoir models, I.e., slope-distributary channels combination model and mound-distributary channels combination model, are generalized, and the pre-Jurassic palaeogeomorphic slope and mound are the profitable areas for the exploration the member 9 of the Lower Yan'an Formation.%以陕北斜坡靖边-鄂托克前旗地区下侏罗统延安组延9油藏为例,运用印模法恢复了前侏罗纪古地貌形态.研究表明:研究区古地貌主要为高地、斜坡、河谷和河间丘4种古地貌单元.在此基础上分析了富县组+延10段沉积相带展布以及前侏罗纪古地貌对延9油藏的控制作用,认为古地貌景观基本控制了富县组及延安组下部的沉积相带展布.古河谷的下切作用不仅使延9段与延长组油源层的接触距离缩短,而且为油气运移提供了良好的通道,如遇到有利的储集体与背斜和鼻隆等构造,即可有机配置和富集成藏.存在两种成藏模式,即河间丘区-分流河道组合式和斜坡区-分流河道组合式.指出前侏罗纪古地貌斜坡区与河间丘区是下一步延9段油藏勘探的有利地区.