鄂尔多斯盆地环江地区侏罗系延安组古地貌特征与油气成藏规律

Paleogeomorphology characteristics and hydrocarbon accumulation law of Jurassic Yan’an Formation in Huanjiang area in Ordos Basin

鄂尔多斯盆地侏罗系延安组广泛发育古地貌油藏,古地貌对该类型油藏的运聚成藏及分布具有重要影响。以印模法恢复该地区的古地貌形态,并结合试油试采资料、油藏剖面等分析古地貌对环江地区延安组下部成藏的控制作用。研究认为:环江地区主要发育古河谷、支河谷、高地、斜坡、河间丘5种古地貌单元;古地貌对研究区侏罗系下部油藏的控制作用主要体现在古地貌的起伏形态直接控制沉积相的展布,古地貌背景下的低幅度鼻隆构造是油藏的富集空间,延长组顶部的不整合面与古河道厚砂带为油气运移提供有利通道;环江地区侏罗系延10油层组发育斜坡成藏和支河谷成藏2种成藏模式。研究成果为环江地区侏罗系油气勘探提供了地质依据。

Paleogeomorphology oilfield is widely developed in Jurassic Yan’an Formation in Ordos Basin.Paleogeomorphology has important influence on migration,accumulation and distribution of this type of reservoir.Paleogeomorphology of Huanjiang area is restored by moldic method,and controlling effect of paleogeomorphology on accumulation of lower Yan’an Formation is analyzed by combining with well testing and production test data and reservoir section.The research shows that Huanjiang area is mainly composed of 5 paleogeomorphic units including valley,branch valley,paleohigh,slope and interchannel mound.Influences of paleogeomorphology on lower Jurassic reservoirs are mainly sedimentary facies extension directly controlled by relief of paleogeomorphology,low amplitude nose structure under background of paleogeomorphology being the enrichment space of reservoir,and unconformity at the top of Yanchang Formation and thick sand belts of paleo-channel providing favorable pathway for hydrocarbon migration.2 types of accumulation patterns developed in Jurassic Yan 10 layers including slope accumulation and branch valley accumulation.The research results provide geological basis for Jurassic oil and gas exploration in Huanjiang area.