鄂尔多斯盆地怀远运动不整合面与深层天然气勘探领域  

The unconformity caused by the Huaiyuan movement and the deep natural gas exploration field in the Ordos Basin

作　　者：刘化清[1] 李相博[1] 马玉虎[1] 白云来[1] 黄军平[1] LIU Huaqing;LI Xiangbo;MA Yuhu;BAI Yunlai;HUANG Junping(Northwest Branch,PetroChina Research Institute of Petroleum Exploration&Development,Lanzhou,Gansu 730020,China)

机构地区：[1]中国石油勘探开发研究院西北分院,甘肃省兰州市730020

出　　处：《天然气工业》2021年第6期1-12,共12页Natural Gas Industry

基　　金：中国石油天然气股份有限公司科技项目“鄂尔多斯盆地下古生界油气成藏条件与目标评价”(编号:kt2018-04-03)。

摘　　要：为了明确鄂尔多斯盆地怀远运动不整合面的油气成藏意义及勘探前景,基于前人的研究成果,通过野外露头/岩心观察、测井资料分析,结合二维、新三维地震资料解释成果,研究了该盆地不整合面的时空分布特点、结构面特征及其与油气成藏的关系。研究结果表明:①该不整合面主要形成于早奥陶世弗洛期,广泛存在于中下奥陶统马家沟组下伏的贾汪组底部、三山子组顶部;相关构造作用持续时间约30 Myr;②盆地边部不整合面之上主要发育厚度不超过1 m的底砾岩、砂岩,盆地腹部不整合面之上主要发育薄层泥岩、泥质云(灰)岩及泥灰岩;③不整合面具有3层结构特征,自上而下为底砾岩层、古土壤层、碳酸盐岩风化及半风化层,其中碳酸盐岩风化及半风化层厚度介于20~90 m,发育溶蚀缝洞,可形成优质储层;④不整合面发育一系列大型沟谷地貌,下切下奥陶统-上寒武统;⑤不整合面可作为良好的烃类运移通道,并且在鄂尔多斯盆地古隆起范围与加里东运动不整合面汇合,有利于该盆地西侧地区不同来源的烃类再次沿其向东运移并聚集成藏。结论认为,与怀远运动不整合面相关的下古生界深层有望成为鄂尔多斯盆地一个重要的天然气勘探新领域。In order to clarify the hydrocarbon accumulation significance and exploration prospect of the unconformity caused by the Huaiyuan movement in the Ordos Basin,this paper studies the spatial distribution characteristics and structural surface characteristics of this unconformity and its relationships with hydrocarbon accumulation by observing field outcrops and cores and analyzing logging data,based on the previous research results and the interpretation results of 2D and new 3D seismic data.And the following research results are obtained.First,the unconformity was mainly formed in the Floian Age of Early Ordovician and widely occurs at the bottom of the Jiawang Formation and the top of the Sanshanzi Formation underlying the Majiagou Formation of Middle-Lower Ordovician.And the related tectonism lasts 30 Myr.Second,basal conglomerate and sandstone less than 1 m in thickness are developed above the unconformity at the edge of the basin,while thin mudstone,argillaceous dolomite(limestone)and marl are developed above the unconformity in the central part of the basin.Third,the unconformity structurally consists of three layers,including a basal conglomerate layer,a paleosoil layer and a fully-semi weathered carbonate layer from top to bottom,among which,the last one is 20-90 m in thickness with developed dissolution fractures and pores to form a quality reservoir.Fourth,the unconformity results in the development of a series of large valleys landforms,which incise the Lower Ordovician-Upper Cambrian.Fifth,the unconformity can act as a good channel for hydrocarbon migration,and it connects with the unconformity caused by the Caledonian movement within the paleo-uplift of the Ordos Basin,which is favorable for the re-migration of hydrocarbon of different sources in the west side of the basin eastwards to accumulate and form a gas reservoir.In conclusion,the deep Lower Paleozoic related to the Huaiyuan unconformity is expected to be an important natural gas exploration field in the Ordos Basin.

关 键 词：鄂尔多斯盆地 怀远运动 不整合面 天然气成藏 天然气勘探 深层 勘探区 

分 类 号：P618.13[天文地球—矿床学]