摘要
依据鄂尔多斯盆地古构造古地理背景、古水动力以及古气候条件,结合单井沉积相分析建立了马家沟组障壁潟湖沉积相模式,该模式分三个阶段即与海侵期相对应的以灰岩沉积为主的障壁潟湖沉积阶段(阶段Ⅰ)、与海退相对应的以灰岩夹蒸发岩沉积为主的障壁咸化潟湖沉积阶段(阶段Ⅱ)和与低海平面期对应的以膏岩盐沉积为主的障壁膏盐湖沉积阶段(阶段Ⅲ)。文章进一步分析并总结了在上述模式下各阶段储层的发育规律,认为阶段Ⅰ中的障壁滩相和阶段Ⅱ中的障壁滩及潟湖边缘坪有利于储层的发育,并指出了马家沟组储层主要为岩溶型储层,分布于马一、马三和马五的顶部。
Lower Ordovician Majiagou Formation is composed of six members in which Ma1,Ma3 and Ma5 are evaporate including dolomite,anhydrite and salt and Ma2,Ma4,Ma6 are limestone with dolomite in Ordos Basin.Majiagou Formation is formed by cyclic sedimentation by intermeshed evaporite and carbonate.Upwarps around the basin and a downwarp in the centre of the basin constitute the Early-Ordovician Palaeogeomorphologic pattern.Upwarps as underwater barriers led to exchange limitation between lagoon and exterior sea and weakness of lagoon hydrodynamic force during high sea level stage.During low sea level stage,upwarps resulted in the entire isolation between lagoon and exterior sea.Owing to the strong evaporation,lagoon level was greatly lower than exterior sea level.So lagoon margin flat was partly exposed to atmosphere and the deep sag in the centre of the basin was covered by concentrated bittern. Analysis of single well and well tie sedimentary facies demonstrates the depositional setting from Ma1 and Ma2 member is composed of two integrating cycles from transgression to regression due to sea water invasion from the east and southeast of the basin.Ma3 member is mainly composed of regressive deposition owing to the rapid extensive transgression in the early Ma3 stage.North China sea,Qilian oceanic trough and Qinling oceanic trough formed a united basin and the centre uplift zone was developed to a platform margin,the west of the centre uplift zone was developed to a basin and a slope and the east of the centre uplift zone was developed to a broad lagoon during the biggest sea water invasion in Ma4 stage.Ordos Basin was isolated from exterior sea and the salty lagoon was changed to a salt lake gradually during Ma5 stage owing to sea level descend and barrier of the centre uplift zone.In Ma6 stage the Basin was changed to a broad lagoon. Based on the pioneer research of paleo-structure,paleo-geography,paleo-hydrodynamic as well as paleo-climate,a new model-barrier-lagoon sedimentary model of Majiagou Formation is developed.The model includes three phases during transgression to high sea level（phaseⅠ）,carbonate deposits in broad barrier-lagoon,and mixed carbonate /evaporate succession in concentrated lagoon during regression（phaseⅡ）,and anhydrite and salt in saline during low sea level（phaseⅢ）. And two main types of carbonate reservoir including the dolomite reservoir in relation to karstification and the crystallization dolomite reservoir in connection with dolomitization are discovered in this paper.The authors further analyze the carbonate reservoir distribution law within the mentioned model,conclude that beach-flat of platform edge of the model（phase Ⅰ）and lagoon margin flat of phaseⅡ are favorable for reservoir growth and point out that the reservoir of Majiagou Formation is karst type and is mainly distributed on the top of Ma5,Ma3 and Ma1 Formation.Anhydrite and salt of phase Ⅲ are important seal rock.
出处
《沉积学报》
CAS
CSCD
北大核心
2011年第1期64-71,共8页
Acta Sedimentologica Sinica
基金
国家科技重大专项资助(编号:2008ZX05004-002)资助
关键词
鄂尔多斯盆地
马家沟组
障壁潟湖
沉积相模式
储层预测
Ordos Basin； Majiagou Formation； barrier lagoon； sedimentary model； reservoir prediction
