鄂尔多斯盆地太原组砂体展布主控因素

Main controlling factors of Taiyuan Formation sand body distribution in Ordos Basin

太原组是鄂尔多斯盆地重要产气层之一,研究该层砂体展布的主控因素,对下一步油气的勘探与开发具有重要意义。利用岩心、野外剖面、测井曲线等资料,结合构造背景和层序地层等,在给出砂体展布的基础上,对鄂尔多斯盆地太原组砂体展布的主控因素进行了重点研究。结果表明:中央古隆起、物源方向、三角洲和海平面变化是太原组砂体展布的主要控制因素。太原期,已被海水淹没的中央古隆起依然控制了盆内的沉积格局,进而控制着砂坪、障壁岛等盆内中南部的砂体,主要沿其本部及两翼发育;盆地北升南降的构造格局使得北部的陆源碎屑源源不断地涌入盆内,致使三角洲沉积在盆地北部大面积发育,形成乌达-平罗区、前乌拉加汗区、伊金霍洛旗区和准格尔旗区等4个主要的砂体聚集区。相对庙沟期、毛儿沟期和斜道期3次海平面的下降,在太原组地层中相应地发育了局限性的桥头、上马兰和七里沟3套砂岩。

Taiyuan Formation is one of important gas pays in Ordos Basin.The research on the main controlling factors of sand body distribution has great practical significance for the exploration and development of hydrocarbon reservoirs.According to the data of core,outcrop and well logs,and combined with the tectonic setting and sequence stratigraphy,this paper studies the main controlling factors of Taiyuan Formation sand body distribution in Ordos Basin based on the given sand body distribution.Research shows that the Central Paleouplift,provenance direction,delta and sea level change are the main controlling factors.The Central Paleouplift which was submerged by sea water in Taiyuan period controlled the sedimentary pattern within the basin,and then it controlled the distribution of sand flat and barrier sand in the central and southern Ordos Basin.The sand body of central and southern basin mainly distributed in the central and both sides of Central Paleouplift.In Taiyuan period,the tectonic framework which uplifted in the north and declined in the south made the northern terrestrial detritus pour into the basin.Thus,the delta facies developed in the northern basin,forming four sand body areas,which were Wuda-Pingluo,Former Wulajiahan,Ejin Horo Banner and Junggar Banner.There were three sea level drops in Miaogou period,Mao′ergou period and Xiedao period.Relative to the sea level drop,the three sets of limiting sandstones such as Qiaotou,Shangmalan and Qiligou correspondingly developed in Taiyuan Formation.