鄂尔多斯盆地南部彬长区块延长组长6-长7段深水重力流沉积特征分析  

Characteristic analysis of deep water gravity flow sediments in Ch6-Ch7 Section of Yanchang Formation in the Binchang Block,southern Ordos Basin,China

作　　者：萧高健 骆杨[1] 刘洪平 Xiao Gaojian;Luo Yang;Liu Hongping(Key Laboratory of Tectonics and Petroleum Resources,China University of Geosciences(Wuhan),Wuhan 430074,China;School of Geosciences,Yangtze University,Wuhan 430100,China)

机构地区：[1]中国地质大学(武汉)构造与油气资源教育部重点实验室,武汉430074 [2]长江大学地球科学学院,武汉430100

出　　处：《地质科技通报》2023年第2期69-82,共14页Bulletin of Geological Science and Technology

基　　金：国家自然科学基金项目(41902147)。

摘　　要：鄂尔多斯盆地南部彬长区块的延长组长6-长7段发育厚层无沉积构造的块状砂岩,具有良好的油气显示和开发效益,然而关于该套砂岩的形成机制尚不清晰。确定长6-长7段砂岩的沉积相及沉积模式,对于该套低渗砂岩储层“甜点”形成机制的理解,“甜点”分布模式的预测,以及后续勘探开发都具有重要的指导意义。对彬长区块36口取心井的长6-长7段1024 m长的岩心进行了沉积学特征描述,结合粒度分析资料及地质制图分析,确定了该套厚层砂岩的沉积相及沉积模式。结果表明:鄂尔多斯盆地南部彬长区块的延长组长6-长7段砂岩共发育15种岩相和3种主要沉积微相类型,即:砂质碎屑流、浊积岩和震积滑塌岩微相,以及它们在空间上的3类组合关系。其深水重力流沉积模式可以概括为扇根(坡折带斜坡上半部分)的震积滑塌相-砂质碎屑流亚相(沉积组合)、扇中(斜坡中下部位-坡脚)的砂质碎屑流-浊积岩沉积亚相(沉积组合)和扇端(坡脚-盆底)浊积砂等亚相(沉积组合)。通过对彬长区块延长组长6-长7段发育的致密砂岩沉积特征的分析与讨论,确定了该厚层块状砂岩的主要沉积相及沉积微相的特征及分布,为致密砂岩储层的高效开发及“甜点”预测提供了科学依据与良好借鉴。Massive sandstone without sedimentary structure is developed in the Ch6-Ch7 Section of Yanchang Formation in the Binchang Block,Southern Ordos Basin,which has a good oil and gas show,good productivities and good exploration and development prospect.However,the formation mechanism of the sandstone is still in dispute.It is of great significance to determine the sedimentary facies and sedimentary model of the sandstone in Ch6-Ch7 Section in order to analyze the formation mechanism of sweet spot in the low permeability sandstone reservoirs,to predict the sweet spot distribution model and guide the subsequent exploration and development.In this paper,15 lithofacies and 3 main types of sedimentary microfacies,namely,sandy debris flow,turbidite and seismite slump microfacies,have been identified by using a large amount of core sedimentary description data,grain size analysis data and geological mapping analysis,and these three kinds of sedimentary assemblies in space.The deep water gravity flow deposition model in the Ch6-Ch7 Section can be summarized as the sublacustrine fan model and can be divided into three subfacies or assemblies:the upper fan subfacies dominated by the assembly of seismite-slump and sandy debris flow,the mid-fan subfacies dominated by the assembly of the sand debris flow-turbidite microfacies and the lower-fan subfacies dominated by turbidite flow-basin plain microfacies assembly.

关 键 词：鄂尔多斯盆地 彬长区块 长6-长7段 砂质碎屑流 重力流沉积物 

分 类 号：P588.2[天文地球—岩石学]