乌夏南斜坡克上组沉积微相及演化特征研究

为明确乌夏南斜坡克上组沉积微相和演化特征,通过岩心和薄片观察,结合测井、录井资料,分析岩石类型、沉积构造和测井相等沉积相识别标志,建立沉积微相模式,探讨沉积演化特征。结果表明:乌夏南斜坡克上组岩性为砂砾岩、含砾中-细砂岩、细砂岩、泥岩,包括粒序层理、平行层理、块状层理、冲刷充填沉积构造;属于三角洲沉积体系,物源来自于北部,河道为北东—南西走向。沉积微相包括水下分流河道、河口坝、分流间湾、滨浅湖、席状砂和决口扇。中三叠世早期,斜坡西北部强烈隆起,存在2～3条主河道,河口坝发育,形成2套厚砂岩、砂砾岩优势储层;中三叠世晚期,发育滨湖相沉积微相,水下分流河道和河口坝微相分布面积减小;克上组水下分流河道及河口坝等优势沉积勘探潜力较大,面积为50～110 km²。此次研究深化了准噶尔盆地乌夏南斜坡重点层系的沉积微相,明确了有利沉积砂体的展布范围,可为下步细化油气勘探开发部署提供借鉴。

Sedimentary Microfacies and Evolution Characteristics of Keshang Formation in Wuxia South Slope

In order to clarify the sedimentary microfacies and evolution characteristics of the Keshang Formation in Wuxia south slope, through core and thin section observation, combined with well logging and mud logging data, the identification marks of rock types, sedimentary structure and logging facies were analyzed, sedimentary microfacies model was established, and sedimentary evolution characteristics were discussed. The research results show that the lithology of the Keshang Formation in Wuxia south slope is composed of glutenite, pebbled medium-fine sandstone, fine sandstone and mudstone, including grain sequence bedding, parallel bedding, massive bedding and scouring filling sedimentary structure. It belongs to delta depositional system, its provenance came from the north, and its channels were NE-SW trending. Sedimentary microfacies include underwater distributary channel, mouth bar, interdistributory bay, shore-shallow lake, sheet sand and crevasse splay. During the early stage of the Middle Triassic, the northwest part of the slope was strongly uplifted, and there were 2-3 main channels and well-developed mouth bars, forming two sets of thick sandstone and glutenite reservoirs. During the late stage of the Middle Triassic, shore lake sedimentary microfacies was developed, the distribution areas of underwater distributary channel and mouth bar microfacies decreased. There is a great potential for exploration of underwater distributary channels and mouth bars of the Keshang Formation, covering an area of 50-110 km². This study deepens cognitions on the sedimentary microfacies of the key strata in the Wuxia south slope of the Junggar Basin, and defines the distribution range of favorable sedimentary sand bodies, which can provide reference for further refining oil and gas exploration and development deployment.