巴音都兰凹陷巴66扇体沉积特征及控制因素

为了确定巴音都兰凹陷巴66扇体的成因类型和特征,利用岩心、岩石薄片、测井和三维地震等资料对其沉积特征、控制因素、沉积模式等进行了系统性研究。研究表明,巴66扇体为间歇性洪流经短距离搬运后快速沉积而成的扇三角洲,扇体水动力以重力驱动为主导,平面延伸短,内部分异差,整体呈朵状,具有“小平原-大前缘”的相带特点。扇体主要特征为:岩石成分成熟度和结构成熟度均低,以杂乱块状砂砾岩为典型岩相;测井曲线具有高幅、齿化、多突变接触等形态特征;地震相包含乱岗状、前积状、席状等类型,并据此划分出平原,前缘(近、中、远端),前三角洲或湖相等相带。综合分析认为斜坡带之所以发育扇三角洲主要受凹陷背景环境、古地貌控制:①隆起物源、盆窄(无宽缓斜坡)、湖阔等背景条件保证了物源供给以及短距离搬运的条件;②凹槽古地貌提供了砂体发育空间,坡折带改变了坡度,分割了可容纳空间并控制了相带分布,水下低凸起影响了扇体平面形态展布,最终构建了巴66扇体的沉积模式。

Sedimentary characteristics and controlling factors of the Ba 66 fan in Bayindulan Sag

Based on the data of core, thin sections, logging and 3D seismic, the sedimentary characteristics, controlling factors and sedimentary model of Ba 66 fan are studied systematically to determine the types and characteristics of the fan.The study shows that Ba 66 fan is a fan delta rapidly deposited by torrent after short-distance transport, and the hydrodynamic force of the fan is mainly driven by gravity.The extension distance of the fan is short on the plane.The fan is lobate as a whole and has the facies feature of " large plain, small front".The main characteristics of the fan are as follows: the maturity of the rock is low, and the disorderly massive glutenite is the typical lithofacies; The fan has the logging characteristics of high amplitude, odonation and abrupt contact.The fan bodies can be divided into plain, front (including proximal, middle and distal), pre-delta or lacustrine facies according to the characteristics of seismic facies, such as random hills, front accumulations, and sheets.The analysis shows that the development of fan delta in the slope belt is mainly controlled by the background environment of the depression and paleogeomorphology: ①The background conditions such as source of uplift area, narrow lake basin (no gentle slope) and wide lake surface ensure the supply of source and short-distance transportation conditions for the formation of fan delta; ②Grooves provide space for sand body development. The slope break changes the slope, divides the accommodation space, and controls the distribution of facies, and the low bulge under the water affects the plane distribution of the fan.Finally, the deposition model of Ba 66 fan is constructed.