松辽盆地古龙南凹陷葡萄花油层储层单砂层沉积微相研究及有利砂体预测

Single-sandstone-layer sedimentary microfacies and favorable sandbody prediction of Putaohua reservoir in south Gulong sag,Songliao Basin

根据研究区单井沉积微相、单砂层的厚度、砂地比等空间分布特征,研究其沉积微相空间展布规律。古龙南凹陷葡萄花油层储层发育水下分流河道、分流河道间、河口坝、前缘席状砂、前三角洲泥和浅湖泥沉积微相,物源主要来自于北部和西部。研究区河口坝发育较少,前缘席状砂分布宽阔,为典型的浅水三角洲沉积。从下向上,湖平面下降,各砂层砂岩的厚度、粒度均有增加的趋势,形成了进积式地层序列。且从下向上三角洲前缘席状砂分布范围扩大,席状砂体形状由下部的东西向条带状向上转化为大面积席状,判定其物源早期以北部物源为主,晚期以西部物源为主。凹陷中心早期条带状砂层及晚期片状大型透镜体砂层为有利砂体。

Based on characteristics and spatial distribution patterns of single-well sedimentary microfacies,gross-to-net ratio and thickness of single sandstone layer of the Putaohua reservoir in south Gulong sag of Songliao Basin,we studied the spatial distribution pattern of sedimentary microfacies and predicted favorable sand bodies. The Putaohua reservoir consists of various sedimentary microfacies including distributary channels,interdistributary channels,mouth bars,front sheet sand,front delta mud and shallow lake mud,with sediments mainly sourced from the north and the west. It is of a typical shallow-delta deposit characterized by poor-developed mouth bars but wide front sheet sandstones. From bottom to top,the thickness and the grain size of sandstone layers increase with the lake level dropping,indicating a progradational stratigraphic sequence. In addition,the areas of front sheet sandstones also enlarge upwards and their shapes change from EWtrending strips in the lower part into large sheets in the upper part. The provenance is mainly located in the north at the early stage,while is mainly located in the west at the late stage. The early banded sand layers and the later large sheetshape lenticular sand layers at the center of the sag are favorable sandbodies.