辽河西部凹陷欢喜岭地区沙河街组沉积特征及其演化

在充分利用岩芯、录井、测井等相关资料的基础上,总结辽河西部凹陷欢喜岭地区沙河街组的沉积相类型,首次提出运用相对单因素综合作图法来绘制各沉积时期的沉积相平面图,综合探讨了沙河街组的沉积特征及空间沉积演化规律。结果表明:欢喜岭地区沙河街组主要发育扇三角洲相、湖底扇相、滨浅湖相和半深湖—深湖相4种沉积相类型;扇三角洲砂体为欢喜岭地区主要的储集砂体,在沙河街组沉积时期持续发育,主要发育于盆地缓坡部位;湖底扇主要发育在SQ3和SQ4沉积时期,主要分布在广阔的半深湖—深湖环境内;相对单因素综合作图法可以弥补传统的沉积相作图方法精度低的不足;沙河街组的沉积相垂向演化的旋回性明显,自下而上分为两个水进旋回,分别为SQ2～SQ5沉积时期和SQ6、SQ7沉积时期;每个水进旋回初期,盆地构造活动相对较弱,水体较浅,扇三角洲沉积广泛发育,湖底扇沉积规模较小;每个水进旋回中后期,盆地构造活动强度大,湖盆水体加深,扇三角洲规模减小,而湖底扇沉积规模明显扩大,形成非常有利的储集砂体,在研究区广泛发育,是研究区深层勘探的有利目标之一。

Sedimentary Characteristics and Evolution of Shahejie Formation of Huanxiling Area in the West Depression,Liaohe Basin

Based on the data of core, drilling and logging, types of sedimentary facies of Shahejie Formation of Huanxiling Area in the west depression, Liaohe Basin were summarized; the relative single-factor comprehensive mapping method was firstly proposed to draw the plan of sedimentary facies in different sedimentary periods; sedimentary characteristics and evolution of Shahejie Formation were discussed. The results showed that there were 4 types of sedimentary facies, which included fan delta, sub-lacustrine fan, littoral-shallow lake and semi-deep and deep lakes, in Shahejie Formation of Huanxiling Area; fan delta sand body, which mainly developed in the gentle slope of the basin during the sedimentary period of Shahejie Formation, was the main reservoir sand body in Huanxiling Area; sub-lacustrine fan, which mainly distributed in the broad semi-deep and deep lakes environments, mainly developed during the sedimentary period of SQ3 and SQ4; compared with the traditional mapping method, the relative single-factor comprehensive mapping method could improve the precision significantly; cyclicity of vertical evolution of sedimentary facies in Shahejie Formation could be obviously divided into two transgressive cycles with the sedimentary periods of SQ2-SQ4 and the periods of SQ6 and SQ7, respectively; at the early stage of transgressive cycle, basin tectonic activity was relatively weak, and the depth of water was relatively shallow, so fan delta sedimentary widely developed, and sub-lacustrine fan sedimentary decreased; at the middle and late stages of transgressive cycle, basin tectonic activity was relatively strong, and the water deepened, so fan delta sedimentary decreased, and sub-lacustrine fan sedimentary increased significantly, and then the favorable reservoir sand body, which formed and developed widely, was one of the favorable reservoirs for the deep exploration in the west depression, Liaohe Basin.