辽河西部凹陷古近系扇三角洲前缘沉积特征

Sedimentary Characterization of Paleogene Period,Fan Delta Front,Liaohe Western Depression

针对研究区砂体成因机制不明确的问题,对辽河西部凹陷A区块于楼油层沉积体系进行了分析。应用丰富的岩芯、测井及粒度等资料,对沉积相特征、平面展布及时空演化过程进行了详细描述。结果表明,研究区发育扇三角洲前缘亚相储层,可进一步划分为水下分流河道、河口砂坝、水下分流河道间砂、水下分流河道间泥及前缘席状砂5种微相。目的油层以水下分流河道沉积为主,呈条带状沿北西—南东向展布,整体上表现为基准面下降的水退旋回。从下至上,y_(24)~1小层表现为基准面上升后又下降的震荡过程,y_(23)~1小层表现为基准面上升的过程,而y_(12)~1小层表现为基准面下降的过程。储层非均质性受沉积展布与沉积演化的影响。通过对研究区沉积体系的精细解剖,为"相控建模"和进一步的剩余油分布研究提供了坚实的地质基础,为开发方式的调整提供了重要依据。

The sedimentary system of A reservoir in the Liaohe Western Depression was analyzed to clear up the uncertainty about the formation mechanism of the sand body in the study area.The characteristics of sedimentary facies,plane distribution,and the space-time evolution process are described in detail based on abundant data on the rock core logging and granularity.The results indicate that the fan-delta front subfacies reservoir developed in the study area can be divided into five microfacies,namely,the underwater distributary channel,distributary mouth bar,underwater distributary inter-channel sand,underwater distributary inter-channel mud,and frontal sheet sand.The underwater distributary channel is the main sedimentary microfacies and has a banded distribution in a northwest-southeast direction.This microfacies is affected by the water withdrawal cycle,with the base level descending generally.From bottom to top,the yI24sublayer shows a process of base level rise and fall,the yI23layer shows a process of base level rise,and the yI12layer shows a process of base level fall.The heterogeneity of the reservoir is controlled by the distribution of sediment,as well as evolution.Detailed research results of the sedimentary system provide a solid geological foundation for facies-controlled modeling and further study on the distribution of the remaining oil deposit.This information provides a critical basis for the adjustment of the development method.