厄瓜多尔奥连特盆地是南美安第斯前陆盆地群中最重要的含油气盆地之一,上白垩统Napo组Main-M1亚段是目前勘探开发的主力层位之一,其沉积环境一直存在争议,沉积体系及演化过程尚不明确。本研究基于岩心、测录井等资 main-M1亚段沉积时期的主要沉积微相类型、沉积体系及演化过程进行了研究。结果表明: 研究区位于水动力条件复杂的海陆过渡环境,在东部发育潮汐三角洲,向西部逐渐过渡为浅海陆棚环境; 研究区内主要识别出水下分流河道、水下分流河道间、潮汐水道、潮汐沙坝、潮汐沙坪、潮汐水道间等8类沉积微相。 根据岩电特征, main-M1亚段划分为3个小层。通过分析3个小层的岩性组合演变特征 main-M1亚段沉积时间内,Auca古隆起逐渐形成,同时挠曲作用导致相对海平面升高,3个小层在垂向上呈水体逐渐变深、潮汐三角洲前缘不断向陆地退缩的形式; 基于对Main-M1亚段沉积时期潮汐三角洲—浅海陆棚沉积体系的重建,研究区东部的水下分流河道及前缘沙坝也被认为具有一定的岩性油气藏勘探潜力。

The Oriente Basin of Ecuador is one of the most important hydrocarbon-bearing basins in the Andean Foreland Basin Group of South America. The Main-M1 submember of the Upper Cretaceous Napo Formation,as one of the main exploration and developement formations,has been controversial in terms of its depositional environment,and its depositional system and evolutionary process remain unclear. Based on core,well logs and borehole cuttings,the main sedimentary microfacies types,depositional systems and evolutionary processes of Main-M1 submember were investigated in this study. The results show that the study area is located in a marine-continental transition environment with complex hydrodynamic conditions,and a tidal delta develops in the east,which gradually transitions into a shallow shelf environment in the west. In the study area,eight types of sedimentary microfaces including subaqueous distributary channel,subaqueous inter-channel,tidal channel,tidal sand bar,tidal flat,and tidal inter-channel,are recognized. According to the petrographic characteristics,the Main-M1 submember is further divided into three sub-layers. By analyzing the lithological assemblages of the three submembers,it is determined that during depositional of the Main-M1 submember,the Auca paleoarchelon gradually formed,and meanwhile the relative sea level of the study area rose due to the flexural effect. The three submembers overall show a gradual deepening upward trend and the tidal delta continuously retreated landward. Based on the reconstruction of the tidal delta-shelf depositional system during deposition of the Main-M1 submember,the subaqueous distributary channel and the leading sand bar in the eastern part of the study area are considered to have certain exploration potential for lithologic reservoirs.