大庆萨尔图油田北部萨一油层组沉积微相再认识

 大庆萨尔图油田北部萨尔图油层组是重要的含油层段。以前一直认为萨一油层组是三角洲外前缘亚相,发育大面积的席状砂,水下分流河道砂体不发育。随着勘探开发的深入和井网的加密,本文根据岩心、测井曲线等特征认为,萨一油层组具有明显水下分流河道特征,为三角洲内前缘亚相；主要发育水下分流河道微相、席状砂间微相、席内缘微相、席外缘微相。水下分流河道微相是区分三角洲内、外前缘亚相的重要标志,本文通过分析研究区沉积特征,建立测井相模式,给出了萨一油层组平面微相中典型水下分流河道的特征。水下分流河道砂体与外前缘席状砂在砂体形态、规模、分布面积、连续状况及储油物性等方面具有非常大的差别,在开发方案及开发效果上具有不同特征。这一认识上的转变将为萨一油层组的开发提供重要的地质依据,为油田剩余油评价提供一个新的增长点。

Study of Sedimentary Microfacies of Sayi Reservoir in North Saertu Oil Field

Sayi Reservoir is one of the most important oil layers in the northern Saertu oil field. For a long time, Sayi Reservoir used to be considered to belong to external delta front microfacies with the front sheet sand well developed, but the underwater distributary channel has not been found. With a further exploration and development and well pattern infilling, the distinct underwater distributary channels are found so it is established that Sayi Reservoir belongs to inner delta front microfacies, which include the underwater distributary channel, the front sheet sand, the inner front sheet sand and the external delta front microfacies. Because the underwater distributary channel is an important mark for identifying external and inner delta front microfacies, the typical underwater distributary channel is recognized from the sedimentary facies maps of Sayi Reservoir through analyzing deposition character and establishing logging facies models. The underwater distributary channel sand and the front sheet sand are distinct in sand shape, scale, distribution area, continuous condition and physical property, which decide the development plan and effect. This study can offer not only a new viewpoint for the remaining oil evaluation but also an important geologic evidence for Sayi Reservoir.