大庆油田肇35区块葡萄花油层沉积微相分布演化规律及有利相带预测

肇35区块是大庆宋芳屯油田新开发的区块,葡萄花油层为主力勘探层位。综合各类地质数据及沉积相分析,认为研究区主要发育三角洲前缘和浅湖两种沉积相类型,进一步划分为水下分流河道、河口坝、席状砂、水下分流间湾和浅湖泥岩等微相类型,建立了相应的测井相模板。垂向上,河口坝在葡上段较发育,砂岩分选较好,PI2小层为主要含油层位;水下分流河道在葡下段发育良好,PI51、PI52和PI7小层为主要含油层位。平面上,研究区主要以西北部和北部物源为主,砂体呈现西北厚、东南薄的分布特点。水下分流河道呈树枝状交叉合并,规模较大,沿河道延伸方向连续性好;河道末端及两侧发育片状、席状砂,厚度较薄,连续性好;河口坝砂体主要分布在河道末端,呈透镜状展布,规模较小。结合各沉积微相含油性、物性特征分析,在研究区预测了3类有利相带,其中水下分流河道砂体为Ⅰ类有利相带区,在研究区分布面积较大;河口坝砂体为Ⅱ类有利相带区,在研究区分布面积较小且分散;席状砂为Ⅲ类有利相带区,仅在研究区南部发育。

Distribution and Evolution of Sedimentary Microfacies and Prediction for Favorable Facies Zones of Putaohua Reservoir in Block Zhao 35, Daqing Oilfield

Block Zhao 35 is a newly developed area of Songfangtun oilfield in Daqing,in which the main target horizon is Putaohua reservoir.According to various geological data and sedimentary facies analysis,it is recognized that delta front and shallow lake are main depositional facies in the study area,which are further divided into underwater distributary channel,mouth bar,sheet sand,interdistributary bay and shallow lake mudstone.A logging facies template was established.Mouth bar developed well in upper of Putaohua reservoir,and in which Layer PI2 was the main oil layer.Underwater distributary channel developed well in lower of Putaohua reservoir,and in which Layers PI51,PI52 and PI7 were the main oil layers.The deposits in the study area mainly came from northwest and north,and the sand body is thicker in the northwest than in the southeast.Underwater distributary channel was branched,and characterized by excellent connectivity along the channel direction.Sheet sand was thin and continually developed around the channel.Mouth bar distributed as lens at the end of the channel.Based on comprehensive study,three types of favorable facies zones were divided.TypeⅠis the underwater distributary channel which was distributed large in the study area;Type Ⅱis the mouth bar which was small and dispersed,Type Ⅲis sheet sand which only developed in south of the study area.