松辽盆地双城区块扶余油层高分辨率层序格架下沉积相及砂体发育特征

Development and characteristics of sedimentary facies and sand-bodies of the Cretaceous Fuyu oil layer within high-resolution sequence framework,Shuangcheng Block,Songliao Basin

随着致密砂岩岩性油气藏勘探开发程度的深入,拗陷型湖盆河流—浅水三角洲储集层已经成为勘探开发重点。以松辽盆地北部双城区块扶余油层为研究对象,运用岩心、测井、录井以及地震资料,系统地开展高分辨率层序地层研究,识别出多级次基准面旋回界面,将双城区块扶余油层划分为2个长期基准面旋回和7个中期基准面旋回。在此基础之上,深入分析高分辨率层序地层格架下的河流—浅水三角洲沉积相及储集层砂体发育特征。研究表明:受长期基准面下降—上升的变化控制,垂向上,从MSC1到MSC7沉积充填响应呈现三角洲平原沉积—曲流河沉积—三角洲平原沉积—三角洲前缘沉积的特点,其岩性、沉积构造、旋回期次以及规模也随之具有明显变化;主要储集层砂体类型依次为分流河道、曲流河道、分流河道和水下分流河道,平面上的砂体呈条带状分布,顺物源方向由西南向东北砂地比逐渐变小,MSC4-MSC5时期砂体最为发育,储集层质量最好;在构造稳定拗陷湖盆背景下,湖平面升降是储集层砂体发育特征的主要控制因素。

As the degree of exploration and development in tight sandstone lithologic petroleum reservoir increases,meandering river-shallow water delta sandstones has become one of the main target areas for current exploration and development activities. The Cretaceous Fuyu oil layer in Shuangcheng block provides an interesting example to study high-resolution sequence stratigraphy in detail. Based on a combination of cores,well logging and seismic data,the boundaries of medium-term and long-term base-level controlled stratigraphic cycles were identified. Fuyu oil layer was divided into two long-term base-level cycles and seven medium-term base-level cycles. Furthermore,the development and characteristics of sedimentary facies and sand-bodies of meandering river-shallow river delta in high-resolution sequence framework were further investigated. The results show that when the long-term base-level showed a trend of rising followed by falling from MSC1 to MSC7,sedimentary facies switched from delta plain,meandering river,delta plain to delta front. The lithology,sedimentary structures,multi-cycles and scales of channel sandbodies changed accordingly. At the same time,the main types of channel sand-bodies changed from distributary channel,meandering river,distributary channel to subaqueous distributary channel vertically.Sand-bodies were dirtributed as ribbons,and the ratio between sandstone and strata thickness reduced gradually from the southwest source direction to northeast. From MSC4 to MSC5 period,high-quality reservoir sand-bodies were most developed. Under the background of depression lake basin with stable tectonic activities,the variation of lake level is considered the main control on the developent and characteristics of reservoir sand-bodies.