三肇凹陷扶余油层沉积特征及油气成藏模式

Sedimentary Characteristics and Hydrocarbon Accumulation Model of Fuyu Reservoir in Sanzhao Depressiom

松辽盆地三肇凹陷扶余油层为典型大型凹陷向斜区油气倒灌式成藏,应用高分辨率层序地层学原理,通过对各级基准面旋回结构、叠加样式的沉积动力学分析,利用11口井岩心和825口井测井曲线,把扶余油层划分为1个长期基准面旋回、4个中期基准面旋回、35个短期基准面旋回,认为扶余油层为先水退后水进的层序格架。短期旋回内储层沉积特征表明:扶余油层主要受北部拜泉—青冈和西南保康物源影响,两物源在徐家围子附近交汇后向东流出;扶余油层发育典型的河控浅水三角洲沉积体系,微相类型以分流河道为主。断层分析表明,T2断层具有平面密集成带、剖面'似花状'组合特征,且油气成藏期活动的油源断层多为继承性活动的密集带边界断层。明水组末期青山口组源岩生成的油气在超压作用下,沿开启的断层密集带边界断层幕式下排后通过河道砂体短距离侧向运移,在两侧上升盘地垒或断阶圈闭中聚集成藏;而断层密集带内多为地堑式组合,不利于油气聚集;在成藏模式指导下刻画出47个油气富集目标区,预测石油地质储量0.5亿t。

Fuyu reservoir of Sanzhao depression in Songliao basin is a typical down migration accumulation in syncline of large depressions. Applying the high-resolution sequence stratigraphy theory,analyzing different scales of base-level cycles and stacking patterns with sediment dynamics, based on 11 well cores and loggings of 825 wells,Fuyu reservoir were classified into 1 long-term level cycle,4 midterm level cycles and 35 short-term level cycles,proposed sequence framework that is regression followed by transgression. The sediment characteristic of short-cycle reservoir suggests that Fuyu reservoir is mainly affected by two sources, the northern Baiquan -Qinggang and the southwest Baokang, which meet around Xujiaweizi then flow to the east, Fuyu reservoir develops typical sedimental system of shallow water delta that controlled by rivers,and distributary channels are main microfacies type. Faults analysis shows that T2 has the features of intensive belts in plane and flower-like in section,and the oil-sources faults that petroleum accumulation period successively active are main boundary faults of concentrated ribbons. At the end of Mingshui Formation, hydrocarbon generated by Qingshankou source rocks migrates down along open boundary faults of concentrated ribbons at the force of overpressure,then short lateral-migration along channel sand, finally accumulated on horsts and fault terraces of the uplifted side of both sides, but in the intensive fault zone, most of the units are grabens, so it is not good for accumulation. Based on of the accumulation model,47 hydrocarbon rich target area were depicted,50 million tons of geological reserves are submitted,which gave a clear direction in the exploration and development for the Fuyu Formation in Songliao basin.