末端分流河道-河口坝三维地震表征及演化——以松辽盆地古龙凹陷英79井区为例  

3D seismic characterization and evolution of terminal distributary channel-mouth bar:a case study of Well Ying79 in Gulong sag,Songliao Basin

作　　者：李磊[1,2] 许璐[1,2] 刘豪[3] 谭卓 唐文[1,2] 

机构地区：[1]西安石油大学地球科学与工程学院,陕西西安710065 [2]陕西省油气成藏地质学重点实验室,陕西西安710065 [3]中国地质大学海洋学院,北京100083 [4]中海油研究总院,北京100028

出　　处：《石油学报》2016年第11期1394-1402,共9页Acta Petrolei Sinica

基　　金：国家自然科学基金项目(No.41302147;No.41372118);陕西省教育厅项目(No.14JK1586);西安石油大学青年科技创新基金项目(2014BS25)资助

摘　　要：以松辽盆地古龙凹陷为例,基于钻、测井数据以及三维地震数据,开展末端分流河道-河口坝三维地震表征,对河口坝的动力学形成机制进行分析,并结合现代赣江三角洲河口坝沉积观测结果,总结分流河道-河口坝的沉积演化模式。古龙凹陷英79井区嫩江组三段可识别出3期分流河道-河口坝。从早期到晚期,泥岩颜色由黑灰色、深灰色到灰绿色转变以及河口坝厚度逐渐减薄(10m、8.5 m和4.25 m),显示湖水由深变浅(17 m、14 m和7 m)。反旋回、漏斗状的河口坝在地震剖面上呈透镜状、高频、中弱振幅反射特征。携带细粒沉积物的水流在末端分流河道出口处,以紊流射流方式注入湖水,形成第1级河口坝。当第1级河口坝坝顶水体较浅时,第1级河口坝停止生长。水流在第1级河口坝两侧分流并水道化,形成次一级分流河道-河口坝。由于水深、分流河道的河口宽度不同,在分流河道末端发育不同级次、不同规模、展布特征差异的河口坝群。河口坝宽度与河口坝长度呈线性正相关,而河口坝长度则与其对应的分流河道口的宽度呈指数相关。Taking Gulong sag in the Songliao Basin as an example, the seismic characterization of terminal distributary channel-mouth bar was performed based on drilling, well logging and 3D seismic data. In combination with observations of mouth bar deposits in the modern Ganjiang Delta, this paper analyzes the dynamic formation mechanism of mouth bar and summarizes the depositional evolve- ment model of distributary channel-mouth bar. Three stages of distributary channel-mouth bar can be identified in the 3rd Member of Nenjiang Formation in Well Ying79, Gulong sag. From the early stage to the late stage, mudstone color changes from black gray, dark gray to gray green and mouth bar gradually thins （10 m, 8.5 m and 4.25 m）, indicating the lake water from deep to shallow （17 m, 14 m and 7 m）. The documented mouth bars show coarsening upward trend and funnel-shaped well-log patterns, and display high frequency, middle-low amplitude, lenticular reflection configuration. Fine-grained sediment-laden flows debouch into the lake in a form of turbulent jet at the outlet of terminal distributary channel, thus forming the Level 1 mouth bar. When the water depth above the interpreted mouth bars is shallow enough, the Level 1 mouth bar stagnates. Water flows bifurcate at the two sides of Level 1 mouth bar and are channelized, thus forming the lower-level distributary channel-mouth bar. Due to the different water depth and width of distributary channel, mouth bar groups with various levels, scales and distribution characteristics are developed at the end of the distributary channel. The width of mouth bar is positively correlated with its length, and the length is exponentially related to the width of corresponding distributary channel.

关 键 词：末端分流河道 河口坝 紊流射流 动力学机制 古龙凹陷 松辽盆地 

分 类 号：P631.4[天文地球—地质矿产勘探]