Sedimentary filling evolution of small-scale lake basins during intensive faulting:an example from the Shahezi Formation of Songzhan region in Xujiaweizi fault depression,Songliao Basin

Cai Quansheng; Hu Mingyi; Hu Zhonggui; Deng Meng

doi:10.11743/ogg20170206

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Sedimentary filling evolution of small-scale lake basins during intensive faulting:an example from the Shahezi Formation of Songzhan region in Xujiaweizi fault depression,Songliao Basin
Vol. 38, Issue 2, Pages: 259-269(2017)
Online First：28 April 2017，

Published：2017
DOI： 10.11743/ogg20170206
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DOI：

Cai Quansheng, Hu Mingyi, Hu Zhonggui, et al. Sedimentary filling evolution of small-scale lake basins during intensive faulting:an example from the Shahezi Formation of Songzhan region in Xujiaweizi fault depression,Songliao Basin[J]. 2017, 38(2): 259-269. DOI： 10.11743/ogg20170206.

摘要

松辽盆地徐家围子断陷北部宋站地区属于小型断陷湖盆沉积区。最新钻井资料显示，该类型断陷盆地也具有较好的天然气勘探潜力，可作为大庆深层天然气勘探的重要接替领域。以徐家围子北部宋站地区沙河子组为研究对象，在总结对比前人研究成果的基础上，综合运用岩心、录井、常规测井以及三维地震资料对强烈断陷期小型湖盆的层序地层、沉积体系以及盆地充填演化规律进行了深入分析。研究认为，宋站地区沙河子组可划分为1个二级层序，4个三级层序。三级层序内部根据湖泛面又可分为低位体系域（LST）、湖侵体系域（TST）和高位体系域（HST）。在沉积过程中，沙河子组主要发育辫状河三角洲、扇三角洲、湖泊以及火山碎屑岩沉积等4种沉积相类型。研究区的沉积充填演化规律与大型的断陷盆地相比有所不同，表现为在强烈断陷早期，无论是在陡坡带还是在缓坡带，均以发育扇三角洲沉积为主；随着盆地范围的扩张，不同构造部位上的沉积相带的分异特征才逐渐显现。但湖泊相带受短轴物源供给的影响分布较为局限，常被分割成若干个小型滨浅湖沉积区，形成多个沉积中心，从而也导致了盆地不同区域沉积地层厚度差异极大的特征。据此，深入探讨了宋站地区沙河子组的沉积充填演化过程，提出了陆相小型窄断陷湖盆的沉积模式。

Abstract

The Songzhan region in northern Xujiaweizi Fault Depression of Songliao Basin is a small-scale faulted basin.The latest drilling data shows great gas potential in the basin and a possible replacement of the depleting deep gas zones in Daqing Oilfield.We chose the Shahezi Formation in the basin as a research object to analyze the stratigraphic sequences

sedimentary systems and filling-up history of small scale lake basins during intensive faulting based on previous studies as well as data of core

mud logging

conventional logging and 3D seismic survey.The result shows that the Shahezi Formation can be divided into one second-order sequence and four third-order sequences

with the latter being further subdivided into LST

TST and HST

according to lake flooding surfaces.Four kinds of sedimentary facies

including braided delta

fan delta

lacustrine and volcaniclastic facies

were recognized.The filling-up history of the Formation appears to be quite different from that of large-scale fault basins.Fan deltas dominated both steep and gentle slopes at the early stage of intensive faulting.And zonation of sedimentary facies was only distinctive with the expansion of the basin.How-ever

they were segmented into many shore-shallow lacustrine sedimentary zones with multiple depocenters due to a sediment supply shortage in the short axis of the basin.As a result

the thickness of layers in the basin varies greatly from one area to another.We proposed in the paper a sedimentary model for the continental narrow faulted lake basins based on the study of the filling-up history of the Shahezi Formation.