徐家围子断陷沙河子组烃源岩形成古环境及主控因素  

Paleoenvironment and Main Controlling Factors of Source Rocks in the Shahezi Formation,Xujiaweizi Fault Depression

作　　者：孙立东[1] 杨亮[1] 李笑梅[1] 周翔[1] 胡博[1] 蔡壮 杜影 SUN LiDong;YANG Liang;LI XiaoMei;ZHOU Xiang;HU Bo;CAI Zhuang;DU Ying(Exploration and Production Research Institute,Daqing Oilfield,CNPC,Daqing,Heilongjiang 163712,China)

机构地区：[1]中国石油大庆油田勘探开发研究院,黑龙江大庆163712

出　　处：《沉积学报》2024年第5期1753-1764,共12页Acta Sedimentologica Sinica

基　　金：国家科技重大专项(2016ZX05001-002);中国石油集团公司前瞻性基础性重大科技项目(2021DJ0205)。

摘　　要：【目的】明确沙河子组优质烃源岩形成的主控因素,为松辽盆地深层天然气勘探方向优选提供地质依据。【方法】综合利用岩心、有机地球化学和元素地球化学等多种资料,系统研究沙河子组沉积环境和水体环境,明确了断裂活动、沉积相和古沉积环境对烃源岩有机质丰度、类型的控制作用。【结果】沙河子组发育暗色泥岩和煤岩两种类型烃源岩,沙Ⅰ段沉积期断裂活动强,水体相对局限、深度大,形成的“深水窄盆”盐度高、还原性好,以半深湖相泥岩为主,沙Ⅱ段时断裂活动弱,湖盆面积达到最大,形成的“浅水宽盆”盐度低、还原性变差,烃源岩以滨浅湖相煤岩为主。【结论】断裂活动在下降盘为泥岩堆积提供可容纳空间,控制了泥岩厚度;沉积环境影响有机质输入,决定了泥岩有机质类型和煤岩分布;由古盐度、古水深和氧化还原组成的古沉积环境影响有机质的富集和保存,是导致现今烃源岩质量差异的主要原因。[Objective]The study make clear the main controlling factors of source rock in Shahezi Formation,and provides geologic basis for the optimal selection of gas exploration in deep layer of Songliao Basin.[Methods]We recovered the sedimentary facies and water property in the Shahazi Formation,based on core observation,organic geochemical analysis,and major and trace elements testing,determining fault activity,sedimentary facies,water properties,and their control on source rock quality.[Results]Two source rock,mudstone and coal,were identified in the Shahezi Formation.The faulting during the deposition of the first source rock in the Shahezi Formation was characterized by strong activity,generating a small lake with great water depth,high salinity,and strong reducing properties.These source rocks were mudstone in a semi-deep lake.The faulting activity during the deposition of the second source rock gradually weakened,with the lake size increasing while water depth decreased.Salinity and reducibility were also weakened,and the coal in shore lake was the primary source rock.[Conclusions]The source rock type was mainly controlled by fault activity,sedimentary facies,and water properties.The downthrown side become important storage for mudstone because of the fault activity,which determined the thickness of mudstone.The sedimentary facies controlled the source rock type through their impact on organic matter import.The difference between paleoenvironments,which was determined by paleosalins,paleowater depth,and redox,is the key factor for the enrichment and preservation of organic matter,and the main controlling factor for source rock quality distribution.

关 键 词：微量元素 古环境 烃源岩 控制因素 沙河子组 

分 类 号：P618.13[天文地球—矿床学]