中国断陷和坳陷湖盆高可容纳空间层序细粒重力流沉积及其页岩油意义  

Fine-grained gravity flow deposits and their significance for shale oil within high-accommodation sequences in faulted and down-warped lacustrine basins of China

作　　者：冯有良[1] 邹才能[1] 杨智[1] 蒋文琦 张天舒[1] 张洪[1] 刘畅[1] 王小妮 FENG Youliang;ZOU Caineng;YANG Zhi;JIANG Wenqi;ZHANG Tianshu;ZHANG Hong;LIU Chang;WANG Xiaoni(Research Institute of Petroleum Exploration and Development,PetroChina,Beijing 100083,China;College of Earth and Space Sciences,Peking University,Beijing 100871,China)

机构地区：[1]中国石油勘探开发研究院,北京100083 [2]北京大学地球与空间科学学院,北京100871

出　　处：《古地理学报》2024年第4期941-961,共21页Journal of Palaeogeography：Chinese Edition

基　　金：中国石油天然气股份有限公司科技部项目(编号:2021DJ18,2021DJ1802)资助。

摘　　要：重力流包括粗粒和细粒重力流,是深湖环境最重要的沉积类型之一,其中,细粒重力流能成为非常规页岩油的“甜点段”。研究该沉积在陆相湖盆层序格架中的分布规律,对页岩油“甜点段”的预测具有重要意义。作者通过对中国主要湖盆重力流发育与层序格架的系统对比研究发现,重力流沉积体系主要发育在高可容纳空间沉积层序中。断陷湖盆的低位域(LST)湖底扇近端发育粗粒重力流沉积,远端发育薄层细粒重力流沉积,其分布受沟谷和同沉积构造坡折的控制。水进体系域(TST)发育细粒水道—堤—朵叶体系。高位体系域(HST)发育非限定水道湖底扇,细粒重力流沉积分布在扇的远端。坳陷湖盆的水进体系域(TST)主要发育受洪泛影响的大型细粒水道—堤—朵叶体系,而在湖盆挠曲坡折的较陡斜坡发育细粒湖底扇体系。高位域(HST)及低位域(LST)既可形成细粒湖底扇体系,也可发育细粒的水道—堤—朵叶体系。分布在湖底扇远端和水道—堤—朵叶体系的细粒重力流沉积能形成页岩油的“甜点段”。泥流沉积形成页理型“甜点段”,细粒碎屑流、细粒浊流、细粒异重流和细粒过渡流沉积形成纹层型、层理型“甜点段”,细粒浓缩密度流沉积只形成层理型“甜点段”。细粒重力流沉积是页岩油勘探开发的有利“甜点段”。Gravity flows,including coarse-grained and fine-grained gravity flows,are the most important sedimentation processes in deep-lake environments.Fine-grained gravity flow sediments hold significant potential as unconventional shale oil“sweet spot intervals”.The distribution characteristics of fine-grained gravity flow sediments within sequence stratigraphic frameworks in lacustrine basins are of great significance to the prediction of shale oil“sweet spot intervals”.Through systematic comparative study of gravity flow deposits and sequence frameworks in major lacustrine basins in China,it is found that gravity flow sedimentary systems are mainly deposited in high accommodation sequences.In the lowstand systems tracts(LST)of the faulted/rifted lacustrine basins,coarse-grained gravity flow deposits are developed at proximal sublauctrine fans and thin fine-grained gravity flow sediments are deposited at distal sublaucustrine fans.The distribution of sublacustine fans is controlled by valley and syn-sedimentary structural slope breaks.Fine-grained channel-levee-lobe systems are developed in transgressive systems tracts(TST).Unconfined-channel sublacustrine fans are developed in highstand systems tracts(HST),and fine gravity flow deposits are distributed in distal sublacustrine fans.Large fine-grained channel-levee-lobe systems influenced by flooding occurred in transgressive systems tracts(TST)of down-warped lacustrine basins.On the steeper slope of syn-depositional flexural breaks,fine-grain sublacustrine fan systems are present.Both fine-grained sublacustrine fan systems and fine-grained channel-levee-lobe systems can be deposited in highstand systems tracts(HST)and lowstand systems tracts(LST).Fine-grained gravity flow deposits at distal sublacustrine fans and channel-levee-lobe systems can form“sweet spot intervals”of shale oil.Mudflow deposits form“sweet spot intervals”of foliation type,fine-grained debris flow,fine-grained turbidity current,fine-grained hyperpycnal flow and fine-grained transition

关 键 词：高可容纳空间层序 细粒重力流沉积 陆相盆地 页岩油 “甜点段” 

分 类 号：P512.32[天文地球—地质学]