摘要
利用三维地震和测录井资料,对东营凹陷梁东地区古近系沙三中亚段的层序地层特征开展了研究,并对层序内部体系域组成、结构、沉积特征以及空间变化规律进行了分析。研究结果表明:①东营凹陷梁东地区古近系沙三中亚段内部可划分出高位体系域(HST)、下降体系域(FSST)、低位体系域(LST)和湖侵体系域(TST),反映其经历了一次完整的基准面变化旋回。受沉积物供给和可容纳空间的侧向变化,供源主体位置沙三中亚段发育完整的层序序列。在沉积主体两侧,各体系域的地层厚度逐渐减薄,岸线迁移特征不明显。②研究区FSST沉积相以三角洲前缘为主体,可划分为水下分流河道、河口坝等微相,也可见少量重力流沉积微相,LST在演化序列上继承了FSST的沉积特征,以三角洲—重力流体系为主,但进一步向盆地方向推进。LST的沉积中心相较FSST西移,显示了LST中沉积体系的远距离推进特征。③研究区F1生长断裂的强烈活动控制了砂体分布,断层上、下盘产生的沉降差异使沉积物供给和可容纳空间均产生了变化,导致各体系域几何形态特征和地层叠置关系沿物源方向发生了变化,断层上盘高沉降、高可容纳空间区域的体系域发育完整,砂地比最大;断层下盘高地势、低沉降、低可容纳空间区域,HST和LST的厚度显著减小,砂地比也相对较小。④研究区HST由厚层暗色泥岩和油页岩构成,可作为良好的烃源岩;LST和FSST的三角洲和重力流砂体是主要储集层;TST形成了广泛的暗色泥岩可作为盖层。沙三中亚段各体系域在垂向上构成了良好的生储盖配置关系。
Using three-dimension seismic and well-logging data,a study was conducted on the sequence stratigraphic characteristics of the middle sub-member of the third member of Paleogene Shahejie Formation in the Liangdong area of the Dongying Sag.The internal systems tracts,composition,structure,sedimentary characteristics,and spatial variation patterns of the sequences were analyzed.The results show that:(1)The middle submember of the third member of Shahejie Formation in the Liangdong area of the Dongying Sag can be divided into highstand systems tract(HST),falling stage systems tract(FSST),lowstand systems tract(LST),and transgressive systems tract(TST),reflecting a complete base-level change cycle.Due to the lateral variations in sediment supply and accommodation space,the main source area in the middle sub-member of Shahejie Formation developed a complete sequence.In contrast,on both sides of the main sedimentary area,the thickness of the systems tracts gradually thins,and shoreline migration characteristics are not obvious.(2)The FSST facies in the study area are dominated by delta front deposits,which can be further subdivided into microfacies such as underwater distributary channels and mouth bars,with some occurrences of gravity flow microfacies.The LST inherits the sedimentary characteristics of the FSST in its evolutionary sequence,mainly represented by a deltagravity flow system,but further extending towards the basin.The sedimentary center of the LST shifted westward compared to the FSST,indicating the long-distance progradation characteristic of the sedimentary system in the LST.(3)The strong activity of growth fault F1 in the study area controlled the distribution of sand bodies.The differential subsidence between the hanging wall and footwall of the fault caused changes in sediment supply and accommodation space,leading to variations in the geometric characteristics of the systems tracts and stratigraphic stacking patterns along the sediment source direction.In the hanging wall of the fault,where there is higher subsidence and greater accommodation space,the systems tracts are fully developed,and the sand-toshale ratio is the highest.In the footwall,with higher elevation,lower subsidence,and smaller accommodation space,the thickness of the HST and LST decreases significantly,and the sand-to-shale ratio is also relatively smaller.(4)The HST in the study area is composed of thick layers of dark mudstone and oil shale,which can serve as excellent source rocks.The deltaic and gravity flow sand bodies in the LST and FSST are the main reservoirs.The TST is characterized by widespread dark mudstone,which can act as a cap rock.The vertical arrangement of the systems tracts in the middle sub-member of the third member of Shahejie Formation forms a favorable source-reservoir-seal configuration.
作者
曲星宇
QU Xingyu(School of Earth and Environment,Anhui University of Science and Technology,Huainan 232001,Anhui,China)
出处
《岩性油气藏》
北大核心
2025年第2期166-177,共12页
Lithologic Reservoirs
基金
重庆市自然科学基金面上项目“三角洲体系物源供给差异对层序构成样式的控制”(编号:cstc2019jcyj-msxmX-0719)资助。
关键词
层序地层学
四分体系域
水下分流河道
河口坝等微相
重力流
可容纳空间
沙河街组三段
古近系
梁东地区
东营凹陷
sequence stratigraphy
fourth-order systems tract
underwater distributary channels
mouth bars and other microfacies
gravity flows
accommodation space
third member of Shahejie Formation
Paleogene
Liangdong area
Dongying Sag
作者简介
第一作者:曲星宇(2002-),男,安徽理工大学在读本科生,研究方向为构造地质学、层序地层学。地址:(232001)安徽省淮南市泰丰大街168号。Email:qxy2446593168@163.com。
