鄂尔多斯盆地西南部三叠系延长组划分与对比关系再认识  

Reconsideration of Division and Correlation of the Yanchang Formation in the Southwestern Ordos Basin

作　　者：李一凡 郭懿萱[2] 姚泾利[2] 赵俊峰[1] 刘鑫[2] 白金莉 李慧琼[1,3] LI YiFan;GUO YiXuan;YAO JingLi;ZHAO JunFeng;LIU Xin;BAI JinLi;LI HuiQiong(State Key Laboratory of Continental Dynamics/Department of Geology,Northwest University,Xi’an 710069,China;Research Institute of Exploration and Development,Changqing Oilfield Company,PetroChina,Xi’an 710018,China;Research Institute of Shaanxi Yanchang Petroleum(Group)Co.Ltd,Xi’an 710065,China)

机构地区：[1]西北大学大陆动力学国家重点实验室/地质学系,西安710069 [2]中国石油长庆油田公司勘探开发研究院,西安710018 [3]陕西延长石油(集团)有限责任公司研究院,西安710065

出　　处：《沉积学报》2024年第4期1297-1308,共12页Acta Sedimentologica Sinica

基　　金：国家自然科学基金项目(42172123,42230815)。

摘　　要：【目的】最新三维地震资料显示,鄂尔多斯盆地西南部三叠系延长组三角洲—深水沉积过渡带存在大量的前积反射现象,指示以往“千层饼”式的近等厚地层划分方案在前积发育区存在“穿时”问题。研究旨在探索建立前积模式下延长组的等时划分与对比方案,并探讨其与传统地层划分方案的衔接对比关系。【方法】以三维地震资料为基础,通过井—震相互约束和标定,结合岩心沉积相标志的识别,明确盆地西南部延长组中上部(长7及以上地层)的等时划分与对比关系。【结果】将庆城、合水地区延长组中上部划分出6期前积斜坡体(F1~F6),环县地区划分出5期前积体(F1~F5)。【结论】各期前积体在顶积段与传统分层可较好地衔接对比,但在前积段和底积段,新、旧方案差异较大。各期前积体在前积段普遍较厚,在深水区,F1~F3厚度明显减薄,F5、F6厚度大幅增加。研究区从西南向东北,各期前积体平面分布呈薄—厚—薄的带状样式;北西向展布的地层较厚带指示前积体向湖盆中心的持续推进,指示了湖盆的收缩和充填过程。研究结果为深入理解延长组三角洲—深水区砂体连通关系、空间分布规律以及湖盆沉积充填过程等提供了重要启示。[Objective]The Yanchang Formation comprises the most important source rock and reservoirs in the Or⁃dos Basin.Recent 3D seismic exploration shows that progradational reflection is widely developed in the delta-deep⁃water transition zone of the Yanchang Formation,which means that the previous“thousand-layer pie-like”and near equal-thickness stratigraphic division and correlation scheme would cause stratigraphic diachronistic correlation in clinoform development area.The aims of this study are to explore the establishment of isochronal division and correla⁃tion of the clinoform pattern for the Yanchang Formation,and to explore its connection and correlation with the tradi⁃tional stratigraphic division scheme.[Methods]Based on the 3D seismic data,seismic profiles in the study area are carefully interpreted to obtain the shape type,migration superposition relationship and internal structure of the clino⁃them,guided by the theories of sequence stratigraphy and sedimentology.Well-seismic mutual calibration(i.e.,drill⁃ing calibration of seismic horizon,seismic calibration of horizontal correlation of drilling profile strata),and con⁃strained by core facies marks,a new isochronous stratigraphic division and correlation scheme is established for the mid-upper Yanchang Formation:divided into six stages of clinothems(F1-F6)in Qingcheng,Heshui area,and five stages of clinothems(F1-F5)in the Huanxian area.In the topsets,these correspond to the traditionally stratified Chang 7-Chang 1 oil layers.[Results and Discussions]The different stratigraphic divisions are mainly reflected in the foreset and bottomset areas.In the foresets,the strata in each clinothem are generally thicker than suggested by the traditional schemes.In the deep-water area,the newly determined F2 and F3 strata are significantly thinner than the traditional values,while the thicknesses of F5 and F6 are dramatically increased.In plan view,the isochronous stratigraphic units of each clinothem show a NW⁃SE zonation.In the study area from SW t

关 键 词：等时地层划分 前积斜坡 坳陷湖盆 延长组 鄂尔多斯盆地 

分 类 号：P618.13[天文地球—矿床学]