鄂尔多斯盆地西缘北段构造地质大剖面解析及棋盘井向斜构造成因新解

Analysis of regional structural cross section in the northern section of the western edge of the Ordos Basin and new insights into Qipanjing syncline structure

西缘冲断带作为鄂尔多斯盆地的西部边界,地处众多不同性质构造单元的过渡区域,其地质特征十分复杂。近年来,西缘冲断带的油气勘探领域不断拓宽,多期次的构造运动影响了油气从生成、运聚到被破坏的整个过程,对这些构造运动产生的构造变形样式和过程的研究可以为进一步油气勘探奠定基础。本文选取鄂尔多斯盆地西缘北段一条最新处理的近东西向高精度二维地震测线,结合钻井以及露头资料对其进行精细解析和刻画,并运用2D-move软件对解析后的剖面进行反演与正演模拟。结果表明:1)鄂尔多斯盆地西缘北段棋盘井镇地区的向斜构造为基底复合构造楔向东楔入形成,向斜核部地层加厚与桌子山—横山堡断裂的活动有关;2)过鄂尔多斯盆地西缘北段的构造地质剖面现今长度120 km,经过反演平衡恢复后的剖面长度为137.68 km,累计构造缩短量17.86 km,整体构造缩短率约13%,其中燕山期的缩短量最大,缩短量12.72 km,缩短率为10%;3)根据地层接触关系及构造演化模拟可知棋盘井向斜的形成时间大致在燕山中期,银川地区在该时期为高部位隆起。

The western margin thrust belt,as a transitional area of numerous structural units with different properties in the western boundary of the Ordos Basin,has complex geological characteristics.In recent years,the exploration field of oil and gas in the western margin thrust belt has been continuously expanding.Multiple tectonic movements have affected the entire process of oil and gas generation,migration and accumulation,and destruction.The study of the styles and processes of structural deformation caused by these tectonic movements can lay a foundation for further oil and gas exploration.This article selects a newly processed high-precision 2D seismic survey line in the northern section of the western edge of the Ordos Basin,and combines drilling and outcrop data to finely analyze and characterize it.The 2D-move software is used to perform inversion and forward modeling of its structural evolution.The results indicate that:1)the syncline structure in the Qipanjing Town area of the northern section of the western edge of the Ordos Basin is formed by the eastward movement of the basement composite tectonic wedge,and the thickening of the strata in the syncline core is related to the activity of the Zhuozi Mountain-Hengshanbu fault.2)The current length of the structural geological profile passing through the northern section of the western edge of Ordos Basin is 120 km.After inversion and balance restoration,the profile length is 137.68 km,with a cumulative structural shortening of about 17.86 km and an overall structural shortening rate of about 13%.Among them,the Yanshanian had the largest shortening,with a shortening amount of about 12.72 km and a shortening rate of 10%.3)According to the geological contact relationship and structural evolution simulation,it can be inferred that the formation time of the Qipanjing syncline was roughly in the middle of the Yanshanian,and the Yinchuan area was a high-altitude uplift during this period.