鄂尔多斯盆地中生代地层剥蚀量估算及其地质意义

盆地演化中地层的沉积与剥蚀及盆地的历史构造形态变动是盆地分析及其矿产富集的重要影响因素。本文考虑到盆地西部白垩系的声波时差资料的分段性和估算中生代三叠纪以来抬升剥蚀事件强度所需选择合理方法的重要性,采用钻井分层资料“点连线,线线相交闭合”方式,应用以地层对比为主的方法估算了三叠纪以来4期地层抬升并遭受剥蚀的剥蚀量。估算结果发现,白垩纪末期为三叠纪以来最强烈一期全盆抬升剥蚀事件,三叠纪末期、中侏罗世和侏罗纪末期等3期剥蚀事件相对较弱。剥蚀强度分布与盆地演化模拟结果表明,盆地自三叠纪以来的构造变动表现为一掀斜过程;对盆地三叠系油气生成、运聚的影响分析认为,三叠系烃源岩在晚侏罗世前已生烃,掀斜构造演化过程使油气运移指向盆地东部及东南地区。

Estimation of Denudation Thickness of Mesozoic Stata in the Ordos Basin and Its Geological Significance

Restorations of the evolution events and basin denudation are crucial contents in basin research. Though many methods can be applied to denudation thickness calculation, these methods have many hypotheses and are limited in some detailed area. Based on the recognition of sedimentary background and exploration data, the paper discovered that the acoustic time curve are made up of several subsections in Cretaceous on the west of Ordos Basin, and that the method applying mudstone compaction curve is not adapted to calculation of Triassic denudation thickness. Based on the correlation of strata, the paper calculated the erosion thickness in these four periods with: Triassic, Middle Jurassic, Jurassic and Late Cretaceous. The results are calibrated with the method of section ties and compared with early research results. The results of restoration indicate that the hardest in the four events took place in Late Cretaceous. The results of burial history restored with the basin model program Temis-3D show that basin has experienced tilting evolution from West to South to Southeast to East since Mesozoic. The simulated result of maturity history indicates that the organic matter in Triassic could have matured before Late Jurassic. Restoration of burial history certainly promoted the cognition to hydrocarbon migration and accumulation in Ordos Basin.