鄂尔多斯盆地南部下古生界岩溶古地貌及储层研究

The Study of Karstic Ancient Landforms and Reservoirs in the Lower Paleozoic of Southern Erdos Basin

摘要: 鄂尔多斯盆地下古生界马家沟组主要以海相碳酸盐岩沉积为主。马家沟组上段地层受到风化剥蚀的影响，古沟槽发育，形成“台中有沟，沟前有河”的古风化壳分布格局。延长探区马家沟组出露的地层主要有马六和马五1，马六地层局部存在，受剥蚀影响，地层厚度变化较大；马五上段的地层发育受古沟槽发育的影响，使得在沟槽中，大多缺失马五1段地层。探区内以古岩溶台地、古岩溶斜坡和古岩溶盆地为主，局部存在岩溶残丘，发育两条近东西向的主要古沟槽和一条南西–北东向的次要古沟槽，探区东部主要发育岩溶盆地，古岩溶斜坡以北西–南东向展布。尽管受目前勘探范围所限，但周边古岩溶盆地内微隆起部位储层的发现，预示着本区岩溶盆地内部的微地貌特征也是今后一个值得关注的对象。

Abstract: The Lower Paleozoic Magmachu Formation in the Erdos Basin is mainly composed of marine carbonate rocks. The upper strata of the Magmachu Formation are affected by weathering and erosion, and the ancient troughs develop, forming a distribution pattern of “platforms with trenches and rivers in front of the trenches” in the ancient weathered crust. The exposed strata of the Magmachu Formation in the Changyan exploration area mainly include the Maliu and Mawu1 layers. The Maliu strata exist locally and are affected by erosion, resulting in significant changes in strata thickness. The development of the upper strata of the Mawu Formation is affected by the development of ancient troughs, so that in the troughs, most of the Mawu1 strata are missing. The exploration area is mainly dominated by ancient karst platforms, karst slopes, and karst basins, with local karst residual hills. There are two main ancient troughs with a nearly east-west orientation and one secondary ancient trough with a south-west-north-east orientation. The eastern part of the exploration area is mainly developed as karst basins, and the karst slopes are distributed in a north-west-south-east direction. Although limited by the current exploration scope, the discovery of reservoirs in the micro-uplift areas within the surrounding ancient karst basins indicates that the micro-geomorphological characteristics within the karst basins in this area are also an object worthy of attention in the future.