鄂尔多斯盆地怀远运动不整合面特征及油气勘探意义

怀远运动不整合面是华北地台上一个重要的区域性不整合面。在对华北地台怀远运动表现形式与地质特征调研分析的基础上，基于大量的露头、岩心观察和地震资料解释工作，对鄂尔多斯盆地怀远运动不整合面存在的证据、特征及其与储层和油气成藏的关系进行了深入分析，并取得了新认识。研究认为：①鄂尔多斯盆地奥陶系深层存在由怀远运动形成的区域不整合面，并可能发育大型喀斯特岩溶沟谷地貌体系；②该区域不整合面及相关沟谷地貌体系为上覆马家沟组中-下组合（马四段—马一段）沉积提供了古地貌背景，并控制了其沉积格局与有利储集相带展布，同时也控制下伏下奥陶统—寒武系—长城系白云岩化与风化壳储层发育；③该区域不整合面为不同来源天然气的区域性横向运移提供了有利通道，是油气运移的“高速公路”，同时也为油气聚集提供了有利场所，其中不整合面附近的上、下层位有利于天然气的大规模聚集与成藏，可能是继奥陶系顶面风化壳领域后又一勘探新领域，值得重视。目前对盆地内部怀远运动不整合面的认识还比较薄弱，建议加强三维地震勘探部署，以推动鄂尔多斯盆地的地质认识创新和勘探新发现。

Characteristics of unconformity resulted from Huaiyuan Movement in Ordos Basin and its significance for oil and gas exploration

The unconformity formed out of Huaiyuan Movement is one of the important regional unconformities in the North China Platform.Following the investigation on and analysis of the occurrence and geological characteristics of the movement, we make an in-depth analysis of the evidences and characteristics manifesting the movement-caused unconformity and its correlation with reservoirs and oil and gas accumulation in the Ordos Basin, with new understandings obtained.The results show that: ①There is a regional unconformity formed by the Huaiyuan Movement in the deep Ordovician of Ordos Basin, and it perhaps associates with a large-scale geomorphology system of karst ravines; ②The regional unconformity and ravine system serve as the paleogeomorphologic setting for the deposition of the overlying strata, to be specific, the middle-to-bottom parts of Majiagou Formation (namely, from Ma 4 to Ma 1 Members), and control the depositional pattern and favorable reservoir facies distribution, as well as the development of dolomitized and weathered crust reservoirs in the underlying Lower Ordovician to Cambrian and to Changcheng Systems; ③The regional unconformity acts as a favorable channel for the lateral migration of natural gas from different sources in certain regions, known as "highway of hydrocarbon migration"; meanwhile, it is also a favorable place for hydrocarbon accumulation, the upper and lower layers near which are conducive to natural gas accumulation and enrichment in large scale.It is possibly a new exploration area worthy of attention in replacement of weathering crust on top of the Ordovician.However, the current understandings have to be deepened on the unconformity in the study area, for which a 3D seismic acquisition is recommended to promote creative geological understandings and new exploration discoveries in the Ordos Basin.