下寺湾地区油气富集特点及勘探方略

Hydrocarbon enrichment characteristics and exploration strategy
in cooperation area of Xiasiwan

戴胜群 夏长淮 周海彬 邹士雷

长江大学地球科学学院3RG研究组，湖北 荆州 434023 长江大学油气资源与勘探技术教育部重点实验室，湖北 荆州 434023 中原石油勘探局钻采处，河南 濮阳 457001

下寺湾地区区域构造位于鄂尔多斯盆地陕北斜坡东南部，目的层段上三叠统延长组地层平缓、构造简单，断裂褶皱不发育，发育的构造为差异压实作用形成的低幅度鼻状隆起，因此长期以来普遍认为岩性变化是油气聚集的主控因素，油藏类型以岩性油藏为主。研究结果表明，油气聚集的控制因素包括构造、沉积相带、古地貌、岩性变化和水动力条件等，其中鼻状构造对油气聚集仍然起控制作用，大面积连片分布的油藏均在一定构造背景下形成。油藏类型以构造、构造＋岩性为主，岩性油藏多但规模小。油气在纵向上主要在长2段富集，平面上油气聚集具有鲜明特点，次级分流河道、河道前缘、侧缘等储层物性相对好部位油气富集，主河道高渗储层油气难以保存，多为水层，因此，构造＋沉积相研究是油气勘探重点和关键。

The regional texture of Xiasiwan cooperation area is located in southeast of Shanbei Slope, Ordos Basin. The target layer, Yanchang Formation of Upper Triassic strata are in gentle and simple structure with faults and folds less developed. The developed structure is the low level nose-shaped uplift, which is formed by differences in compaction. So it is generally believed that lithological change is the main controlling factor for oil-gas accumulation in a long time. The oil reservoir type is mainly lithological. The results show that the controlling factors of oil and gas accumulation includes structure, sedimentary facies zones, palaeogeomorphic, lithological change and hydrodynamic condition and so on. The nose-shaped structure is still the mainly controlling factor and reservoirs of large -scale distribution are formed under a certain structure context. The reservoir type is mainly of structure and structure-lithology. There are many lithological reservoirs but all in small size.Oil and gas are enriched in Chang2 section vertically and with distinct characteristics laterally. The oil and gas are enriched in secondary distributary channel, river front, lateral margin, where the reservoir property is better. The oil and gas are difficult to be saved in rocks with high permeability in the main watercourse, which are mainly water layers. Therefore, research on tectonic and sedimentary facies is the focus and key of oil and gas exploration.