桐湾不整合面对鄂西渝东区灯影组油气成藏的影响

Impact on Hydrocarbon Accumulation of Dengying Formation by Tongwan Unconformity Surface

为了厘清鄂西渝东区桐湾不整合对下伏灯影组油气成藏的影响,基于野外露头及岩心薄片的观察,孔隙度、渗透率和包裹体均一温度等的取样测试,研究桐湾不整合的发育特征及其对灯影组油气成藏的影响。桐湾不整合是由上部的海侵体系沉积、中间的风化粘土层和下部的风化淋滤带三者组成的空间结构。其下部灯影组遭受了明显的古岩溶改造,垂向上分带明显,顶部表层岩溶带为富含铁铝质结核、灰岩或白云岩角砾的粘土层;之下的渗流岩溶带和潜流岩溶带交替出现,两个带相同之处在于均见表征淡水淋滤的葡萄石发育,不同之处在于渗流岩溶带葡萄石穿层分布,而潜流岩溶带多顺层发育。多个样品实测证实鄂西渝东区遭受古岩溶改造的灯影组储层物性较好。桐湾不整合下部淋滤带中的"孔-洞-缝"系统在印支期为湘鄂西区生烃中心的烃类向鄂西渝东区运聚提供了良好的运移通道。

Tongwan unconformity surface is a space structure which consists of upper transgressive tract deposition, middle air--slake daypan and lower air--slake leached zone. Actual measurement of multiple samples proves that Dengying formation underlying Tongwan unconformity surface in Western Hubei and Eastern Chongqing, which experienced paleokarst transformation, has better reservoir physical properties. The cavity--crack system in lower leached zone provided favorable migration pathway for hydrocarbon＇s migration and accumulation from hydrocarbon generation center in the Hunan--Hubei west base to the region of Western Hubei and Eastern Chongqing.