江汉盆地西南缘万城断层的封闭性及其对油气成藏的控制

万城断层是江汉盆地的主要控洼断层,不仅控制梅槐桥洼陷的沉积特征,同时对油气成藏具有重要的控制作用。利用断层泥岩比率(SGR)等参数对万城断层的封闭性研究发现,万城断层的封闭性在空间上具有明显的非均质性特征,纵向上以新沟嘴组上段为拐点,断层上部封闭性好,下部封闭性差或不封闭;横向上断层封闭性由南向北封堵性逐渐增强,同时从潜江组沉积以来断层封闭性在构造演化中没有明显的变化。由于梅槐桥洼陷是该地区主要的生油洼陷,油气沿万城断层向上运移时,其封闭性对油气的运移方向存在明显的影响,控制着沿断层分布的断鼻构造的油气成藏,谢凤桥构造与丁家湖构造含油气的差异性就是封闭性非均质性造成的。

Seal of Wancheng Depression and Control to Reservoir Formation in the Southwest of Jianghan Basin

Wancheng fault,which is the main control fault in southwest of Jianghan Basin, not only controls the sediment features of stratums, but also significantly controls hydrocarbon migration and entrapment in southwest areas. The parameter of smearing of fault gouge rate (SGR) is used to study the seals of Wancheng fault. It's found that Wancheng fault seals are spatially heterogeneous. Vertically, the upside of Xingouzui Formation is as an inflexion, then the seal in top section of the fault is fine, while the bottom has a poor seal or without seals. Laterally, the Wancheng fault seals increase gradually from the south to the north. Meanwhile, because of Qianjiang formation deposits, fault seals have no apparent changes in the structural evolution. As Meihuaqiao Depression is the main petroleum generation depression, fault seals significantly affect the migration direction of hydrocarbons when they migrate along Wancheng fault and also control hydrocarbon migration and entrapment of structure distributing along the fault. The oil-bearing differences between Xiefengqiao and Dingjiahu are caused by the heterogeneity of fault seals.