东海西湖凹陷中南部晚中新世构造反转与油气运聚

Late Miocene tectonic inversion and hydrocarbon migration and accumulation in central and southern Xihu sag, East China Sea

解剖了西湖凹陷中南部晚中新世反转构造的结构特征,认为本区反转构造的发育部位受伸展期的基底断裂带控制。在巨厚的沉积盖层条件下,断陷构造层与拗陷构造层之间的构造特征差异明显。反转构造形态自下而上表现为叠加在断块基础上的顶厚褶皱、平行褶皱和顶薄褶皱。在伊豆小笠原弧及九州帛琉海岭与日本南缘碰撞产生的近东西向区域挤压力作用下,构造反转作用具有“下逆上褶”特征,即断陷构造层沿基底断层发生逆向反转,而拗陷构造层在力偶作用下发生不对称褶皱作用。构造反转对油气运移的控制通过构造增压和断层泄压作用进行,油气主要在断陷构造层与拗陷构造层的转换构造层聚集。

Based on an analysis of late Miocene tectonic inversion in central and southern Xihu sag,it is considered that the tectonic inversion positions were controlled by basement fault zones active in the rifting stage.Covered by a set of very thick sediments,there are significant structure differences between the rifted layers and depressed layers.The inversion structures are composed of the thick-top folds,the parallel folds and the thin-top folds from the base to the top on faulted blocks.Compressed by a roughly EW stress caused by the collision between the Izu-Bonin arc-Kyushu-Ryukyu ridge and the southern margin of Japan,the inversion structures are characterized by a lower thrusting and an upper folding,in other words,the rifted layers are inverted in reverse along the basement faults,while the depressed layers was folded asymmetrically by the couple of force.The tectonic inversion has a control on hydrocarbon migration through a structural pressure increasing and faulting pressure decreasing,and the hydrocarbon mainly accumulated in transform zones between the rifted and depressed layers.