西湖凹陷南段新生代岩浆岩时空分布特征及对成藏的影响

Temporal and spatial distribution characteristics of Cenozoic magmatic rocks and their influence on reservoir formation in the southern part of Xihu Depression

西湖凹陷南部新生代岩浆活动强烈,厘清岩浆岩时空分布特征,对认识该区岩浆活动与油气成藏关系具有重要意义。本文基于三维地震资料,通过边缘检测、振幅属性过滤、多Z值联合解释、层面自动追踪等多种地球物理手段对区内岩浆岩体形成时间和空间分布进行刻画,分析了岩浆岩体分布规律及控制因素;结合岩浆活动演化规律,探讨了岩浆活动对油气成藏的影响作用。研究结果表明:西湖凹陷南部新生代岩浆活动区主要分布在天台斜坡北段和天台西断裂附近,中新世以来南部岩浆活动逐渐强烈,在上新世早期岩浆活动作用达到高峰;岩浆岩体的分布主要受断裂体系的发育、岩浆活动的滞后效应、沉积盖层厚度等因素影响;岩浆活动加快烃源岩成熟,同时也有利于强制背斜等圈闭的形成,但是晚期岩浆活动也会使早期形成的圈闭破坏。本次研究将助力西湖凹陷南部的区带评价,并指导岩浆岩相关圈闭的勘探。

The Cenozoic era in the southwest of Xihu Depression has undergone great changes in tectonic environment such as faultdepression-reversal,and magmatic activity has become frequent,which is of great significance for understanding the relationship between magmatic activity and hydrocarbon accumulation in this area.In this paper,the formation time and spatial distribution location of magma rock mass in this area are depicted by various geophysical means such as edge detection,amplitude attribute filtering,multi-Z value interpretation,and automatic tracking,and the distribution rules and controlling factors of magma rock mass are analyzed.Combined with the evolution of magmatic activity,the influence of magma activity on hydrocarbon accumulation was discussed.The understanding is as follows:(1)The Cenozoic magmatic activity in the southwest of the Xihu Depression was mainly distributed in the northern section of the Tiantai slope belt and near the Tiantai West Fault,and the magmatic activity in the southwest gradually became stronger since the Miocene,and the magmatic activity reached its peak in the early Santan Formation.(2)The distribution of magmatic rock mass is mainly affected by the development of the basement fault system,the hysteresis effect of magmatic activity,the thickness of the sedimentary cover and other factors.(3)The relationship between magmatic activity and hydrocarbon accumulation in this area is positive and negative.Regional magmatic activity accelerates the maturation of hydrocarbon source rocks in the southwest,and is also conducive to the formation of trap morphology.However,late magmatic activity can also destroy early formed traps.