低勘探程度区域压力分布预测及超压形成机制:以东海盆地西湖凹陷为例

Prediction of pressure distribution and formation mechanism in low exploration area:A case study of Xihu Depression,East China Sea Basin

基于地震速度谱资料,结合实测钻井压力、测井数据分析结果,从单井-剖面-平面系统预测了东海陆架盆地西湖凹陷的压力分布。研究结果表明:西湖凹陷储层呈现两套压力系统,分别为正常压力系统和超压系统,超压系统主要发育于花港组和平湖组内,层位上由西至东逐渐变新。泥岩亦表现为浅部常压、深部超压,不同的区带有所差异。西湖凹陷超压顶界面分布受深度控制不显著,主要受层位控制,超压顶界面通常位于花港组下段以及平湖组上段。西湖凹陷关键界面超压带覆盖范围、连续性总体较好,且具一定的区域展布方向,在规模较大断层具较明显的差异性。断层对压力的积累起着一定输导、分割和破坏作用。不均衡压实作用和生烃作用是西湖凹陷超压形成的主要机制,但在不同的区带存在较大差异。

The distribution of pressure was predicted in Xihu Depression,East China Sea Basin by combining with the existing measured drilling pressure,log data analysis results and seismic velocity spectrum geophysical data.The results show that there are two sets of pressure systems,normal pressure system and overpressure system in Xihu Depression.The overpressure is mainly developed in Huagang Formation and Pinghu Formation,and the formation gradually changes younger from west to east.Mudstone is also characterized by shallow atmospheric pressure and deep overpressure,but varies in different zones.The interface of overpressure is mainly located in the lower part of Huagang Formation and the upper part of Pinghu Formation.The characteristics of the interface distribution of the overpressure are mainly controlled by the formation,and the depth has little effect on the distribution of the interface.The overpressure zone of the key interface covers a good continuity and has a certain regional distribution direction.There are obvious differences in large scale faults,which play a certain role in transporting,dividing and destroying the accumulation of pressure.Under-compaction and hydrocarbon generation are the main factors that produce overpressure in Xihu Depression,but there are great differences in different areas.