高邮凹陷北斜坡辉绿岩识别及其形成时期的确定

Identification of the Diabase in the Northern Slope of Gaoyou Sag and Determination of Its Formation Period

高邮凹陷北斜坡多层位内发育辉绿岩侵入体,使破碎断块区的构造条件、石油地质条件更为复杂,与油气成藏密切相关的辉绿岩的形成时期成为广泛关注的问题。通过对测井资料和地震资料的解释和统计,得出北斜坡辉绿岩测井响应具有低自然伽马、低声波时差、低中子孔隙度、高密度和高电阻率的明显特征,地震剖面上表现为低频率、强振幅、连续性好等特征。在识别解释资料的基础上,结合相应时期的断裂展布情况,分析认为上套辉绿岩平面上展布范围比较集中,主要沿北东向和东西走向的大断层分布,下套辉绿岩展布范围更广,受大断层的转换带控制较为明显。以同位素测年为依据,综合考虑上下两套辉绿岩的展布范围、厚度分布特征以及不同期次构造活动强度等因素,分析认为该区上套辉绿岩形成于三垛运动期,下套辉绿岩在吴堡运动期和三垛运动期均有形成。

Diabase intruded into multi-horizon of the northern slope of Gaoyou Sag makes the structural conditions and the petroleum geology conditions of broken block area more complex.The formation period of diabase closely related to the hydrocarbon reservoir formation has become a deeply concerned problem.Diabase is identified and interpreted by core observation,thin section identification,well-drilling,well-logging,and seismic data,it shows that logging response characters of the diabase in the northern slope are low natural gamma ray,low acoustic,low neutron porosity,high density,and high resistivity,its characteristics with the seismic reflection profiles are low frequency,strong amplitude,and good continuity,the upper sets of diabase are intruded into the fourth member of Funing Formation to Sanduo Formation and the lower sets of diabase are intruded into the second member to the third member of Funing Formation.Based on the above facts,with fault distribution of the corresponding period,the analysis results indicate that distribution range of the upper sets of diabase is more centralized,and is mainly along the major faults in north east direction and east west direction,and the lower sets of diabase is more extensive,and is obviously controlled by the transfer zone of major faults.According to the isotopic dating,and by comprehensively consideration of every factor involving spreading range,distribution characteristics of thickness,and tectonic activity of different stages,it is concluded that the upper sets of diabase are the products of Sanduo Event,and the lower sets of diabase are the products of Wubao Event and Sanduo Event.