涪陵页岩气田焦石坝区块五峰组—龙马溪组一段页岩气储层地球物理特征分析

开展了四川盆地东南部焦石坝区块奥陶系五峰组—志留系龙马溪组一段页岩气储层地球物理特征的系统性分析研究。测井资料统计分析表明,五峰组—龙马溪组一段页岩气储层具有“高自然伽马,高铀,相对高声波时差,相对高电阻率;低密度,相对低中子,低无铀伽马”的“四高三低”测井响应特征。通过井资料精细标定和地震正演模拟分析,明确了页岩气储层顶界面呈连续波谷,底界面呈连续波峰,储层内部呈中强-弱波峰的地震反射特征;波峰强弱与页岩气储层厚度及物性有关,当页岩气储层中优质页岩段(总有机碳(TOC)含量大于2%)发育时,储层底界和储层内部波峰能量变强,之间夹强波谷特征,波谷越宽,优质页岩发育厚度越大。经地震相分析，总结出表征五峰组—龙马溪组一段页岩气储层的两类地震相,其中I类地震相是物性相对较好、发育厚度较稳定的页岩气储层的地震响应,占研究区面积的63%,为最有利的页岩气勘探区。

The geophysical characteristics of shale gas reservoir was systematically analyzed and summarized for Ordovician Wufeng member to Silurian Longmaxi member in Jiaoshiba block,southeast of Sichuan basin.Firstly,from the statistics of logging curves,the logging response characteristics was determined.Secondly,through fine calibration from well data and geophysical forward simulation,the top interface responses of shale gas reservoir showed as the continuous wave trough and the bottom interface responses showed as the continuous wave peak.The seismic responses from the internal reservoir showed as the medium,strong-hard peaks.The strength of peaks was associated with the formation thickness and physical properties of shale gas reservoir.If the quality shale section(TOC>2%)developed in the reservoir,the strength of wave peaks from the bottom interface and internal reservoir will become strong as well as sandwiching a strong wave trough.The wider the wave trough is,the thicker the quality shale is.At last,two types of seismic facies for the shale gas reservoir of Wufeng member-Longmaxi member were summarized.The seismic facies Type I was seismic response from the shale gas reservoir with the relatively better physical properties and stable formation thickness,taking up 63% of target area,as the most favorable shale gas exploration area.