致密油储层核磁共振测井响应机理研究  

Study on the response mechanisms of nuclear magnetic resonance(NMR) log in tight oil reservoirs

作　　者：赵培强[1,2] 孙中春[3] 罗兴平[3] 王振林[3] 毛志强[1,4] 吴义志[1,2] 夏培[1,2] 

机构地区：[1]中国石油大学(北京)地球物理与信息工程学院,北京102249 [2]中国石油大学(北京)油气资源与探测国家重点实验室,北京102249 [3]中国石油新疆油田分公司勘探开发研究院,新疆克拉玛依834000 [4]中国石油大学(北京)地球探测与信息技术北京市重点实验室,北京102249

出　　处：《地球物理学报》2016年第5期1927-1937,共11页Chinese Journal of Geophysics

基　　金：国家油气重大专项(2016ZX05050)资助

摘　　要：中国西部某盆地致密油储层孔隙结构差,而核磁共振测井T2谱宽,其复杂的核磁测井响应认识不清,且响应机理也不明确.本文基于致密油储层的特性,通过对三组岩样不同系列的实验测量,包括核磁共振、毛管压力曲线、X衍射矿物分析和润湿性实验,主要研究了碳酸盐岩矿物含量对T2谱的影响和由润湿性引起的T2弛豫机制.根据实验结果分析和讨论,明确了致密油岩石核磁共振响应的影响因素及孔隙流体的弛豫机制.综合分析认为,所述的核磁测井响应特征是由两方面因素综合作用的结果,一是水的T2信号主要取决于表面弛豫,低表面弛豫率的碳酸盐岩矿物导致水的T2信号的长弛豫分量增多;二是由于岩石亲油孔隙表面的存在且其弛豫率低于亲水孔隙表面的弛豫率,使得油的T2信号由表面弛豫和体弛豫贡献.The nuclear magnetic resonance（NMR）log responses of Permian tight oil reservoirs of X-Basin in West China are extremely complicated.To be specific,the T2 spectra of the tight oil reservoirs with poor pore structures behave widely,which are incomprehensible and hard to interpret.What′s more,the NMR log responses of the tight oil reservoirs are paid little attention currently.Based on the characteristics of tight oil reservoirs,this paper mainly study the effectsof carbonate contents on the T2 spectra and the relaxation mechanisms caused by different wettability through the experiments on three groups of samples,including NMR on different state samples,mercury injection capillary,X-ray diffraction（XRD）and Amott wettability measurements.The results indicate that both the pore size distribution and carbonate contents have influences on T2 spectra.Although the shapes of T2 spectra are controlled by pore distribution,the T2 spectra show more long relaxation components and less short relaxation components with increasing carbonate contents.And the T2 relaxation mechanism of ＂as received＂state samples and vacuum and water saturated samples are more complex due to oil wet surface.The analysis suggests that the T2 relaxation signals of＂as received＂state samples are attributed to the surface relaxation of water and the surface and bulk relaxation of oil,and that the T2 relaxation signals of vacuum and water saturated samples are dominated by the surface and bulk relaxation of water.Further,the NMR log responses are interpreted reasonably by using those results.Besides the effects of pore size distribution,the complicated NMR log responses are mainly caused by two other factors.One is that the low relaxivity of water wet surface of carbonate minerals make the T2 distributions of water move to long relaxation positions.The other is that the relaxivity of oil wet surface is even lower,causing the oil signals dependent on the surface and bulk relaxation.Thus,in turn,result in the wide T2 distributions.

关 键 词：致密油储层 核磁共振测井 响应机理 碳酸盐岩矿物 润湿性 

分 类 号：P631[天文地球—地质矿产勘探]