基于二维核磁共振弛豫谱的雷四段孔隙度计算方法  

Calculating Porosity From Two-Dimensional NMR Relaxation Spectra of the Leikoupo Group’s 4th Section

作　　者：侯克均 吴见萌 葛祥 张世懋 HOU Ke-jun;WU Jian-meng;GE Xiang;ZHANG Shi-mao(Well logging Branch of Sinopec Xinan Oilfield Service Corporation,Chengdu 610100,China)

机构地区：[1]中石化西南石油工程有限公司测井分公司,四川成都610100

出　　处：《波谱学杂志》2020年第2期162-171,共10页Chinese Journal of Magnetic Resonance

基　　金：国家科技重大专项资助项目(2017ZX05005-005-010).

摘　　要：基于常规测井资料的体积模型和一维核磁共振(NMR)测井资料的固定截止值法,可以计算地层孔隙度,但是扩径段孔隙度计算结果偏大.本文通过川西海相雷四段岩心样品NMR实验和实测二维NMR测井资料,开展扩径段的T2、T1孔隙度计算方法研究.首先总结不同孔径流体在T2谱和T1谱上的响应特征,分析钻井液流体峰截止值的分布范围和影响因素,建立钻井液流体弛豫时间截止值的计算模型;然后根据未扩径段和扩径段的粘土束缚水弛豫时间截止值确定原则,确立变粘土束缚水弛豫时间截止值的有效孔隙度计算方法.多口井的应用效果表明,基于T1谱的孔隙度计算结果精度更高、定量分析误差小,能有效解决扩径段孔隙度计算结果偏大的问题,满足储层评价的要求.Formation porosity can be calculated from one-dimensional nuclear magnetic resonance(NMR) logging data with a fixed cutoff value and the volume model of conventional logging data. However, the porosity calculated with this method often appears to be overestimated in the enlarged hole section. In this work, the calculation methods for T2 and T1 nuclear magnetic porosity from NMR results of core samples and two-dimensional NMR logging data were investigated. Firstly, the characteristics of NMR relaxation spectra of fluids at different pore sizes were obtained and used to analyze the distribution range of pore diameter and affecting factors of the cutoff value of the drilling fluid peak. A model for estimating the cutoff value of the drilling fluid relaxation time was then established. A method for calculating the effective porosity was then proposed with variable cutoff value of clay bond water relaxation time, according to the deterministic principle about cutoff value of clay bond water relaxation time in un-enlarged and enlarged hole section. The method proposed was applied to the data from many wells, and demonstrated better accuracy than the traditional method using T1 distribution spectra. The method can effectively solve the problem of overestimated porosity in the enlarged hole section and meet the requirement for reservoir evaluation.

关 键 词：二维核磁共振测井 流体响应 雷四气藏 变粘土束缚水弛豫时间截止值 孔隙度 

分 类 号：O482.53[理学—固体物理]