泥页岩储层孔隙度测量方法分析与评价

Comparison of measurement methods for porosity of the shale reservoir

泥页岩属于非常规储层,孔隙度普遍小于10%,渗透率普遍低于1 mD。低孔低渗的特征致使常规实验方法和测井解释方法难以准确获取其孔隙度值。这里选取沧东凹陷孔二段泥页岩样品,对其孔隙度分别进行压汞法、气测法、液测法以及核磁共振法的测量,并将核磁共振实验与核磁共振测井的孔隙度值进行对比。结果表明,核磁共振技术是获取泥页岩孔隙度相对适用的方法,高精度核磁共振仪器在选择较小回波间隔(T_(E)=0.1 ms)的条件下,可测得更为全面的泥页岩孔隙度值。在有机质含量较高(TOC≥9%)的泥页岩层段,核磁共振测井信噪比呈现出一定的相关性,低信噪比可能是造成核磁共振测井获取孔隙度值偏高的原因。因此在实际测井评价过程中,要考虑信噪比的影响。

The shale is an unconventional reservoir with porosity generally less than 10%and permeability generally less than 1mD.This feature of low porosity and low permeability makes it difficult to accurately obtain the porosity value by conventional experimental methods and logging interpretation methods.In this paper,the shale samples of the Ek 2 in Cangdong sag are selected to test their porosity values separately by mercury intrusion,gas,liquid,and nuclear magnetic resonance(NMR)methods.The porosity values of the NMR experiment and NMR logging are compared.The experimental results show that NMR technology is a relatively suitable method for obtaining shale porosity,and the high-precision NMR instruments can measure more comprehensive shale porosity values under the condition of selecting a smaller echo interval(T_(E)=0.1 ms).However,in the shale section with high organic matter content(TOC≥9%),the signal-to-noise ratio of NMR logging shows a certain correlation.Low signal-to-noise ratio(SNR)may cause the high porosity value obtained by NMR logging.Therefore,in the actual logging evaluation process,the influence of SNR should be considered.