核磁共振技术在低渗低黏油层孔隙结构评价中的应用

摘要

Both NMR T2 spectrum and mercury injection analysis of cores can reflect characteristics of pore structure in rocks.A transformation model from T2 spectrum to pore throat radius distribution is established by using non-linear relationship.The average pore throat radius obtained from the transformation model is very close to that obtained from mercury injection analysis,which verifies the validity of the model.Based on the analysis of NMR T2 spectrum of the same low-permeability core which is saturated by oil of different viscosities,a viscosity range suitable for the transformation model from T2 spectrum to pore throat radius distribution is determined.The method overcomes the NMR's limitation that the technology can only be used for aquifer pore structure evaluation,and realizes pore structure evaluation for oil reservoirs,providing a significant research means and theoretical basis for evaluation and reasonable development of low-permeability and low-viscosity oil reservoirs.%岩心核磁共振T2谱与压汞分析均能反映岩石孔隙结构特征,利用非线性关系建立T2谱与孔喉半径分布的转换模型.该模型得到的平均孔喉半径与压汞分析得到的结果非常接近,验证了模型的有效性.通过对饱和不同黏度模拟油的同一低渗岩心的核磁共振T2谱分析,确定了T2谱与孔喉半径分布转换模型适用的黏度范围.该方法克服了核磁共振技术只适用于水层孔隙结构评价的局限性,达到了油层孔隙结构评价的目的,为低渗低黏油层的评价与合理开发提供了重要的研究手段和理论依据.