岩石孔喉结构特征对核磁T_2谱影响的数值模拟(英文)

本文建立了能够考虑孔喉特征的储层岩石三维非规整网络模型,用数值模拟方法进一步研究饱含水岩样的核磁T_2谱特征。通过模拟储层岩石孔喉核磁共振T_2谱的特征,表明核磁共振T_2谱同岩心孔喉半径分布具有很好的相似性,对T_2谱中孔隙体、喉道信号的分解可以评价储层岩石孔隙体、喉道的半径大小及分布情况。分别模拟喉道半径、孔喉比以及孔隙连通性等孔隙结构特征对T_2谱的影响,发现:1.随着喉道半径的增大,T_2谱峰值向右移动,而且峰值处的驰豫信号强度增大;2.随着孔喉比的增大,T_2谱峰值向右移动,峰值处的驰豫信号强度增大,而且孔隙体T_2谱和喉道T_2谱逐渐分开;3.随着连通性的增大,曲线左端上升,短驰豫时间信号所占比列增大,右边的峰值有所降低。

Numerical simulation of rock pore-throat structure effects on NMR T_2 distribution

We built a three-dimensional irregular network model which can adequately describe reservoir rock pore-throat structures.We carried out numerical simulations to study the NMR T_2 distribution of water-saturated rocks.The results indicate that there is a good correlation between T_2 distribution and the pore radius frequency histogram.The total T_2 distribution can be partitioned into pore body and pore throat parts.The effect of parameters including throat radius,pore-throat ratio,and coordination number of the micro- pore structure on the T_2 distribution can be evaluated individually.The result indicates that:1) with the increase of the pore throat radius,the T_2 distribution moves toward longer relaxation times and its peak intensity increases;2)with the increase of the pore-throat ratio,the T_2 distribution moves towards longer T_2 with the peak intensity increasing and the overlap between pore body T_2 and pore throat T_2 decreasing;3)With the increase of connectivity,the short T_2 component increases and peak signal intensity decreases slightly.