低渗沉积岩可动流体饱和度核磁共振实验

NMR experimental study of movable fluid saturation in low permeability sedimentary rocks

对于低渗透储层而言,孔喉细小,孔隙连通性差,仅测量孔隙度与渗透率不能全面地反映岩石的渗流能力,还需考虑可动流体在饱和流体中所占的比例。为了准确获得低渗沉积岩可动流体饱和度,通过低场核磁共振技术测得了低渗沉积岩在饱和水与离心状态下的核磁共振T2谱,并以此为基础对岩样进行了可动流体饱和度评价研究。分析了低渗沉积岩可动流体的分布规律与影响因素,重点探讨了计算可动流体饱和度的3种方法之间的区别。结果表明:低渗透储层岩石中微细孔隙所占比例较大,由于岩石表面作用强,可动流体含量较少,且主要存在于大孔隙或极少部分的小孔隙中。通过相关性分析发现,可动流体饱和度与孔隙度、渗透率以及渗透率与孔隙度的比值k/φ均呈较好的幂函数关系。

For low-permeability reservoirs,the pore throat is small and the pore connectivity is poor.Only measuring the porosity and permeability cannot fully reflect the seepage capacity of the rock,and the proportion of the movable fluid in the saturated fluid should also be considered.In order to accurately obtain the movable fluid saturation of low permeability sedimentary rock,in this paper,the low-field NMR technique was used to test the T2 spectrum of low-permeability sedimentary rocks under saturated and centrifugal conditions.Based on this,the movable fluid saturation evaluation of rock samples was carried out.The distribution and influencing factors of the movable fluid in low permeability sedimentary are analyzed,and the differences between the three different methods for calculating the saturation of the movable fluid are discussed.The results show that the micro-porosity in the low-permeability reservoir rocks accounts for a large proportion,due to the strong surface action of the rock,the content of the movable fluid is small,and it mainly exists in the macropores or a small part of the small pores.Correlation analysis shows that the movable fluid saturation has a power function relationship with porosity,permeability and permeability to porosity k/φ.