低渗储层可动流体核磁共振研究

摘要

The movable fluid evaluation was conducted based on a total of 277 matrix block samples from three typical domestic low-permeability reservoirs of different lithologies,mainly using nuclear magnetic resonance (NMR) core analysis technique of low magnetic field and supplemented by other routine test means including rock thin section,environment scanning electron microscopy (ESEM),high-resolution computed tomography (CT) and imaging logging.The distribution law and influencing factors of reservoir movable fluid were analyzed,and the cutoff value for T2 and pore-throat radius of movable fluid were calculated.The results show that the movable fluid parameters of low permeability reservoirs have wide range.The relation of the movable fluid parameters and the permeability gets better with the increase of permeability.The correlation among percentage of movable fluid,porosity,permeability is better in sandstone reservoirs.The values calculated by nonlinear optimization method well agreed with the measured values.Micropore structures,such as development degree of micro-fracture,pore size distribution,clay mineral and the filling degree,determine the distribution of movable fluids in low permeability reservoirs.%以低磁场核磁共振岩心分析技术为主,辅助以岩石薄片、环境电镜扫描、高分辨率CT、成像测井等常规测试手段,对国内3种不同岩性的典型低渗储层共计277块基质岩样进行可动流体评价研究,分析储层可动流体分布规律和影响因素,计算可动流体的T2截止值和孔喉半径下限值.研究表明:低渗储层可动流体参数变化范围较宽；岩样渗透率越高,其与可动流体参数的相关性越强；低渗透砂岩储层可动流体百分数与孔隙度、渗透率之间相关性均较好,利用非线性最优化方法得到的计算值与实测值吻合很好；微裂缝的发育程度、孔径分布、粘土矿物含量及其充填程度等微观孔隙结构特征是低渗储层可动流体的主要影响因素.