特低渗透储层微观孔隙结构和可动流体饱和度特征

鄂尔多斯盆地镇北地区延长组长4+5特低渗透储层微观孔隙结构复杂,应用常规方法较难对其品质进行合理评价。在利用铸体薄片、扫描电镜和物性分析等常规方法定性研究储层岩石学、孔隙类型的基础上,结合恒速压汞、核磁共振等非常规方法定量研究了其微观孔隙结构和可动流体特征。研究结果表明,沉积、成岩作用共同造成了储层微观孔隙结构和物性的差异,表现为平均喉道半径越大,特低渗透储层渗透率和可动流体饱度越大,储层品质越好,尤其当平均喉道半径小于1.26μm,气测渗透率小于1.0×10-3μm2时。综合研究表明,喉道是影响特低渗透储层微观孔隙结构和开发效果的主控因素。 

Microscopic Pore Structure and Movable Fluid Saturation of Ultra Low Permeability Reservoir

The reservoir of Chang 4+5 Member of Yanchang Formation is characterized by ultra low permeability and complicated microscopicpore structure in Zhenbei area,Odors Basin.Conventional methods such as casting slice,scanning electron microscope(SEM)and physical properties can analyze petrological characteristics and pore structure types qualitatively,and can't analyze the quality of this reservoir reasonably.It should be combined with unconventional methods such as contant-speed mercury injection and nuclear magnetic resonance technique(NMR),in order to analyze the microscopicpore structure and movable fluid quantitatively of ultra low permeability reservoir.The results showed that the microscopicpore structure and physical properties of ultra low permeability reservoir were caused by impact of sedimentation and diagenesis.Ultra low permeability reservoir is characterized by the average throat radius,usually the bigger average throat radius,the bigger permeability,the more movable fluid saturation,and the better quality,especially if the average throat radius was smaller than 1.26 μm and the permeability smaller than 1.0×10-3 μm2.Comprehensive studies have shown that the microscopicpore structure and the development quality of ultra low permeability reservoir was mainly controlled by throats.