延安气田北部山1段储层微观孔隙结构对可动流体赋存的影响

The influence of micropore structure on movable fluid of theShan 1 reservoir in the north of Yan′an Gas Field

以延安气田北部山1段储层为研究对象,通过铸体薄片、扫描电镜、恒速压汞、核磁共振等实验方法,分析其储层微观孔隙结构特征,研究其对可动流体赋存的影响。结果表明,研究区储层主要为岩屑石英砂岩和岩屑砂岩,溶孔、晶间孔和微裂隙为主要的孔隙类型,发育缩颈喉道,片状、弯片状喉道。储层具有中—大孔隙、微细喉道的特征,喉道为影响储层渗流的关键因素,微裂隙及溶蚀影响孔隙、喉道的发育。微裂隙型储层喉道半径大,喉道频谱分布宽,渗透性最好。储层样品可动流体饱和度为14.82%~55.16%,平均为32.23%。研究认为,喉道半径、孔隙半径、孔喉比及分选性影响着可动流体的饱和度,喉道半径为影响可动流体赋存的主要因素,尤其是半径≥1.5μm的喉道,其所占比例越高,可动流体饱和度越高;而半径≤0.3μm的微喉道比例越高,可动流体饱和度越低。分选系数越高,可动流体饱和度越高。

It is difficult to exploit tight sandstone gas in Shan 1 reservoir of Upper Paleozoic in Yan′an Gas Field,and the understanding of movable fluid e characteristics is poor.Based on casting thin-section,scanning electron microscope,constant speed mercury penetration and nuclear magnetic resonance,micropore structure characteristics and its influence on movable fluid of Shan 1 reservoir are analyzed in the north of Yan′an Gas Field.The results show that:The lithology of the reservoirs is mainly lithic quartz sandstone and lithic sandstone,and dissolution pore,intercrystalline pore and microfracture are the main pore types,with necked throat,sheets and bent sheet throat.The reservoir has the characteristics of medium large pore micro throat.The throat is the key factor to affect the reservoir permeability,and the microfracture and dissolution pore can affect the property of pore and throat.The microfracture reservoir has large throat radius,wide throat spectrum distribution and the best permeability.The movable fluid saturation of reservoir samples is 14.82%~55.16%,with average of 32.23%.Throat radius,pore radius,ratio of pore to throat and separation affect the saturation of movable fluid.Throat radius is the main factor affecting the occurrence of movable fluid,the higher the proportion of throat with radius≥1.5μm,the higher the movable fluid saturation;the higher the proportion of throat with radius≤0.3μm,the lower the movable fluid saturation.The higher the separation coefficient,the higher the movable fluid saturation.