Tnere is a case of deep low-permeabuity and ultra-lower permeability reservoir of Es formation on west slope area of Qikou Sag,Huanghua depression.Applying capillary theory model and experimental data analysis of constant-speed mercury injection,this paper calculates the size and distribution of pore and throat.The existing state of the bound water and the movable fluid in the pores is analyzed by NMR core,and it points out that the bound water saturation obtained by quantitative NMR core is more than that derived from the mercury injection.The reason is that part of the water-film bound water may be converted into the movable water displaced out because of the displaced effect of the mercury injection method.Capillary channel pressure analysis showed that the cylindrical surface of the pores produce a capillary pressure directed toward the tube to thicken the water-film and gas column in pore and throat produce a capillary pressure directed toward the pipe wall to thin the water-film.In the process of reservoir development,with the continuous production of gas,gas reservoir pressure gradually decreases,gas volume in the pores rapidly expands,and it produces driving power on bound water in the throat.So that part of the water-film within the bound water in the pores converts into the mobile water.%以黄骅坳陷歧口西斜坡沙二段深层低渗-特低渗透气藏为例,应用毛管理论模型与恒速压汞实验数据计算出孔隙、喉道大小及分布,通过岩心核磁共振实验分析孔隙内的束缚水和可动流体的赋存状态,指出核磁共振试验得到的束缚水饱和度大于压汞实验得到的束缚水饱和度,其原因是压汞法的驱替作用,部分水膜束缚水可能转化为可动水被驱替出来.孔道应力分析表明,孔隙内柱形曲面产生指向管心的毛管力使水膜增厚,孔隙-喉道内气柱对曲面管壁产生的毛管力使颗粒表面水膜变薄.气藏开发过程中,随着天然气的不断开采,气藏压力逐步下降,孔隙内气体体积迅速膨胀,并对微细孔喉处的水相产生驱替动力,使孔隙内的部分水膜束缚水转变为可动水.
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