致密砂岩凝析气藏微观结构及渗流特征

为了搞清吐哈油田凝析气藏致密岩心的储层特征和两相渗流规律，基于恒速压汞原理研究了微观结构特征，并利用稳压安全阀设计出一套稳态法相渗实验流程开展真实油气相渗曲线研究。研究表明:孔隙半径分布因渗透率不同而差别较大;平均喉道半径、主流喉道半径和最大喉道半径随渗透率的增加而增加，喉道半径主要分布在0.6μm左右，渗透率受喉道控制，且主要由微细喉道贡献;孔喉连通性差，排驱压力高，开发难度大;束缚水饱和度较高，相渗曲线存在气体单相流动区和液体单相流动区;气相相对渗透率随着含液体饱和度增加下降速度较快;共渗区跨度平均为13.7%，等渗点相对渗透率平均为0.015;油相相对渗透率曲线较低，因此，合理控制生产压差对凝析油气开采具有重要意义。

The Micro-structure and Seepage Characteristics of Condensate Gas Reservoir for Tight Sandstone

Based on constant speed mercury injection technology and two phase percolation theory, the micro-pore structure and relative permeability curve with the steady-state method of Tuha oil/gas field condensate gas reservoir of tight sandstone core were investigated.The result shows that the core pore radius is mainly less than 230μm, and the throat is mainly smaller than 0.6μm.Permeability is mainly controlled by throat, especially the micro-throat.The poor connectivity between pore and throat, leads to the weak seepage ability.Therefore, it belongs to poor reservoir.The relative permeability curve includes gas and liquid single-phase flow zones,which is decided by the characteristics of tight sandstone micro-structure.In addition, gas phase relative permeability declines fast with the increase of liquid saturation.Two-phase flow zone is very narrow, the relative permeability value of equal-permeability point is averaged at 0.015. Oil phase relative permeability curve is relatively low.Therefore,it is important to control production pressure difference reasonably in the process of production.