对致密气藏水膜厚度的再认识

摘要

In the actual gas layer, the bound water exists in the form of capillary bound water and water film.According to the theoretical calculation model of total separation pressure and water film thickness established by Derjaguin-Landau-Verwey-Overbee theory, in combination with the extended Young-Laplace formula, an iterative algorithm was adopted to calculate the reservoir water film thickness.By utilizing the measured temperature and pressure data of the actual formation, the total separation pressure and water film thickness curve were obtained, indicating that the thickness of water film in the pores of the middle reservoir is much smaller than that of the gasbearing pore radius.In the high salinity aqueous solution of the actual gas reservoir, the electrostatic repulsion is small, and only the Van der Waals gravitation can maintain the stability of water film, so the water film thickness in the pores of gas reservoir is small.Comparing the calculated values of critical pore radius and water film thickness, the bound water mainly exists in the form of capillary-bound water.Since the water film thickness is much smaller than the radius of gas-bearing pores, its influence on natural gas seepage is limited.%在实际气层中, 束缚水以毛管束缚水和水膜形式存在.根据由Derjaguin-Landau-Verwey-Overbee理论建立的总分离压和水膜厚度的理论计算模型, 结合扩展Young-Laplace公式, 采用迭代算法, 提出了计算储层水膜厚度的图解法.利用实际地层实测温度、压力数据, 得到总分离压与水膜厚度曲线, 求得在气藏中部孔隙中的水膜厚度远小于含气孔隙半径.在实际气藏的高矿化度水溶液中, 静电斥力较小, 只有Van der Waals引力是保持水膜稳定的主要作用力, 因此气藏孔隙中水膜厚度小.对比临界孔隙半径和水膜厚度的计算值表明, 束缚水主要以毛管束缚水的形式存在, 水膜厚度远小于含气孔隙的半径, 对天然气渗流的影响小.