用离子交换法确定粘土表面结合水界限

针对泥页岩吸附结合水诱发或加剧井壁不稳定问题,采用离子交换法对粘土表面结合水界限进行了定性确定。结果表明:粘土表面结合水分强吸附结合水、松散结合水(渗透结合水)、自由水三大类;相对水气平衡压P/P_s分别为0.9和0.98是粘土—水体系的两个特征湿度。前者为粘土表面强结合水与松散结合水(渗透结合水)之间的交界点(界限);后者为松散结合水(渗透结合水)与自由水之间的交界点(界限)。

DETERMINATION OF THE TYPES AND BOUNDARY LINE OF BOUND WATER ON CLAY SURFACE BY ION EXCHANGE

In accordance with wellbore instability induced by bound water on clay surface, the types and boundary line of bound water on clay surface is quantitatively determined by ion exchange.The results show that the bound water on clay surface includes strong bound water, loose bound water(osmotic bound water)and free water. The relative vapor pressure p/p_s=0.9 or 0.98 is the special moisture, the fomer is the boundary line betweenthe strong bound water and the loose bound water(osmotic bound water)on clay surface, the latter is the boundary line between the loose bound water and free water on clay surface.