When the gas driven pressure is low, the water in the macropore will be first driven out. along with the increase of the gas driven pressure, the water in the fine pore will be then driven out.

• 气驱压力较小时，首先驱出大孔隙中的水，随着气驱压力的增大，逐步将小一些孔隙中的水驱出；