Based on the characteristics of gas in water-dissolving phase
and its low speed flow through caprock ,this paper made a deep
research for seal mechanism of caprock to gas in water-dissolving
phase. Pointed out adsorption to be main sea1 mechanism of
caprock to gas in water-dissolving phase.After free water in pore
of caprock was displaced ,caprock formed seal ability of caprock
to gas in water-dissolving phase.With increase of compaction and
diagenesis ,seal ability of caprock to gas in water-dissolving phase
has increased. Using the relation between compaction and
diagenesis degree and seal ability of caprock to gas in water-
dissolving phase , this paper established a method studying seal
ability of caprock to gas in water2dissolving phase ,in Sanzhao sag
of Songliao Basin. The results tally with actual geological
conditions. It indicates that the method is practical to study seal
ability of caprock to gas in water-dissolving phase.