摘要
The Neopaleozoic Formation water in the Ordos Basin is mainly distributed in updip reservoir beds on the margin of the basin and characterized by high salinity (>40000mg/L), while the downdip beds are largely full of gas associated with a little formation water that has low salinity and was encountered in several drills. The present study suggested that it was the phase state transform that caused the decrease of formation water salinity. During the formation of the deep-basin gas, the gradually elevated paleotemperature resulted in not only the decrease of formation water solubility but also a complete depletion in cationic ions for the formation water as it vapored into a gas. At the same time,vast amounts of gas were generated from coal beds and all the natural gases together further diluted, dissolved and diffused the "vapored" water, leading to the accumulation of deep-basin gas without water.