Abstract: To solve the lack of equipment that can directly measure formation water’s ion content in the condition of high
temperature and high pressure at home and abroad. The static experiment for test ion content and scaling amount in formation
fluid under the condition of high temperature and high pressure was made. PVT analysis for the actual gas field’s fluid of
high temperature and high pressure and ion content detection experiments were carried on in this paper. Water content in
gas，amount of gas dissolved in water and the icon formation content in water are tested，scaling amount of formation fluid was
firmed. The change rule of gas and water’s phase state and ionic content have been studied comprehensively，the internal relation
influence was analyzed. The results show that quantity of dissolved gas in water reduces with formation pressure decreasing，
the evaporation water to natural gas formation intensifies，electrolyticion’s concentration and salinity increases，and the scaling
trends increase. In certain low pressure and high temperature conditions，the inorganic salt in formation fluid began scaling. The
scaling quantity increases with experiment pressure increasing，and decreases with the experimental temperature decreasing.
Scaling quantity of the under actual production condition is lower than that of the degassing formation water，and change trend
of scaling quantity with temperature and pressure is more obvious.

Key words: high temperature and high pressure, ion content, formation water, occurrence state, scaling