The processes of solution in, and exsolution from, formation water influence the component
content of natural gas by contrasting the relative contents of components before the natural gas dissolves
in water and those after exsolving from water under different conditions of high temperatures and
pressures. Compared with the composition of original natural gas, the relative content of methane and
nitrogen increased after the natural gas dissolved in water. The increase of nitrogen content exceeds that
of methane, but the content of ethane, propane, pentane etc reduced. At the same temperature and with
pressure increasing the content of methane increased and that of heavier hydrocarbons reduced. At the
same pressure the content of methane increased quickly from 90°C to 120°C, and the content of heavier
hydrocarbons reduced. But at even higher temperatures, the increase of methane slowed down and the
content of heavier hydrocarbons increased slightly. At the same temperature and different pressures,
heavier hydrocarbons reduced much more with increasing carbon atom number, while with temperature
increasing the content difference of heavier hydrocarbons reduced. Therefore, the influence of the solution
and exsolution should be considered in the study of the migration and accumulation mechanism of natural
gas.