In Situ Observation of Critical Phenomena of Multicomponent Geofluids and Seawater by Using Visible-type Autoclave

Spectroscopic characteristics of critical phenomena of multicomponent geofluids and seawater were observed by using autoclave with transparent windows (visible-type autoclave). First, pure H2O fluids were observed by spectroscopic measurements at 500-800nm under high temperature and pressure conditions. The intensity of light transmitted decreased significantly as the critical point of H2O fluid was approached, and the local minimum intensity of transmitted light corresponded to the critical temperature and pressure of all fluids tested. The experimentally determined critical temperature and pressure of H2O were similar to the results of previous work. Critical temperatures and pressures of multicomponent geofluids and seawaters were determined. Spectroscopic measurement could provide information of molecular behaviours of aqueous fluid involving several kinds of electrolytes.