Complex geological environment

such as high temperature

pressure and salinity

is involved in the recovery of deep oil and gas resources. It is well known that there exists high concentration of brine in natural reservoirs and salts deposit during the recovery of oil and brine

when temperature

pressure and the amount of dissolved gases vary. Reservoir damage or well-bore jam is caused by the deposition of salts in the reservoir and well-bore. These are the major factors reducing oil and gas recovery. Currently

phase equilibrium model for describing the deposition behavior of salts from high pressure and salinity reservoir fluids is under development. In this paper

the progress in improving the mixing rule of equation of state parameters by combining a group contribution activity model for electrolyte solutions is reported.