A system and method for boosting the pressure of a low-pressure multiphase mixture into a high-pressure multiphase mixture. The system includes a gas-liquid separator, a liquids pump and a liquid piston compressor. The method includes introducing the low-pressure multiphase mixture into the pressure boost system, operating such that a low-pressure liquid and a low-pressure gas form, boosting the pressure of the low-pressure liquid to a high-pressure liquid, introducing low-pressure gas during a charging period into the liquid piston compressor, converting the low-pressure gas into high-pressure gas using the high-pressure liquid during a compression period, discharging the high-pressure gas form the liquid piston compressor, and mixing the high-pressure liquid and gas such that the high-pressure multiphase mixture.