Subsea system connected to a subsea well for boosting a process fluid flowing out of the well, comprising: - a preconditioning arrangement connectable to a process fluid line from a well, wherein the preconditioning arrangement comprises: o at least one sensor for measuring temperature and one sensor for measuring pressure of the process fluid, o means for estimating density of the process fluid based on measured temperature and pressure, o a cooler system comprising at least a first cooler for cooling the process fluid, wherein the first cooler comprises a bypass line for guiding a portion of the process fluid therethrough and wherein the bypass line comprises a control valve for varying the amount of process fluid flowing therethrough and a temperature control unit for measuring a temperature in the process fluid in the bypass line, wherein the subsea system further comprises: - a pressure boosting device arranged downstream of the preconditioning arrangement and wherein the pressure boosting device is characterized in that it comprises an inlet for receiving a process fluid with at least 30 volume percentage of CO2 at operational subsea conditions and an outlet for discharge of pressurized process fluid, the pressure boosting device having an operational window dictating operational parameter in terms of maximum and minimum allowable density of the process fluid entering the pressure boosting device, and wherein the preconditioning arrangement ensures that the process fluid is within the operational window of the pressure boosting device before entering the pressure boosting device. - a preconditioning arrangement connectable to a process fluid line from a well, wherein the preconditioning arrangement comprises: o at least one sensor for measuring temperature and one sensor for measuring pressure of the process fluid, o means for estimating density of the process fluid based on measured temperature and pressure, o a cooler system comprising at least a first cooler for cooling the process fluid, wherein the first cooler comprises a bypass line for guiding a portion of the process fluid therethrough and wherein the bypass line comprises a control valve for varying the amount of process fluid flowing therethrough and a temperature control unit for measuring a temperature in the process fluid in the bypass line, o at least one sensor for measuring temperature and one sensor for measuring pressure of the process fluid, o means for estimating density of the process fluid based on measured temperature and pressure, o a cooler system comprising at least a first cooler for cooling the process fluid, wherein the first cooler comprises a bypass line for guiding a portion of the process fluid therethrough and wherein the bypass line comprises a control valve for varying the amount of process fluid flowing therethrough and a temperature control unit for measuring a temperature in the process fluid in the bypass line, - a pressure boosting device arranged downstream of the preconditioning arrangement and wherein the pressure boosting device is characterized in that it comprises an inlet for receiving a process fluid with at least 30 volume percentage of CO2 at operational subsea conditions and an outlet for discharge of pressurized process fluid, the pressure boosting device having an operational window dictating operational parameter in terms of maximum and minimum allowable density of the process fluid entering the pressure boosting device, and wherein the preconditioning arrangement ensures that the process fluid is within the operational window of the pressure boosting device before entering the pressure boosting device.