Integration of CO2 power and refrigeration cycles with a desalination unit to recover geothermal heat in an oilfield

Abstract Onshore oilfields are considered as geothermal fields producing hot water in the high water cut stage (HWCS). In the present study, a supercritical CO2 power cycle is proposed to recover the heat of the hot water obtained at a temperature close to 140 °C from the oilfield in the HWCS. The output power of the supercritical CO2 power cycle is expensed to run the compressor of an ejector expansion CO2 refrigeration cycle. Rejected heat of CO2 cycles is partially utilized by the HDH (Humidification-dehumidification) desalination unit. It is observed that though there exists an optimum turbine back pressure (TBP) corresponding to a maximum refrigeration effect, fresh water production rate increases with an increasing TBP. However, for each specified evaporator temperature, there is an optimum TBP corresponding to the minimum payback period (PP) of the energy system. The optimum TBP is close to 8.4 MPa for all considered evaporator temperatures and corresponding values of PP varies between 7.65 and 8.25 years. For an evaporator temperature of −15 °C, the refrigeration effect and fresh water production rate are 380.32 kW and 0.349 kg/s, respectively. The proposed energy system is capable of partially satisfying localized energy services like cooling and fresh water supply.