Heat recovery from export gas compression: Analyzing power cycles with detailed heat exchanger models

Offshore oil and gas production platforms release substantial amounts of heat to the sea. A major source of waste heat is the cooling unit for the compressed export gas. In this paper, the potential for power production from this heat source is analyzed. The emphasis was not only put on net power output, but also on system size, which is a key parameter for offshore operation. To find a suitable trade-off between those two values, a cycle calculation tool was programmed which uses detailed heat exchanger models to ensure a fair comparison of the different working fluids. A subcritical propane cycle, a transcritical CO2 cycle and a transcritical cycle with a mixture of propane and ethane were analyzed. It was shown that more than 10% of the export gas compression work could be recovered. The hydrocarbon mixture shows very promising results, but a more comprehensive study is required to reach an economical decision between power output and system size.