Comparative analysis of series and parallel geothermal systems combined power, heat and oil recovery in oilfield

The option of combined heat, power generation and oil recovery (CHPO) was considered for the associated geothermal water ranging from 100 to 150 °C. Series and parallel circuits of an organic Rankine cycle (ORC) subsystem, an oil gathering and transportation heat tracing (OGTHT) subsystem and an oil recovery subsystem were first put forward and then compared by first and second law analyses. In addition, a case study was conducted based on the data from an actual series circuit geothermal system in an oilfleld. The objective was to ascertain their respective applicabilities of the two circuit systems. Results indicate that R601a shows the highest cycle performance. The series circuit is preferable for high geothermal water inlet temperatures and low heat source inlet temperatures of the OGTHT, whereas the parallel circuit is just the reverse. Moreover, for each working condition, there exists a specific critical mass flowrate ratio, making the net power output of the parallel circuit equal to that of the series circuit.