Stochastic performance assessment on long-term behavior of multilateral closed deep geothermal systems

Increasing the contribution of geothermal systems to green energy generation requires designing new innovative systems producing a significant amount of thermal power in a sustainable manner. The focus of this study is the performance evaluation of multilateral closed deep geothermal (MCDG) systems as a novel environmentally friendly approach for energy extraction from earth. The investigations on these synthetic systems assume a probabilistic number of borehole sections with several vertical and horizontal wellbores connected through some manifolds and doglegs. To reduce possible thermal losses, the circulated fluid is extracted through only one production wellbore. The findings of this study demonstrated that the heat absorption per meter of MCDG systems is much higher than for simple closed geothermal systems (CDG). Operating with these systems will not necessarily yield better performance. It is also found that the long-term performance of MCDG systems can be predicted as a function of their short-term behavior through stochastic analysis. This correlation is interestingly independent of the number of wellbores and flow rate. By defining specific criteria, the high-performance MCDG systems can be filtered to demonstrate common features as a specific relation between flow rates per vertical and horizontal wellbores. This characterization of MCDG systems should support the design of future high-performance systems.