In the recent years, geothermal technology has received substantial attention as an alternative source of energy. However, the lack of detailed information about subsurface formations of interest often introduces significant uncertainties to the technological and economic planning of geothermal projects. As the result, some important technological parameters, affecting geothermal projects, cannot be predicted with enough certainty. One of the most important technological characteristics in low enthalpy geothermal projects is the time when cold fluid from the injection well breaks into the production well. The large variation in thermal breakthrough time against the exact location of the well doublet was identified. These variations can largely impact the lifetime of the low enthalpy geothermal project, thereby affecting the quantification of the projects economy.
In our study, we investigate the main factors responsible for the variation of breakthrough time by performing a sensitivity analysis of different hydraulic and thermal properties. A geometry/rule-based modeling software Flumy was used to generate a detailed fluvial facies distributed, similar to that observed in the West Netherlands Basin (Nieuwerkerk Formation). The models were then populated with various thermal and hydraulic properties, correlated with the facies map. Ensembles of models were run in ADGPRS (Automatic-Differentiation General Purpose Research Simulator) to perform a sensitivity analysis.
For a given technological characteristics (distance between doublet wells, injection and production rates, drainage area etc.), a difference of approximately 50% was observed in the lifetime of the project while relocating the doublets positions and keeping the same distance between the doublet pair. The major numerical and geological factors, contributing to the difference in breakthrough time, were identified in our study. In addition, the best simulation strategy and numerical parameters for uncertainty quantification in low enthalpy geothermal projects were suggested.