Simulation and prediction of conditions for effective development of shallow geothermal energy

• Established a numerical model of the underground heat exchanger system.
• Took the groundwater seepage field and temperature field as the content of evaluation.
• The land subsidence was also be evaluated.
• Predicted the migration trend of groundwater seepage field and temperature field.
• Predicted the heat exchanger's influence on the groundwater environment.

A geothermal heat exchanger system is mathematically quantified, and simulated and modeled to understand heat transfixion and strata deformation caused by groundwater exploitation via groundwater heat pump systems. This is done to determine the requirements and parameters governing the development of shallow geothermal energy in an efficient and safe manner. The model takes into account the groundwater seepage and temperature fields, as well as land subsidence. Using an example of a groundwater heat pump project in Nantong, China, and taking into account fixed conditions of borehole layout and operation of one pumping well with two recharge wells, the underground heat exchange system is simulated. The simulations vary the circulation ratio from 100% to 80%–60%, and the extent of heat transfixion and land subsidence development is predicted over 10 working periods, each being one year in duration. The results show that heat accumulation is alleviated with a decreasing circulation ratio, but land subsidence increases. Nevertheless, a circulation ratio of 60% is found to be ideal for sufficient alleviation of heat accumulation with only limited land subsidence.