Analysis of Wellbore Integrity using DTS Monitoring and Numerical Modelling in the Practice of ATES

Surplus heat as stored in an ATES (Aquifer Thermal Energy Storage) system in summer could partly meet the increasing demand of energy in winter. Better assessment on the wellbore integrity permits sustainable operation of such systems. Therefore, an artesian flow test was conducted in a research well located in Berlin, Germany. In this test, artesian flow of 16.8°C from Jurassic sand at depths from 220 m to 230 m was produced at 14°C and at a flow rate of 3.6m³/h from the annular space between the production casing and the anchor casing. The depth-resolved temperature at the production casing as monitored using the distributed temperature sensing (DTS) technique manifested the depths of the artesian aquifer. A hydro-thermal coupled numerical model for the artesian flow was calibrated by matching the simulated flow rate to the wellhead-measured values. The simulated and the DTS-monitored temperatures suggested that the heating-up in the near-wellbore materials by the artesian flow was hindered by the deployment-related inclusion of water behind the anchor casing, and the cooling in these materials in the shut-in test stage was enhanced by such inclusion.