Abstract: As a type of generable energy, shallow geothermal energy has been widely noticed. It’s very important to establish a long-term effective shallow geothermal field monitoring system in the process of developing and utilizing shallow geothermal energy. In order to better monitor shallow geothermal field and the temporal and spatial distribution of energy, four kinds of temperature sensors used in the project, DTS, FBG, Pt100 and iButton, were analyzed and compared from measurement accuracy, applicable range and characteristics through field and indoor tests. Combined with the results of tests and current application,
the advantages and disadvantages of DTS, FBG, Pt100 and iButton on shallow geothermal field monitoring are summarized and a more completed monitoring plan is developed, which provides a reference for monitoring shallow geothermal field and its temporal and spatial distribution of energy. The follows are shown. Distributed temperature sensing fiber is buried in all boreholes, and two typical ones will be selected according to the soil layer distribution of the geothermal borehole and the obtained geothermal distribution data. Along the borehole, FBG temperature sensing string is arranged in the borehole. iButton is arranged at 5cm from the surface of all drilling points; Use Pt100 to monitor the precise temperature along the borehole within 25 m below. According to the obtained data, the general distribution of the shallow geothermal energy in the vertical direction in Nanjing can be summarized, and the distribution is found to be spatially different. The shallow geothermal energy near surface is related to the surface cover, the atmosphere and solar radiation, while the deeper energy is affected by factors such as geological structures and hydrogeological conditions.

Key words: shallow geothermal field, DTS, FBG, Pt100, iButton