Analysis of the Influence of Reducing the Duration of a Thermal Response Test in a Water-Filled Geothermal Borehole Located in Spain

Nieto, Ignacio Martín; Blázquez, Cristina Sáez; Martín, Arturo Farfán; González‐Aguilera, Diego

doi:10.3390/en13246693

Cited by 3 publications

(1 citation statement)

References 36 publications

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“…With the use of the TRT method, Bujok [32] measured eight boreholes and demonstrated that the test duration was decreased to 24 h and that the differences between the calculated values of the soil thermal conductivity and borehole thermal resistance were smaller than those between individual boreholes during the actual measurements. The findings of the thermal response test involving a water-filled borehole performed by Nieto [33] in the Spanish province of Avila revealed that there was little variance in the thermal conductivity measured at different times. However, these studies still ignore the temperature change within the formation.…”

Section: Introductionmentioning

confidence: 99%

Influence of Different Heat Loads and Durations on the Field Thermal Response Test

Zhang

Cheng

et al. 2022

Energies

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Geothermal energy exhibits considerable development potential in space heating. Shallow geothermal energy stored in the soil in the form of low-grade energy is mainly extracted via the ground source heat pump (GSHP) system. GSHP systems use the subsoil as a heat source, typically involving a vertical borehole heat exchanger (BHE) to extract heat from the formation. Accurate measurement of the thermal properties of the formation is very important for the design of BHEs. At present, the most common and effective method to measure the thermal conductivity of the formation in the field is the thermal response test (TRT). However, the test conditions (heat load, test time) during the thermal response test can impact the test results. Therefore, in this study, a borehole with a depth of 130 m was evaluated in the field. The TRT module and the distributed thermal response test (DTRT) module based on distributed optical fiber temperature sensor (DOFTS) technology were used to monitor the test with different working conditions in real-time. In the field tests, geothermal conditions and the evolution of the formation temperature with time and depth were determined. Based on the test results under different heat loads and test times, the influence of the test conditions on the thermal conductivity results was analyzed and described. A constant temperature zone was located at a depth from 25 m to 50 m, and an increasing temperature zone was located at a depth from 50 m to 130 m, with a geothermal gradient of 3 °C/100 m. The results showed that the heat load slightly influenced the thermal conductivity test results. At the initial stage of the test, the temperature significantly increased from 0 to 12 h. After reaching the quasi-stable state, the test time slightly influenced the thermal conductivity test results. The characteristics of the formation thermal recovery stage after the test stage were studied. The heat load decreased, which could shorten the time for the formation to recover the initial temperature. The results could provide a basis for the optimization of thermal response test conditions.

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Section: Introductionmentioning

confidence: 99%