| Title | EXPERIMENTAL AND NUMERICAL STUDY OF GEOTHERMAL WELLBORE HEAT EXCHANGER IN ABANDONED GAS WELLS: A CASE STUDY FROM TAIWAN |
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| Authors | B. Hsieh, M. Hsu, B. Chen and T. Chen |
| Year | 2019 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Abandoned oil and gas well, Geothermal energy, Numerical simulation, Wellbore heat exchanger |
| Abstract | Deep abandoned gas wells can be retrofitted to convert into geothermal energy extraction wells. For example a geothermal wellbore heat exchanger (GWHE), a closed-loop geothermal energy extraction system, can be used to harvest the heat energy from a high-temperature sedimentary rock formation. The purpose of this study is to investigate the performance of the GWHE system in a deep abandoned gas well by using a field experiment and numerical simulation. A three-thousand-meter deep abandoned gas well located in northwestern Taiwan is selected to conduct a field experiment of the GWHE. This test well is retrofitted by a workover job to ensure the wellbore integrity. The tubing used for the GWHE system is coated with an insulation material in order to avoid heat loss in the outflow. The field test successfully collects experimental profile of the output temperature. The experimental data is used for the history matching in the numerical study. A numerical model is built based on the configurations of the field experiment. A thermal simulator, STARS, is used in this study. The numerical model is validated by matching the experiment data from the field test. After the history match is done, the validated model is obtained and can be used to predict the performance of the GWHE system. Our simulation results show rhat the performance of the GWHE system is strongly sensitive to the pumping rate, the formation temperature gradient and the formation temperature. The high-temperature sedimentary rocks can continuously contribute heat energy to the GWHE system even though the output water temperature has a slow decline. |