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Háskólinn í Reykjavík > Tæknisvið / School of Technology > MEd/MPM/MSc Verkfræðideild (áður Tækni- og verkfræðideild) og íþróttafræðideild -2019 / Department of Engineering (was Dep. of Science and Engineering) >

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  • Titill er á ensku Finite element study on quenching time’s impact on a geothermal well
  • Meistara
  • Útdráttur er á ensku

    It can be said that a geothermal well goes through three stages during a single production cycle with the kill procedure. Firstly water is heated through the geothermal energy in the ground, then the water is discharged out of the well and flashed into steam to power turbines for electrical production. The last step is when water is pumped down into the well and the well is quenched or "killed". In this thesis, a single production cycle with quenching of the geothermal well HE-60 is simulated in order to answer two questions. Was there any damages done to the well during the production cycle, and how does quenching time impact these damages? To solve this, a geothermal well was simulated using a finite element analysis in ANSYSWorkbench 2019 to find the plastic strain experienced on the production casing of thewell. Thewell is made from four casings, where the innermost one, the production casing, was suspected to be most likely to experience the largest damages from previous studies. The well was heated over a four month period before the discharge heated the production casing up to 315°C. After this the well was simulated to be quenched down to 10°C over seven different time intervals. From the literature, any damages to the well was expected to happen during the upper regions of the well since it experiences the largest temperature changes. Because of this, only the top 400 meters of the well was simulated. All of the casings were simulated to be made from K55 with cement between them with rocks surrounding the well. The simulation showed that the largest plastic strain for the production casing happened at the coupling 295 meters down in the well for all seven quenching times, but neither the location or magnitude of the strain is certain because the model did not converge for an increasing amount of elements. Because of this the results are considered conservative, but the results did indicate that the casing did experience plastic strain in both the tensile and compressive direction. When comparing different quenching times, the results showed little change for a quenching time larger than 100 seconds in terms of plastic strain. The next steps to confirm the results presented in this simulation would be experiments on test pieces, investigations of geothermal wells, and improvements on the model especially in terms of convergence. If these results are confirmed, it would improve on the operations of deep, warm geothermal wells by allowing more efficient production.

  • 20.6.2019

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