Viðburðir eftir árum


Thesis defense School of Science and Engineering – Brage Eidsvik

MSc Mechanical Engineering

  • 24.5.2019, 14:00 - 15:00

Student: Brage Ariel Lindell Eidsvik

Title: Finite Element Study on Quenching Time's Impact on Geothermal Wells.

Date and Location: Friday, May 24th, 2019 at 14:00 in M105

Supervisors: María Sigríður Guðjónsdóttir, Professor, Reykjavík University, Iceland
Einar Jón Ásbjörnsson, Professor, Reykjavík University, Iceland

Advisor: Gunnar Skúlason Kaldal, Engineer, ISOR, Iceland

Examiner: Magnús Þór Jónsson, Professor, University of Iceland

Abstract: 

It can be said that a geothermal well goes through three stages during a single production
cycle. 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. The last step of
the cycle is when water is pumped down into the well again and the well is quenched. In
this thesis, a single production cycle 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, the geothermal well was
simulated using a finite element analysis in ANSYS Workbench 2019 in order to find the
plastic strain experienced on the production casing of the well. The well 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. 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.



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