Pulsed plasma coiled tubing drilling in crystalline rock environment

Bruno Beljo

Research output: ThesisMaster's Thesis

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Abstract

Geothermal energy is related to the thermal energy stored in the Earth¿s crust and it originates from the radioactive decay of materials and from the planet¿s formation. There are a couple of ways of utilizing geothermal energy. The most common classification is deep and shallow geothermal systems. The feasibility of such systems depends mostly on the geothermal gradient and accessibility of the aimed reservoir. Due to the high temperatures in greater depths (which are mostly aimed at geothermal projects), a well construction can be challenging. This challenge is highly affected by the thermal effects, chemical properties of the circulated fluid, and production rate. The heat which is contained in such depths is necessary to bring to the surface, that is why, there is a special emphasis on the well design and well integrity, as well as the materials being used. Before designing the well, it is needed to describe what kind of the geothermal system is going to be approached. Otaniemi project, which is going to be discussed in this thesis, is an Enhanced Geothermal System (EGS). This kind of system needs to be stimulated in order to make a fracture system, because of enhancing the permeability of the same. Afterward, the circulated medium (water or CO2) is pumped from the injection well through the fractured system, where the fluid extracts the heat from the rock, and it migrates towards the production well. In order to utilize such projects, very often it is needed to reach great depths, where the drilling cost takes the biggest amount of the financing part. That is why there is a desire to reduce the cost of drilling in order to reach such depths and make the deep geothermal projects financially acceptable. Pulsed plasma drilling is a new developing technology utilizing the coiled tubing concept, which aims to reach such great depths with lower costs in order to utilize various geothermal projects around the world. The working principle of this technology is using a contactless plasma bit, which develops electrical discharges in order to disintegrate the rock in the subsurface. This method will be discussed as a possible technology to enable the more economically viable geothermal energy production. The advantage of this drilling method is a higher rate of penetration and reduced tripping time. The latter is explained by using coiled tubing (continuous pipe) drilling technology compared with the separated pipes in the conventional drill string. Another potential benefit could be the increased running time of the bit, compared to the conventional ones, due to the avoidance of the mechanical impact on the formation.
Translated title of the contributionPulsiertes Plasma coiled tubing Tiefenbohren im kristallinen Gestein
Original languageEnglish
QualificationDipl.-Ing.
Awarding Institution
  • Montanuniversität
Supervisors/Advisors
  • Gelfgat, Mikhail, Supervisor (internal)
Award date21 Oct 2022
DOIs
Publication statusPublished - 2022

Bibliographical note

no embargo

Keywords

  • Plasmabit
  • coiled tubing
  • drilling
  • crystalline rock
  • GA Drilling
  • Pulsed plasma drilling
  • geothermal
  • deep drilling

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