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Analysis of Premium Connections of Oil Well Equipment Under Very High Pressure Conditions

Akbari, Alireza | 2024

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56895 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Arghavani Hadi, Jamal
  7. Abstract:
  8. Thread connections are widely used in tubular downhole equipment. Connections are usually weaker than tubulars and their failure will result in very high cost. Thread connections of downhole equipment are divided into two groups: standard connections and premium connections. Standard connections, despite being widely used, have limitations and will loose their efficiency in complex loadings. According to the mentioned limitations, premium connections have been proposed according to the existing need related to improving the strength of the structure, proper sealing and resistance to galling. One of the most obvious applications of premium connections is in downhole tubulars that are subjected to very high pressure (more than 5000 psi). The purpose of this research is to investigate and analysis premium connections, in accordance with the approach expressed in international standards, in order to provide a broader insight into the design and construction of this type of connections. For this purpose, in this research, a widely used international thread for a pipe with a diameter of 4.5 inch is considered. First, the standard of tests to determine the connection assessment levels, which are essential for the design and construction of premium connections, has been explained, the finite element analysis of this threaded connection have then been examined with ABAQUS software. After ensuring the achievement of an eligible finite element modeling, the analysis of the loading results including high pressures showed that with the increase of the internal pressure, the stress distribution will differ from concentrated state and will have a more uniform distribution, and the same is true for the contact stress of the seal part. On the other hand, by adding external pressure, it was observed that it does not have much effect on the connection performance and stress distribution. Moreover, in order to investigate the effect of type of alloy, using finite element analysis, it was shown that the average value of the stress distribution increases and creates a uniform contact stress in the initial part of the seal. In the investigation of the yield strength of the tubular body, for example, for the L80 alloy, it was observed that if the safety factor is 1.5, it is allowed to apply pressure up to 7500 psi. At the end, the works done in this research are summarized in connection with the design process of premium threads so that with its help, the path taken in the present research can be generalized to other premium threads
  9. Keywords:
  10. High Pressure ; Finite Element Analysis ; Oil Pipelines ; Oil and Gas Industry ; Downhole Equipment ; Premium Connections ; Threaded Connections

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