«Oilfield engineering»

Approaches to calculating the radius of permafrost thawing

UDC: 622.276:551.345
DOI: -

Authors:

¹ LUKOIL-Engineering, Perm, Russia

Keywords: permafrost, thawing, thawing radius, thermal conductivity, phase transition, engineering geo-cryology, wells design, cryolithozone

Annotation:

The authors of the article present a comparative analysis of various approaches to calculating the thaw radius of permafrost rocks in the near-well zone. The advantages, limitations, and constraints of the considered methodologies are discussed. The first approach is based on a graphical solution employing a nomogram and accounts for the latent heat of phase transition; however, it neglects thermal insulation effects and predicts an unbounded increase of thaw radius over time. The second approach is based on an analytical solution of the steady-state heat conduction problem, incorporates well design details and predicts that a limiting thaw radius will be reached within 3...5 years of operation. Comparative calculations for conditions in the northern region of the Komi Republic demonstrate the fact that after a 20-year operational period the thaw radius predicted by the first approach exceeds the second approach data by more than 2 times. The authors recommend adopting the second approach, which is more physically substantiated, despite the necessity of refining regulatory provisions concerning the design period and depth considerations.

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