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Title: Euler buckling of geothermal well casing

Geothermal well operators have expressed concern over the vulnerability of unsupported casing to buckling from thermal elongation. Preliminary numerical and theoretical calculations are presented, which indicate the buckling phenomenon should not be serious in N-80 casing if the string is tension preloaded. Buckling would be detrimental for K-55 casing. The effect of wall contact was found to be beneficial for closely confined pipe strings and of no detriment when hole gaps are large. The weakness of API screw joints in bending appears to be the structural limitation. The analysis assumed stresses above yield constituted failure, that thermal expansion was strain controlled, and that the casing was continuous. Excessive internal pressure instability was ignored. The temperature variation considered was between cementing conditions of 100 to 200/sup 0/F (40 to 95/sup 0/C) and shut-in conditions of 425 to 450/sup 0/F (220 to 230/sup 0/C).
Authors:
;
Publication Date:
OSTI Identifier:
6314661
Report Number(s):
SAND-82-0863
ON: DE83010292
DOE Contract Number:
AC04-76DP00789
Resource Type:
Technical Report
Resource Relation:
Other Information: Portions are illegible in microfiche products. Original copy available until stock is exhausted
Research Org:
Sandia National Labs., Albuquerque, NM (USA)
Country of Publication:
United States
Language:
English
Subject:
15 GEOTHERMAL ENERGY; GEOTHERMAL WELLS; WELL CASINGS; DEFORMATION; FAILURES; JOINTS; PIPES; STRESSES; THERMAL EXPANSION; YIELD STRENGTH; EXPANSION; MECHANICAL PROPERTIES; WELLS Geothermal Legacy 150901* -- Geothermal Engineering-- Drilling Technology & Well Hardware