Post-Yield Strain Tests of 20-in. Casing With Weld-on Connectors

Abstract

Soils in permafrost regions may undergo significant subsidence due to thawing. Oil well surface casing embedded in such soils may be subjected to strains well beyond yield, whatever the casing properties might be. To deal with this, the State of Alaska has issued a specification defining the amount of axial strain that the casing, together with its connectors, must be able to withstand without parting. This paper presents full-scale tension and compression test data demonstrating that a particular weight and grade of 20-in. casing with premium weld-on connectors is a system exceeding those requirements. It is shown that, in tension, the material ultimate strength is reached first in the casing. Similarly, it is shown that, in compression, the casing buckles plastically before the connector fails.