Low Cycle Fatigue Analysis of Threaded Connectors for Subsea Drilling and Production

Abstract

Abstract Threaded connectors are utilized in a wide range of subsea oil & gas applications, from large diameter conductor casings to smaller diameter risers. As oil & gas drilling and production continues to progress into deeper waters the demand for reliable, cost effective, and high performance connectors will continue to grow. During the development phase of new threaded connectors Finite Element Analysis (FEA) is utilized to evaluate the structural capacity and performance of the connector under a wide range of load scenarios. When tension or bending loads are applied to a threaded connector, the start and end of the thread take significantly more load than the center of the thread. The stress in the thread resulting from this load distribution takes the form of a bathtub and is referred to as a "bathtub curve". Under high cyclic bending and/or tension loading, the start and end of the thread can yield, resulting in a more even load sharing between the entire thread. The magnitude of this re-distribution of load has been analyzed to illustrate its impact on the fatigue performance of threaded connectors.