Design of Suction Piles for Deepwater HPHT Subsea Pipelines

Abstract

Thermal expansion management of high pressure and high temperature (HPHT) pipelines using buckle initiators and anchors has proven to be a viable approach for projects in the deepwater Gulf of Mexico. In this study, using suction piles as pipeline anchors is discussed, as suction piles represent the most commonly used anchoring technology in deepwater. Considerations and issues particular to the pipeline anchoring application are discussed and possible solutions are presented. In this study, the traditional suction pile analysis and design procedures (based on simple calculations and/or the finite element method) are discussed, and modifications and simplifications are proposed to suit the new application. In particular, applying the anchor loads at the mudline level, long-term loading and the absence of significant axial loading are examples of issues and particulars that are common to pipeline anchoring that would either simplify analysis or put restrictions on the validity of current suction pile design procedures. Different types of connections to pipelines and subsea structures are also proposed and addressed. This study extends the applicability of suction piles from mooring applications to thermal buckle and walking management for HPHT pipeline applications. It presents solutions to connection and design issues particular to suction piles as anchoring means for HPHT pipeline thermal management.