Qualification of Mechanical Interference Fit Connection for Offshore Pipeline Application

Subsea pipeline is still considered a major cost contributor for offshore oil and gas field development. One of the major factors which affect this high cost is expensive installation cost due to expensive pipelay barge mobilization/demobilization cost, daily charter rate, as well as low speed for pipelay using welding. Several technologies were being considered to further optimize capital expenditure (CAPEX) for subsea pipeline installation. Mechanical Interference Fit Connector (MIFC) is currently being considered as an option to optimize the cost for rigid offshore pipeline installation. However, this technology is new in Malaysia, and the normal regulatory requirement for the application is still based on welding. There was a requirement to demonstrate the design and integrity of the MIFC to meet the conventional requirement for pipeline welding as part of the regulatory requirement for a permit to install (PTI) and permit to operate (PTO). This paper presents the approach to assess the design and performance of the MIFC joint. The assessment includes design verification using finite element analysis (FEA), and subsequent validation by full-scale testing. Several cases have been analyzed and tested to simulate the full-life cycle loading of the pipeline, starting from joint preparation, offshore installation loading, hydrotest loading and in-place loading during operation. The outcome of the modeling and verification by full-scale testing concluded that the MIFC was able to meet and even exceed the minimum requirement of the joint integrity during the full life cycle of the pipeline loading from installation until operation. As a result, the joint acceptance criteria envelope can be designed as acceptance criteria for regulatory purposes and for offshore application quality assurance and control purpose in-lieu of the acceptance criteria by welding. This approach has then been accepted by Malaysian Regulatory for PTI/PTO requirement and successfully applied for one of the pipeline projects in one of PETRONAS subsidiary as first application in Malaysia and the world longest MIFC application for a single subsea pipeline. This successful application opens the possibility for replication to other fields and other pipeline operators in Malaysia.