Tools and Techniques for the Selection and Design of Safe Deepwater Riser Systems for Mobile Offshore Drilling Units

Abstract The deepwater drilling industry has been rocked by the tragic Deepwater Horizon event in the Gulf of Mexico. The incident identified a number of possible failings by operator, service contractors and the regulator which combined to lead to the ultimate results which were evident in mid 2010. This paper will assess the options available to the deepwater drilling industry in assessing the risk of various riser and BOP configurations for drilling and completing deepwater wells in moderate metocean environments. The paper will address two different systems:A classic subsea BOP stack configuration,A surface BOP stack with a subsea isolation device (SID). Both of these configurations have merits depending upon a number of factors which include rig availability and schedule, project economics, riser integrity, BOP configuration, geological issues and, most importantly, the hazard and risks associated with each concept. This paper will identify the various technical analyses and risk analysis techniques that must be undertaken to assure the operator of the system is comfortable with each system. These include riser analysis, rig mooring and station keeping analyses, system HAZIDs and HAZOPs, and more. The idea of the paper is to provide the operator and drilling contractor with a ‘road map’ which will allow them to navigate their way through the various issues to be addressed. This road map will start with the concept stage (rig contracting early well planning) where issues such as project economics, rig availability and risk tolerance will provide input into the overall decision making process. The paper will next address the preliminary and detailed design stages where issues surrounding metocean criteria, rig characteristics and rig configuration and geological conditions will play a part in the overall input. The paper will describe how a project team would approach the issues. Finally as the project moves to the implementation stage the paper will describe the techniques for final assurance that the concept can be managed in the implementation stage.