Drilling Riser Conductor Monitoring: A Practical Approach for Operational Integrity Verification

Abstract With an increase in the number of drilling operations in harsh environments and ultra deepwater, combined with the limited availability of drilling rigs and qualified personnel, it is increasingly important to maximize safety and operability while minimizing structural damage to the riser, wellhead and conductor system. Great efforts to improve drilling equipment, safety features and overall structural integrity of drilling riser systems have occurred in recent years. Subsequently, trends have shifted the focus of integrity concerns from the drilling riser onto the wellhead and conductor system. The integrity of the wellhead and conductor system is of utmost importance – as it provides a vital barrier to contain hydrocarbons and drilling mud inside of the drilling system. A structural breach of this system could have catastrophic consequences and must be avoided at all cost. Significant challenges remain in accurately predicting and tracking actual fatigue damage on wellhead and conductor systems. This papers details the findings of several monitoring campaigns designed to track the actual vibration of the BOP and LMRP stack due to riser VIV, and its contribution to wellhead and conductor strength and fatigue concerns. The measurements have been used to provide operational guidance, validate design tools and thus provide a more realistic fatigue and strength data set for wellhead and conductor systems. The paper will discuss the monitoring application including state of the art sensor systems with practical attachment systems that can be retrofit installed via ROV or diver. Furthermore, is discusses data processing methodologies and software with the aim to provide operational guidance to the drilling team (while providing uninterrupted continuation of drilling operations). Furthermore, detailed engineering studies are presented that correlate conductor fatigue as a function of drilling riser VIV and stack excitation. Two case studies illustrate the application of these technologies. Through research findings and field application, this paper summarizes the operational benefits of an integrity monitoring systems for the wellhead and conductor system from an operator perspective. The target is to increase the understanding of Drilling Riser VIV and its effect on the wellhead and conductor systems. This provides assurance to the operator that the system has not been compromised during a specific drilling campaign and that any risk and uncertainties have been captured and has been evaluated.